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The natural cutoff scale for the quadratically divergent top quark contribution to the Higgs mass parameter can be significantly raised above the surprisingly low standard model value, with important consequences for the LHC: the physics that cancels the top quark divergence may be out of reach, while an electroweak sector with "improved naturalness" may be discovered. Such a sector, consistent with electroweak precision tests, arises in the two Higgs doublet model with heavy Higgs and top quark interactions that approach strong coupling.
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arxiv:hep-ph/0510243
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I discuss the physical picture underlying the evolution equations with Pomeron loops recently derived in multicolor QCD at high energy and qualitatively explain the notion of `self-duality'.
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arxiv:hep-ph/0510265
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In these lectures we discuss condensates which are formed in quark matter when it is squeezed and in a gas of fermionic atoms when it is cooled. The behavior of these two seemingly very different systems reveals striking similarities. In particular, in both systems the Bose-Einstein condensate to Bardeen--Cooper-Schrieffer (BEC-BCS) crossover takes place.
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arxiv:hep-ph/0510302
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Using the seesaw mechanism and a discrete symmetry, we construct a class of models for the neutrino mass matrix where the inverse of that matrix is the sum of a mu-tau antisymmetric background and a perturbation. We consider various possibilities for that perturbation. The simplest possible perturbations lead to four-parameter neutrino mass matrices which are unable to fit the experimental data. More complicated perturbations give rise to viable six-parameter mass matrices; we present detailed predictions of each of them.
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arxiv:hep-ph/0510326
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Two-photon decays of vector mesons and dilepton decays of scalar mesons which are forbidden in vacuum and can occur in dense baryonic matter due to the explicit violation of Lorentz symmetry are described within a quark model of the Nambu--Jona-Lasinio type. The temperature and chemical potential dependence of these processes is investigated. It is found that their contribution to the production of photons and leptons in heavy-ion collisions is enhanced near the conditions corresponding to the restoration of chiral symmetry. Moreover, in the case of the a_0 meson and especially the \rho-meson, a resonant behaviour (an additional amplification) is observed due to the degeneration of \rho and a_0 masses when a hot hadron matter is approaching a chirally symmetric phase.
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arxiv:hep-ph/0510329
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We review supersymmetric models where R-parity is broken either explicitly or spontaneously. The simplest unified extension of the MSSM with explicit bilinear R--Parity violation provides a predictive scheme for neutrino masses and mixings which can account for the observed atmospheric and solar neutrino anomalies. Despite the smallness of neutrino masses R-parity violation is observable at present and future high-energy colliders, providing an unambiguous cross-check of the model. This model can be shown to be an effective model for the, more theoretically satisfying, spontaneous broken theory. The main difference in this last case is the appearance of a massless particle, the majoron, that can modify the decay modes of the Higgs boson, making it decay invisibly most of the time.
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arxiv:hep-ph/0510411
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In the precedent paper of the authors (hep-ph/0510410), the $b\bar b$ states were treated in the framework of the spectral integral equation, together with simultaneous calculations of radiative decays of the considered bottomonia. In the present paper, such a study is carried out for the charmonium $(c\bar c)$ states. We reconstruct the interaction in the $c\bar c$-sector on the basis of data for the charmonium levels with $J^{PC}=0^{-+}$, $1^{--}$, $0^{++}$, $1^{++}$, $2^{++}$, $1^{+-}$ and radiative transitions $\psi(2S)\to\gamma\chi_{c0}(1P)$, $\gamma\chi_{c1}(1P)$, $\gamma\chi_{c2}(1P)$, $\gamma\eta_{c}(1S)$ and $\chi_{c0}(1P)$, $\chi_{c1}(1P)$, $\chi_{c2}(1P)\to\gamma J/\psi$. The $c\bar c$ levels and their wave functions are calculated for the radial excitations with $n\le 6$. Also, we determine the $c\bar c$ component of the photon wave function using the $e^+e^-$ annihilation data: $e^+e^- \to J/\psi(3097)$, $\psi(3686)$, $\psi(3770)$, $\psi(4040)$, $ \psi(4160)$, $\psi(4415)$ and perform the calculations of the partial widths of the two-photon decays for the $n=1$ states: $\eta_{c0}(1S)$, $\chi_{c0}(1P)$, $\chi_{c2}(1P)\to\gamma\gamma$, and $n=2$ states: $\eta_{c0}(2S)\to\gamma\gamma$, $\chi_{c0}(2P)$, $\chi_{c2}(2P)\to \gamma\gamma$. We discuss the status of the recently observed $c\bar c$ states X(3872) and Y(3941): according to our results, the X(3872) can be either $\chi_{c1}(2P)$ or $\eta_{c2}(1D)$, while Y(3941) is $\chi_{c2}(2P)$.
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arxiv:hep-ph/0511005
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We investigate matter effects on highly relativistic neutrinos. The self-energy of neutrinos is determined in an electron or neutrino background taking into account resonance and finite width effects of the gauge bosons. We find minor changes compared to the formerly used formula for the propagator function and large deviations of the effective width from the decay width of the gauge bosons considering higher moments of the electron or neutrino distribution function.
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arxiv:hep-ph/0511010
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This thesis examines the non-leptonic B-decays within QCD factorisation and beyond, to challenge the assumptions and limitations of the method. We analyse the treatment of the distribution amplitudes of light mesons and present a new model described by simple physical parameters. The leading twist distribution amplitudes of light mesons describe the leading non-perturbative hadronic contributions to exclusive QCD reactions at large energy transfer, for instance electromagnetic form factors. Importantly, they also enter into the two-body B decay amplitudes described by QCD factorisation. They cannot be calculated from first principles and are described by models based on a fixed-order conformal expansion, which is not always sufficient in phenomenological applications. We derive new models that are valid to all orders in the conformal expansion and characterised by a small number of parameters related to experimental observables.Motivated by the marginal agreement between the QCD factorisation results with the experimental data, in particular for $B\to\pi\pi$, we scrutinise the incalculable non-factorisable corrections to charmless non-leptonic decays. We use the available results on $B\to\pi\pi$ to extract information about the size and nature of the required non-factorisable corrections that are needed to reconcile the predictions and data. We find that the best-fit scenarios do not give reasonable agreement to $2\sigma$ until at least a 40% non-factorisable contribution is added. Finally we consider the exclusive $B\to V\gamma$ decays, where we analyse the recently updated experimental data within QCD factorisation and present constraints on generic supersymmetric models using the mass insertion approximation.
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arxiv:hep-ph/0511022
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We identified a set of four rephasing invariant parameters of the CKM matrix. They are found to exhibit hierarchies in powers of $\lambda^2$, from $\lambda^2$ to $\lambda^8$. It is shown that, at the present level of accuracy, only the first three parameters are needed to fit all available data on flavor physics.
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arxiv:hep-ph/0511037
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The interplay of strong and weak decay amplitudes for B -> pion-pion-kaon and B -> kaon-antikaon-kaon, with the pion-pion and kaon-antikaon pairs interacting in isospin-0 S-wave, is analyzed for pion-pion effective mass from threshold to 1.2 GeV. To improve agreement with experiment of a factorization approach with some QCD corrections, addition of long-distance contributions, called charming penguins is necessary.
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arxiv:hep-ph/0511044
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We apply the soft-collinear effective theory (SCET) to deep inelastic scattering near the endpoint region. The forward scattering amplitude, and the structure functions are shown to factorize as a convolution of the Wilson coefficients, the jet functions, the parton distribution functions. The behavior of the parton distribution functions near the endpoint region is considered. It turns out that it evolves with the Altarelli-Parisi kernel even in the endpoint region, and the parton distribution function can be factorized further into a collinear part and the soft Wilson line. The factorized form for the structure functions is obtained by the two-step matching, and the radiative corrections or the evolution for each factorized part can be computed in perturbation theory. We present the radiative corrections of each factorized part to leading order in alpha_s, including the zero-bin subtraction for the collinear part.
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arxiv:hep-ph/0511066
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We take a critical view of the treatment of threshold effects in SUSY spectrum computations from high-scale input. We discuss the two principal methods of (a) renormalization at a common SUSY scale versus (b) integrating out sparticles at their own mass scales. We point out problems in the implementations in public spectrum codes, together with suggestions for improvements. In concrete examples, we compare results of Isajet7.72 and Spheno2.2.3, and present the improvements done in Isajet7.73. We also comment on theoretical uncertainties. Last but not least, we outline how a consistent multiscale approach may be achieved.
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arxiv:hep-ph/0511123
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Effect of the quark intrinsic motion on the proton spin structure functions is demonstrated. It is shown, that the covariant version of the quark-parton model taking into account the orbital motion gives the consistent picture of the proton spin structure, which is based on the valence quarks. This picture is supported by the recent data, which indicate, that the spin contributions from the sea quarks and gluons are compatible with zero.
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arxiv:hep-ph/0511142
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Branching ratios and polarization amplitudes for B decaying to all allowed pseudoscalar, vector, axial-vector, scalar and tensor combinations of D_s and D mesons are calculated in the Isgur Scora Grinstein Wise (ISGW) quark model after assuming factorization. We find good agreement with other models in the literature and the limited experimental data and make predictions for as yet unseen decay modes. Lattice QCD results in this area are very limited. We make phenomenological observations on decays in to D_s(2317) and D_s(2460) and propose tests for determining the status and mixings of the axial mesons. We use the same approach to calculate branching ratios and polarization fraction for decays in to two D type mesons.
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arxiv:hep-ph/0511169
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Higgs multiplet in the vector-spinor representations of SO(10), i.e., the $144+\bar{144}$ multiplet can break the SO(10) gauge symmetry spontaneously in one step down to the Standard Model gauge group symmetry $SU(3)_C\times SU(2)_L\times U(1)_Y$ and a recent analysis has used such vector-spinors for building a new class of SO(10) grand unification models (hep-ph/0506312) . Here we discuss the techniques for the computation of several classes of vector-spinor couplings using the Basic Theorem on the SO(2N) vertex expansion developed by the authors. The computations include the cubic couplings of the vector-spinors with SO(10) tensors, quartic self-couplings of the vector-spinors, and couplings of the vector-spinors with spinor representations of SO(10). The last set include couplings of vector-spinors with the 16-plets of quarks and lepton and with the 16 and $\bar{16}$ of Higgs. These couplings provide a crucial tool for further development of the SO(10) grand unification using vector-spinor representations. These include study of quark-lepton masses, analysis of dimension five operators including baryon and lepton number violating operators, and study of neutrino masses and mixings. Illustrative examples are given for their computation using a sample of vector-spinor couplings.
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arxiv:hep-ph/0511172
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Deviations from Newton's Inverse-Squared Law at the micron length scale are smoking-gun signals for models containing Supersymmetric Large Extra Dimensions (SLEDs), which have been proposed as approaches for resolving the Cosmological Constant Problem. Just like their non-supersymmetric counterparts, SLED models predict gravity to deviate from the inverse-square law because of the advent of new dimensions at sub-millimeter scales. However SLED models differ from their non-supersymmetric counterparts in three important ways: (i) the size of the extra dimensions is fixed by the observed value of the Dark Energy density, making it impossible to shorten the range over which new deviations from Newton's law must be seen; (ii) supersymmetry predicts there to be more fields in the extra dimensions than just gravity, implying different types of couplings to matter and the possibility of repulsive as well as attractive interactions; and (iii) the same mechanism which is purported to keep the cosmological constant naturally small also keeps the extra-dimensional moduli effectively massless, leading to deviations from General Relativity in the far infrared of the scalar-tensor form. We here explore the deviations from Newton's Law which are predicted over micron distances, and show the ways in which they differ and resemble those in the non-supersymmetric case.
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arxiv:hep-ph/0511216
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We study QED corrections to chiral symmetry breaking in the Nambu--Jona-Lasinio (NJL) model with two flavors of quarks. In this model, the isospin symmetry is broken by the differences between the current quark masses and the electromagnetic charges of the up and down quarks. To leading order in the 1/N expansion, we calculate the effective potential of the model with one-loop QED corrections at finite temperature. Evaluating the effective potential, we study the influence of the isospin symmetry breaking on the orientation of chiral symmetry breaking. The current quark mass plays an essential role in maintaining the orientation of the chiral symmetry breaking. If the average of the up and down quark masses is small enough, we find a phase in which the pion field has non-vanishing expectation value and dynamical CP violation takes place.
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arxiv:hep-ph/0511218
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We present analyses of the sixty hybrid textures of neutrino mass matrix, which have an equality of matrix elements and one zero. These textures are possibly derived in the models with discrete flavor symmetry. Only six textures among sixty ones are excluded by the present experimental data. Since there are many textures which give similar predictions, the textures are classified based on the numerical results. The neutrinoless double beta decay is also examined in these textures. Our results suggest that there remain still rich structures of the neutrino mass matrix in the phenomenological point of view.
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arxiv:hep-ph/0511251
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We investigate the restoration of chiral SU$(3)\otimes$SU$(3)$ and axial U$_A$(1) symmetries, at finite temperature and density, in the framework of the three flavor Nambu-Jona-Lasinio model with anomaly. We implement a temperature (density) dependence of the anomaly coefficient motivated by lattice results for the topological susceptibility and we discuss the restoration of symmetries by analyzing the behavior of the mesonic chiral partners and of the mixing angles. The results indicate that the axial part of the symmetry is restored before the possible restoration of the full U(3)$\otimes$U(3) chiral symmetry can occur.
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arxiv:hep-ph/0511284
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The saturation of QCD chiral sum rules is reanalyzed in view of the new and complete analysis of the ALEPH experimental data on the difference between vector and axial-vector correlators (V-A). Ordinary finite energy sum rules (FESR) exhibit poor saturation up to energies below the tau-lepton mass. A remarkable improvement is achieved by introducing pinched, as well as minimizing polynomial integral kernels. Both methods are used to determine the dimension d=6 and d=8 vacuum condensates in the Operator Product Expansion, with the results: {O}_{6}=-(0.00226 \pm 0.00055) GeV^6, and O_8=-(0.0053 \pm 0.0033) GeV^8 from pinched FESR, and compatible values from the minimizing polynomial FESR. Some higher dimensional condensates are also determined, although we argue against extending the analysis beyond dimension d = 8. The value of the finite remainder of the (V-A) correlator at zero momentum is also redetermined: \Pi (0)= -4 \bar{L}_{10}=0.02579 \pm 0.00023. The stability and precision of the predictions are significantly improved compared to earlier calculations using the old ALEPH data. Finally, the role and limits of applicability of the Operator Product Expansion in this channel are clarified.
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arxiv:hep-ph/0511293
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We discuss the possibility to probe leptonic mixing parameters at high-energy neutrino telescopes in a model-independent way, using astrophysical neutron and pion sources. In particular we show how the octant of the 2-3 mixing angle might be determined independently of prior knowledge of the source, even when current uncertainties on the other mixing parameters are included. We also argue that non-trivial neutrino oscillation effects should be taken into account when using high-energy flavor ratios for astrophysical diagnostics.
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arxiv:hep-ph/0511313
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We investigate the possibility of generating the $\mu$-term in the MSSM by the condensation of a field that is a singlet under the SM gauge group but charged under an additional family-independent $U(1)_X$ gauge symmetry. We attempt to do so while preserving the gauge coupling unification of the MSSM. For this, we find that SM non-singlet exotics must be present in the spectrum. We also prove that the pure $U(1)_X$ anomalies can always be solved with rationally charged fields, but that a large number of SM singlets are often required. For $U(1)_X$ charges that are consistent with an embedding of the MSSM in SU(5) or SO(10), we show that the $U(1)_X$ charges of the MSSM states can always be expressed as a linear combination of abelian subgroups of $E_6$. However, the SM exotics do not appear to have a straightforward embedding into GUT multiplets. We conclude from this study that if this approach to the $\mu$-term is correct, as experiment can probe, it will necessarily complicate the standard picture of supersymmetric grand unification.
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arxiv:hep-ph/0512019
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In this letter we make use of the Background Field Method (BFM) to compute the effective potential of an SU(2) gauge field theory, in the presence of chemical potential and temperature. The main idea is to consider the chemical potential as the background field. The gauge fixing condition required by the BFM turns out to be exactly the one we found in a previous article in a different context.
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arxiv:hep-ph/0512042
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We discuss effective interactions among brane matter induced by modifications of higher dimensional Einstein gravity via the replacement of Einstein-Hilbert term with a generic function f(R) of the curvature scalar R. After deriving the graviton propagator, we analyze impact of virtual graviton exchanges on particle interactions, and conclude that f(R) gravity effects are best probed by high-energy processes involving massive gauge bosons, heavy fermions or the Higgs boson. We perform a comparative analysis of the predictions of f(R) gravity and of Arkani-Hamed-Dvali-Dimopoulos (ADD) scenario, and find that the former competes with the latter when f''(0) is positive and comparable to the fundamental scale of gravity in higher dimensions. In addition, we briefly discuss graviton emission from the brane as well as its decays into brane-localized matter, and find that they hardly compete with the ADD expectations. Possible existence of higher-curvature gravitational interactions in large extra spatial dimensions opens up various signatures to be confronted with existing and future collider experiments.
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arxiv:hep-ph/0512078
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We show that, in the light-cone gauge, it is possible to derive in a very simple way the solution of the classical Yang-Mills equations for the collision between a nucleus and a proton. One important step of the calculation is the derivation of a formula that describes the propagation of a gluon in the background color field of the nucleus. This allows us to calculate observables in pA collisions in a more straightforward fashion than already proposed. We discuss also the comparison between light-cone gauge and covariant gauge in view of further investigations involving higher order corrections.
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arxiv:hep-ph/0512079
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The main part of coherent pion production by neutrinos on nuclei is essentially determined by PCAC, provided that the leptonic momentum transferred square Q^2 remains sufficiently small. We give the formulas for the charged and neutral current cross sections, including also the small non-PCAC transverse current contributions and taking into account the effect of the \mu^- mass. Our results are compared with the experimental ones and other theoretical treatments.
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arxiv:hep-ph/0512139
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Quasi two-body decays B^0(t)-> a_1^{+-}(1260) pi^{-+} identified by four charged pions determine a phase alpha_eff, which is equal to the weak phase alpha in the limit of vanishing penguin amplitudes. Applying flavor SU(3) to these decays and to B->a_1 K and B->K_1 pi, with K_1 an admixture of K_1(1270) and K_1(1400), we derive expressions providing bounds on alpha-alpha_{eff}. Higher precision in alpha may be achieved by an overall fit to a complete set of SU(3) related measurements. A method is sketched applying isospin symmetry to time-dependent invariant mass distributions in B->pi^+ pi^- pi^0 pi^0.
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arxiv:hep-ph/0512148
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Results from a recent analysis of the zero-skewness generalized parton distributions (GPDs) for valence quarks are reviewed. The analysis bases on a physically motivated parameterization of the GPDs with a few free parameters adjusted to the nucleon form factor data. The Fourier transforms of the GPDs representing quark densities in the impact parameter plane, as well as moments of the GPDs are also discussed. The 1/x moments in particular form the soft physics input to Compton scattering off protons within the handbag approach. The Compton cross section evaluated from this information is found to be in good agreement with experiment.
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arxiv:hep-ph/0512229
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In this article we extract soft distribution functions for Drell-Yan and Higgs production processes using mass factorisation theorem and the perturbative results that are known upto three loop level. We find that they are maximally non-abelien. We show that these functions satisfy Sudakov type integro differential equations. The formal solutions to such equations and also to the mass factorisation kernel upto four loop level are presented. Using the soft distribution function extracted from Drell-Yan production, we show how the soft plus virtual cross section for the Higgs production can be obtained. We determine the threshold resummation exponents upto three loop using the soft distribution function.
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arxiv:hep-ph/0512249
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We consider general field theories in six dimensions, with two of the dimensions compactified on a T_{2}/Z_{4} orbifold. Six-dimensional Weyl fermions propagating on this background give rise to a chiral zero-mode, which makes them interesting for phenomenological applications. The compact two-dimensional space is flat and has three conical singularities. We consider the one-loop structure of these theories, and show that the presence of logarithmic divergences requires the introduction of counterterms precisely at these three singular points. We also show that the corresponding localized operators are rotationally symmetric in the plane of the two extra dimensions, as expected from the geometry about the singularities. We derive the propagators for spin-0, spin-1/2 and spin-1 fields in momentum space, in such a way that the appropriate boundary conditions are satisfied. This allows us to efficiently calculate loop diagrams in any given model. We give general expressions for the mass splittings among Kaluza-Klein modes within a given level. Our results can also be used to obtain interesting KK-parity preserving interactions among Kaluza-Klein modes. We pay special attention to the components of six-dimensional gauge fields that transform as scalars under the four-dimensional Lorentz group. These states provide a characteristic signature for these scenarios. In particular, we find that they can easily be the lightest particles in the Kaluza-Klein spectrum.
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arxiv:hep-ph/0512304
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We have reinvestigated the collision of gluonic bubbles in a SU(2) model of QCD which was studied by Johnson, Choi and Kisslinger in the context of the instanton-inspired model of QCD phase transition bubbles with plane wave approximation. We discuss treacherous points of the instanton-inspired model that cause the violation of causality due to the presence of imaginary gluon fields. By constructing a new slightly modified Lorentzian model where we have three independent real gluon fields, we reanalyzed the process of bubble collisions. Our numerical results show some indication of forming a bubble wall in colliding region.
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arxiv:hep-ph/0512314
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We present a supersymmetric extension of the Standard Model with a gauged SU(2) family symmetry for the leptons. It is shown that this family symmetry can be consistently broken at the TeV scale along with supersymmetry. If supersymmetry breaking is driven by anomaly mediation, this model can provide positive squared masses for the sleptons and thus cure the tachyon problem. We analyze the constraints and consequences of this scenario. A characteristic feature of this model is the non-degeneracy of the first two family sleptons. The model predicts large value of tan(beta) and observable \tau to e \gamma and B to \mu^+ \mu^- decay rates.
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arxiv:hep-ph/0512333
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We compute the 1-loop (alpha_s^2) correction to hard spectator scattering in non-leptonic B decay tree amplitudes. This forms part of the NNLO contribution to the QCD factorization formula for hadronic B decays, and introduces a new rescattering phase that corrects the leading-order result for direct CP asymmetries. Among the technical issues, we discuss the cancellation of infrared divergences, and the treatment of evanescent four-quark operators. The infrared finiteness of our result establishes factorization of spectator scattering at the 1-loop order. Depending on the values of hadronic input parameters, the new 1-loop correction may have a significant impact on tree-dominated decays such as B -> pi pi.
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arxiv:hep-ph/0512351
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In these lectures I briefly review the Higgs mechanism of spontaneous symmetry breaking and focus on the most relevant aspects of the phenomenology of the Standard Model and of the Minimal Supersymmetric Standard Model Higgs bosons at both hadron and lepton colliders. Some emphasis is put on the perturbative calculation of both Higgs boson branching ratios and production cross sections, including the most important radiative corrections.
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arxiv:hep-ph/0512377
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The $B_K$ parameter is computed in quenched lattice QCD with Wilson twisted mass fermions. Two variants of tmQCD are used; in both of them the relevant $\Delta S = 2$ four-fermion operator is renormalised multiplicatively. The renormalisation adopted is non-perturbative, with a Schroedinger functional renormalisation condition. Renormalisation group running is also non-perturbative, up to very high energy scales. In one of the two tmQCD frameworks the computations have been performed at the physical $K$-meson mass, thus eliminating the need of mass extrapolations. Simulations have been performed at several lattice spacings and the continuum limit was reached by combining results from both tmQCD regularisations. Finite volume effects have been partially checked and turned out to be small. Exploratory studies have also been performed with non-degenerate valence flavours. The final result for the RGI bag parameter, with all sources of uncertainty (except quenching) under control, is $\hat B_K =0.789 \pm 0.046$.
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arxiv:hep-ph/0601002
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Cosmic strings in the brane Universe have recently gained a great interest. I think the most interesting story is that future cosmological observations distinguish them from the conventional cosmic strings. If the strings are the higher-dimensional objects that can (at least initially) move along the compactified space, and finally settle down to (quasi-)degenerated vacua in the compactified space, then kinks should appear on the strings, which interpolate between the degenerated vacua. These kinks look like ``beads'' on the strings, which means that the strings turn into necklaces. Moreover, in the case that the compact manifold is not simply connected, the string loop that winds around a non-trivial circle is stable due to the topological reason. Since the existence of degenerated vacua and a non-trivial circle is the common feature of the brane models, it is important to study cosmological constraints on the cosmic necklaces and their stable winding states in the brane Universe.
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arxiv:hep-ph/0601014
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We examine the mass loss rates and lifetimes of TeV-scale extra dimensional black holes (BH) in ADD-like models with Lovelock higher-curvature terms present in the action. In particular we focus on the predicted differences between the canonical and microcanonical ensemble statistical mechanics descriptions of the Hawking radiation that results in the decay of these BH. In even numbers of extra dimensions the employment of the microcanonical approach is shown to generally lead to a significant increase in the BH lifetime as in case of the Einstein-Hilbert action. For odd numbers of extra dimensions, stable BH remnants occur when employing either description provided the highest order allowed Lovelock invariant is present. However, in this case, the time dependence of the mass loss rates obtained employing the two approaches will be different. These effects are in principle measurable at future colliders.
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arxiv:hep-ph/0601029
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The doublet-triplet splitting problem can be simply solved in product-group GUT models, using a global symmetry that distinguishes the doublets from the triplets. Apart from giving the required mass hierarchy, this ``triplet symmetry'' can also forbid some of the triplet couplings to matter. We point out that, since this symmetry is typically generation-dependent, it gives rise to non-trivial flavor structure. Furthermore, because flavor symmetries cannot be exact, the triplet-matter couplings are not forbidden then but only suppressed. We construct models in which the triplet symmetry gives acceptable proton decay rate and fermion masses. In some of the models, the prediction m_b ~ m_\tau is retained, while the similar relation for the first generation is corrected. Finally, all this can be accomplished with triplets somewhat below the GUT scale, supplying the right correction for the standard model gauge couplings to unify precisely.
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arxiv:hep-ph/0601039
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Single pion and prompt photon large transverse momentum spectra in p-p and Au-Au collisions are computed in perturbative QCD at RHIC energy, s^1/2 = 200 GeV. Next-to-leading order calculations are discussed and compared with p-p scattering data. Subsequently, quenching factors are computed to leading order for both pions and photons within the same energy loss model. The good agreement with PHENIX preliminary data allows for a lower estimate of the energy density reached in central Au-Au collisions, epsilon > 10 GeV/fm^3. Double inclusive photon-pion production in p-p and Au-Au collisions is then addressed. Next-to-leading order corrections prove rather small in p-p scattering. In Au-Au collisions, the quenching of momentum-correlation spectra is seen to be sensitive to parton energy loss processes, which would help to understand how the fragmentation dynamics is modified in nuclear collisions at RHIC.
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arxiv:hep-ph/0601075
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The worldline variational approach is extended beyond the quenched approximation, i.e. to include virtual pair production of heavy particles. This is achieved either by an expansion of the functional determinant to second order or by an hybrid ansatz for the quadratic trial action consisting of fields for the light particles and worldlines for the heavy ones as in the linear polaron model. Numerical results and analytic approximations show a reduction of radiative effects with increasing number of flavors.
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arxiv:hep-ph/0601088
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The orbital angular momentum is one of the least understood of the spin characteristics of a proton. There are no direct ways to model the orbital angular momentum. However, the Jz=1/2 sum rule includes an angular momentum component and can provide indirect access to its properties. One of the other unknowns in the sum rule is the gluon polarization. We can define the gluon spin asymmetry in a proton as the ratio of the polarized to unpolarized gluon distributions. This can be written as a sum of a scale-invariant piece and a small scale-dependent term. The x-dependence of the asymmetry can be calculated and a suitable parametrization for scale-dependent term can be made to estimate this asymmetry. When combined with the measured unpolarized gluon density, this provides a model independent prediction for the polarized gluon distribution. This eliminates one unknown in the Jz=1/2 sum rule and allows a reasonable estimate for the size and evolution of the orbital angular momentum of the constituents.
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arxiv:hep-ph/0601141
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An improved analysis of the $b\to s+\gamma$ decay in the minimal flavor violating case is given taking into account additional contributions in the supersymmetric sector which enter in the next-to-leading-order (NLO) and are enhanced by $\tan\beta$ factors. Specifically, we compute a set of twenty one-loop diagrams to give the most complete analysis to date of the NLO supersymmetric corrections. These modifications are computed from the effective charged Higgs and neutral Higgs couplings involving twelve loop diagrams for the charged Higgs sector and eight loop diagrams for the neutral Higgs sector. While the computations of these corrections are available in the literature, their full forms including the complex phase dependence has not be considered. Our analysis takes account of the full allowed set of twenty one-loop diagrams and is more general since it also includes the full dependence on CP phases in non universal sugra and MSSM models. A numerical analysis is carried out to estimate the size of the corrections to $b\to s+\gamma$. We also briefly discuss the implications of these results for the search for supersymmetry.
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arxiv:hep-ph/0601163
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In this work we study an SO(10) GUT model with minimum Higgs representations belonging only to the 210 and 16 dimensional representations of SO(10). We add a singlet fermion S in addition to the usual 16 dimensional representation containing quarks and leptons. There are no Higgs bi-doublets and so charged fermion masses come from one-loop corrections. Consequently all the fermion masses, Dirac and Majorana, are of the see-saw type. We minimize the Higgs potential and show how the left-right symmetry is broken in our model where it is assumed that a D-parity odd Higgs field gets a vacuum expectation value at the grand unification scale. From the renormalization group equations we infer that in our model unification happens at 10^{15} GeV and left-right symmetry can be extended up to some values just above 10^{11} GeV. The Yukawa sector of our model is completely different from most of the standard grand unified theories and we explicitly show how the Yukawa sector will look like in the different phases and briefly comment on the running of the top quark mass. We end with a brief analysis of lepton number asymmetry generated from the interactions in our model.
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arxiv:hep-ph/0601170
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We investigate the threshold-enhanced QCD corrections to the cross sections for direct top quark productions induced by model-independent flavor changing neutral current couplings at hadron colliders. We use the soft-collinear effective theory to describe the incoming massless partons and use the heavy quark effective theory to treat the top quark. Then we construct the flavor changing operator based on the above effective theories, and resum the large logarithms near threshold arising from soft gluon emission. Our results show that the resummed QCD corrections further enhance the next-to-leading order cross sections significantly. Moreover, the resummation effects vastly reduce the dependence of the cross sections on the renormalization and factorization scales, especially in cases where the next-to-leading order results behave worse than the leading order results. Our results are more sensitive to the new physics effects. If signals of direct top quark production are found in future experiments, it is more appropriate to use our results as the theoretical inputs for extracting the anomalous couplings.
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arxiv:hep-ph/0601180
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We calculate the one-loop flavor violating top quark decay t -> cgg in the Minimal Supersymmetric Standard Model. We discuss the branching ratios obtained with minimal flavor violation, as well as with soft-supersymmetry induced general flavor violation. Based on this rate we calculate the cross section for the single top quark production via gluon fusion, gg -> t cbar, and evaluate its contribution to the cross section for single top quark production in pp collisions at the Large Hadron Collider. We calculate all contributions coming from the standard model and charged Higgs loops, as well as gluino (and neutralino)-up-type squarks, and chargino-down-type squarks loops. Our numerical results show that the gluino and the chargino contributions are largest over the whole parameter range in the unconstrained Minimal Supersymmetric Standard Model. While in general the gluino contributions dominate the cross section, this result depends on the supersymmetric flavor violating parameters in the up and down squark sector, the relative mass of the gauginos, and whether or not the Grand Unified Theory relationships between gaugino masses are satisfied. In the most promising scenarios, the pp -> t cbar + tbar c + X cross section at the Large Hadron Collider can reach a few hundreds fb.
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arxiv:hep-ph/0601253
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We consider the modification of the Cahn-Hilliard equation when a time delay process through a memory function is taken into account. We then study the process of spinodal decomposition in fast phase transitions associated with a conserved order parameter. Finite-time memory effects are seen to affect the dynamics of phase transition at short times and have the effect of delaying, in a significant way, the process of rapid growth of the order parameter that follows a quench into the spinodal region. These effects are important in several systems characterized by fast processes, like nonequilibrium dynamics in the early universe and in relativistic heavy-ion collisions.
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arxiv:hep-ph/0601256
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We provide an up-to-date analysis of the parameter space of the minimal supergravity model (mSUGRA). Novel features include the new central value of the top quark mass, an improved calculation of the masses of the supersymmetric particles and the neutral Higgs bosons, constraints from b to s \ell^+ \ell^- decays, and a careful treatment of the most important experimental and theoretical uncertainties. In addition to the by now traditional plots of the allowed region in the (m_0, m_{1/2}) plane, we show allowed regions in the planes spanned by pairs of {\em physical} sparticle or Higgs boson masses. Moreover, we search for the minimal allowed masses of new particles for various sets of constraints. We find that in many cases the direct experimental limits from collider and Dark Matter searches can be saturated even in this minimal model, and even after including the by now quite restrictive constraint on the Dark Matter relic density.
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arxiv:hep-ph/0602001
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We discuss, in the context of precision measurement of Delta m^2_{31} and theta_{13}, physics capabilities enabled by the recoilless resonant absorption of monochromatic antineutrino beam enhanced by the M\"ossbauer effect recently proposed by Raghavan. Under the assumption of small relative systematic error of a few tenth of percent level between measurement at different detector locations, we give analytical and numerical estimates of the sensitivities to Delta m^2_{31} and sin^2 2theta_{13}. The accuracies of determination of them are enormous; The fractional uncertainty in Delta m^2_{31} achievable by 10 point measurement is 0.6% (2.4%) for sin^2 2theta_{13} = 0.05, and the uncertainty of sin^2 2theta_{13} is 0.002 (0.008) both at 1 sigma CL with the optimistic (pessimistic) assumption of systematic error of 0.2% (1%). The former opens a new possibility of determining the neutrino mass hierarchy by comparing the measured value of Delta m^2_{31} with the one by accelerator experiments, while the latter will help resolving the theta_{23} octant degeneracy.
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arxiv:hep-ph/0602046
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In this paper we have analyzed the production of pair charmonium mesons in the reactions $e^+ e^- \to J/ \Psi \chi_{c0}, e^+ e^-\to \Psi(2S) \chi_{c0}$ at energy $\sqrt s = 10.6$GeV in the framework of the light cone formalism. In comparison with NRQCD the numerical results for the cross sections are in better agreement with experiment.
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arxiv:hep-ph/0602047
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We discuss how experiments measuring B -> pi pi and B -> rho rho may be used to search for a Delta I = 5/2 amplitude component. This component could be the explanation for a recent (albeit very tentative) hint from B(Bbar) -> rho rho decays that the isospin triangles do not close.
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arxiv:hep-ph/0602060
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The resonance X(1810) discovered in $J/\psi\to \gamma\omega\phi$ by BESII is considered as a candidate of $0^{++}$ $Q^2\bar{Q}^2$ state. This model predicts that $X\to\omega\phi, K^* K^*$ are the two dominant decay channels and $X\to KK, \eta\eta, \eta\eta'$ are suppressed. The cross sections of $\gamma\gamma\to X\to \omega\phi, K^* K^*$ are estimated.
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arxiv:hep-ph/0602072
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We discuss the finite-size effects on the chiral phase transition in QCD. We employ the Nambu-Jona-Lasinio model and calculate the thermodynamic potential in the mean-field approximation. Finite-size effects on the thermodynamic potential are taken into account by employing the multiple reflection expansion. The critical temperature is lowered and the order of the phase transition is changed form first to second as the size of the system of interest is reduced.
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arxiv:hep-ph/0602086
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This contribution to the published Proceedings records the opening talk I presented on the first morning of the 2005 International Linear Collider Workshop in Snowmass, CO, August 14 - 27, 2005. It includes a summary of the motivation for the workshop, the scientific goals and charges for the working groups, the initial plans of the accelerator, detector, and physics groups, and the activities of the communication, education, and outreach group. This document also describes organizational aspects of the meeting, particularly the scientific committee structure, the self-organization of the working groups, the composition of the indispensable secretariat and computer support teams, and the sources of funding support. The report serves as an introduction to the proceedings whose individual papers and summary documents must be consulted for an appreciation of the accomplishments and progress made at Snowmass in 2005 toward the realization of an International Linear Collider.
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arxiv:hep-ph/0602117
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We calculate semileptonic decays of light and heavy baryons in a relativistically covariant constituent quark model. The model is based on the Bethe-Salpeter-equation in instantaneous approximation. It generates satisfactory mass spectra for mesons and baryons up to the highest observable energies. Without introducing additional free parameters we compute on this basis helicity amplitudes of electronic and muonic semileptonic decays of baryons. We thus obtain form factor ratios and decay rates in good agreement with experiment.
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arxiv:hep-ph/0602152
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If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the next generation of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark matter. From this, we can predict the cosmic density, the annihilation cross sections, and the cross sections relevant to direct detection. In this paper, we present studies in supersymmetry models with neutralino dark matter that give quantitative estimates of the accuracy that can be expected. We show that these are well matched to the requirements of anticipated astrophysical observations of dark matter. The capabilities of the proposed International Linear Collider (ILC) are expected to play a particularly important role in this study.
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arxiv:hep-ph/0602187
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We present a new technique to extract information on the Unitarity Triangle from the study of Bs -> K pi pi Dalitz plot. Using isospin symmetry and the possibility to access the decay amplitudes from Dalitz analyses, we propose a new strategy to extract the weak phase gamma from Bs to K pi pi.
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arxiv:hep-ph/0602207
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The modification of the Paschos-Wolfenstein relation is investigated when the charge symmetry violations of valence and sea quark distributions in the nucleon are taken into account. We also study qualitatively the impact of charge symmetry violation (CSV) effect on the extraction of $\sin^{2}\theta_{w}$ from deep inelastic neutrino- and antineutrino-nuclei scattering within the light-cone meson-baryon fluctuation model. We find that the effect of CSV is too small to give a sizable contribution to the NuTeV result with various choices of mass difference inputs, which is consistence with the prediction that the strange-antistrange asymmetry can account for largely the NuTeV deviation in this model. It is noticeable that the effect of CSV might contribute to the NuTeV deviation when the larger difference between the internal momentum scales, $\alpha_{p}$ of the proton and $\alpha_{n}$ of the neutron, is considered.
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arxiv:hep-ph/0602241
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Based on the behavior of the elastic scattering data, we introduce an almost model-independent parametrization for the imaginary part of the scattering amplitude, with the energy and momentum transfer dependences inferred on empirical basis and selected by rigorous theorems and bounds from axiomatic quantum field theory. The corresponding real part is analytically evaluated by means of dispersion relations, allowing connections between particle-particle and particle-antiparticle scattering. Simultaneous fits to proton-proton and antiproton-proton experimental data in the forward direction and also including data beyond the forward direction, lead to a predictive formalism in both energy and momentum transfer. We compare our extrapolations with predictions from some popular models and discuss the applicability of the results in the normalization of elastic rates that can be extracted from present and future accelerator experiments (Tevatron, RHIC and LHC).
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arxiv:hep-ph/0603035
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Nonperturbative effects in event shape distributions can be characterized by shape functions derived in the eikonal approximation or, equivalently, from soft-collinear effective theory. The use of energy flow operators and the boost invariance of the Wilson lines of soft gluons in the shape functions leads to a proof of universality for power corrections to the mean values of event shapes, without invoking the single gluon approximation.
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arxiv:hep-ph/0603066
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In this paper we address the question: ``do the limits on technirho production at the Tevatron mean what we think they do ?'' These limits are based on calculations that rely on Vector Meson Dominance (VMD). VMD was invented in order to describe the interaction of electrons with hadrons (the rho meson and pions). The method has been used also as a tool in the study of Technicolor phenomenology. Nevertheless there are evidences in the sense that, even in its original, context VMD is not completely realized. In this work we investigate the consequences of a deviation from complete VMD for the phenomenology of colored technihadrons. We focus specially on the production of the color octet technirho and color triplet technipions. We found that a relative small direct coupling of the proto-technirho to quarks is enough to suppress or even eliminate the interaction among quarks and the physical technirho. On the other hand, it is possible to suppress the coupling of the physical technirho to technipions but in this case a large interaction among the technipions and the proto-gluon must be introduced. The consequences for the limits on the mass of the color octet technirho are also investigated.
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arxiv:hep-ph/0603094
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If the lowest lying Kaluza-Klein states in Randall-Sundrum (RS1) models have masses in the 10-100 TeV range, direct production of these states at the LHC or ILC is impossible, and electroweak precision measurements may not be sufficiently sensitive. We address the possibility that high-precision measurements of top pair production at the ILC may provide the first evidence of these states. We consider RS1 models with fermions on and off the brane, with bulk left and right handed mass terms, discuss brane kinetic terms and calculate corrections to top pair production in these models.
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arxiv:hep-ph/0603105
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By studying the Paschos-Wolfenstein (PW) ratio of deep inelastic $\nu{\rm Fe}$ and $\bar \nu{\rm Fe}$ scattering cross sections, we show that it should be possible to explain the NuTeV $\sin ^2 \theta_{\rm W}$ anomaly with quite conventional physics, by introducing mutually different nuclear modifications for the valence-$u$ and valence-$d$ quark distributions of the protons in iron. Keeping the EKS98 nuclear modifications for $u_V+d_V$ as a baseline, we find that some 20-30 % nuclear modifications to the $u_V$ and $d_V$ distributions account for the change induced in the PW ratio by the NuTeV-suggested increase $\Delta \sin ^2 \theta_{\rm W}=0.005$. We show that introduction of such nuclear modifications in $u_V$ and $d_V$ individually, does not lead into contradiction with the present global DGLAP analyses of the nuclear parton distributions, where deep inelastic $lA$ scattering data and Drell-Yan dilepton data from $pA$ collisions are used as constraints. We thus suggest that the NuTeV result serves as an important further constraint in pinning down the nuclear effects of the bound nucleon PDFs. We also predict that if the NuTeV anomaly is explained by this mechanism, the NOMAD experiment should see an increase in the weak mixing angle quite close to the NuTeV result.
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arxiv:hep-ph/0603155
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In the framework of Supersymmetric Grand Unified Theories (SUSY GUTs), the universe undergoes a cascade of symmetry breakings, during which topological defects can be formed. We address the question of the probability of cosmic string formation after a phase of hybrid inflation within a large number of models of SUSY GUTs in agreement with particle and cosmological data. We show that cosmic strings are extremely generic and should be used to relate cosmology and high energy physics. This conclusion is employed together with the WMAP CMB data to strongly constrain SUSY hybrid inflation models. F-term and D-term inflation are studied in the SUSY and minimal SUGRA framework. They are both found to agree with data but suffer from fine tuning of their superpotential coupling (\lambda \lesssim 3\times 10^(-5) or less). Mass scales of inflation are also constrained to be less than M \lesssim 3\times 10^(15) GeV.
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arxiv:hep-ph/0603169
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We investigate the quark masses and mixings by including vector-like down-type quark singlets in universality of strength for Yukawa couplings (USY). In contrast with the standard model with USY, the sufficient $ CP $ violation is obtained for the Cabibbo-Kobayashi-Maskawa matrix through the mixing between the ordinary quarks and quark singlets. The top-bottom mass hierarchy $ m_t \gg m_b $ also appears naturally in the USY scheme with the down-type quark singlets.
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arxiv:hep-ph/0603219
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The amplitude for scalar Higgs boson production in a fusion of two off-shell gluons is calculated including finite (not infinite) masses of quarks in the triangle loop. In comparison to the effective Lagrangian approach, we have found a new term in the amplitude. The matrix element found can be used in the kt-factorization approach to the Higgs boson production. The results are compared with the calculations for on-shell gluons. Small deviations from the cos(phi)^2-dependence are predicted. The off-shell effects found are practically negligible.
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arxiv:hep-ph/0603258
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It is shown that in the large-N_c limit radial Regge trajectories give rise in a natural way to the presence of the dimension-2 gluon condensate, <A^2>, in meson correlators. We match these models to QCD and provide estimates for <A^2> in terms of other physical quantities. In particular, in the simplest strictly linear radial Regge model with equal residues <A^2> is proportional to the pion decay constant squared. However, the linear model fails a consistency condition based on matching the short- and long-distance string tensions, nor reproduces the phenomenological values of the gluon condensates. On the contrary, in Regge models departing from strict linearity one may reproduce both the consistency condition and the signs of condensates. We demonstrate this in a simple explicit model.
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arxiv:hep-ph/0603263
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The decay of the Standard Model Higgs boson into four leptons via a virtual W-boson or Z-boson pair is one of the most important decay modes in the Higgs-boson search at the LHC. We present the complete electroweak radiative corrections of O(\alpha) to these processes, including improvements beyond O(\alpha) originating from heavy-Higgs effects and final-state radiation. The intermediate W- and Z-boson resonances are described (without any expansion or on-shell approximation) by consistently employing complex mass parameters for the gauge bosons (complex-mass scheme). The corrections to partial decay widths typically amount to some per cent and increase with growing Higgs mass M_H, reaching about 8% at M_H \sim 500 GeV. For not too large Higgs masses (M_H <\sim 400 GeV) the corrections to the partial decay widths can be reproduced within <\sim 2% by simple approximations. For angular distributions the corrections are somewhat larger and distort the shapes. For invariant-mass distributions of fermion pairs they can reach several tens of per cent depending on the treatment of photon radiation. The discussed corrections have been implemented in a Monte Carlo event generator called PROPHECY4F.
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arxiv:hep-ph/0604011
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A recent model of dark energy and dark matter was proposed, involving a new gauge group $SU(2)_Z$ whose coupling grows strong at a scale $\Lambda_Z \sim 10^{-3} eV$, a result which is obtained from a simple assumption that its initial value at some high energy scale $M \sim 10^{16} GeV$ is of the order of a typical Standard Model (SM) coupling at a similar scale. (This assumption comes naturally from an embedding of $SU(2)_Z$ and the SM into a grand unified group $E_6$.) It is found that the proposed model contains a SM lepton-number violating Yukawa coupling involving a scalar ``messenger field'' ${\tilde{\bm{\phi}}}^{(Z)}$ (which carries both $SU(2)_Z$ and electroweak quantum numbers), a $SU(2)_Z$ fermion $\psi^{(Z)}$ and a SM lepton $l$. The interference between the tree-level and one-loop decay amplitude for ${\tilde{\bm{\phi}}}^{(Z)} \to \psi^{(Z)} + l$ generates a SM lepton asymmetry which is subsequently converted into a baryon asymmetry through electroweak sphaleron processes. This constrains the mass of the messenger field to be less than $1 TeV$, making it accessible to searches at future colliders: the ``progenitor'' of a net lepton number (and hence a net baryon number) could possibly be found and identified experimentally.
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arxiv:hep-ph/0604063
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The pion mass difference generates a pronounced cusp in K --> 3 pi decays. As has recently been pointed out by Cabibbo and Isidori, an accurate measurement of the cusp may allow one to pin down the S-wave pi pi scattering lengths to high precision. Here, we present and illustrate an effective field theory framework that allows one to determine the structure of this cusp in a straightforward manner. The strictures imposed by analyticity and unitarity are respected automatically.
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arxiv:hep-ph/0604084
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Using the chiral model of pseudoscalar, vector, and axial vector mesons based on the hidden local symmetry added with the terms induced by the Wess-Zumino anomaly, the results of calculations of the branching fractions of the decays omega(782) and phi(1020) mesons to the 2pi+ 2pi- pi0, pi+ pi -3pi0 multipion states are presented.
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arxiv:hep-ph/0604099
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We argue that in the measured $p_T$ domain of RHIC, collisional rather than the radiative energy loss is the dominant mechanism for jet quenching. Accordingly we calculate nuclear suppression factor for light hadrons by taking only the elastic energy loss in sharp contrast with the previous calculations where only the radiative loss are considered.
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arxiv:hep-ph/0604131
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In the extra dimension models of ADD and RS we study the dependence of the various parton distribution functions on observable of Drell-Yan process to NLO in QCD at LHC and Tevatron energies. Uncertainties at LHC due to factorisation scales in going from leading to next-to-leading order in QCD for the various distributions get reduced by about 2.75 times for a $\mu_F$ range $0.5 ~Q < \mu_F < 1.5 ~Q$. Further uncertainties arising from the error on experimental data are estimated using the MRST parton distribution functions.
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arxiv:hep-ph/0604135
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We identify ``spurious'' states in meson-baryon scattering, those that appear in QCD for N_c > 3 but decouple for N_c = 3. The key observation is that the relevant flavor SU(3) Clebsch-Gordan coefficients contain factors of 1 - 3/N_c. We show that this method works even if SU(3) is badly broken. We also observe that resonant scattering poles lying outside naive quark model multiplets are not necessarily large N_c artifacts, and can survive via configuration mixing at N_c = 3.
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arxiv:hep-ph/0604175
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We consider extra dimensional field theory descriptions of backgrounds with N different throats where one of the extra dimensions in each throat is much larger than the others. Such backgrounds can be described by field theory on N 5D warped spaces which intersect on a ultraviolet (UV) brane. Given a field that propagates in all N throats there are N boundary conditions on the UV brane (which are determined by the effective Lagrangian on the UV brane) in addition to the boundary conditions on the N infrared branes. We derive a general set of UV boundary conditions and give examples of how they are applied to particular situations. Three simple example applications are given: in the first the number of families is determined by the number of throats and the SUSY flavor problem is solved via an S_3 symmetry of the throats; in the second we embed this scenario in a SUSY GUT with a solution of the doublet-triplet splitting problem based on the product group approach; while in the final example we show a simple geometric implementation of a SUSY trinification model on three throats.
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arxiv:hep-ph/0604218
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The Beta Beam CERN design is based on the present LHC injection complex and its physics reach is mainly limited by the maximum rigidity of the SPS. In fact, some of the scenarios for the machine upgrades of the LHC, particularly the construction of a fast cycling 1 TeV injector (``Super-SPS''), are very synergic with the construction of a higher $\gamma$ Beta Beam. At the energies that can be reached by this machine, we demonstrate that dense calorimeters can already be used for the detection of $\nu$ at the far location. Even at moderate masses (40 kton) as the ones imposed by the use of existing underground halls at Gran Sasso, the CP reach is very large for any value of $\theta_{13}$ that would provide evidence of $\nu_e$ appearance at T2K or NO$\nu$A ($\theta_{13}\geq 3^\circ$). Exploitation of matter effects at the CERN to Gran Sasso distance provides sensitivity to the neutrino mass hierarchy in significant areas of the $\theta_{13}-\delta$ plane.
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arxiv:hep-ph/0604229
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We consider examples of ``hidden-valley'' models, in which a new confining gauge group is added to the standard model. Such models often arise in string constructions, and elsewhere. The resulting (electrically-neutral) bound states can have low masses and long lifetimes, and could be observed at the LHC and Tevatron. Production multiplicities are often large. Final states with heavy flavor are common; lepton pairs, displaced vertices and/or missing energy are possible. Accounting for LEP constraints, we find LHC production cross-sections typically in the 1-100 fb range, though they can be larger. It is possible the Higgs boson could be discovered at the Tevatron through rare decays to the new particles.
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arxiv:hep-ph/0604261
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A library for reading and writing data in the SUSY Les Houches Accord 2 format is presented. The implementation is in native Fortran 77. The data are contained in a single array conveniently indexed by preprocessor statements.
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arxiv:hep-ph/0605049
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We calculate the new physics contributions to the rare semileptonic decay $B \to X_s l^+ l^-$ $(l=e,\mu)$ induced by the charged-Higgs loop diagrams appeared in the top quark two-Higgs doublet model (T2HDM). Within the considered parameter space, we found that (a) the effective Wilson coefficients $\widetilde{C}_{i}^{eff}(m_b)$ ($i =7\gamma, 9V$ and $10A$) in the T2HDM are always standard model like; (b) the new physics contributions to $\widetilde{C}_{7\gamma}^{eff}$ and $\widetilde{C}_{9V}^{eff}$ can be significant, but they tend to cancel each other; and (c) the T2HDM predictions for $Br(B \to X_s l^+ l^-)$ agree well with the measured value within one standard deviation.
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arxiv:hep-ph/0605076
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We investigate the effects of flavor SU(3)-symmetry breaking on the QCD condensates, based on the nonlocal effective chiral action from the instanton vacuum, focusing on the quark-gluon mixed one. We employ two different parameterizations for the dependence of the momentum-dependent dynamical quark mass on the strange current quark mass. We obtain the ratios of the mixed condensates:$[<\bar{s}\sigma_{\mu\nu}G^{\mu\nu}s><\bar{u}\sig ma_{\mu\nu}G^{\mu\nu}u>]^{1/5}=0.87$. It turns out that the dimensional parameter $m^2_0=<\bar{q} \sigma_{\mu\nu}G^{\mu\nu}q>/ <\bar{q}q> =1.60\sim 1.92 {\rm GeV}^2$.
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arxiv:hep-ph/0605093
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We revisit Nambu's model of quark confinement by a tube of magnetic flux, with two additional features. The quarks are taken to be magnetic monopoles external to the tube, which seal the ends, and are also taken to be fermions. This ensures that the model is inconsistent unless there are at least two species of fermions being confined.
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arxiv:hep-ph/0605107
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We demonstrate a possibility of computation of inelastic scattering cross-section in a multi-peripheral model by application of the Laplace method to multidimensional integral over the domain of physical process. The constrained maximum point of scattering cross-section integral under condition of the energy-momentum conservation has been found. In the vicinity of this point the integrand is substituted for an expression of Gaussian type, which made possible to compute this integral numerically. The paper has two parts. The hunting procedure of the constrained maximum point is considered and the properties of this maximum point are discussed in the given part of the paper. It is shown that virtuality of all internal lines of the "comb" diagram reduced at the constrained maximum point with energy growth. In the second part of the paper we give some arguments in favor of consideration of the mechanism of virtuality reduction as the mechanism of the total hadron scattering cross-section growth, which is not taken into account within the framework of Regge theory.
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arxiv:hep-ph/0605110
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For the D=5 Majorana neutrino mass operator to have a see-saw ultraviolet completion that is viable up to the Planck scale, the see-saw scale is bounded above due to triviality limits on the see-saw couplings. For supersymmetric see-saw models, with realistic neutrino mass textures, we compare constraints on the see-saw scale from triviality bounds, with those arising from experimental limits on induced charged-lepton flavour violation, for both the CMSSM and for models with split supersymmetry.
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arxiv:hep-ph/0605144
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We prove that - even at a low TeV scale - the canonical seesaw mechanism can be naturally implemented in the exact solution of a particular 3-3-1 gauge model, since a very small alteration $\epsilon$ in the parameter matrix of the Higgs sector is taken into account. Therefore, this new parameter can act as an appropriate mass source for neutrinos, while - due to the main parameter $a$ - all the previously achieved results in the exact solution of the model are recovered. Moreover, this mathematical artifice does separate the boson mass spectrum from the neutrino mass issue, hence giving more flexibility in tuning the model. Possible phenomenological results and their implications - such as dark matter plausible candidates that can occur - are also briefly discussed.
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arxiv:hep-ph/0605155
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A study of various SUSY scenarios is presented in which the lightest supersymmetric particle is the gravitino $\sG$ and the next-to-lightest supersymmetric particle is a scalar tau $\stau$ with lifetimes ranging from seconds to years. Gravitinos are interesting dark matter candidates which can be produced in decays of heavier sparticles at the International Linear Collider (ILC), but remain undetected in direct searches of astrophysical experiments. We investigate the detection and measurement of metastable staus, which may be copiously produced at the ILC either directly or via cascade decays. A proper choice of the experimental conditions will allow one to stop large samples of staus in the calorimeters of the ILC detector and to study the subsequent decays $\stau\to\tau\sG$. Detailed simulations show that the properties of the stau and the gravitino, such as stau mass and lifetime and gravitino mass, can be accurately determined at a future ILC and may provide direct access to the gravitational coupling, respectively Planck scale.
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arxiv:hep-ph/0605257
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In this paper we estimate the influence of the shadowing effect and initial state parton energy loss in the quarkonium production at HERA-B. We analyze the $x_F$ behavior of the effective exponent $\alpha (x_F)$ and present a comparison with the preliminary HERA-B data for $J/\Psi$ production. Moreover, we estimate the magnitude of these effects in the $J/\Psi$ production at RHIC.
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arxiv:hep-ph/0605258
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A host of dark energy models and non-standard cosmologies predict an enhanced Hubble rate in the early Universe: perfectly viable models, which satisfy Big Bang Nucleosynthesis (BBN), cosmic microwave background and general relativity tests, may nevertheless lead to enhancements of the Hubble rate up to many orders of magnitude. In this paper we show that strong bounds on the pre-BBN evolution of the Universe may be derived, under the assumption that dark matter is a thermal relic, by combining the dark matter relic density bound with constraints coming from the production of cosmic-ray antiprotons by dark matter annihilation in the Galaxy. The limits we derive can be sizable and apply to the Hubble rate around the temperature of dark matter decoupling. For dark matter masses lighter than 100 GeV, the bound on the Hubble-rate enhancement ranges from a factor of a few to a factor of 30, depending on the actual cosmological model, while for a mass of 500 GeV the bound falls in the range 50-500. Uncertainties in the derivation of the bounds and situations where the bounds become looser are discussed. We finally discuss how these limits apply to some specific realizations of non-standard cosmologies: a scalar-tensor gravity model, kination models and a Randall-Sundrum D-brane model.
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arxiv:hep-ph/0605287
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I discuss some puzzles observed in exclusive $B$ meson decays, concentrating on the large difference between the direct CP asymmetries in the $B^0\to \pi^\mp K^\pm$ and $B^\pm\to \pi^0 K^\pm$ modes, the large $B^0\to\pi^0\pi^0$ branching ratio, and the large deviation of the mixing-induced CP asymmetries in the $b\to sq\bar q$ penguins from those in the $b\to c\bar c s$ trees.
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arxiv:hep-ph/0605331
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We consider different methods and observables which can be obtained by the measurement of neutrino scattering off nucleons and nuclei with the purpose of finding evidence for the strange form factors of the nucleon, which enter into structure of the nucleonic weak neutral current.
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arxiv:hep-ph/0605340
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In the first part of the talk, I explain what empirical evidence points to the need for having an effective grand unification-like symmetry possessing the symmetry SU(4)-color in 4D. If one assumes the premises of a future predictive theory including gravity--be it string/M theory or a reincarnation--this evidence then suggests that such a theory should lead to an effective grand unification-like symmetry as above in 4D, near the string-GUT-scale, rather than the standard model symmetry. Advantages of an effective supersymmetric G(224) = SU(2)$_L \times$ SU(2)$_R \times$ SU(4)$^c$ or SO(10) symmetry in 4D in explaining (i) observed neutrino oscillations, (ii) baryogenesis via leptogenesis, and (iii) certain fermion mass-relations are noted. And certain distinguishing tests of a SUSY G(224) or SO(10)-framework involving CP and flavor violations (as in $\mu \to e\gamma$, $\tau \to\mu\gamma$, edm's of the neutron and the electron) as well as proton decay are briefly mentioned. Recalling some of the successes we have had in our understanding of nature so far, and the current difficulties of string/M theory as regards the large multiplicity of string vacua, some comments are made on the traditional goal of understanding {\em vis a vis} the recently evolved view of landscape and anthropism.
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arxiv:hep-ph/0606089
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The SuperKamiokande atmospheric neutrino measurements leave substantial room for nonstandard interactions (NSI) of neutrinos with matter in the nu_e- nu_tau sector. Large values of the NSI couplings are accommodated if the vacuum oscillation parameters are changed from their standard values. Short and medium baseline neutrino beams can break this degeneracy by measuring the true vacuum oscillation parameters with the muon neutrino disappearance mode, for which the matter effects are negligible or subdominant. These experiments can also search for the nu_e-nu_tau flavor changing effects directly, by looking for nu_mu->nu_e conversion caused by the intervening matter. We discuss both of these methods for the case of MINOS. We find that, while the present MINOS data on nu_mu disappearance induce only minor changes on the constraints on the NSI parameters, the situation will improve markedly with the planned increase of the statistics by an order of magnitude. In that case, the precision will be enough to distinguish certain presently allowed NSI scenarios from the no-NSI case. NSI per quark of about 10% the size of the standard weak interaction could give a nu_mu - nu_e conversion probability of the order ~ 10^{-2}, measurable by MINOS in the same high statistics scenario. In this nu_mu - nu_e channel, the small effects of NSI could be comparable or larger than the vacuum contribution of the small angle theta_{13}. The expected theta_{13} bound at MINOS should be more properly interpreted as a bound in the theta_{13}-NSI parameter space.
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arxiv:hep-ph/0606101
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We stress that the lack of direct evidence for supersymmetry forces the soft mass parameters to lie very close to the critical line separating the broken and unbroken phases of the electroweak gauge symmetry. We argue that the level of criticality, or fine-tuning, that is needed to escape the present collider bounds can be quantitatively accounted for by assuming that the overall scale of the soft terms is an environmental quantity. Under fairly general assumptions, vacuum-selection considerations force a little hierarchy in the ratio between m_Z^2 and the supersymmetric particle square masses, with a most probable value equal to a one-loop factor.
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arxiv:hep-ph/0606105
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A coupled-channel model previously employed to describe the narrow $D_{s0}^*$(2317) and broad $D_0^*$(2400) charmed scalar mesons is generalized so as to include all ground-state pseudoscalar-pseudoscalar and vector-vector two-meson channels. All parameters are chosen fixed at published values, except for the overall coupling constant, which is fine-tuned to reproduce the $D_{s0}^*$(2317) mass. Thus, the radial excitations $D_{s0}^*$(2850) and $D_0^*$(2740) are predicted, both with a width of about 50 MeV. The former state appears to correspond to the new $D_{sJ}$(2860) resonance decaying to $DK$ announced by BABAR in the course of this work. Also the $D_0^*$(2400) resonance is roughly reproduced, though perhaps with a somewhat too low central resonance peak.
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arxiv:hep-ph/0606110
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We determine the fermionic collective modes of a quark-gluon plasma which is anisotropic in momentum space. We calculate the fermion self-energy in both the imaginary- and real-time formalisms and find that numerically and analytically (for two special cases) there are no unstable fermionic modes. In addition we demonstrate that in the hard-loop limit the Kubo-Martin-Schwinger condition, which relates the off-diagonal components of the real-time fermion self-energy, holds even for the anisotropic, and therefore non-equilibrium, quark-gluon plasma considered here. The results obtained here set the stage for the calculation of the non-equilibrium photon production rate from an anisotropic quark-gluon plasma.
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arxiv:hep-ph/0606160
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In the Minimal Supersymmetric Standard Model with bilinear R-parity violation, only one neutrino eigenstate acquires a mass at tree level, consequently experimental data on neutrinos cannot be accommodated at tree level. We show that in the Next-to-Minimal extension, where a gauge singlet superfield is added to primarily address the so-called $\mu$-problem, it is possible to generate two massive neutrino states at tree level. Hence, the global three-flavour neutrino data can be reproduced at tree level, without appealing to loop dynamics which is vulnerable to model-dependent uncertainties. We give analytical expressions for the neutrino mass eigenvalues and present examples of realistic parameter choices.
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arxiv:hep-ph/0606179
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Recently, a reconsideration of Drell-Yan cross sections at moderate energies and masses has suggested the possibility of relevant enhancements of the cross sections in some kinematical regions. If confirmed, these predictions could largely affect the planning of Drell-Yan experiments aimed at transverse spin measurements after 2010. More in general, the problem is present of a precision measurement of the $\tau$ dependence of Drell-Yan cross sections. Here we discuss the feasibility of such a measurement within short time at the COMPASS apparatus, and its relevance for the PANDA experiment.
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arxiv:hep-ph/0606195
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We extract the $Q$-$\bar Q$ potential by using the thermodynamic quantities obtained in lattice gauge calculations. The potential is tested and found to give dissociation temperatures that agree well with those from lattice gauge spectral function analysis. Using such a $Q$-$\bar Q$ potential, we examine the quarkonium states in a quark-gluon plasma and determine the `quark drip lines' which separate the region of bound color-singlet $Q\bar Q$ states from the unbound region. The characteristics of the quark drip lines severely limit the region of possible bound $Q\bar Q$ states with light quarks to temperatures close to the phase transition temperature. Bound quarkonia with light quarks may exist very near the phase transition temperature if their effective quark mass is of the order of 300-400 MeV and higher.
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arxiv:hep-ph/0606200
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We investigate the transition of the polarized photon structure function $g_1^\gamma(x,Q^2,P^2)$ when the target photon shifts from on-shell ($P^2=0$) to far off-shell ($P^2\gg \Lambda^2$) region. The analysis is performed to the next-to-leading order in QCD. The first moment of $g_1^\gamma$ which vanishes for the real photon, turns to be a negative value when target photon becomes off-shell. The explicit $P^2$-dependence of the first moment sum rule as well as of the structure function $g_1^\gamma(x,Q^2,P^2)$ as a function of $x$ is studied in the framework of the vector meson dominance model.
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arxiv:hep-ph/0606267
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Modern spectroscopic data on light non-strange meson spectrum is analyzed. It is argued that the observed regularities of experimental spectrum for highly excited states favour a partial restoration of all approximate classical symmetries of QCD Lagrangian (conformal, chiral and axial) broken by the quantum corrections. The rate of restoration of classical symmetries is estimated. The dependence of the resonance widths from the corresponding masses is systematically checked. On average, it turns out to be universal for the high excitations as predicted by the effective string description.
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arxiv:hep-ph/0606310
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Using the high temperature approximation we study, within the linear response theory, the wake in the quark-gluon plasma by a fast parton owing to dynamical screening in the space like region. When the parton moves with a speed less than the average speed of the plasmon, we find that the wake structure corresponds to a screening charge cloud traveling with the parton with one sign flip in the induced charge density resulting in a Lennard-Jones type potential in the outward flow with a short range repulsive and a long range attractive part. On the other hand if the parton moves with a speed higher than that of plasmon, the wake structure in the induced charge density is found to have alternate sign flips and the wake potential in the outward flow oscillates analogous to Cerenkov like wave generation with a Mach cone structure trailing the moving parton. The potential normal to the motion of the parton indicates a transverse flow in the system. We also calculate the potential due to a color dipole and discuss consequences of possible new bound states and $J/\psi$ suppression in the quark-gluon plasma.
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arxiv:hep-ph/0606316
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