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Two methods for the nonperturbative solution of field-theoretic bound-state problems, based on light-front coordinates, are briefly reviewed. One uses Pauli-Villars regularization and the other supersymmetry. Applications to Yukawa theory and super Yang-Mills theory with fundamental matter are emphasized.
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arxiv:hep-ph/0310140
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We study the QCD corrections to neutrino deep-inelastic scattering on a nucleus, and analytically estimate their size. For an isoscalar target, we show that the dominant QCD corrections to the ratio of the neutral- to charged-current events are suppressed by sin^4 theta_W, where theta_W is the weak mixing angle. We then discuss the implications for the NuTeV determination of sin^2 theta_W.
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arxiv:hep-ph/0310154
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Recent preliminary PHENIX data are consistent with a negative and sizable longitudinal double-spin asymmetry A_LL^pi for pi^0 production at moderate transverse momentum p_perp \simeq 1 - 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p_perp produces at best a very small negative asymmetry in this kinematic range.
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arxiv:hep-ph/0310197
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QCD motivated effective models coupled with the cosmological dilaton field are analyzed. It is shown that all models possess confining solutions with the linear potential of confinement even thought such solutions are not observed in the original effective theory. In case of the Pagels-Tomboulis model analytical solutions are explicit found.
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arxiv:hep-ph/0310236
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With the aim of generating new constraints on the OZI suppressed couplings of chiral perturbation theory a set of six equations of the Roy and Steiner type for the $S$- and $P$-waves of the $\pi K$ scattering amplitudes is derived. The range of validity and the multiplicity of the solutions are discussed. Precise numerical solutions are obtained in the range $E\lapprox 1$ GeV which make use as input, for the first time, of the most accurate experimental data available at $E > 1$ GeV for both $\pi K\to\pi K$ and $\pi\pi\to K\bar{K}$ amplitudes. Our main result is the determination of a narrow allowed region for the two S-wave scattering lengths. Present experimental data below 1 GeV are found to be in generally poor agreement with our results. A set of threshold expansion parameters, as well as sub-threshold parameters are computed. For the latter, matching with the SU(3) chiral expansion at NLO is performed.
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arxiv:hep-ph/0310283
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We discuss a model for the study of quark-hadron duality in inclusive electron scattering based on solving the Dirac equation numerically for a scalar confining linear potential and a vector color Coulomb potential. We qualitatively reproduce the features of quark-hadron duality for all potentials considered, and discuss similarities and differences to previous models that simplified the situation by treating either the quarks or all particles as scalars. We discuss the scaling results for PWIA and FSI, and the approach to scaling using the analog of the Callan-Gross relation for y-scaling.
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arxiv:hep-ph/0310298
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We discuss the impact of the true value of the CP phase on the mass hierarchy, CP violation, and CP precision measurements at neutrino superbeams and related experiments. We we use a complete statistical experiment simulation including spectral information, systematics, correlations, and degeneracies to produce the results. However, since it is very complicated to understand the results in terms of a complete experiment simulation, we show the corresponding bi-rate graphs as useful tools to investigate the CP phase-dependencies qualitatively. Unlike bi-probability graphs, which are based upon oscillation probabilities, bi-rate graphs use the total event rates of two measurements simultaneously as a function of the CP phase. Since they allow error bars for direct quantitative estimates, they can be used for a direct comparison with a complete statistical experiment simulation. We find that one can describe the CP phase dependencies of the mentioned measurements at neutrino superbeam setups, as well as one can understand the role of the $\mathrm{sgn} (\Delta m_{31}^2)$-degeneracy. As one of the most interesting results, we discuss the dependence of the CP precision measurement as a function of the CP phase itself, which leads to ``CP patterns''. It turns out that this dependence is rather strong, which means that one has to be careful when one is comparing the CP precisions of different experiments.
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arxiv:hep-ph/0310307
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We propose to test CP symmetry in the decay $\jp\to \gamma \phi\phi$, for which large data sample exists at BESII, and a data sample of $10^{10}$ $J/\psi$'s will be collected with BESIII and CLEO-C program. We suggest some CP asymmetries in this decay mode for CP test. Assuming that CP violation is introduced by the electric- and chromo-dipole moment of charm quark, these CP asymmetries can be predicted by using valence quark models. Our work shows a possible way to get information about the electric- and chromo-dipole moment of charm quark, which is little known. Our results show that with the current data sample of $J/\psi$, electric- and chromo-dipole moment can be probed at order of $10^{-14}e cm$. In the near future with a $10^{10}$ data sample, these moments can be probed at order of $10^{-16}e cm$.
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arxiv:hep-ph/0311012
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We review recent results in lattice QCD from numerical simulations that allow for a much more realistic QCD vacuum than has been possible before. Comparison with experiment for a variety of hadronic quantities gives agreement to within statistical and systematic errors of 3%. We discuss the implications of this for future calculations in lattice QCD, particularly those which will provide input for B factory experiments.
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arxiv:hep-ph/0311041
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We present a method to construct infrared-finite amplitudes for gauge theories with massless fermions. Rather than computing $S$-matrix elements between usual states of the Fock space we construct order-by-order in perturbation theory dressed states that incorporate all long-range interactions. The $S$-matrix elements between these states are shown to be free from soft and collinear singularities. As an explicit example we consider the process $e^+ e^-\to 2$ jets at next-to-leading order in the strong coupling. We verify by explicit calculation that the amplitudes are infrared finite and recover the well-known result for the total cross section $e^+ e^-\to$ hadrons.
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arxiv:hep-ph/0311059
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Vector-Meson-Dominance model contribution to $\pi^0 \to 4\gamma$ is calculated. The result confirms old estimates that this contribution is much smaller than the purely electromagnetic photon spliting graph contribution calculated earlier.
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arxiv:hep-ph/0311089
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In this thesis we study the b-quark fragmentation in top decay as well as the effect of the threshold resummation on heavy quark production in charged-current DIS. To predict the spectrum of b-flavored hadrons in top decay, we calculate at NLO the QCD corrections for bottom production in top decay with the b-mass fully taken into account. Using the perturbative fragmentation function formalism we then resum with NLL accuracy large collinear logs of the ratio of bottom-to-top mass, which leads to an essential improvement of the result. Next we perform the threshold resummation for the coefficient function for top decay with NLL accuracy. That resummation leads to an important improvement of the b-spectrum in the large energy fraction region. Finally, we extract information for the non-perturbative b-fragmentation into hadrons from e^+e^- data and make a prediction for the spectrum of those b-flavored hadrons produced in top-quark decay. Our second application is to charm production in charged-current DIS. We first calculate with NLL accuracy the soft-gluon resummed coefficient function for heavy quark production (initiated by a light quark) in DIS. Our result is applicable for the case of low momentum transfer that is of the order of the mass of the heavy quark. We also make a connection of this result to the known result for massless quark production. We then apply this result for charm quark production at NuTeV and HERA for a wide range of the transferred momentum, and present the effect of the resummation on the charm structure functions.
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arxiv:hep-ph/0311101
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We analyze the extraction of weak phases from CP violation in $B\to\pi^+\pi^-$ decays. By combining the information on mixing induced CP violation in $B\to\pi^+\pi^-$, namely $S_{\pi\pi}$, with the precision observable $\sin 2\beta$ obtained from the ``gold-plated''mode $B\to\psi K_S$, we propose the determination of the unitarity triangle. We also discuss alternative ways to analyze $S_{\pi\pi}$ which can be useful if new physics affects $B_d$--$\bar B_d$ mixing. Predictions and uncertainties for $r$ and $\phi$ in QCD factorization are examined in detail. It is pointed out that a simultaneous expansion in $1/m_b$ and $1/N_C$ leads to interesting simplifications. At first order infrared divergences are absent, while the most important effects are retained. Independent experimental tests of the factorization framework are briefly discussed.
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arxiv:hep-ph/0311104
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The cross section data for $\pi^0$ inclusive production in $pp$ collisions is considered in a rather broad kinematic region in energy $\sqrt{s}$, Feynman variable $x_F$ and transverse momentum $p_T$. The analysis of these data is done in the perturbative QCD framework at the next-to-leading order. We find that they cannot be correctly described in the entire kinematic domain and this leads us to conclude that the single-spin asymmetry, $A_N$ for this process, observed several years ago at FNAL by the experiment E704 and the recent result obtained at BNL-RHIC by STAR, are two different phenomena. This suggests that STAR data probes a genuine leading-twist QCD single-spin asymmetry for the first time and finds a large effect.
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arxiv:hep-ph/0311110
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We consider the phenomenological description of the two pion invariant mass spectrum in the $V' \to V \pi\pi$ decays. We study the parametrization of the amplitude involving both $S$ and $D$ wave contributions. From a fit to the two pion decays of the $ \Upsilon(nS)$ and $\Psi(nS)$ we determine the $f_0 (600)$ mass and width to be $m_{f_0}=528 \pm 32$ MeV and $\Gamma_{f_0}=413\pm 45$ MeV. The mass and width values we report correspond to the real and imaginary part of the S matrix pole respectively.
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arxiv:hep-ph/0311133
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The measurement of the pion form factor and, more generally, of the cross section for electron--positron annihilation into hadrons through the radiative return has become an important task for high luminosity colliders such as the $\Phi$- or $B$-meson factories. This quantity is crucial for predictions of the hadronic contributions to $(g-2)_\mu$, the anomalous magnetic moment of the muon, and to the running of the electromagnetic coupling. But the radiative return opens also the possibility of many other physical applications. The physics potential of this method at high luminosity meson factories is discussed and recent results are reviewed.
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arxiv:hep-ph/0311158
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Within the Quantum Field Theory context the idea of a "cosmological constant" (CC) evolving with time looks quite natural as it just reflects the change of the vacuum energy with the typical energy of the universe. In the particular frame of Ref.[30], a "running CC" at low energies may arise from generic quantum effects near the Planck scale, M_P, provided there is a smooth decoupling of all massive particles below M_P. In this work we further develop the cosmological consequences of a "running CC" by addressing the accelerated evolution of the universe within that model. The rate of change of the CC stays slow, without fine-tuning, and is comparable to H^2 M_P^2. It can be described by a single parameter, \nu, that can be determined from already planned experiments using SNe Ia at high z. The range of allowed values for \nu follow mainly from nucleosynthesis restrictions. Present samples of SNe Ia can not yet distinguish between a "constant" CC or a "running" one. The numerical simulations presented in this work show that SNAP can probe the predicted variation of the CC either ruling out this idea or confirming the evolution hereafter expected.
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arxiv:hep-ph/0311171
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The parton distributions functions (PDFs) derived from the NNLO QCD analysis of existing light-targets deep-inelastic-scattering data are presented. The NLO and NNLO PDFs are compared in order to analyze perturbative stability of the analysis and estimate impact of the higher-order QCD corrections. The main theoretical uncertainties and experimental uncertainties in PDFs due to all sources of experimental errors in data are estimated and used to assess corresponding uncertainties in the cross sections of other hadronic processes.
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arxiv:hep-ph/0311184
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We calculate the cosmic microwave background (CMB) anisotropy spectrum in models with millicharged particles of electric charge q\sim 10^{-6}-10^{-1} in units of electron charge. We find that a large region of the parameter space for the millicharged particles exists where their effect on the CMB spectrum is similar to the effect of baryons. Using WMAP data on the CMB anisotropy and assuming Big Bang nucleosynthesis value for the baryon abundance we find that only a small fraction of cold dark matter, Omega_{mcp}h_0^2 < 0.007 (at 95% CL), may consists of millicharged particles with the parameters (charge and mass) from this region. This bound significantly narrows the allowed range of the parameters of millicharged particles. In models without paraphoton millicharged particles are now excluded as a dark matter candidate. We also speculate that recent observation of 511 keV gamma-rays from the Galactic bulge may be an indication that a (small) fraction of CDM is comprised of the millicharged particles.
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arxiv:hep-ph/0311189
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The paper develops the idea that the dynamics of both classical and quantum processes is time reversible. It is shown how this classical analogy allows one to define the measure for the path integral in quantum mechanics.
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arxiv:hep-ph/0311196
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The production of the Standard Model (SM) Higgs boson (H) in association with a jet is compared with that of the lightest scalar Higgs boson (h^0) and the pseudoscalar Higgs boson (A^0) of the Minimal Supersymmetric Model (MSSM) at both the CERN Large Hadron Collider (LHC) and the Fermilab Tevatron. We include both top and bottom quark loops to lowest order in QCD and investigate the limits of zero quark mass and infinite quark mass.
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arxiv:hep-ph/0311199
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Results from the new Monte Carlo event generator Herwig++ are presented. This first version simulates Hadron Emission Reactions With Interfering Gluons in electron-positron annihilation. The parton shower evolution is carried out using new evolution variables suited to describing radiation from heavy quarks as well as light partons. The partonic final state is fragmented into hadrons by means of an improved cluster hadronization model. The results are compared with a wide variety of data from LEP and SLC.
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arxiv:hep-ph/0311208
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The aim of this contribution is to illustrate two basic aspects of quantum mechanics applied to the neutral kaon system. We first describe a recent quantitative formulation of Bohr's complementarity principle for free--space evolution of single kaons and entangled kaon pairs. We then show that the neutral kaon system is also suitable for an optimal demonstration of the ``quantum eraser'', including its operation in the ``delayed choice'' mode. In our discussions, strangeness oscillations play the role of the traditional interference pattern linked to wave--like behaviour. The role of the two interferometric paths taken by particle--like objects is played by the differently propagating $K_S$ and $K_L$ components. Their distinct decay widths provide a quantum ``mark'' which can be erased by appropriate strangeness measurements.
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arxiv:hep-ph/0311232
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The motion of spectator quarks in decay of a beauty hadron is a nonperturbative effect which can usually be neglected. We find that the motion in some decay channels, which contribute total decay widths of beauty hadrons, can not be neglected.The contributions from these decay channels to decay widths are proportional to certain averages of the squared inverse of the momentum carried by a spectator quark. This fact results in that these contributions, suppressed by $1/m_b^3$ formally, are effectively suppressed by $1/m_b$. We find these contributions can be factorized into products of perturbative coefficients and nonperturbative parameters. We calculate these coefficients and define these nonperturbative parameters in terms of HQET matrix elements.Since these parameters are unknown, we are unable to give numerical predictions in detail. But with a simple model it can be shown that these contributions can be large.
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arxiv:hep-ph/0311234
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In this talk I comment on some theoretical expectations for exotic light meson spectroscopy below 2 GeV and their potential interest for a future energy upgrade of DAFNE.
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arxiv:hep-ph/0311235
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Generalized parton distributions at large $x$ are studied in perturbative QCD approach. As $x\to 1$ and at finite $t$, there is no $t$ dependence for the GPDs which means that the active quark is at the center of the transverse space. We also obtain the power behavior: $H_q^\pi(x,\xi,t)\sim (1-x)^2/(1-\xi^2)$ for pion; $H_q(x,\xi,t)\sim (1-x)^3/(1-\xi^2)^2$ and $E_q(x,\xi,t)\sim (1-x)^5/(1-\xi^2)^3f(\xi)$ for nucleon, where $f(\xi)$ represents the additional dependence on $\xi$.
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arxiv:hep-ph/0311288
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We study the dilaton stabilization in models with anomalous U(1) symmetry by adding specific string-motivated, non-perturbative corrections to the tree-level dilaton K\"{a}hler potential. We find that the non-perturbative effects can stabilize the dilaton at a desirably large value. We also observe that the size of Fayet-Iliopoulos term is reduced at the stabilized point.
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arxiv:hep-ph/0311315
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Black hole production in elementary particle collisions is among the most promising probes of large extra spacetime dimensions. Studies of black holes at particle colliders have assumed that all of the incoming energy is captured in the resulting black hole. We incorporate the inelasticity inherent in such processes and determine the prospects for discovering black holes in colliders and cosmic ray experiments, employing a dynamical model of Hawking evolution. At the Large Hadron Collider, inelasticity reduces rates by factors of 10^3 to 10^6 in the accessible parameter space, moderating, but not eliminating, hopes for black hole discovery. At the Pierre Auger Observatory, rates are suppressed by a factor of 10. We evaluate the impact of cosmic ray observations on collider prospects.
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arxiv:hep-ph/0311365
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Combining the QCD dipole model with the Good and Walker picture, we formulate diffractive dissociation of a photon of virtuality Q^2 off a hadronic target, in the kinematical regime in which Q is close to the saturation scale and much smaller than the invariant mass of the diffracted system. We show how the obtained formula compares to the HERA data and discuss what can be learnt from such a phenomenology. In particular, we argue that diffractive observables in these kinematics provide useful pieces of information on the saturation regime of QCD.
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arxiv:hep-ph/0312022
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We use the perturbation method to calculate the masses and widths for 27-plet baryons with spin 3/2 from chiral soliton models. According to the masses and quantum numbers, we find all the candidates for non-exotic members of 27-plet. The calculation of the widths shows that these candidates manifest an approximate symmetry of the 27 representation of the SU(3) group, and the quantum numbers of $\Xi(1950)$ seem to be $I(J^P)={1/2}({3/2}^+)$. Up to leading order of the strange quark mass, we find that the exotic members have widths much larger than those of the anti-decuplet members.
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arxiv:hep-ph/0312041
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Solar neutrino problem and atmospheric neutrino anomaly which are both long-standing issues studied intensively by physicists in the past several decades, are reckoned to be able to be solved simultaneously in the framework of the assumption of the neutrino oscillation. For the presence of the Lorentz invariance in the Standard Model, the massless neutrino can't have flavor mixing and oscillation. However, we exploit the q-deformed noncommutative theory to derive a general modified dispersion relation, which implies some violation of the Lorentz invariance. Then it is found that the application of the q-deformed dispersion relation to the neutrino oscillation can provide a sound explanation for the current data from the reactor and long baseline experiments.
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arxiv:hep-ph/0312099
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This contribution provides a pedagogical introduction to and review of the current status and ongoing progress in the development of Monte Carlo tools for the calculation and simulation of high-Q^2 processes in hadronic collisions.
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arxiv:hep-ph/0312117
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We study the neutralino dark matter phenomenology in the context of effective field theories derived from the weakly--coupled heterotic string. We consider in particular direct detection and indirect detection with neutrino telescopes rates. The two cases of moduli dominated and dilaton dominated SUSY breaking lead to completely different phenomenologies. Even if in both cases relic density constraints can be fulfilled, moduli domination generically leads to detection rates which are much below the present and future experimental sensitivities, whereas dilaton domination gives high detection rates accessible to the next generation of experiments. This could make dark matter searches an alternative way to constrain high energy fundamental parameters.
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arxiv:hep-ph/0312155
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The electromagnetic and axial form factors of the nucleon and its lowest positive parity excitations, the Delta(1232) and the N*(1440), are calculated with constituent-quark models that are specified by simple algebraic representations of the mass-operator eigenstates. Poincar\'e covariant current operators are generated by the dynamics from single-quark currents that are covariant under a kinematic subgroup. The dependence of the calculated form factors on the choice of kinematics and on the gross features of the wave functions is illustrated for instant-form, point-form, and front-form kinematics. A simple algebraic form of the orbital ground state wave function, which depends on two parameters, allows a fair description of all the form factors over the empirically accessible range, although with widely different choices of the parameters, which determine the range and shape of the orbital wave function. The neutron electric form factor requires additional features, for instance the presence of mixed symmetry S-state component with 1 -- 2 % probability in the ground state wave function. Instant and front form kinematics demand a spatially extended wave function, whereas in point form kinematics the form factors may be described with a quite compact wave function.
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arxiv:hep-ph/0312169
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The charged-Higgs boson contributions to the Wilson coefficients C_7 and C_8, relevant for the decay B -> X_s gamma, are discussed in supersymmetric models at large tan beta. These contributions receive two-loop O(alpha_s tan beta) corrections by squark-gluino subloops, which are possibly large and nondecoupling in the limit of heavy superpartners. In previous studies, the relevant two-loop Feynman integrals were approximated by using an effective two-Higgs-doublet lagrangian. However, this approximation is theoretically justified only when the typical supersymmetric scale M_SUSY is sufficiently larger than the electroweak scale m_weak \sim (m_W,m_t) and the mass of the charged-Higgs boson m_{H^\pm}. Here we evaluate these two-loop integrals exactly and compare the results with the existing, approximated ones. We then examine the validity of this approximation beyond the region where it has been derived, i.e. for m_H \gtap M_SUSY and/or M_SUSY \sim m_weak.
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arxiv:hep-ph/0312228
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We consider the possibility that the gravitino might be the lightest supersymmetric particle (LSP) in the constrained minimal extension of the Standard Model (CMSSM). In this case, the next-to-lightest supersymmetric particle (NSP) would be unstable, with an abundance constrained by the concordance between the observed light-element abundances and those calculated on the basis of the baryon-to-entropy ratio determined using CMB data. We modify and extend previous CMSSM relic neutralino calculations to evaluate the NSP density, also in the case that the NSP is the lighter stau, and show that the constraint from late NSP decays is respected only in a limited region of the CMSSM parameter space. In this region, gravitinos might constitute the dark matter.
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arxiv:hep-ph/0312262
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We extend the POMWIG Monte Carlo generator developed by B.Cox and J.Forshaw, to include new models of central production through inclusive and exclusive Double Pomeron Exchange in proton-proton collisions. Double photon Exchange processes are described as well, both in proton-proton and heavy-ion collisions. In all contexts, various models have been implemented, allowing for comparisons and uncertainty evaluation and enabling detailed experimental simulations.
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arxiv:hep-ph/0312273
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It is believed that quark stars or neutron stars with mixed phase in the core have smaller radii compared to ordinary compact stars. With the recent observation of several low radius objects, typically a radius of $<10 Km.$ for star of mass $< 1M_0$ in low mass X-ray binaries (LMXB), it has become very important to understand the nature of these objects. An accurate determination of mass-radius relationship of these objects provide us with a physical laboratory to study the composition of high density matter and the nature of phase transition. We study the effect of quark and nuclear matter mixed phase on mass radius relationship and radial oscillations of neutron stars. We find that the effect of the mixed phase is to decrease the maximum mass of a stable neutron star and to decrease the radial frequencies .
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arxiv:hep-ph/0312297
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We report on the results of a phenomenological study of top squarks (stop_{1,2}) and bottom squarks (sbottom_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. In particular we focus on the CP phase dependence of the branching ratios of stop_{1,2} and sbottom_{1,2} decays. We find that the effect of the phases on the stop_{1,2} and sbottom_{1,2} decays can be quite significant in a large region of the MSSM parameter space. We also study a CP asymmetry in sfermion decays.
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arxiv:hep-ph/0312306
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The LDC formalism for DIS can describe HERA structure functions, and also agrees well with CTEQ and MRST gluon distributions. It is also suitable for hadronic collisions, and provides a strong connection between ep and pp reactions. Some preliminary results are presented.
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arxiv:hep-ph/0312310
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Finite-energy topological spherically symmetrical solutions of Chiral Born-Infeld Theory are studied. Properties of these solution are obtained, and a possible physical interpretation is also given. We compute static properties of baryons (mass,main radius, magnetic main radius, axial coupling constant) whose solutions can be interpreted as the baryons of QCD.
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arxiv:hep-ph/0312343
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Present-day experimental and phenomenological situation about pseudoscalar ($\pi^0$, $\eta$, $\eta'$) meson transition form factors is briefly reviewed. Necessity of more sophisticated behaviours in time-like region of these form factors is emphasized. Four-resonance unitary and analytic model of the pseudoscalar meson transition form factors is constructed, which describes well all existing experimental information.
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arxiv:hep-ph/0401007
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A numerical solution is presented for the non-linear evolution equation that governs the dynamics of high parton density QCD. It is shown that thesolution falls off as $e^{-b/R}$ at large values of the impact parameter $b$. The power-like tail of the amplitude appears in impact parameter distributions only after the inclusion of dipoles of size larger than the target, a configuration for which the non-linear equation is not valid. The value, energy and impact parameterof the saturation scale $Q_s(y=\ln(1/x),b)$) are calculated both for fixed and running QCD coupling cases. It is shown that the solution exhibits geometrical scaling behaviour. The radius of interaction increases as the rapidity in accordance with the Froissart theorem. The solution we obtain differs from previous attempts, where an anzatz for $b$ behaviour was made. The solutions for running and fixed $\as$ differ. For running $\as$ we obtain a larger radius of interaction (approximately twice as large), a steeper rapidity dependence, and a larger value of the saturation scale.
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arxiv:hep-ph/0401021
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The production of strange pentaquark states (e.g. Theta baryons and Xi^-- states) in hadronic interactions within a Gribov-Regge approach is explored. In this approach the Theta^+(1540) and the Xi Pentaquark are produced by disintegration of remnants formed by the exchange of pomerons between the two protons. We predict the rapidity and transverse momentum distributions as well as the 4 pi multiplicity of the Theta^+, Xi^--, Xi^-, Xi^0 and Xi^+ for sqrt{s} = 17 GeV (SPS) and 200 GeV (RHIC). For both energies more than 10^{-3} Theta^+ and more than 10^{-5} Xi per pp event should be observed by the present experiments.
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arxiv:hep-ph/0401049
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The modified Dirac equation in the Lorentz-violating Standard-Model Extension (SME) is considered. Within this framework, the construction of a hermitian Hamiltonian to all orders in the Lorentz-breaking parameters is investigated, discrete symmetries and the first-order roots of the dispersion relation are determined, and various properties of the eigenspinors are discussed.
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arxiv:hep-ph/0401084
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We show that gauge couplings unify more precisely in the region of SUSY parameter space already preferred by Yukawa unification. While proton decay due to dimension 5 operators is maximally suppressed in this region, the contribution from dimension 6 operators is enhanced as a consequence of lower unification scale.
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arxiv:hep-ph/0401109
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The present situation on a comparison of theoretical evaluation of the muon anomalous magnetic moment with experimental one is roughly reviewed. Then by means of a recently elaborated unitary and analytic model of the meson transition form factors the contributions of $e^+e^-\to P(S) \gamma$ processes to muon $g-2$ is estimated.
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arxiv:hep-ph/0401134
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We use solar neutrino data to derive stringent bounds on Majorana neutrino transition moments (TMs). Such moments, if present, would contribute to the neutrino-electron scattering cross section and hence alter the signal observed in Super-Kamiokande. Using the latest solar neutrino data, combined with the results of the reactor experiment KamLAND, we perform a simultaneous fit of the oscillation parameters and TMs. Furthermore, we include data from the reactor experiments Rovno, TEXONO and MUNU in our analysis, improving significantly the current constraints on TMs. A comparison with previous works shows that our bounds are the strongest and most general results presented up to now. Finally, we perform a simulation of the future Borexino experiment and show that it will improve the bounds from today's data by order of magnitude.
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arxiv:hep-ph/0401135
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We present two possibilities to determine the P-parity of the pentaquark $\Theta^+$, in a model independent way, via the measurement of polarization observables in $p+p\to \Theta^+ +\Sigma^+$, or $n+p\to \Theta^+ +\Lambda^0$, in the near threshold region. Besides the measurement of the spin correlation coefficient, $A_{xx}=A_{yy}$, (in collisions of transversally polarized nucleons), the coefficient $D_{xx}$ of polarization transfer from the initial proton to the final $ \Sigma^+(\Lambda^0)$ hyperon is also unambiguously related to the $\Theta^+$ parity.
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arxiv:hep-ph/0401162
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The united rest mass and charge of a particle correspond to the two forms of the same regularity of the unified nature of its ultimate structure. Each of them contains the electric, weak, strong and the gravitational contributions. As a consequence, the force of an attraction among the two neutrinos and force of their repulsion must be defined from the point of view of any of the existing types of the actions. Therefore, to understand the nature of the micro world interaction at the fundamental level, one must use the fact that each of the four types of well known forces includes both a kind of the Newton and a kind of the Coulomb components. The opinion has been spoken that the existence of the gravitational parts of the united rest mass and charge would imply the availability of such a fifth force which come forwards in the system as a unified whole.
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arxiv:hep-ph/0401230
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Semileptonic and nonleptonic decays of the B_c meson are studied in the framework of the relativistic quark model. The heavy quark expansion in inverse powers of the heavy (b,c) quark mass is used to simplify calculations while the light final quarks in the B and D mesons are treated relativistically. The decay form factors are explicitly expressed through the overlap integrals of the meson wave functions in the whole accessible kinematical range. The obtained results are compared with the predictions of other approaches.
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arxiv:hep-ph/0401237
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We obtain a 3+2 neutrino spectrum within a left-right symmetric framework by invoking a singular double see-saw mechanism. Higgs doublets are employed to break $SU_{R}(2)$ and three additional fermions, singlets under the left-right symmetric gauge group, are included. The introduction of a singularity into the singlet fermion Majorana mass matrix results in a light neutrino sector of three neutrinos containing predominantly $\nu_{\alpha L}$, $\alpha=e,\mu,\tau$, separated from two neutrinos containing a small $\nu_{\alpha L}$ component. The resulting active-sterile mixing in the $5\times 5$ mixing matrix is specified once the mass eigenvalues and the $3\times3$ submatrix corresponding to the MNS mixing matrix are known.
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arxiv:hep-ph/0401241
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Phase structure and phase transitions in dense QCD are studied using the Cornwall-Jackiw-Tomboulis (CJT) potential in the improved ladder approximation. The gap function, the condensation energy and the structure of Cooper pairs are investigated at finite temperature and density. Due to strong coupling effects at low densities, the gap, critical temperature and their ratio deviate from the weak coupling values. It is shown that the internal structure of Cooper pairs are robust against the thermal effects, despite the fact that the pairs are strongly correlated near the critical temperature. Also, the effect of the strange quark mass, Ms on the phase diagram is examined using a simple kinematical criterion. We discuss the behavior of the unlocking line, on which the CFL turns into the 2SC, through the variation of Ms.
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arxiv:hep-ph/0401247
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In this talk I will give a brief introduction to Little Higgs models in general, including an overview of all models in existence thus far. I then review some of the generic constraints on these models from electroweak precision measurements.
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arxiv:hep-ph/0402036
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Quantum algebras U_q(su_n) used as the algebras of flavour symmetry (usually described by SU(n)) to study static properties of hadrons lead to intriguing results. In this contribution we focus on the peculiar properties manifested by different q-deformed structures (e.g., the braided line, the quantum algebras U_q(su_2) and U_q(su_n), n >= 3) in the special limit of q = -1. Similarities (complete or partial) with supersymmetry that emerge in this special limit are discussed.
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arxiv:hep-ph/0402082
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The recent progress in understanding the QCD phase diagram and the physics of the QCD critical point is reviewed.
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arxiv:hep-ph/0402115
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We have developed the system for the automatic computation of cross-sections, {\tt GRACE/SUSY}, including the one-loop calculations for processes of the minimal supersymmetric extension of the the standard model. For an application, we investigate the pair-production of the heavy chargino in electron-positron collisions.
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arxiv:hep-ph/0402144
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We classify the extensions of the Standard Model (SM) according to the structure of local operators in the weak effective Hamiltonian and the presence or absence of new flavour and CP-violating interactions beyond those represented by the CKM matrix. In particular we review characteristic properties of models with minimal flavour violation (MFV), models with significant contributions from Higgs penguins and models with enhanced Z^0 penguins carrying a large new CP-violating phase. Within the latter models, the anomalous behaviour of certain B\to\pi K observables implies large departures from the SM predictions for rare and CP-violating K and B decays. Most spectacular is the enhancement of Br(K_L->pi^0 nu nubar) by one order of magnitude and a strong violation of the MFV relation (\sin2\beta)_{\pi\nu\bar\nu}=(\sin2\beta)_{\psi K_S}. On the other hand our prediction for (\sin2\beta)_{\phi K_S}\approx 0.9 differs from the Belle result by the sign but is consistent with the BaBar value. We give a personal shopping list for the coming years.
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arxiv:hep-ph/0402191
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The possibility to measure an electric dipole moment (EDM) of nuclei in the range $10^{-27} \div 10^{-32}$ $e \cdot cm$ in experiments for search of time-reversal violating generation of magnetic and electric fields is discussed.
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arxiv:hep-ph/0402209
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The sensitivity of the $B \to \pi K$ mode to electroweak penguins and the recent experimental data for the $B \to \pi \pi$, $\pi K$ modes has given rise to what is known as the ``$B \to \pi K$ puzzle''. Recently it has been observed that this {\sl puzzle} can be resolved by considering the new physics which can enter via $Z^0$ penguins. In this note we analyze the effect of this enhanced $Z^0$ penguins on the lepton polarization asymmetries of $b \to s \ell^+ \ell^-$.
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arxiv:hep-ph/0402273
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A personal overview on the present status of SU(3) chiral perturbation theory in the baryonic sector is given. Recent developments are presented and remaining challenges are pointed out.
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arxiv:hep-ph/0402292
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QCD predicts the existence of the perturbative Pomeron and of the Odderon. But both of them appear to be rather difficult to observe experimentally. We describe the experimental status of these two objects, discuss possible reasons for their elusive behavior, and point out promising search strategies.
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arxiv:hep-ph/0403051
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Based on Bbar to D{(*)}K-K{*0} decay data, which supports factorization, we propose to extract the kaon axial form factor in the factorization framework. Experiment indicates that the K-K{*0} pair is produced by an axial current where only one out of three axial form factors is dominant. The axial form factor can be extracted by fitting the K-K{*0} mass spectrum with an a_1(1260)-resonance plus QCD-motivated non-resonant contributions, which can be improved as data improves.
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arxiv:hep-ph/0403079
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Using data from RHIC we are able to systematically improve the two-component Dual Parton Model (DPM) event generator DPMJET-III. Introducing percolation parametrized as fusion of chains the model describes multiplicities and pseudorapidity distributions in nucleus-nucleus collisions at all centralities. Guided by the d-Au data from RHIC we recalibrate the model to obtain collision scaling in h-A and d-A collisions.
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arxiv:hep-ph/0403084
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Quantum mechanical equations of motion are obtained for particles and spin in media with polarized electrons in the presence of external fields. The motion of electrons and their spins is governed by the exchange interaction, while the motion of positrons and their spins is governed by the annihilation interaction. The equations obtained describe the motion of particles and spin in both magnetic and nonmagnetic media. The evolution of positronium spin in polarized media is investigated. Media with polarized electrons can be used for polarization of positronium beams.
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arxiv:hep-ph/0403107
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Supersymmetry analyses will potentially be a central area for experiments at the LHC and at a future e+ e- linear collider. Results from the two facilities will mutually complement and augment each other so that a comprehensive and precise picture of the supersymmetric world can be developed. We will demonstrate in this report how coherent analyses at LHC and LC experiments can be used to explore the breaking mechanism of supersymmetry and to reconstruct the fundamental theory at high energies, in particular at the grand unification scale. This will be exemplified for minimal supergravity in detailed experimental simulations performed for the Snowmass reference point SPS1a.
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arxiv:hep-ph/0403133
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Enhancement of strangeness production has since long been proposed as a promising signal of quark-gluon plasma production. A convenient indicator for it is the Wroblewski parameter which has been shown to be about a factor two higher in heavy ion collisions. Using a method proposed by us earlier, we obtained lattice QCD results for the Wroblewski parameter from our simulations of QCD with two light quarks both below and above the chiral transition. Our first principles based and parameter free result compare well with the A-A data.
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arxiv:hep-ph/0403172
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We present predictions for flavour-violating charged-lepton decays induced by the seesaw mechanism implemented within the constrained minimal supersymmetric standard model (CMSSM) with universal input soft supersymmetry breaking terms. We assume that one heavy singlet neutrino almost decouples from the see-saw mechanism, as suggested by the pattern of light neutrino masses and mixing angles. This is suggested independently by sneutrino inflation with a low reheating temperature, T(RH)<10^7 GeV, so as to avoid overproducing gravitinos. This requirement further fixes the mass of the weakly-coupled sneutrino, whose decays may lead to leptogenesis. We find that BR(mu->e gamma)>10^(-13) but BR(tau->mu gamma)<10^(-9) in the bulk of the acceptable parameter space, apart from a few isolated points. The ratio BR(mu->e gamma)/BR(tau->mu gamma) depends on only one complex parameter, and is particularly interesting to compare with experiment.
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arxiv:hep-ph/0403180
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We study the perturbative Odderon in the quasidiffractive process gamma(*) gamma(*) to eta_c eta_c. At high energies this process is dominated by Odderon exchange and can be viewed as the theoretically cleanest test of the perturbative Odderon. We calculate the differential and total cross section, as well as the dependence on the energy and on the photon virtualities taking into account the effects of resummation of logarithms of the energy. The results are compared with those obtained with a simple exchange of three noninteracting gluons. We present the expected cross section for this process at a future Linear Collider and discuss implications for other processes involving the perturbative Odderon.
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arxiv:hep-ph/0403197
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We discuss the inclusive dilepton cross section for proton (quark)-nucleus collisions at high energies in the very forward rapidity region. Starting from the calculation in the quasi-classical approximation, we include low-x evolution effects in the nucleus and predict leading twist shadowing together with anomalous scaling behaviour.
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arxiv:hep-ph/0403201
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The gluon collisional width in hot QCD plasmas is discussed with emphasis on temperatures near $T_c$, where the coupling is large. Considering its effect on the entropy, which is known from lattice calculations, it is argued that the width, which in the perturbative limit is given by $\gamma \sim g^2 \ln(1/g) T$, should be sizeable at intermediate temperatures but has to be small close to $T_c$. Implications of these results for several phenomenologically relevant quantities, such as the energy loss of hard jets, are pointed out.
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arxiv:hep-ph/0403225
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The Gr\"obner basis technique for calculating Feynman diagrams proposed in [O.V. Tarasov, Acta Physica Polonica, v. B29 (1998) 2655] is applied to the two-loop propagator type integrals with arbitrary masses and momentum. We describe the derivation of Gr\"obner bases for all integrals with 1PI topologies and present elements of the Gr\"obner bases.
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arxiv:hep-ph/0403253
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A weakly coupled new neutral gauge boson forms a narrow resonance that is hard to discover directly in e+e- collisions. However, if the gauge boson mass is below the center-of-mass energy, it can be produced through processes where the effective energy is reduced due to initial-state radiation and beamstrahlung. It is shown that at a high-luminosity linear collider, such a gauge boson can be searched for with very high sensitivity, leading to a substantial improvement compared to existing limits from the Tevatron and also extending beyond the expected reach of the LHC in most models. If a new vector boson is discovered either at the Tevatron Run II, the LHC or the linear collider, its properties can be determined at the linear collider with high precision, thus helping to reveal origin of the new boson.
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arxiv:hep-ph/0403288
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Recently the \mu_{\Delta ^{++}} was found from a fit to (\pi^+)p scattering. This enable us to pinpoint condensate parameters more precisely in the context of QCD sum rules (QCDSR). In the octet sector, the Coleman-Glashow sum rule (CGSR) is violated by the experimental \mu-s. QCDSR allows us to write down two sum rules similar to the CGSR, which are obeyed by the experimental magnetic moments, whereas they rule out a specific model using the Wilson loop approach and a particular chiral quark model. It is amusing to note that the QCDSR allows us to write down the quark and gluon condensates in terms of measurables like the \mu-s of the nucleons and the \Sigma^{+/-}.
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arxiv:hep-ph/0404027
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New, radiatively generated, NLO quark (u,d,s,c,b) and gluon densities in a real, unpolarized photon are presented. We perform three global fits, based on the NLO DGLAP evolution equations for Q^2>1 GeV^2, to all the available structure function F_2^gamma(x,Q^2) data. As in our previous LO analysis we utilize two theoretical approaches. Two models, denoted as FFNS_{CJK}1 & 2 NLO, adopt the so-called Fixed Flavour-Number Scheme for calculation of the heavy-quark contributions to F_2^gamma(x,Q^2), the CJK NLO model applies the ACOT(chi) scheme. We examine the results of our fits by a comparison with the LEP data for the Q^2 dependence of the F_2^gamma, averaged over various x-regions, and the F_2,c^gamma. Grid parametrizations of the parton densities for all fits are provided.
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arxiv:hep-ph/0404063
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We investigate the implications of the nontrivial vacuum structure of little Higgs models. In particular, focusing on the littlest Higgs model, we demonstrate the existence of three types of topological defects. One is a global cosmic string that is truly topological. The second is more subtle; a semilocal cosmic string, which may be stable due to dynamical effects. The final defect is a $Z_2$ monopole solution with an unusual structure. We briefly discuss the possible cosmological consequences of such nonperturbative structures, although we note that these depend crucially on the fermionic content of the models.
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arxiv:hep-ph/0404105
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The LHC / LC Study Group investigates how analyses at the LHC could profit from results obtained at a future Linear Collider and vice versa, leading to mutual benefits for the physics program at both machines. Some examples of results obtained within this working group so far concerning searches for new physics are briefly summarised.
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arxiv:hep-ph/0404108
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Using the SU(3) flavor symmetry, we construct the chiral Lagrangians for the light and heavy pentaquarks. The correction from the nonzero quark is taken into account perturbatively. We derive the Gell-Mann$-$Okubo type relations for various pentaquark multiplet masses and Coleman-Glashow relations for anti-sextet heavy pentaquark magnetic moments. We study possible decays of pentaquarks into conventional hadrons. We also study the interactions between and within various pentaquark multiplets and derive their coupling constants in the symmetry limit. Possible kinematically allowed pionic decay modes are pointed out.
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arxiv:hep-ph/0404123
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We construct a phenomenological model of electroweak-scale inflation that is in accordance with recent cosmic microwave background observations by WMAP, while setting the stage for a zero-temperature electroweak transition as assumed in recent models of baryogenesis. We find that the scalar spectral index especially poses tight constraints for low-scale inflation models. The inflaton-Higgs coupling leads to substantial mixing of the scalar degrees of freedom. Two types of scalar particles emerge with decay widths similar to that of the Standard Model Higgs particle.
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arxiv:hep-ph/0404128
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We present the general formalism for studying CP-violating phenomena in the production, mixing and decay of a coupled system of CP-violating neutral Higgs bosons at high-energy colliders. Considering the Minimal Supersymmetric Standard Model (MSSM) Higgs sector in which CP violation is radiatively induced by phases in the soft supersymmetry-breaking third-generation trilinear squark couplings and gaugino masses, we apply our formalism to neutral Higgs production via {\bar b}b, gg and W^+ W^- collisions at the LHC. We discuss CP asymmetries in the longitudinal and transverse polarizations of \tau^+ \tau^- pairs. The signatures of CP violation are more prominent in the production via gg and W^+ W^- than via {\bar b}b, and are resonantly enhanced when two (or all three) neutral Higgs bosons are nearly degenerate with mass differences comparable to their decay widths. Such scenarios occur naturally in the MSSM for values of \tan\beta >~ 5 (30) and large (small) charged Higgs-boson masses. We analyze representative examples with large mixing between the three neutral Higgs bosons weighing about 120 GeV, that may exhibit observable CP asymmetries even as large as 80%.
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arxiv:hep-ph/0404167
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We show that the f_0(980) and a_0(980) states appearing in scattering and production processes can be described quite well by the two-channel Oller-Oset-Pel\'aez (OOP) version of unitarized chiral theories. It is impossible, however, to deduce a conclusion on the nature of them from the fitting to experimental data alone. Using explicit N_c dependence of parameters in OOP amplitudes we demonstrate that light scalar resonances are not of q\bar q states but dynamical rescattering effects generated under chiral symmetry, unitarity and channel couplings.
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arxiv:hep-ph/0404221
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We present a program for the reduction of large systems of integrals to master integrals. The algorithm was first proposed by Laporta; in this paper, we implement it in MAPLE. We also develop two new features which keep the size of intermediate expressions relatively small throughout the calculation. The program requires modest input information from the user and can be used for generic calculations in perturbation theory.
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arxiv:hep-ph/0404258
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Interpreting the recently discovered narrow exotic baryons as pentaquark states, we discuss, along an old argument of ours, the isospin mixing occurring within the two doublets of $Q = -1$ and Q=0 states lying inside the $S=-2$ ($\Xi$-cascade) sector. We argue that, at least within the Jaffe-Wilczek assignment, presently available data already indicate that mixing should occur at an observable level in both charge sectors, with mixing angles that can be predicted in terms of ratios of observable mass splittings.
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arxiv:hep-ph/0404262
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We study the structure of generalized parton distributions in impact parameter space with the aim of determining the size and role of small transverse separations components in the quarks wave function. We analyze the relation between transverse momentum components and transverse separations. Wave functions with large transverse momentum components can simultaneously reproduce the behavior of the Dirac form factor at large momentum transfer, and of the deep inelastic structure functions at Bjorken x -> 1. The presence of large momentum components does not ensure, however, the dominance of small transverse distances at large x. We suggest that experiments measuring the attenuation of hadrons in the nuclear medium, or the onset of color transparency, can provide an alternative source of information on generalized parton distributions, by mapping out the behavior of the transverse components of the wave function.
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arxiv:hep-ph/0405014
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Supersymmetry with breaking of R-parity provides an attractive way to generate neutrino masses and lepton mixing angles in accordance to present neutrino data. We review the main theoretical features of the bilinear R-parity breaking (BRpV) model, and stress that it is the simplest extension of the minimal supersymmetric standard model (MSSM) which includes lepton number violation. We describe how it leads to a successful phenomenological model with hierarchical neutrino masses. In contrast to seesaw models, the BRpV model can be probed at future collider experiments, like the Large Hadron Collider or the Next Linear Collider, since the decay pattern of the lightest supersymmetric particle provides a direct connection with the lepton mixing angles determined by neutrino experiments.
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arxiv:hep-ph/0405015
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We show that definite polarization observables for the simplest electroproduction processes, $\ell+N\to \ell+B(1/2^\pm)+M(0^\pm)$, $B=Y(\Lambda, \Sigma$ or $Y_c$-hyperon, $\Theta^+$-pentaquark) and $M=K$, $\bar{K}$ or $D$, are sensitive to the relative P-parity $\pi(B)$ of the NBM-system. The interference of the longitudinal and transversal amplitudes for the collinear regime of the processes $\gamma^*+N\to B+M $($\gamma^*$ is the virtual photon) - at any value of momentum transfer squared and excitation energy of the $BM$-system - generates model independent relations between analyzing powers (in unpolarized lepton scattering by polarized target), from one side, and the components of the produced baryon $B$ polarization. It is important to stress that these relations depend on the above mentioned P-parity, and constitute a model independent method for the determination of unknown parities of strange and charm particles.
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arxiv:hep-ph/0405027
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The decays eta, eta-prime -> pi^+ pi^- gamma are investigated within an approach that combines one-loop chiral perturbation theory with a coupled channel Bethe-Salpeter equation which satisfies unitarity constraints and generates vector mesons dynamically from composite states of two pseudoscalar mesons. It is furthermore shown that the inclusion of the eta-prime as a dynamical degree of freedom does not renormalize the Wess-Zumino-Witten term.
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arxiv:hep-ph/0405039
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We review recent developments in double-beta decay, focusing on what can be learned about the three light neutrinos in future experiments. We examine the effects of uncertainties in already measured neutrino parameters and in calculated nuclear matrix elements on the interpretation of upcoming double-beta decay measurements. We then review a number of proposed experiments.
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arxiv:hep-ph/0405078
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Predictions for $e^+e^-\to J/\psi \eta_c$ from previous studies are made by taking charmonia as a nonrelativistic bound state and by using nonrelativistic QCD(NRQCD) approach. The predicted cross-section is smaller by an order of magnitude than the experimentally observed. We study the process by taking charm quark as a light quark and use light-cone wave-functions to parameterize nonperturbative effects related to charmonia. The total cross section of $e^+e^-\to J/\psi \eta_c$ can be predicted, if these wave-functions are known. Motivated by studies of light-cone wave-functions of light hadrons, we make a reasonable assumption of the forms of light-cone wave-functions. With these light-cone wave-functions we can obtain the cross section which is more closer to the experimentally observed than that from NRQCD approach. We also discuss in detail the difference between two approaches.
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arxiv:hep-ph/0405111
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We compute the rates for $q \bar{q}$ annihilation into charginos and neutralinos by taking into account the effects of supersymmetric soft phases. In particular, the phase of the $\mu$ parameter gains direct accessibility via the production of dissimilar charginos and neutralinos. The phases of the trilinear soft masses do not have a significant effect on the cross sections. Our results can be important for sparticle searches at the LHC.
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arxiv:hep-ph/0405131
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We compute the genuine SUSY one-loop quantum contributions to flavour-changing MSSM Higgs-boson decays into $b \bar s$ and $s \bar b$ using the full diagrammatic approach that is valid for all $\tan \beta$ values and do not rely on the mass-insertion approximation for the characteristic flavour-changing parameter. We analyze in full detail the dependence of these flavour-changing partial widths on all the relevant MSSM parameters and also study the non-decoupling behaviour of these widths with the SUSY mass parameters. We find that these contributions are sizable as compared to the SM ones, and can be very efficient as an indirect method in the future search for Supersymmetry.
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arxiv:hep-ph/0405138
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Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space-time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.
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arxiv:hep-ph/0405165
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We present a calculation of the complete electroweak O(alpha) corrections to pp/ppbar -> W+/- -> l+/- nu (l=e, mu) in the Standard Model of electroweak interactions, focusing on those corrections which do not contribute in the pole approximation. We study in detail the effect of these corrections on the transverse mass distribution, the W-width measurement, and the transverse mass ratio and cross section ratio of W and Z bosons.
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arxiv:hep-ph/0405191
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We construct a family-unified model on a Z_2xZ_2 orbifold in five dimensions. The model is based on a supersymmetric SU(7) gauge theory. The gauge group is broken by orbifold boundary conditions to a product of grand unified SU(5) and SU(2)xU(1) flavor symmetry. The structure of Yukawa matrices is generated by an interplay between spontaneous breaking of flavor symmetry and geometric factors arising due to field localization in the extra dimension.
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arxiv:hep-ph/0405199
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The region of small transverse momentum in q qbar- and gg-initiated processes must be studied in the framework of resummation to account for the large, logarithmically-enhanced contributions to physical observables. In this paper, we will calculate the fixed order next-to-leading order (NLO) perturbative total and differential cross-sections for both a Standard Model (SM) scalar Higgs boson and the Minimal Supersymmetric Standard Model's (MSSM) pseudoscalar Higgs boson in the Heavy Quark Effective Theory (HQET) where the mass of the top quark is taken to be infinite. Resummation coefficients B^2_g, C^2_gg for the total cross-section resummation for the pseudoscalar case are given, as well as C^1_gg for the differential cross-section.
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arxiv:hep-ph/0405219
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Decays of radionuclides throughout the Earth's interior produce geothermal heat, but also are a source of antineutrinos. The (angle-integrated) geoneutrino flux places an integral constraint on the terrestrial radionuclide distribution. In this paper, we calculate the angular distribution of geoneutrinos, which opens a window on the differential radionuclide distribution. We develop the general formalism for the neutrino angular distribution, and we present the inverse transformation which recovers the terrestrial radioisotope distribution given a measurement of the neutrino angular distribution. Thus, geoneutrinos not only allow a means to image the Earth's interior, but offering a direct measure of the radioactive Earth, both (1) revealing the Earth's inner structure as probed by radionuclides, and (2) allowing for a complete determination of the radioactive heat generation as a function of radius. We present the geoneutrino angular distribution for the favored Earth model which has been used to calculate geoneutrino flux. In this model the neutrino generation is dominated by decays in the Earth's mantle and crust; this leads to a very ``peripheral'' angular distribution, in which 2/3 of the neutrinos come from angles > 60 degrees away from the downward vertical. We note the possibility of that the Earth's core contains potassium; different geophysical predictions lead to strongly varying, and hence distinguishable, central intensities (< 30 degrees from the downward vertical). Other uncertainties in the models, and prospects for observation of the geoneutrino angular distribution, are briefly discussed. We conclude by urging the development and construction of antineutrino experiments with angular sensitivity. (Abstract abridged.)
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arxiv:hep-ph/0406001
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In recent years the perturbative expansion of the pressure of massless QCD has been driven to order g^6ln(g) at high temperatures and finite chemical potentials, which has required calculations up to three-loop order in the full theory and up to four-loop order in three-dimensional effective theories. In the present paper we briefly review the theoretical background behind this work and explain some of the methods used in the computations.
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arxiv:hep-ph/0406012
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We present an approach to solve a Bethe-Salpeter (BS) equation exactly without any approximation if the kernel of the BS equation exactly is instantaneous, and take positronium as an example to illustrate the general features of the solutions. As a middle stage, a set of coupled and self-consistent integration equations for a few scalar functions can be equivalently derived from the BS equation always, which are solvable accurately. For positronium, precise corrections to those of the Schr\"odinger equation in order $v$ (relative velocity) in eigenfunctions, in order $v^2$ in eigenvalues, and the possible mixing, such as that between $S$ ($P$) and $D$ ($F$) components in $J^{PC}=1^{--}$ ($J^{PC}=2^{++}$) states as well, are determined quantitatively. Moreover, we also point out that there is a problematic step in the classical derivation which was proposed first by E.E. Salpeter. Finally, we emphasize that for the effective theories (such as NRQED and NRQCD etc) we should pay great attention on the corrections indicated by the exact solutions.
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arxiv:hep-ph/0406050
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The radiative B -> K* gamma mode is caused by a penguin operator which is a quantum correction. Thus this mode may be useful in the search for physics beyond the standard model. In this paper, we compute the branching ratio, direct CP asymmetry, and isospin breaking effects within the Standard Model in the framework perturbative QCD, and discuss how new physics might show up in this decay.
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arxiv:hep-ph/0406055
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We use a Monte Carlo implementation of recently developed models of double diffraction to assess the sensitivity of the LHC experiments to Standard Model Higgs bosons produced in exclusive double diffraction. The signal is difficult to extract, due to experimental limitations related to the first level trigger, and to contamination by inclusive double diffractive background. Assuming the above difficulties can be overcome, the expected signal-to-background ratio is presented as a function of the experimental resolution on the missing mass. Injecting a missing mass resolution of 2 GeV, a signal-to-background ratio of about 0.5 is obtained; a resolution of 1 GeV brings a signal to background ratio of 1. This result is lower than previous estimates, and the discrepancy is explained.
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arxiv:hep-ph/0406061
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