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We construct the density of states for quarks and gluons using the `Thomas - Fermi model' for atoms and the `Bethe model' for nucleons as templates. With parameters to take care of the plasma (hydrodynamical) features of the QGP with a thermal potential for the interaction, we find a window in the parametric space of the model where observable QGP droplets of $ \sim $ 5 fm radius can occur with transition temperature in the range 140 MeV to 250 MeV. By matching with the expectations of Lattice Gauge estimates of the QGP-hadron transitions, we can further narrow the window, thereby restricting the allowed values of the flow-parameters of the model.
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arxiv:hep-ph/0406092
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The requirement that the supersymmetric scalar potential be stable in the minimal supergravity (mSUGRA) model imposes an upper bound on the universal gaugino mass $m_{1/2}$ as function of the common scalar mass $m_0$. Combining this with the experimental lower bound on $m_{1/2}$ from LEP data, we find a new lower bound on $m_0$, stronger than the one that comes from experimental data alone. If the corresponding upper and lower limits on the superparticle masses, presented in this letter, are found to be violated at Tevatron Run II or at the LHC, it would imply that we are living on a false vacuum. Special attention has been paid in estimating the uncertainties in these predictions due to the choice of the renormalization scale. The implications of our limits for the constraints obtained by indirect methods(SUSY dark matter, g - 2 of the muon, $ b \to s \gamma$....) are briefly discussed.
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arxiv:hep-ph/0406129
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The status of solutions to the ultra-high energy cosmic ray puzzle that involve particle physics beyond the standard model is reviewed. Signatures and experimental constraints are discussed for most proposals like the Z burst model and topological defects (both allowed only as subdominant contribution), supermassive dark matter (no positive evidence from its key signatures galactic anisotropy and photon dominance), strongly interacting neutrinos or new primaries (no viable models known), and violation of Lorentz invariance (possible).
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arxiv:hep-ph/0406174
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We present a case study for the synergy of combined LHC and LC analyses in Susy searches where simultaneous running of both machines is very important. In case that only light non-coloured Susy particles are accessible at a Linear Collider with an initial energy of $\sqrt{s}=500$ GeV, the precise analysis at the LC nevertheless leads to an accurate Susy parameter determination. This allows the prediction of heavy Susy particles. Providing these LC results as input for LHC analyses could be crucial for the identification of signals resulting in a direct measurement of the heavy neutralinos. These results provide an important consistency test of the underlying model. Furthermore, feeding back the LHC results into LC analyses leads to an improvement in the parameter determination.
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arxiv:hep-ph/0406180
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We test an optimised hopping parameter expansion on various Z_2 lattice scalar field models: the Ising model, a spin-one model and lambda (phi)^4. We do this by studying the critical indices for a variety of optimisation criteria, in a range of dimensions and with various trial actions. We work up to seventh order, thus going well beyond previous studies. We demonstrate how to use numerical methods to generate the high order diagrams and their corresponding expressions. These are then used to calculate results numerically and, in the case of the Ising model, we obtain some analytic results. We highlight problems with several optimisation schemes and show for the best scheme that the critical exponents are consistent with mean field results to at least 8 significant figures. We conclude that in its present form, such optimised lattice expansions do not seem to be capturing the non-perturbative infra-red physics near the critical points of scalar models.
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arxiv:hep-ph/0406202
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We reexamine the democratic neutrino mixing ansatz, in which the mass matrices of charged leptons and Majorana neutrinos arise respectively from the explicit breaking of S(3)_L x S(3)_R and S(3) flavor symmetries. It is shown that a democracy term in the neutrino sector can naturally allow the ansatz to fit the solar neutrino mixing angle \theta_sun \approx 33^\circ. We predict \sin^2 2\theta_atm \approx 0.95 for atmospheric neutrino mixing and J \approx 1.2% for leptonic CP violation in neutrino oscillations without any fine-tuning. Direct relations between the model parameters and experimental observables are also discussed.
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arxiv:hep-ph/0406206
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A general discussion is given of signals for broken Lorentz symmetry in short-baseline neutrino experiments. Among the effects that Lorentz violation can introduce are a dependence on energy differing from that of the usual massive-neutrino solution and a dependence on the direction of neutrino propagation. Using the results of the LSND experiment, explicit analysis of the effects of broken Lorentz symmetry yields a nonzero value (3+/-1) x 10^{-19} GeV for a combination of coefficients for Lorentz violation. This lies in the range expected for effects originating from the Planck scale in an underlying unified theory.
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arxiv:hep-ph/0406255
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We first suppose that low-energy hadron pair photoproduction reactions gamma(*) gamma(*) -> h h-bar are dominated by s-channel resonance contributions. Their normalization is then calculated by their correspondence with the Reggeon term in the Regge parametrization of the gamma h total cross sections. For the case of p p-bar, we make use of the measured gamma p total cross section, and for the case of K+K-, we make use of the corresponding total cross section that is estimated using Regge factorization. For hadrons that have no such data, we can only provide rough estimation based on the additive quark rule. As an effective approach that is convenient and parameter-free, we adopt the Veneziano model in the simplest form. The model is only applicable to the region of low centre-of-mass energy. When the transverse momentum is large, perturbative QCD takes over, whereas in the Regge region, it is known that the Regge pole picture fails in photoproduction. Despite the shortcomings of the model, we find that the parameter-free amplitudes offer a sound description of the data at hand.
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arxiv:hep-ph/0406267
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A method is presented in which matrix elements for some processes are calculated recursively. This recursive calculational technique is based on the method of basis spinors.
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arxiv:hep-ph/0407055
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Last year I talked at this meeting about a possible time dependence of the QCD coupling constant $\alpha_s$. This year I shall look into the problem once more, without fully repeating the arguments given last year. Astrophysical indications that the fine structure constant has undergone a small time variation during the cosmological evolution are discussed within the framework of the standard model of the electroweak and strong interactions and of grand unification. A variation of the electromagnetic coupling constant could either be generated by a corresponding time variation of the unified coupling constant or by a time variation of the unification scale, or by both. The various possibilities, differing substantially in their implications for the variation of low energy physics parameters like the nuclear mass scale, are discussed. The case in which the variation is caused by a time variation of the unification scale is of special interest. It is supported in addition by recent hints towards a time change of the proton-electron mass ratio.
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arxiv:hep-ph/0407068
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In a recently proposed model of ``ghost condensation'', spatially homogeneous states may mix, via tunneling, with inhomogeneous states which are somewhat similar to bubbles in the theory of false vacuum decay, the corresponding bubble nucleation rate being exponentially sensitive to the ultraviolet completion of the model. The conservation of energy and charge requires that the energy density is negative and the field is strongly unstable in a part of the nucleated bubble. Unlike in the theory of false vacuum decay, this region does not expand during subsequent real-time evolution. In the outer part, positive energy outgoing waves develop, which eventually form shocks. Behind the outgoing waves and away from the bubble center, the background settles down to its original value. The outcome of the entire process is thus a microscopic region of negative energy and strong field -- ``hole in the ghost condensate'' -- plus a collection of outgoing waves (particles of the ghost condensate field) carrying away finite energy.
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arxiv:hep-ph/0407081
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We aim to construct quark hadron physics based on QCD. First, using lattice QCD, we study mass spectra of positive-parity and negative-parity baryons in the octet, the decuplet and the singlet representations of the SU(3) flavor. In particular, we consider the lightest negative-parity baryon, the $\Lambda$(1405), which can be an exotic hadron as the $N \bar K$ molecular state or the flavor-singlet three-quark state. We investigate the negative-parity flavor-singlet three-quark state in lattice QCD using the quenched approximation, where the dynamical quark-anitiquark pair creation is absent and no mixing occurs between the three-quark and the five-quark states. Our lattice QCD analysis suggests that the flavor-singlet three-quark state is so heavy that the $\Lambda$(1405) cannot be identified as the three-quark state, which supports the possibility of the molecular-state picture of the $\Lambda$(1405). Second, we study thermal properties of the scalar glueball in an anisotropic lattice QCD, and find about 300 MeV mass reduction near the QCD critical temperature from the pole-mass analysis. Finally, we study the three-quark potential, which is responsible to the baryon properties. The detailed lattice QCD analysis for the 3Q potential indicates the Y-type flux-tube formation linking the three quarks.
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arxiv:hep-ph/0407093
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In this paper I show that it is possible to use Regge theory to constrain the initial parton distribution functions of a global DGLAP fit. In this approach, both quarks and gluons have the same high-energy behaviour which may also be used to describe soft interactions. More precisely, I show that, if we parametrise the parton distributions with a triple-pole pomeron, {\em i.e.} like $\log^2(1/x)$ at small $x$, at $Q^2=Q_0^2$ and evolve these distribution with the DGLAP equation, we can reproduce $F_2^p$, $F_2^d$, $F_2^n/F_2^p$, $F_2^{\nu N}$ and $xF_3^{\nu N}$ for $W^2\ge 12.5$ GeV$^2$. In this case, we obtain a new leading-order global QCD fit with a Regge-compatible initial condition. I shall also show that it is possible to use Regge theory to extend the parton distribution functions to small $Q^2$. This leads to a description of the structure functions over the whole $Q^2$ range based on Regge theory at low $Q^2$ and on QCD at large $Q^2$. Finally, I shall argue that, at large $Q^2$, the parton distribution functions obtained from DGLAP evolution and containing an essential singularity at $j=1$ can be approximated by a triple-pole pomeron behaviour.
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arxiv:hep-ph/0407098
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THERMUS is a package of C++ classes and functions allowing statistical-thermal model analyses of particle production in relativistic heavy-ion collisions to be performed within the ROOT framework of analysis. Calculations are possible within three statistical ensembles; a grand-canonical treatment of the conserved charges B, S and Q, a fully canonical treatment of the conserved charges, and a mixed-canonical ensemble combining a canonical treatment of strangeness with a grand-canonical treatment of baryon number and electric charge. THERMUS allows for the assignment of decay chains and detector efficiencies specific to each particle yield, which enables sensible fitting of model parameters to experimental data.
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arxiv:hep-ph/0407174
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We analyze a thought neutrino oscillation experiment in which neutrinos are produced by electrons colliding with atomic nuclei of a target. The neutrinos are detected by observing charged leptons, which are produced by neutrinos colliding with nuclei of the detector. We consider the case when both the target and detector nuclei have finite masses. (The case of infinitely heavy nuclei was considered in the literature earlier.)
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arxiv:hep-ph/0407189
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Flavour changing neutral current decays are a very sensitive test of the standard model and its extensions. In particular the decay K -> pi nu nubar constitutes a clean way to provide constraints, independent of long distance effects. Motivated by the recent experimental data of the E787 and E865 collaborations and by the difference between the standard model prediction and data, we consider in detail new physics scenarios such as the minimal supersymmetric standard model and R-parity violating supersymmetry. We begin with analysing the impact of new measurements on the standard model result obtaining B(K^+ -> pi^+ nu nubar)=(8.18 +/- 1.22) x 10^(-11). Predictions for other rare kaon decays are discussed, too. Our results allow to improve the limits on R-parity violating couplings with respect to previous analyses.
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arxiv:hep-ph/0407216
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We have analyzed the K+K- photoproduction on hydrogen in the effective mass region around the mass of the phi(1020) meson. The interference of the S-wave contribution with the P-wave has been studied. Both scalar resonances f0(980) and a0(980) have been taken into account. We have obtained a good description of the available experimental data, in particular the mass distributions and the moments of the kaon angular distribution. Our calculations give values of the integrated S-wave total photoproduction cross section between 4 and 7 nb for the K+K- effective mass range around the phi(1020) mass and at the laboratory photon energy near 5 GeV. These numbers favor lower experimental estimates obtained at DESY.
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arxiv:hep-ph/0407237
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The LHC data will provide sensitivity to an unification of the couplings at low energies in the range $\sim$10-100 TeV. It is demonstrated in this note that the lack of knowledge on the proton structure, specifically its gluon distribution, can lower dramatically the sensitivity of bare cross section measurements to this physics. However, some more elaborated strategies could probably be developped to recover an important part of the sensitivity
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arxiv:hep-ph/0407303
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This talk gives a brief discussion of the motivations and principles behind computer automated expert semi-analytical resummation (CAESAR) for QCD final states.
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arxiv:hep-ph/0407367
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Recent experimental results on hadronic tau decays into strange particles by the OPAL collaboration are employed to determine V_us and m_s from moments of the invariant mass distribution. Our results are V_us = 0.2208+-0.0034 and m_s(2 GeV) = 81+-22 MeV. The error on V_us is dominated by experiment, and should be improvable in the future. Nevertheless, already now our result is competitive to the standard extraction of V_us from K_e3 decays, and it is compatible with unitarity.
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arxiv:hep-ph/0408044
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The accuracy of the equivalent photon approximation (EPA) of the proton in describing the inelastic process $ep\to \nu W X$ is investigated. In particular, the scale dependence of the corresponding inelastic photon distribution is discussed. Furthermore, an estimate of the total number of events, including the ones coming from the elastic and quasi-elastic channels of the reaction, is given for the HERA collider.
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arxiv:hep-ph/0408101
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We suggest searching for excited charmonium states in $e^+e^-$ annihilation via double charmonium production at $\sqrt{s}=10.6$ GeV with $B$ factories, based on a more complete leading order calculation including both QCD and QED contributions for various processes. In particular, for the C=+ states, the $\chi_{c0}(nP)$ (n=2,3) and $\eta_c(mS)$ (m=3,4) may have appreciable potentials to be observed; while for the C=- states, the $\eta_ch_c$ production and especially the $\chi_{c1}h_c$ production might provide opportunities for observing the $h_c$ with higher statistics in the future. A brief discussion for the X(3940) observed in the double charmonium production is included.
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arxiv:hep-ph/0408141
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We discuss the kinetics of phase conversion, through the nucleation of bubbles and spinodal decomposition, after a chiral transition within an effective field theory approach to low-energy QCD. We study possible effects resulting from the finite size of the expanding system for both the initial and the late-stage growth of domains, as well as those effects due to inhomogeneities in the chiral field which act as a background for the fermionic motion.
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arxiv:hep-ph/0408143
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We have calculated the diffractive dijet cross section in low-Q^2 ep scattering in the HERA regime. The results of the calculation in LO and NLO are compared to recent experimental data of the H1 collaboration. We find that in LO the calculated cross sections are in reasonable agreement with the experimental results. In NLO, however, some of the cross sections disagree, showing that factorization breaking occurs in that order. By suppressing the resolved contribution by a factor of approximately three, good agreement with all the data is found. The size of the factorization breaking effects in diffractive dijet photoproduction agrees well with absorptive model predictions.
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arxiv:hep-ph/0408203
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We analyze various possible interpretations of the narrow state $D_{sJ}^+(2632)$ observed by SELEX Collaboration recently, which lies above threshold and has abnormal decay pattern. These interpretations include: (1) several versions of tetraquarks; (2) conventional $c\bar s$ meson such as the first radial excitation of $D_s(2112)$ with abnormally large SU(3) symmetry breaking; (3) conventional $c\bar s$ meson with abnormally large $\eta_1$ coupling; (4) heavy hybrid meson. We discuss the physical implications of each interpretation. For example, if the existence of $D_{sJ}^+(2632)$ is confirmed as the first radial excitation of $D_s(2112)$ by other experiments, it will be helpful to look for (1) its SU(3) flavor partners $D_{J}^{0,+}(2530)$; (2) its B-meson analogues $B_{J}^{0,+}(5840), B_{sJ}^+(5940)$; (3) S-wave two pion decay modes.
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arxiv:hep-ph/0408234
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For gauge theories with direct product internal symmetry groups, the relationship between internal quantum numbers (charges) and coupling strengths is examined. In these types of theories, the Lagrangian density may contain non-trivial factors multiplying the matter field terms, and these factors can modify the interaction coupling strengths i.e., the gauge/matter field vertex factors. Consequently, a matter field can carry a given internal charge yet couple to the associated gauge field with an apparent fractional charge. An example with $SU(3)\otimes U(2)$ symmetry is presented in which the matter fields can have integer U(2) charges but fractional U(2) coupling strengths.
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arxiv:hep-ph/0408266
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I briefly review the theory and phenomenology of bottom production at colliders. When all theoretical uncertainties are taken into proper account, and modern measurements are considered, no significant discrepancy is seen between data and QCD predictions
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arxiv:hep-ph/0408317
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Recent results on the gapless 2SC phase are reviewed. These include: the thermal stability under the constraint of the local charge neutrality condition, the properties at zero and nonzero temperatures, and the color screening properties.
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arxiv:hep-ph/0408325
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A resonance X(3872), first observed in the decays $B \to K X$, has been seen to decay to $J/\psi \pi^+ \pi^-$. The $\pi^+ \pi^-$ mass spectrum peaks near its kinematic upper limit, prompting speculation that the dipion system may be in a $\rho^0$. The decay $X(3872) \to J/\psi \omega$ also has been observed. The reaction $\gamma \gamma \to J/\psi \pi^+ \pi^-$ has been studied. Consequently, angular distributions in decays of $J/\psi (\rho^0,\omega)$ states near threshold are of interest, and results are presented.
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arxiv:hep-ph/0408334
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An overview of Chiral Perturbation Theory calculations in the mesonic sector at the two Loop level is given. Discussed in some detail are the partially quenched case relevant for lattice QCD, the general fitting procedures and $\pi\pi$,$\pi K$ scattering as well as the determination of $V_{us}$ and $K_{\ell3}$ decays.
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arxiv:hep-ph/0409068
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Antineutrinos born inside the Earth (``geoneutrinos'') carry out information of fundamental importance for understanding of the origin and evolution of our planet. We show that Baksan Neutrino Observatory is one of the best sites for detection and analysis of geoneutrinos using large liquid scintillation spectrometer. Also we present a short story of concept of Earth as antineutrino source (1960 - 2004 yy)
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arxiv:hep-ph/0409069
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A lattice calculation shows that the Casimir scaling hypothesis is well verified in QCD, that is to say that the potential between two opposite color charges in a color singlet is proportional to the value of the quadratic Casimir operator. On the other hand, in a bag model calculation for the same system, a scaling of the string tension with the square root of the quadratic Casimir operator is obtained. It is shown that, within the same formalism but with the assumption that the width of the string is independent of the color charges, the string tension is proportional to value of the quadratic Casimir operator. Some considerations about the color behavior of the total interaction are given.
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arxiv:hep-ph/0409105
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The status of the QCD-based heavy quark expansion is briefly reviewed. A good agreement between properly applied theory and new precision data is observed. Critical remarks on certain recent claims from HQET are presented. Recent applications to the exclusive heavy flavor transitions are addressed. The `1/2 > 3/2' problem for the transitions into the charm P-wave states is discussed.
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arxiv:hep-ph/0409125
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Dynamical gauge-Higgs unification is presented in higher dimensional gauge theory, in which both adjoint and fundamental Higgs fields are a part of gauge fields. Dynamical gauge symmetry breaking is induced through the Hosotani mechanism. Gauge theory, including the U(3) x U(3) model, is examined on M^4 x (T^2/Z_2).
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arxiv:hep-ph/0409154
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We present an experimental and theoretical analysis of the ratio of branching ratios R=BR(H^+ -> tau^+ nu)/BR(H^+ -> t b-bar) of charged Higgs boson decays as a discriminant quantity between supersymmetric and non-supersymmetric models.
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arxiv:hep-ph/0409189
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We consider the rate of fermion-antifermion pair creation by an external field. We derive a rate formula that is valid for a coupling with arbitrary vector and axial vector components to first order in perturbation theory. This is then applied to study the creation of neutrinos by nuclear matter, a problem with astrophysical relevance. We present an estimate for the creation rate per unit volume, compare this to previous results and comment on the role of the neutrino mass.
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arxiv:hep-ph/0409259
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Using the $1/N_c$ expansion of QCD we analyze the spectrum of positive parity resonances with strangeness $S = 0, -1, -2$ and -3 in the 2-3 GeV mass region, supposed to belong to the $[\textbf{56},4^+]$ multiplet. The mass operator is similar to that of $[\textbf{56},2^+]$, previously studied in the literature. The analysis of the latter is revisited. In the $[\textbf{56},4^+]$ multiplet we find that the spin-spin term brings the dominant contribution and that the spin-orbit term is entirely negligible in the hyperfine interaction, in agreement with constituent quark model results. More data are strongly desirable, especially in the strange sector in order to fully exploit the power of this approach.
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arxiv:hep-ph/0409261
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The cross section of heavy-ion collisions is represented as a double functional integral with the saddle point being the classical solution of the Yang-Mills equations with boundary conditions/sources in the form of two shock waves corresponding to the two colliding ions. I develop the expansion of this classical solution in powers of the commutator of the Wilson lines describing the colliding particles and calculate the first two terms of the expansion.
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arxiv:hep-ph/0409314
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Neutrinoless double beta decay pops up almost in any extension of the standard model. It is perhaps the only process, which can unambiguously determine whether the massive neutrinos are Majorana or Dirac type particles. In addition from the lifetime of this decay, combined with sufficient knowledge of the relevant nuclear matrix elements, one can set a constraint involving the neutrino masses. Furthemore, if one incorporates the recent results of the neutrino oscillation experiments, one can determine or set a stringent limit on the neutrino mass scale. In addition one may obtain usefull information regarding the presence of right handed currents and the right handed neutrino mass scale. One can also constrain the parameters of supersymmetry and, in particular, set limits in of R-parity violating couplings as well as get information about extra dimensions.
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arxiv:hep-ph/0409319
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After a brief summary of the neutrino oscillation formalism and the solar neutrino sources and experiments I discuss the matter effect on solar neutrino oscillation. Then I discuss how the resulting alternative solutions are experimentally resolved in favour of the LMA solution, with particular exphasis on the SK, SNO and KL data.
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arxiv:hep-ph/0409336
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Large extra dimensions lower the Planck scale to values soon accessible. Motivated by String Theory, the models of large extra dimensions predict a vast number of new effects in the energy range of the lowered Planck scale, among them the production of TeV-mass black holes and gravitons. But not only is the Planck scale the energy scale at which effects of modified gravity become important. String Theory as well as non-commutative quantum mechanics suggest that the Planck length acts as a minimal length in nature, providing a natural ultraviolet cutoff and a limit to the possible resolution of spacetime. Within the extra dimensional scenario, the minimal length effects thus become important in the same energy range in which the effective extra dimensional models predict new physics. We examine a model which includes the minimal length into the extra dimensional extension of the Standard Model. To appear in the Proceedings of the conference Physics at LHC, Vienna, Austria, July 2004.
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arxiv:hep-ph/0409350
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The Two-Scale Model and its improved version were used to perform the fit to the HERMES data for $\nu$ (the virtual photon energy) and z (the fraction of $\nu$ carried by hadron) dependencies of nuclear multiplicity ratios for $\pi^+$ and $\pi^-$ mesons electro-produced on two nuclear targets ($^{14}$N and $^{84}$Kr). The quantitative criterium $\chi ^2$ was used for the first time to analyse the results of the model fit to the nuclear multiplicity ratios data. The two-parameter's fit gives satisfactory agreement with the HERMES data. Best values of the parameters were then used to calculate the $\nu$- and $z$ - dependencies of nuclear attenuation for $\pi^0$, K$^+$, K$^-$ and $\bar{p}$ produced on $^{84}$Kr target, and also make a predictions for $\nu$, z and the Q$^2$ (the photon virtuality) - dependencies of nuclear attenuation data for those identified hadrons and nuclea, that will be published by HERMES.
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arxiv:hep-ph/0409359
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We calculate Higher Order corrections to the resolved component of the electroproduction cross section of large-Et hadrons. The parton distributions in the virtual photon are studied in detail and a NLO parametrization of the latter is proposed. The contribution of the resolved component to the forward production of large-Et hadrons is calculated and its connection with the BFKL cross section is discussed.
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arxiv:hep-ph/0410021
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We show that in a decay of the form B_d or B_s-> P_1 P_2 gamma (where P_1 and P_2 are pseudoscalar mesons), through a flavor changing dipole transition, time dependent oscillations can reveal the presence of physics beyond the Standard Model. If P_1 and P_2 are CP eigenstates (e.g. as in B_d -> K_S pi0 gamma), the oscillation is independent of the resonance structure. Thus data from resonances as well as from nonresonant decays can be included. This may significantly enhance the sensitivity to new physics of the method. If P_1 is a charged particle, and P_2 its anti-particle (e.g. as in B_d -> pi+ pi- gamma), one has the additional advantage that both the magnitude and the weak phase of any new physics contribution can be determined from a study of the angular distribution. These signals offer excellent ways to detect new physics because they are suppressed in the Standard Model. We also show that the potential contamination of these signals originating from the Standard Model annihilation diagram gives rise to photons with, to a very good approximation, the same helicity as the dominant penguin graph and thus causes no serious difficulty.
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arxiv:hep-ph/0410036
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I review work on diffractive vector meson production in photon-proton collisions at high energy and large momentum transfer, accompanied by proton dissociation and a large rapidity gap. This process provides a test of the high energy scattering dynamics, but is also sensitive to the details of the treatment of the vector meson vertex. The emphasis is on the description of the process by a solution of the non-forward BFKL equation, i.e. the equation describing the evolution of scattering amplitudes in the high-energy limit of QCD. The formation of the vector meson and the non-perturbative modeling needed is also briefly discussed.
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arxiv:hep-ph/0410073
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We consider the most general gauge-invariant, chirality-conserving contact interactions in the process e +e- -> gamma Z, of the type proposed Abraham and Lampe, in order to explore the possibility of CP violation at future linear colliders in the presence of polarized beams. We hereby extend recent work on CP violation due to anomalous triple-gauge boson vertices. We isolate combinations of couplings which are genuinely CP violating, pointing out which of these can only be studied with the use of transverse polarization. We place constraints on these couplings that could arise from suitably defined CP-odd asymmetries, considering realistic polarization (either longitudinal or transverse) of 80% and 60% for the electron and positron beams respectively, and with an integrated luminosity \int dt L of 500 fb^{-1} at a centre of mass energy of \sqrt{s}=500 GeV.
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arxiv:hep-ph/0410084
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The accuracy in the measurement of the masses of sleptons and heavy Higgs bosons in cMSSM scenarios, compatible with the WMAP result on cold dark matter, has been re-analysed in view of the requirements for predicting this density to a few percent level from SUSY measurements at the linear collider.
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arxiv:hep-ph/0410123
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Due to asymptotic freedom, QCD is guaranteed to be accessible to perturbative methods at asymptotically high temperatures. However, in 1979 Linde has pointed out the existence of an "infrared wall", beyond which an infinite number of Feynman diagrams contribute. Following a proposal by Braaten and Nieto, it is shown explicitly how the limits to computability that this infrared problem poses can be overcome in the framework of dimensionally reduced effective theories.
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arxiv:hep-ph/0410130
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We propose a new mass reconstruction technique for SUSY processes at the LHC. The idea is to completely solve the kinematics of the SUSY cascade decay by using the assumption that the selected events satisfy the same mass shell conditions of the sparticles involved in the cascade decay. Using this technique, we study the measurement of the mass of the bottom squarks in the cascade decay of the gluino. Based on the final state including two high p_T leptons and two b-jets, we investigate different possible approaches to the mass reconstruction of the gluino and the two bottom squarks. In particular we evaluate the performance of different algorithms in discriminating two bottom squark states with a mass difference as low as 5%.
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arxiv:hep-ph/0410160
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We present measurements of the scale (bin-size) dependence of event-wise mean transverse momentum $<p_{t}>$ fluctuations for Au-Au collisions at $\sqrt{s_{NN}} = 200$ GeV simulated with the Hijing-1.37 Monte Carlo. We invert those scale distributions to obtain autocorrelation distributions on pseudorapidity $\eta$ and azimuth $\phi$ difference variables $(\eta_\Delta,\phi_\Delta)$. The autocorrelations have a simple structure dominated by a same-side (on azimuth) peak with similar widths on the two difference variables. With jet quenching imposed, the same-side peak widths increase slightly in both directions, and the amplitude is substantially reduced. The same-side peaks are attributed to minijets, observed in this study as local {\em velocity} correlations of charged particles with $p_t < $ 2 GeV/c.
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arxiv:hep-ph/0410180
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We extend the earlier suggested QCD-motivated model for the $Q^2$-dependence of the generalized Gerasimov-Drell-Hearn (GDH) sum rule which assumes the smooth dependence of the structure function $g_T$, while the sharp dependence is due to the $g_2$ contribution and is described by the elastic part of the Burkhardt-Cottingham sum rule. The model successfully predicts the low crossing point for the proton GDH integral, but is at variance with the recent very accurate JLAB data. We show that, at this level of accuracy, one should include the previously neglected radiative and power QCD corrections, as boundary values for the model. We stress that the GDH integral, when measured with such a high accuracy achieved by the recent JLAB data, is very sensitive to QCD power corrections. We estimate the value of these power corrections from the JLAB data at $Q^2 \sim 1 {GeV}^2$. The inclusion of all QCD corrections leads to a good description of proton, neutron and deuteron data at all $Q^2$.
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arxiv:hep-ph/0410228
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Two photons can annihilate into a neutral pion-like resonance via the anomaly coupling, just like $\pi^0\gamma\gamma$ in QCD. In some strongly interacting electroweak symmetry breaking models, e.g., technicolor type models, there often exist neutral pion-like resonances. TeV photon colliders have a strong capability to discover such particles, because the standard model background in photon scattering goes through box diagrams and is therefore highly suppressed. In this study, we perform a signal-background comparison. We show that $e^+ e^-$ linear colliders running in $\gamma\gamma$ mode can discover such neutral-pion-like resonances with a decent sensitivity.
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arxiv:hep-ph/0410231
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Roles of instanton induced interactions (III) in the masses of pentaquark baryons, Theta^+ (J=1/2 and 3/2) and Xi^{--}, and a dibaryon, H, are discussed using the MIT bag model. It is shown that the two-body terms in III give a strong attraction mainly due to the increase of the number of pairs in multi-quark systems. In contrast, the three-body $u$-$d$-$s$ interaction is repulsive. It is found that III lowers the mass of negative-parity Theta^+ as much as 100 MeV from the mass predicted by the bag model without III.
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arxiv:hep-ph/0410234
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We study the structure of fermionic mass eigenstates in a pure four-dimensional deconstruction approach. Unlike the case with the usual higher dimensional deconstruction (or latticized extra dimension), here the doubling of fermionic degrees of freedom is physical, thus there is no need to invoke Wilson terms to eliminate them. The fermionic structure is shaped by two key factors, namely the boundary conditions on fermions and the ratio of two breaking scales involved. The singular value decomposition theorem of linear algebra is employed to shed light into the phenomenologically crucial role of chiral boundary conditions. In this approach, we can explain the "localization" or "delocalization" nature of fermionic zero mode in flavor space and obtain analytically all higher modes. The application of boundary conditions on fermions to the implementation of CKM quark mixing is also found.
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arxiv:hep-ph/0410269
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Various mechanisms of thermal photon production are reviewed and their implications for heavy ion collisions are briefly sketched.
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arxiv:hep-ph/0410282
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We have investigated negative-parity uudd\bar{s} pentaquarks by employing a quark model with the meson exchange and the effective gluon exchange as qq and q\bar{q} interactions. The system for the five quarks is dynamically solved; the effects of qq and q\bar{q} correlations on the wave function are taken into account. It is found that the masses of the pentaquarks are reasonably low. The lowest-mass state is found to be TJ^P=0{1/2}^-, and the next lowest one is 0{3/2}^-. The former is reported to have a large width. We argue the observed narrow peak corresponds to the latter state. It is still necessary to introduce an extra attraction to reduce the mass further by 140 -- 280 MeV to reproduce the observed \Theta^+ mass. Since their level splitting is found to be less than 80 MeV, the lower level will not become a bound state below the NK threshold even after such an attraction is introduced. It is also found that the relative distance of two quarks with the attractive interaction is found to be by about 1.2 -- 1.3 times closer than that of the repulsive one. The two-body correlation seems important in the pentaquark systems.
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arxiv:hep-ph/0410286
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We argue that low-energy gluodynamics can be explained in terms of semi-classical Yang-Mills solutions by demonstrating that lattice gluon correlation functions fit to instanton liquid predictions for low energies and, after cooling, in the whole range.
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arxiv:hep-ph/0410347
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If supersymmetry (SUSY) is realized at the electroweak scale, its underlying structure and breaking mechanism may be explored with great precision by a future linear $e^+ e^-$ collider (LC) with a clean environment, tunable collision energy, high luminosity polarized beams, and additional $e^-e^-$, $e\gamma$ and $\gamma\gamma$ modes. In this report we summarize four papers submitted to the ICHEP04 conference about the precise measurements of the top squark parameters and $\tan\beta$, the impacts of the CP phases on the search for top/bottom squarks, the Majorana nature and CP violation in the neutralino system, the implications of the SUSY dark matter scenario for the LC experiments, and the characteristics of the neutralino sector of the next--to--minimal supersymmetric standard model at the LC
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arxiv:hep-ph/0410359
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The KN and KbarN low-energy elastic scattering is consistently studied in the framework of the QCD-inspired quark potential model. The model is composed of the t-channel one-gluon exchange potential, the s-channel one-gluon exchange potential and the harmonic oscillator confinement potential. By means of the resonating group method, nonlocal effective interaction potentials for the KN and KbarN systems are derived and used to calculate the KN and KbarN elastic scattering phase shifts. By considering the effect of QCD renormalization, the contribution of the color octet of the clusters (qqbar) and (qqq) and the suppression of the spin-orbital coupling, the numerical results are in fairly good agreement with the experimental data.
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arxiv:hep-ph/0410376
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Recently, we developed a strategy to analyse the B -> pi pi,pi K data. We found that the B -> pi pi measurements can be accommodated in the Standard Model (SM) through large non-factorizable effects. On the other hand, our analysis of the ratios R_c and R_n of the CP-averaged branching ratios of the charged and neutral B -> pi K modes, respectively, suggested new physics (NP) in the electroweak penguin sector, which may have a powerful interplay with rare decays. In this paper, we confront our strategy with recent experimental developments, addressing also the direct CP violation in B_d -> pi^-+ K^+-, which is now an established effect, the relation to its counterpart in B^+- -> pi^0 K^+-, and the first results for the direct CP asymmetry of B_d -> pi^0 pi^0 that turn out to be in agreement with our prediction. We obtain hadronic B -> pi pi,pi K parameters which are almost unchanged and arrive at an allowed region for the unitarity triangle in perfect accordance with the SM. The ``B -> pi K puzzle'' persists, and can still be explained through NP, as in our previous analysis. In fact, the recently observed shifts in the experimental values of R_c and R_n have been predicted in our framework on the basis of constraints from rare decays. Conversely, we obtain a moderate deviation of the ratio R of the CP-averaged B_d -> pi^-+ K^+- and B^+- -> pi^+- K rates from the current experimental value. However, using the emerging signals for B^+- -> K^+- K modes, this effect can be attributed to certain hadronic effects, which have a minor impact on R_c and do not at all affect R_n. Our results for rare decays remain unchanged.
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arxiv:hep-ph/0410407
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We calculate the non-zero (na\"{i}ve) T-odd transverse momentum dependent transversity distribution $h_1^{\perp}(x,\kp^2)$ of the pion in a quark-spectator-antiquark model. The final-state interaction is modelled by the approximation of one gluon exchange between the quark and the antiquark spectator. Using our model result we estimate the unsuppressed cos2$\phi$ azimuthal asymmetry in unpolarized $\pi^-p$ Drell-Yan process. We find that the transverse momentum dependence of $h_1^{\perp}(x,\kp^2)$ of the pion is the same as that of $h_1^{\perp}(x,\kp^2)$ of the proton calculated from the quark-scalar-diquark model, although the $x$ dependencies of them are different from each other. This suggests a connection between cos2$\phi$ asymmetries in Drell-Yan processes with different initial hadrons.
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arxiv:hep-ph/0411043
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We use exact results in a new approach to quantum gravity to discuss some issues in black hole physics.
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arxiv:hep-ph/0411049
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Over the past years a lot of progress has been made in the understanding of single spin asymmetries in hard scattering processes. We briefly review this subject, covering the non-vanishing of time-reversal odd parton distributions, universality of fragmentation functions, and the discovery of previously unknown time-reversal odd parton distributions at subleading twist. Interestingly enough, all these developments were initiated by simple model calculations.
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arxiv:hep-ph/0411118
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The interesting state X(1600) with $J^{PC}I^G=2^{++}2^+$ can't be a conventional $q \bar q$ meson in the quark model. Using a mixed interpolating current with different color configurations, we investigate the possible existence of X(1600) in the framework of QCD finite energy sum rules. Our results indicate that both the "hidden color" and coupled channel effects may be quite important in the multiquark system. We propose several reactions to look for this state.
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arxiv:hep-ph/0411140
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The study of QCD processes at the LHC will serve two main goals. First, the predictions of Quantum Chromodynamics will be tested and precision measurements will be performed, allowing additional constraints to be established, and providing measurements of the strong coupling constant. Second, QCD processes represent a major part of the background to other Standard Model processes and signals of new physics at the LHC and therefore need to be understood in depth. An overview of various measurements of QCD-related processes to be performed at the LHC is presented, based on final states containing high-pT leptons, photons and jets. Moreover, possible deviations from QCD predictions indicating presence of new physics are discussed.
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arxiv:hep-ph/0411147
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We summarize results presented at this conference with special emphasis on hard processes with jets and heavy quarks, soft particle production, small x structure functions and diffraction as well as heavy ion collisions and quark gluon plasma.
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arxiv:hep-ph/0411167
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Lattice Monte Carlo simulations now include the effects of 2 light sea quarks and 1 strange sea quark through the use of an improved staggered fermion action. Consequently, results important to phenomenology are free of the approximate 10% errors inherent in the quenched approximation. This talk reports on calculations of the B and Bs decay constants and B -> pi l nu form factors. Accurate determinations of these quantities will lead to tighter constraints on CKM matrix elements.
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arxiv:hep-ph/0411236
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Under assumption of singular behavior of invariant charge alpha_s(q^2) at q^2 sim 0 and of large q^2 behavior, corresponding to the perturbation theory up to four loops, a procedure is considered of smooth matching the beta-function at a boundary of perturbative and nonperturbative regions. The procedure results in a model for alpha_s for all q^2>0 with dimensionless parameters being fixed and dimensional parameters being expressed in terms of only one quantity Lambda_QCD. The gluon condensate which is defined by the nonperturbative part of the invariant charge is calculated for two variants of ``true perturbative'' invariant charge, corresponding to freezing option and to analytic one in nonperturbative region. Dimensional parameters are fixed by varying normalization condition alpha_s(m^2_tau) = 0.29, 0.30, ..., 0.36. It is obtained that on the boundary of perturbative region alpha_0 = alpha_s(q_0^2) simeq 0.44, the procedure results in nonperturbative Coulomb component alpha_Coulomb simeq 0.25, the nonperturbative region scale q_0 simeq 1 GeV, the model parameter sigma simeq (0.42 GeV)^2 which suits as string tension parameter, the gluon condensate appears to be close for two variants considered, K simeq (0.33 -- 0.36 GeV)^4 (for alpha_s(m^2_tau) = 0.33).
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arxiv:hep-ph/0411339
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In a cosmological phase transition in theories that admit Q-balls there is a value of the soliton charge above which the soliton becomes unstable and expands, converting space to the true vacuum, much like a critical bubble in the case of ordinary tunneling. Here I consider the effects of gravity on these solitons and I calculate the lowest gravitational corrections to the critical radius and charge.
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arxiv:hep-ph/0411385
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We study the scaling regime of hadron-(anti)-hadron annihilation into a deeply virtual photon and a real photon, H anti-H -> gamma^* gamma, and deep backward virtual Compton scattering, gamma^* H -> H gamma. We advocate that there is a kinematical region where the scattering amplitude factorizes into a short-distance matrix element and a long-distance dominated object: a transition distribution amplitude which describes the hadron to photon transition.
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arxiv:hep-ph/0411387
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The transverse energies and the charged particle multiplicities at midrapidity as well as their ratio, $dE_{T}/d\eta\mid_{mid} / dN_{ch}/d\eta|_{mid}$, are evaluated in a statistical model with expansion for the wide range of heavy-ion collisions, from AGS to RHIC at $\sqrt{s_{NN}}=200$ GeV. Full description of decays of hadron resonances is applied in calculations of both $dE_{T}/d\eta|_{mid}$ and $dN_{ch}/d\eta|_{mid}$. The predictions of the model at the freeze-out parameters, established independently from observed particle yields and $p_{T}$ spectra, agree well with the experimental data.
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arxiv:hep-ph/0412006
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aITALC, a new tool for automating loop calculations in high energy physics, is described. The package creates Fortran code for two-fermion scattering processes automatically, starting from the generation and analysis of the Feynman graphs. We describe the modules of the tool, the intercommunication between them and illustrate its use with three examples.
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arxiv:hep-ph/0412047
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Within the minimal supergravity model (mSUGRA) framework, the expectation for the relic density of neutralinos exceeds the WMAP determination unless neutralinos a) have a significant higgsino component, b) have a mass close to half that of a heavy Higgs boson, or c)can efficiently co-annihilate with a charged or colored particle. Within a 1-parameter extension of the mSUGRA model which includes non-universal Higgs masses, we show that agreement with the WMAP data can be obtained over a wide range of mSUGRA parameters for scenarios a) and b), so that the phenomenological implications may be much more diverse than in mSUGRA. We show that direct and/or indirect detection of neutralino dark matter should be possible at various current and planned facilities.
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arxiv:hep-ph/0412059
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I discuss the basic ideas of the light-cone path integral approach to the induced radiation in QED and QCD and recent applications to the induced parton energy loss.
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arxiv:hep-ph/0412117
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Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson $Z^{0}$. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic ($10^{21}$ -- $10^{25}$-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time-evolution of the relic-neutrino density and the consequences of neutrino decay. We consider the sensitivity of the lineshape to the age and character of extremely energetic neutrino sources, and to the thermal history of the Universe, reflected in the expansion rate. We take into account Fermi motion arising from the thermal distribution of the relic-neutrino gas. We also note the implications of Dirac vs. Majorana relics, and briefly consider unconventional neutrino histories. We ask what kinds of external information would enhance the potential of cosmic-neutrino absorption spectroscopy, and estimate the sensitivity required to make the technique a reality.
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arxiv:hep-ph/0412122
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Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for radiative Ke3 decays (neutral kaons). Special emphasis is given on the stability of the inner bremsstrahlung-dominated relative branching ratio vs. the Ke3 form factors, and on the separation of the structure dependent amplitude in differential distributions over the phase space. For the structure dependent terms, an assessment of the order p^6 corrections is given. In particular, a full next-to-leading order calculation of the axial component is performed. The experimental analysis of the photon energy spectrum is discussed, and other potentially useful distributions are introduced.
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arxiv:hep-ph/0412130
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The standard definition of the electromagnetic radius of a charged particle (in particular the proton) is ambiguous once electromagnetic corrections are considered. We argue that a natural definition can be given within an effective field theory framework in terms of a matching coefficient. The definition of the neutron radius is also discussed. We elaborate on the effective field theory relevant for the hydrogen and muonic hydrogen, specially for the latter. We compute the hadronic corrections to the lamb shift (for the polarizability effects only with logarithmic accuracy) within heavy baryon effective theory. We find that they diverge in the inverse of the pion mass in the chiral limit.
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arxiv:hep-ph/0412142
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Using the OPE, we formulate new sum rules in the heavy quark limit of QCD. These sum rules imply that the elastic Isgur-Wise function $\xi (w)$ is an alternate series in powers of $(w-1)$. Moreover, one gets that the $n$-th derivative of $\xi (w)$ at $ w=1$ can be bounded by the $(n-1)$-th one, and an absolute lower bound for the $n$-th derivative $(-1)^n \xi^{(n)}(1) \geq {(2n+1)!! \over 2^{2n}}$. Moreover, for the curvature we find $\xi ''(1) \geq {1 \over 5} [4 \rho^2 + 3(\rho^2)^2]$ where $\rho^2 = - \xi '(1)$. We show that the quadratic term ${3 \over 5} (\rho^2)^2$ has a transparent physical interpretation, as it is leading in a non-relativistic expansion in the mass of the light quark. These bounds should be taken into account in the parametrizations of $\xi (w)$ used to extract $|V_{cb}|$. These results are consistent with the dispersive bounds, and they strongly reduce the allowed region of the latter for $\xi (w)$. The method is extended to the subleading quantities in $1/m_Q$, namely $\xi_3(w)$ and $\bar{\Lambda}\xi (w)$.}]
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arxiv:hep-ph/0412144
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ALEPH/OPAL data on the V-A spectral functions from hadronic tau decays are used in connection with a set of Laplace transform sum rules (LSR) for fixing the size of the QCD vacuum condensates up to dimension 18. Our results favour the ones from large-N_c QCD within the Minimal Hadronic Approximation (MHA) and show a violation of about a factor 2-5 of the vacuum saturation estimate of the dimension-six to -ten condensates. We scrutinize the different determinations of the QCD vacuum condensates using tau-decays data. After revisiting some of the existing results, we present coherent values of the condensates from different methods.
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arxiv:hep-ph/0412152
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The Drell-Yan $K$-factors for transversely polarised hadrons are examined. Since transverse spin is peculiar in having no DIS reference point, the effects of higher-order corrections on DY asymmetries are examined via a DIS definition for transversity devised using a hypothetical scalar vertex. The results suggest that some care may be required when interpreting experimentally extracted partonic transversity, particularly when comparing with model calculations or predictions.
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arxiv:hep-ph/0412159
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We present an extension of the twistor-motivated MHV vertices and accompanying rules presented by Cachazo, Svrvcek and Witten to the construction of vector-boson currents coupling to an arbitrary source. In particular, we give rules for constructing off-shell vector-boson currents with one fermion pair and n gluons of arbitrary helicity. These currents may be employed directly in the computation of electroweak amplitudes. The rules yield expressions in agreement with previously-obtained results for Z,W,\gamma^* --> qbar q + n gluons (analytically up to n=3, beyond via the Berends--Giele recursion relations). We also confirm that the contribution to a seven-point amplitude containing the non-abelian triple vector-boson coupling obtained using the next-to-MHV currents matches the previous result in the literature.
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arxiv:hep-ph/0412167
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A brief review is given of the ways of testing SUGRA unified models and a class of string models using data from precision electroweak experiments, Yukawa unification constraints, and constraints from dark matter experiments. Models discussed in detail include mSUGRA, extended SUGRA model with non-universalities within SO(10) grand unification, and effective theories with modular invariant soft breaking within a generic heterotic string framework. The implications of the Hyperbolic Branch including the focus point and inversion regions for the discovery of supersymmetry in collider experiments and for the detection of dark matter in the direct detection experiments are also discussed.
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arxiv:hep-ph/0412168
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The FLUKA Monte Carlo code, presently used in cosmic ray physics, contains packages to sample soft hadronic processes which are built according to the Dual Parton Model. This is a phenomenological model capable of reproducing many of the features of hadronic collisions in the non perturbative QCD regime. The basic principles of the model are summarized and, as an example, the associated Lambda-K production is discussed. This is a process which has some relevance for the calculation of atmospheric neutrino fluxes.
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arxiv:hep-ph/0412178
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A method to compute the scattering solutions of a spinless Salpeter equation (or a Schrodinger equation) with a central interaction is presented. This method relies on the 3-dimensional Fourier grid Hamiltonian method used to compute bound states. It requires only the evaluation of the potential at equally spaced grid points and yields the radial part of the scattering solution at the same grid points. It can be easily extended to the case of coupled channel equations and to the case of non-local interactions.
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arxiv:hep-ph/0412186
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We review some recent developments in nonperturbative studies of quantum field theory (QFT) using the Schwinger-Dyson equations formulated directly in Minkowski space. We begin with the introduction of essential ideas of the integral representation in QFT and a discussion of renormalization in this approach. The technique based on the integral representation of Green's functions is exploited to solve Schwinger-Dyson equations in several quantum field models, eg. in scalar models and in strong coupling $QED_{3+1}$ in the quenched and in the unquenched approximation. The phenomenon of dynamical chiral symmetry breaking in regularized theory is touched. In QCD, the analyticity of gluon propagator on the complex momentum square plane is exploited to continue some recent lattice data to timelike momentum axis. We find non-positive absorptive part contribution in the Landau gauge gluon propagator which is in agreement with some other new recent analyzes.
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arxiv:hep-ph/0412188
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Exclusive decays of $\chi_{cJ}(J=0,2)$ into $\phi\phi$ are investigated in the framework of perturbative quantum chromodynamics(pQCD) and $\tpz$ quark pair creation model. The results show that these two mechanisms exhibit a quite different behavior in evaluating the decay width for the $\chi_{c0}$ and $\chi_{c2}$. In pQCD method with nonrelativistic(NR) approximation, while the calculated $\cxpp{2}$ decay width is comparable with measured one, the result for the $\cxpp{0}$ decay width is suppressed and much smaller than experimental value. However, in $\tpz$ quark pair creation model, the situation is reversed: the decay width of $\cxpp{0}$ is greatly enhanced and can reproduce the large measured value, while the contribution to the $\cxpp{2}$ decay width is small. The results suggest that while the pQCD mechanism is the dominant mechanism for $\cxpp{2}$ decay, the $\tpz$ quark pair creation mechanism is the dominant one for $\cxpp{0}$ decay.
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arxiv:hep-ph/0412221
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We present a proper off-mass-shell extension of the chiral reduction formula (CHRF) proposed by Yamagishi and Zaned. This is achieved by rewriting the CHRF in a manifestly consistent form with the conventional LSZ reduction formula.
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arxiv:hep-ph/0412281
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We study the narrow decay width of low-lying penta-quark baryons in the QCD string theoryin terms of gluonic excitations. In the QCD string theory, the penta-quark baryon decays via a gluonic-excited state of a baryon and meson system, where a pair of Y-shaped junction and anti-junction is created. Since lattice QCD shows that the lowest gluonic-excitation energy takes a large value of about 1 GeV, the decay of the penta-quark baryon near the threshold is considered as a quantum tunneling process via a highly-excited state (a gluonic-excited state) in the QCD string theory. This mechanism strongly suppresses the decay and leads to an extremely narrow decay width of the penta-quark system.
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arxiv:hep-ph/0412296
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The C2/M1 ratio of the electromagnetic N->Delta(1232) transition, which is important for determining the geometric shape of the nucleon, is shown to be related to the neutron elastic form factor ratio G_C^n/G_M^n. The proposed relation holds with good accuracy for the entire range of momentum transfers where data are available.
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arxiv:hep-ph/0412421
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In the frame of flavor SU(2) Nambu--Jona-Lasinio model with $U_A(1)$ breaking term we found that, the structure of two chiral phase transition lines does not exist at low isospin density in real world, and the critical isospin chemical potential for pion superfluidity is exactly the pion mass in the vacuum.
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arxiv:hep-ph/0501024
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The amplitudes for decays of the type $B_{d,s} \to D_{s,d} D_{s,d}$, have no factorizable contributions, while $B_{d,s} \to D_{s,d} D^*_{s,d}$, and $B_{d,s} \to D^*_{s,d} D^*_{s,d}$ have relatively small factorizable contributions through the annihilation mechanism. The dominant contributions to the decay amplitudes arise from chiral loop contributions and tree level amplitudes which can be obtained in terms of soft gluon emissions forming a gluon condensate. We predict that the branching ratios for the processes $\bar B^0_d \to D_s^+ D_s^-$, $\bar B^0_d \to D_s^{+*} D_s^- $ and $\bar B^0_d \to D_s^+ D_s^{-*}$ are all of order $(2- 3) \times 10^{-4}$, while $\bar B^0_s \to D_d^+ D_d^-$, $\bar B^0_s \to D_d^{+*} D_d^- $ and $\bar B^0_s \to D_d^+ D_d^{-*}$ are of order $(4- 7) \times 10^{-3}$. We obtain branching ratios for two $D^*$'s in the final state of order two times bigger.
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arxiv:hep-ph/0501031
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Experimental results from HERA on diffractive vector meson production and their theoretical interpretation within microscopic QCD are reviewed with an emphasis on the BFKL color dipole and kt-factorization approaches.
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arxiv:hep-ph/0501034
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Within of the framework of semiclassical approximation a general formalism for deriving an effective current generating bremsstrahlung of arbitrary number of soft gluons (longitudinal or transverse ones) in scattering of higher-energy parton off thermal parton in hot quark-gluon plasma with subsequent extension to two and more scatterers, is obtained. For the case of static color centers an expression for energy loss induced by usual bremsstrahlung of lowest-order with allowance for an effective temperature-induced gluon mass and finite mass of the projectile (heavy quark), is derived. The detailed analysis of contribution to radiation energy loss associated with existence of effective three-gluon vertex induced by hot QCD medium, is performed. It is shown that in general, the bremsstrahlung associated with this vertex have no sharp direction (as in the case of usual bremsstrahlung) and therefore here, we can expect an absence of suppression effect due to multiple scattering. For the case of two color static scattering centers it was shown that the problem of calculation of bremsstrahlung induced by four-gluon hard thermal loop (HTL) vertex correction can be reduced to the problem of the calculation of bremsstrahlung induced by three-gluon HTL correction. It was shown that for limiting value of soft gluon occupation number $N_{\bf k}\sim 1/\alpha_s$ all higher processes of bremsstrahlung of arbitrary number of soft gluons become of the same order in coupling, and the problem of resummation of all relevant contributions to radiation energy loss of fast parton, arises. An explicit expression for matrix element of two soft gluon bremsstrahlung in small angles approximation is obtained.
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arxiv:hep-ph/0501062
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The features of a model interpreting the light scalar mesons as diquark-antidiquark bound states and the consequences of its natural extension to include heavy quarks are briefly reviewed.
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arxiv:hep-ph/0501077
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This is the first paper of a series that will examine the options for embedding supersymmetric orbifold-GUTs into five-dimensional N=2 Yang-Mills-Einstein supergravity theories (YMESGTs). In particular, we focus on the allowed couplings of charged hypermultiplets in the lowest dimensional reps of the gauge groups SU(5), SO(10) and E(6). Our results are within the classification of homogeneous quaternionic scalar manifolds. In the minimal coupling of a generation of bulk matter hypermultiplets, supergravity requires the field content of an SO(10) scenario. In the minimal coupling of $n$ bulk generations of matter and higgs hypermultiplets, supergravity requires the field content of an E(6) scenario. We also discuss the coupling of tensors and non-compact gaugings in 5D YMESGTs, which can serve as alternative ways to obtain four-dimensional Higgs sectors. Charged tensor couplings seem to be difficult to work with phenomenologically since a U(1) gauge factor is always required when they are present, and it is not clear if tensors can be put in unified multiplets with other fields, if this is desired. This seems to imply that tensor coulpings in GUT scenarios may be better suited in higher dimensional settings. The non-compact gaugings discussed here are simple, and offer a novel unification scenario in which the supergravity and vector multiplets are connected by gauge transformations. The main points are summarized in tables and the conclusion. Although the discussion is in the spirit of a "bottom-up" approach, M-theory is taken as a motivating background.
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arxiv:hep-ph/0501091
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Different approaches to describe Compton scattering and the polarizability of the nucleon have been discussed up to now. We show that the most appropriate ones are provided by non-subtracted dispersion theories of the fixed-$t$ and fixed-$\theta$ types, where the properties of these two versions are complementary so that advantage can be taken from both of them. In the frame of fixed-$t$ dispersion theory it was possible to precisely reproduce experimental differential cross sections obtained for the proton in a wide angular range and for energies up to 1 GeV. At energies of the first resonance region and below, precise values for the electromagnetic polarizabilities and spin-polarizabilities have been determined for the proton and the neutron. The data show that diamagnetism is a prominent property of nucleon structure, where the underlying mechanism is a $t$-channel $\sigma$-meson exchange. A similar mechanism is responsible for the backward spin-polarizability where the relevant meson is the $\pi^0$. It is a challenge for further research to integrate the $\sigma$ and $\pi^0$ intermediate states into a consistent description of the structure of the nucleon.
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arxiv:hep-ph/0501167
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This paper is withdrawn by the authors, a better version is available as hep-ph/0505139.
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arxiv:hep-ph/0501219
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We consider production of prompt photons in high energy gold-gold and deuteron-gold collisions in the forward rapidity region of RHIC ($y \sim 3.8$). In this kinematics, the projectile partons typically have large $x_{bj}$ while the target partons are mostly at very small $x_{bj}$ so that the primary partonic collisions involve valence quarks from the projectile and gluons from the target. We take the target nucleus to be a Color Glass Condensate while the projectile deuteron or nucleus is treated as a dilute system of partons. We show that the photon production cross section can be written as a convolution of a quark-nucleus scattering cross section, involving a quark anti-quark dipole, with the Leading Order quark-photon fragmentation function. We consider different models of the quark anti-quark dipole and show that measurement of photons in the forward rapidity region at RHIC can distinguish between different parameterizations of the dipole cross section as well as help clarify the role of parton coalescence models in hadron production at RHIC.
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arxiv:hep-ph/0501222
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We point out that in the case of a heavy top quark T, present in the Littlest Higgs model (LH), and the t-T mixing parameter x_L > 0.90 the contribution to B^0_{d,s}-\bar B^0_{d,s} mixing from box diagrams with two T exchanges cannot be neglected. Although formally O(v^4/f^4) with v = 246 GeV and f > 1 TeV, this contribution increases linearly with x_T = m_T^2/M^2_W and with x_T = O(f^2/v^2) constitutes effectively an O(v^2/f^2) correction. For x_L ~ 1, this contribution turns out to be more important than the genuine O(v^2/f^2) corrections. In particular it is larger than the recently calculated O(v^2/f^2) contribution of box diagrams with a single T exchange that increases only logarithmically with x_T. For x_L = 0.95 and f/v = 5,10,15, the short distance function S governing the B^0_{d,s}-\bar B^0_{d,s} mixing mass differences \Delta M_{d,s} receives 56%, 15% and 7% enhancements relative to its Standard Model (SM) value, implying a suppression of the CKM element V_td and an enhancement of \Delta M_s. The short distance functions X and Y, relevant for rare K and B decays, increase only logarithmically with x_T. With the suppressed V_td, K->\pi\nu\bar\nu and B_d->\mu^+\mu^- decays are only insignificantly modified with respect to the SM, while the branching ratio Br(B_s->\mu^+\mu^-) receives 66%, 19% and 9% enhancements for x_L = 0.95 and f/v = 5,10,15, respectively. Similar enhancement is found for Br(B_s->\mu\bar\mu)/Br(B_d->\mu\bar\mu).
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arxiv:hep-ph/0501230
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We describe a chiral formalism for processes involving both energetic hadrons and soft Goldstone bosons, which extends the application of soft-collinear effective theory to multibody B decays. The nonfactorizable helicity amplitudes for heavy meson decays into multibody final states satisfy symmetry relations analogous to the large energy form factor relations, which are broken at leading order in Lambda/mb by calculable factorizable terms. We use the chiral effective theory to compute the leading corrections to these symmetry relations in B -> M_n pi ell\bar\nu and B -> M_n pi e+e- decays.
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arxiv:hep-ph/0501237
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