A detailed study of fragmentation of vector mesons at the next-to-leading order (NLO) is given for e^+ e^- scattering. A model with broken SU(3) symmetry uses three input fragmentation functions alpha(x, Q^2), beta(x,Q^2) and gamma(x,Q^2) and a stran
geness suppression parameter lambda to describe all the light quark fragmentation functions for the entire vector meson octet. At a starting low energy scale of Q_0^2 = 1.5 GeV^2 for three light quarks (u, d, s) along with initial parameterization, the fragmentation functions are evolved through DGLAP evolution equations at NLO and the cross-section is calculated. The heavy quarks contribution are added in appropriate thresholds during evolution. The results obtained are fitted at the momentum scale of sqrt{s}= 91.2 GeV for LEP and SLD data. Good-quality fits are obtained for rho, K^*, omega and phi mesons, implying the consistency and efficiency of this model that explains the fragmentation functions of vector mesons both at the leading and the next to leading order in QCD. Keywords: vector meson, fragmentation, SU(3) symmetry, NLO .
We follow up on the analysis of Mecozzi and Bellini (arXiv:1110:1253v1) where they showed, in principle, the possibility of superluminal propagation of neutrinos, as indicated by the recent OPERA result. We refine the analysis by introducing wave pac
kets for the superposition of energy eigenstates and discuss the implications of their results with realistic values for the mixing and mass parameters in a full three neutrino mixing scenario. Our analysis shows the possibility of superluminal propagation of neutrino flavour in a very narrow range of neutrino parameter space. Simultaneously this reduces the number of observable events drastically. Therefore, the OPERA result cannot be explained in this frame-work.
Inclusive hadro production in e^+ e^- annihilation processes is examined to study the fragmentation process. A broken SU(3) model is used to determine the quark and gluon fragmentation functions of octet vector mesons, rho and K^*, in a simple way wi
th an SU(3) breaking parameter lambda. These are expressed in terms of just two light quark fragmentation functions, V(x, Q2) and gamma(x, Q2) and the gluon fragmentation function Dg(x, Q2). These functions are parameterized at the low input scale of Q0^2 = 1.5 GeV2, evolved through LO DGLAP evolution including charm and bottom flavour at appropriate thresholds, and fitted by comparison with data at the Z-pole. The model is extended with the introduction of a few additional parameters to include a study of singlet--octet mixing and hence omega and phi fragmentation. The model gives good fits to the available data for x >~ 0.01, where x is the scaled energy of the hadron. The model is then applied successfully to omega, phi production in pp collisions at the Relativistic Heavy Ion Collider, RHIC; these data form an important base-line for the study of Quark Gluon Plasma in heavy nucleus collisions at RHIC, and also in future at the LHC.
