No Arabic abstract
The tau -> (omega, phi)P^- u decays, where P^-=pi^-, K^-, are considered within a phenomenological model with dominance of meson intermediate states. We assume SU(3) flavor symmetry to fix some of the unknown strong interaction couplings. Our predictions for the tau -> phi (pi^-, K^-) u branching fractions are in good agreement with recent measurements of the BABAR and BELLE Collaborations.
We study the effects induced by excited leptons on the leptonic tau decay at one loop level. Using a general effective lagrangian approach to describe the couplings of the excited leptons, we compute their contributions to the leptonic decays and use the current experimental values of the branching ratios to put limits on the mass of excited states and the substructure scale.
We search for lepton-flavor-violating tau decays into three leptons (electron or muon) using 535 fb-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. No evidence for these decays is observed, and we set 90% confidence level upper limits on the branching fractions of (2.0-4.1)x10^-8. These results improve upon our previously published upper limits by factors of 4.9 to 10.
The high accuracy $phi $-meson photoproduction data from the CLAS experiment in Hall~B of Jefferson Laboratory allow us to determine the near-threshold total cross section of the $gamma ptophi p$ reaction and use it for evaluating the $phi p$ scattering length $alpha_{phi p}$. These data result in an absolute value of $|alpha_{phi p}| = (0.063pm 0.010)$~fm, which is smaller than the typical hadron size. A comparative analysis of $alpha_{phi p}$ with the previously determined scattering lengths for $omega p$ and $J/psi p$ from the A2 and GlueX experiments is performed.
We compute the mass shifts and mixing of the Omega and Phi mesons at finite temperature due to scattering from thermal pions. The Rho and b_1 mesons are important intermediate states. Up to a temperature of 140 MeV the Omega mass increases by 12 MeV and the Phi mass decreases by 0.6 MeV. The change in mixing angles is negligible.
The cross sections and polarization components of the $tau$ leptons produced in the charged current induced quasielastic $ u_tau~(bar u_tau) - N$ scattering have been studied. The theoretical uncertainties arising due to the use of different vector form factors and the axial dipole mass in the axial vector form factor have been investigated. Due to the high mass of $tau$ lepton, the contributions from the term containing pseudoscalar and second class current form factors are non-negligible and contribute to the uncertainty in the cross section and polarization observables as these form factors are not well known. In view of the currently proposed experiments by DUNE, SHiP and DsTau collaborations to study the production of $tau$ lepton, an updated calculation of the cross sections and polarizations of tau leptons in the case of quasielastic production have been done and the numerical results have been presented along with a discussion of the theoretical uncertainties.