Isospin and the tau hadronic decay modes

Isospin constraints onτ decay modes are revisited with a special interest for the low branching ratio channels. It is shown that dominance of the vector current in the channel is suggested by the present data and that some discrepancies exist betweenτ partial width ande ⁺ e ⁻ cross-section measurements in the 6π channel.     

Asymptotic chiral symmetry,meson masses and decay constants

Weinberg’s spectral function sum rules are examined to study the axial vector mass spectrum at the level of SU(4). New mass relations and general mass constraints are derived to predict the masses of the charmed axial vector mesons and theI=0 pseudoscalar decay constants.     

Precise measurement of B meson lifetimes with hadronic decay final states

The lifetimes of the B(0) and B- mesons are extracted from 29.1 fb(-1) of data collected with the Belle detector at the KEK B factory. A fit to the decay length differences of neutral and charged B meson pairs, measured in events where one of the B mesons is fully reconstructed in several hadronic modes, yields tau(B(0)) = 1.554+/-0.030(stat)+/-0.019(syst) ps, tau(B-) = 1.695+/-0.026(stat)+/-0.015(syst) ps, and tau(B-)/tau(B(0)) = 1.091+/-0.023(stat)+/-0.014(syst).     

Ratios ofB andD meson decay constants with heavy quark symmetry

SU(3) flavor symmetry allows the decay constantsf _{D 1} andf _{D 2} as well asf _{B 1} andf _{B 1} to be equal. But due toSU(3) flavor symmetry breaking the ratiosf _{B 1}/f _{B 2} andf _{D 1}/f _{D 2} are deviated from unity. We have estimated these ratios in the heavy quark effective theory and obtainedf _{B 1}/f _{B 2}=0.93,f _{D 1}/f _{D 2}=0.94 and the double ratio (f _{B 1}/f _{B 2})/(f _{D 1}/f _{D 2})=0.99.     

Running mass m s at low scale from the heavy-light meson decay constants

It is shown that a 25(20)% difference between the decay constants $f_{D_s } $ ( $f_{B_s} $ ) and f _D (f _B ) occurs due to large differences in the pole masses of the s and d(u) quarks. The values η _D = $f_{D_s } $ /f _D ～ 1.23(15), recently observed in the CLEO experiment, and η _B = $f_{B_s } $ /f _B ～ 1.20, obtained in unquenched lattice QCD, can be reached only if, in the relativistic Hamiltonian the running mass, m _s at low scale is m _s (～0.5 GeV) = 170–200 MeV. Our results follow from the analytical expression for the pseudoscalar decay constant f _P based on the path-integral representation of the meson Green’s function.     

Charmless hadronic decays of B mesons to a pseudoscalar and a tensor meson

We study two-body charmless hadronic decays of B mesons to a pseudoscalar meson (P) and a tensor meson (T) in the frameworks of both flavor SU(3) symmetry and generalized factorization. Certain ways to test the validity of the generalized factorization are proposed, based on the flavor SU(3) analysis. We present a set of relations between a flavor SU(3) amplitude and the corresponding amplitude in the generalized factorization which bridge both approaches in decays. The branching ratios and CP asymmetries are calculated using the full effective Hamiltonian including all the penguin operators and the form factors obtained in the non-relativistic quark model of Isgur, Scora, Grinstein and Wise. We identify the decay modes in which the branching ratios and CP asymmetries are expected to be relatively large. Received: 6 July 2001 / Revised version: 8 October 2001 / Published online: 30 November 2001     

A model for vector-vector-tensor meson coupling constants

By the joint assumptions of vector-meson dominance for the electromagnetic current and tensor-meson dominance for the energy-momentum tensor a model for the vector-vector-tensor meson vertex is developed, including also the coupling of two photons to a tensor meson and the coupling of one photon to the vector-tensor meson system. In its simplest possible form the model has no undetermined parameters. Tentatively the vertex is applied to compute a tensor-meson exchange contribution to vector-meson scattering from an unpolarized target, and s-channel helicity conservation is found at large energies.     

Leptonic and hadronic decay rates of winos

We show that, in wide classes of supergravity models, the ratio of the leptonic and hadronic decay widths of winos is very different from that of heavy leptons which decay via the standard weak interaction. For example, it becomes 20% in one case and 70% in another case, while it will be 36% in case of heavy leptons. The production of wino pairs in next e⁺e^- experiments will be tested by the ratio of leptonic and hadronic final states.     

Photon and light meson production in hadronic Z^0decays

The inclusive production rates and differential cross-sections of photons and mesons with a final state containing photons have been measured with the OPAL detector at LEP. The light mesons covered by the measurements are the , , , , and a. The particle multiplicities per hadronic Zdecay, extrapolated to the full energy range, are: where the first errors are statistical and the second systematic. In general, the results are in agreement with the predictions of the JETSET and HERWIG Monte Carlo models. Received: 9 April 1998 / Published online: 12 August 1998     

Rho meson propagation and dilepton enhancement in hot hadronic matter

A realistic model for the free rho meson with coupling to two-pion states is employed to calculate the rho propagator in a hot and dense hadron gas. The medium modifications are based on hadronic rescattering processes: intermediate two-pion states are renormalized through interactions with surrounding nucleons and deltas, and rho meson scattering is considered off nucleons, deltas, pions and kaons. Constraints from gauge invariance as well as the full off-shell dynamics of the interactions are accounted for. Within the vector dominance model we apply the resulting in-medium rho spectral function to compute e⁺e⁻ production rates from π⁺π⁻ annihilation. The calculation of corresponding e⁺e⁻ spectra as recently measured in central collisions of heavy-ions at CERN/SpS energies gives reasonable agreement with the experimental data.     

Semileptonic decay of the B meson

Using the CUSB detector we have measured the production of electrons from the decay B→eνX. We obtain a branching ratio for B→eνX of (13.2±0.8±1.4)%. The observed energy spectrum of the electrons implies that the coupling (bc)W dominates over (bu)W. An upper limit Γ(B→eνX_u)/Γ(B→eνX_c)<5.5% at 90% confidence level is obtained, where X_c contains a c-quark and X_u contains no charmed particles.