Constant-cutoff approach to magnetic moments of hyperons

We calculate the magnetic moments of hyperons in the simplified CHK model, with the stabilizing term proportional toe ^–2 omitted, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishna, Sanyuk, Schechter, and Subbaraman, which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. Thus we show that there is qualitative agreement with the experimental values and the accuracy is similar to that obtained with the complete CHK model.     

Pion asymmetry in the three-body radiative decays of polarized hyperons

We have calculated the energy dependence of pion asymmetry relative to the direction of hyperon polarization in the three-body radiative decays of polarized hyperons, using the inner bremsstrahlung model. We find that in the low pion energy region, the pion asymmetry in the radiative decay relative to the non-radiative decay is kinematically enhanced. For certain decays, this effect could be exploited experimentally to obtain additional information about the properties of the hyperons.     

Constituent gluons and a new mechanism for radiative weak decays of hyperons

An effective quark-gluon-photon operator is considered as the mechanism for radiative weak decays of hyperons. The coefficient function is unsuppressed by GIM cancellations, suggesting a significant decay rate, and a substantial amount of parity violation (large decay asymmetry) is expected. Attempted model calculations confirm this last feature but fail to provide an adequate absolute decay rate.     

Mixing of pseudoscalar mesons and M1 radiative decays

We discuss the mixing of pseudoscalar mesons, in particular SU(3) breaking effects, based on ideas abstracted from QCD. The admixtures of η and η′ in η_c are calculated and utilized to estimate the M1 radiative decays ψ → ηγ, η′γ. A reasonably consistent picture emerges for these decays as well as others involving only the light quarks.     

Weak radiative decays of hyperons within theSU(6) broken quark-diquark model

In view of persisting discrepancy between experimental and theoretical results, specially in the weak radiative decays of∑ ⁺ andΞ ⁰, we analyse these decays within the framework of the QCD inspired quark-diquark model. On introducing a slightSU(6) breaking we obtainα(∑ ⁺→p+γ)≈?0.9 which is in excellent agreement with experimental value. Other decays are also improved in this scheme.     

A “unified” phenomenological approach to the non-leptonic decays of hyperons

In analogy with the pole model for the non-leptonic hyperon decays, a new model is proposed, and which gives satisfactory results for all the non-leptonic decays of the hyperons (B→B′π,B→B′γ andB→B′πγ).     

A chiral Lagrangian approach to radiative vector meson decays

The radiative decays of vector mesons are considered from an effective Lagrangian point of view. It is pointed out that the crucial question of flavour symmetry breaking in these decays has an almost unique solution in this approach; this solution involves non orthogonal mixing of the ω and the π. The decay rates are calculated and compared with experiment.     

Radiative corrections to semileptonic decays of charged hyperons

We have studied the radiative corrections to the lepton energy spectrum in semileptonic hyperon decays. The calculation is performed relativistically for the baryons as well as for the leptons, under the assumption of the effective current-current interaction of the V-?A type for the baryonic part. We obtain the explicit formula of radiative corrections to the lepton energy spectrum which we can exactly evaluate in case of charged hyperon decays. Numerical values of the radiative corrections to the decays rate and the shape of the lepton energy spectrum are also given for some decay modes. It is shown that the spectral shape is little affected by the radiative corrections.     

Measurement of psi2S radiative decays

Using 14 x 10(6) psi(2S) events accumulated at the BESII detector, we report first measurements of branching fractions or upper limits for psi(2S) decays into gammapp, gamma2(pi+pi-), gammaKS0K+pi-+c.c., gammaK+K-pi+pi-, gammaK*0K-pi++c.c., gammaK*0K*0, gammapi+pi-pp, gamma2(K+K-), gamma3(pi+pi-), and gamma2(pi+pi-)K+K- with the invariant mass of hadrons below 2.9 GeV/c2. We also report branching fractions of psi(2S) decays into 2(pi+pi-)pi0, omegapi+pi-, omegaf2(1270), b1+/-pi-/+, and pi02(pi+pi-)K+K-.