Radiative decays of heavy baryons with heavy quark symmetry

The decay widths for the radiative decays of heavy baryons are calculated in the heavy quark effective theory. Introducing the interpolating fields for heavy baryons we obtain the transition matrix elements and the corresponding decay widths. Considering theSU(6) flavor-spin wave functions for heavy baryons, the coupling constants are calculated in the nonrelativistic quark model. Since the masses of the heavy baryons are not available, we have taken the predicted bag model masses. We find our results are quite different from that of the heavy quark bag model calculations.     

Polarization and forward-backward asymmetry of \Lambda baryons in hadronic Z^0 decays

The longitudinal polarization, the transverse polarization, and the forward-backward asymmetry of baryons, have been measured using a sample of 4.34 million hadronic decays collected with the OPAL detector at LEP between 1990 and 1995. These results are important as an aid to the understanding of hadronization mechanisms. Significant longitudinal polarization has been observed at intermediate and high momentum. For ( 0.3, the longitudinal polarization has been measured to be (stat) 5.2 (syst)%. We have observed no transverse polarization. A significant forward-backward asymmetry has been measured and can be described by a JETSET model. Received: 30 July 1997     

Radiative and non-radiative decays from the excited state of Ti3+ ions in oxide crystals

The fluorescence spectra of Ti³⁺ in Y₃Al₅O₁₂ (YAG), Al₂O₃ (sapphire), YAlO₃ (YAP) observed at 10 K are composed of zero-phonon lines accompanied by the broad vibronic sidebands. The temperature dependence of the fluorescence lifetime and of the total intensity of the broadband measured in YAG and Al₂O₃ indicate that the radiative decay times from the excited states are nearly constant in the range 10–300 K. This demonstrates that the broadband radiative emissions in Ti³⁺:YAG and Ti³⁺:Al₂O₃ are due to magnetic dipole transitions or to electric dipole transitions induced by static odd-parity distortion, respectively. The decrease of the fluorescence lifetime with increasing temperature in Ti³⁺:YAG and Ti³⁺:Al₂O₃ is due to non-radiative decay from the excited state which occurs through phonon-assisted tunnelling between the excited and ground states. The radiative decay of Ti³⁺:YAP is enhanced with increasing temperature, indicating that radiative decay rate contains a term associated with odd-parity phonons. Nevertheless, a non-radiative decay rate of 3.6 × 10⁴ s^–1 observed in the temperature range 10–300 K is due to excited state absorption, which depopulates the excited state and quenches the fluorescence at the laser wavelength.     

Radiative decays of radially excited pseudoscalar mesons in the extended Nambu-Jona-Lasinio model

In the extended NJL model the radiative decay widths of the radially excited states of the pseudo-scalar π, η, and η′ mesons are calculated. The predictions for the decay widths of the processes π(1300) → (ρ⁰, ω)γ, η(1295) → (ρ⁰, ω, φ)γ, and η(1475) → (ρ⁰, ω, φ)γ are given. Nowadays, there are no solid experimental data for these processes. The comparison of the results obtained in the framework of the standard and the extended NJL models for decays of the ground states of mesons is given. It is shown that these calculations correspond to each other and are also in satisfactory agreement with experimental data. This allows one to expect that the extended NJL can give reliable predictions for the excited states of mesons.     

Leptonic decays of baryons

Formulae are obtained for the differential decay rate, lepton spectrum, and partial lifetime for the leptonic decays of baryons, which cover effects down to the order of one percent. A weak, linearq ²-dependence of the form factors is included, which should be a sufficiently good approximation in the physicalq ²-range allowed in the decays. The one percent discrepancy arises as a consequence of the above-mentioned approximation to the form factors, whose value and slope atq ²=0 are left open in the formulae;SU(3) symmetry, CVC, and PCAC yield an estimate for these parameters.     

Dipion decays of heavy baryons

Compared with the charmed baryons, the bottom baryons are not very well known, either experimentally or theoretically. In this paper, we investigate the dipion strong decays of the P-wave and D-wave excited bottom baryons in the framework of the QPC model. We also extend the same analysis to the charmed baryons.     

Semi-leptonic decays of charmed baryons

We present estimates of semi-leptonic decays of the charmed $\text{1+}\text{2}$ baryons, members of the SU(3) 3¹ and 6 multiplets, into ordinary $\text{1+}\text{2}\text{and}\text{3+}\text{2}$ baryons. We give general expressions for decay rates and the mass M(B⁺?) spectra. We relate the relevant form factors for the $\text{1+}\text{2}\text{→}\text{1+}\text{2}$ transitions to the electromagnetic ones by means of CVC and SU(4). The form factors for $\text{1+}\text{2}\text{→}\text{3+}\text{2}$ transitions are related through SU(4) to those measured in Δ production. We discuss the dependence of the results on the masses of charmed baryons. The $\text{1+}\text{2}\text{→}\text{1+}\text{2}$ and $\text{1+}\text{2}\text{→}\text{3+}\text{2}$ transitions turn out to be dominant for the decays of the multiplets 3¹ and 6, respectively. The partial lifetimes are O(10^?10 ? 10^?14) sec as the masses of the decaying baryons are varied from 2 to 2.9 GeV. Possible ways of getting an idea about the masses of the charmed baryons are given.     

Weak radiative decays of baryons

Using recent experimental baryon weak radiative decay data for the fiveB→B′γ decays, we employ the pole model self-consistently to extract the reduced matrix elements 〈B′|H _w|B〉. The resulting pattern is compatible with weak pion decaysB→B′π and also with the quark model.