Two-body non-leptonic decays on the lattice

We show that, under reasonable hypotheses, it is possible to study two-body non-leptonic weak decays in numerical simulations of lattice QCD. By assuming that final-state interactions are dominated by the nearby resonances and that the couplings of the resonances to the final particles are smooth functions of the external momenta, it is possible indeed to overcome the difficulties imposed by the Maiani-Testa no-go theorem and to extract the weak decay amplitudes, including their phases. Under the same assumptions, results can be obtained also for time-like form factors and quasi-elastic processes.     

Soft gluonic effects in non-leptonic decays

The effects of soft gluonic corrections to non-leptonic processes are considered. Implications for hyperon, charmed baryon and heavy meson decays are discussed. Methods to disentangle the effects of final-state gluons, initial-state gluons and other soft effects such as final-state hadronic interactions are given.     

Exploiting non-leptonic decays in top searches

We show that a massive use of statistical event correlations, learned by means of Monte Carlo event generators, makes it feasible to employ a pure jet signature in top quark searches. A relevant ingredient for that is also the less diffuse angular distribution of energy deposition and of particles in top events, which are dominated by quark jets. On the other, hand, we show that the utilization of mass cuts on jet combinations to identify top non-leptonic decays meets severe limitations already at the parton level, largely because of QCD radiation.     

Quark dynamics and the weak non-leptonic decays of K and D mesons

Quark model predictions for K → 2π and D → Kπ decays were investigated in dynamical frameworks based on the separable approximation (SA), current algebra (CA), current algebra modified for the meson moment dependence (CAC) and current algebra with final-state interactions (CAF). Relativistic and non-relativistic quark model predictions were compared. The effective weak hamiltonian was modified by changing the relative strengths of its flavour $\text{20}\text{and}\text{84}$ parts. All these approaches were also applied to hyperon and $\text{Ω}{}^{\mathrm{?}}$ non-leptonic decays. When using standard QCD enhancement, the best approximation for K → 2π (CAC) works poorly with D → Kπ. The best approximatiob for D→Kπ (CAF) fails in the case of K → 2π. Only CAC with the $\text{84}$ piece of the hamiltonian quenched might be in agreement with studied weak decays.     

Final states in non-leptonic bottom meson decays

We use Isospin-Statistical Models to study many body final states in the non-leptonic decays of bottom mesons in the framework of the Kobayashi-Maskawa weak current. Estimates of charge multiplicities, branching ratios and inclusive hadron momentum distributions are presented.     

Ω− non-leptonic decays

Non-leptonic decay rates for Ω^? are calculated in a model where strong interactions introduce new ΔI = 1/2 operators in the effective hamiltonian. Both Ω^?→Ξ^0,?π^?,0 and Ω^?→Λ⁰K^? are predicted to be nearly parity conserving. ΔI = 1/2 contributions are found to dominate the sum of the pionic rates, while ΔI = 3/2 contributions are non-negligible in each of them. Rough agreement in magnitude with experimental data is obtained.     

Enhancement of non-leptonic decays of charmed particles

We suggest that non-leptonic decays of charmed particles are enhanced over semi-leptonic decays by a sizeable factor, in analogy with the situation encountered in strange particle decays. This conjecture is verified in a model octet enhancement based on asymptotically-free gauge theories of strong interactions. Arguments are given to support a specific SU(3) behavior of the enhanced part of the non-leptonic Hamiltonian for charmed particle decays. Consequent selection and intensity rules are discussed.     

Exclusive decays of upsilons

The leading order contributions to decay rates of two-meson decays of an upsilon, in particular Y → K⁺K^?, D⁺D^?, are calculated using perturbative quantum chromodynamics. An interesting enhancement of Y → D⁺D^? is found. The branching ratio of Y → D⁺D^? to the upsilon's total hadronic width is larger than that of Y → K⁺K^? by two orders of magnitude.     

Quark dynamics and non-leptonic weak decays of K and D mesons (II)

This paper presents an investigation of quark dynamics, which, combined with soft-gluonic corrections, leads to fits of K → 2π (D → Kπ) decay amplitudes.     

A detailed analysis ofD-,D s - andB-meson transition form factors and the determination of |V cb |

We study various transition form factors in semi-leptonic decays ofD-,D _s -,B- andB _s -mesons using the pole dominance assumption. The vector current form factor is found to have only a negligible contribution to the decay rates involving pseudoscalar to vector transitions. In view of this fact we evaluate the form factors from present experimental data on the exclusive semi-leptonic decay rateΓ and the ratioΓ _l /Γ _T of the longitudinal and transverse partial decay rates. Some non-leptonic two-body decay rates are also investigated using the factorization ansatz. Consistency with the semi-leptonic decays is found. The transition form factors of theD- andD _s -mesons are found to contradict the predictions of quark model. In contrast, the experimental data on the transition form factors ofB-mesons are found to be consistent with the quark model predictions. The KM matrix element |V _cb | is determined to be |V _cb |=0.040±0.010, a value somewhat smaller than is usually chosen.     

Final-state interactions with inelastic effects in non-leptonic hyperon decays

A recent work by Reid and Trofimenkoff seemed to indicate that a satisfactory model using current algebra, PCAC and the soft-pion limit can be formulated to obtain the s- and p-wave amplitudes of the non-leptonic decays of Λ and Σ, as well as the $\text{ΔI =}\text{1}\text{2}$rule if final state interactions are included. We demonstrate in this paper that by including inelastic effects in the final-state interactions (that is without the usual approximation of elastic unitarity) the results bring us back full circle. The disagreement between theory and experiment for the p-wave amplitudes still persists and no significant suppression of the $\text{I =}\text{3}\text{2}$ state for the final particles can be predicted.     

Possibility of CP violation in the cascade non-leptonic decays

There is more than one parameter expressing CP violation in the non-leptonic hyperon decays. The recent experimental results provide us with indications that CP conservation may not be valid for the Ξ decays. Especially for the Ξ dacays this is not due to the deviations from the exact ΔI=1/2 rule.     

Difficulties with a quantum chromodynamic formulation of non-leptonic decays

A new model for non-leptonic weak interactions has been recently proposed which is based on the introduction of a right handed charm and strangeness changing weak current. We show that this model can be made to fit the data on B→B′π and B→B′γ decays only if several ad hoc assumptions of large SU₃ breaking are made. We also review the success of the conventional Cabibbo current-current model in fitting all of the non-leptonic data.     

Weak decays of J/ψ: the non-leptonic case

In our previous study, we calculated the transition form factors of J/ψ→D^(*) _(s) using the QCD sum rules. Based on the factorization approximation, the form factors obtained can be applied to evaluate the weak non-leptonic decay rates of J/ψ→D^(*) _(s)+M, where M stands for a light pseudoscalar or vector meson. We predict that the branching ratio for inclusive non-leptonic two-body weak decays of J/ψ, which are realized via the spectator mechanism, can be as large as 1.3×10^-8; in particular, the branching ratio of J/ψ→D^*± _s+ρ^∓ can reach 5.3×10^-9. Such values will be marginally accessed by the ability of BESIII, which will begin running very soon. PACS  13.20.Gd; 13.25.Gv