Spin observables in the pn→pΛpn \to p \Lambda reaction

The T matrix of the LambdaN-> NN reaction, which is a strangeness changing weak process, is derived. The explicit formulas of the spin observables are given for s-wave p-Lambda final states which kinematically corresponds to inverse reaction of the weak nonmesonic decay of Lambda hypernuclei. One can study interferences between amplitudes of parity- conserving and violating, spin- singlet and triplet and isospin- singlet and triplet. Most of them are not available in the study of the nonmesonic decay. They clarify structure of the reaction and constrain strongly theoretical models for weak hyperon nucleon interaction.Comment: 7pages,ReVTeX,no figure

Nonmesonic Hyperon Weak Decay Spectra in Λ12^{12}_{\Lambda}C}

We study the nonmesonic weak decay (NMWD) $\Lambda N \to nN$ of the ${}^{12}_{\Lambda} C$ hypernucleus induced by the nucleon $N=n,p$ with transition rate $\Gamma_N$. The nuclear process is described by the interplay of two models; one describing the NMWD of hyperon $\Lambda$ in the nuclear environment, and the other taking into account the Final State Interaction (FSI) of the two outgoing nucleons with the residual nucleus. The first one is done in the framework of the Independent-Particle Shell-Model (IPSM), with the decay dynamics represented by the exchange of $\pi+ \eta+ K+\rho+\omega+K^*$ mesons with usual parametrization. For the second one is used a time dependent multicollisional intranuclear cascade schema (implemented in the CRISP code - Collaboration Rio-S\~ao Paulo). The results obtained for inclusive and exclusive kinetic energy spectra, and the angular correlation are compared with recent data from KEK and FINUDA experiments. The calculated ratio $(\Gamma_n / \Gamma_p)^{\partial{\tiny FSI}}$, between the numbers of emitted back-to-back $nn$ and $np$ pairs, is in good agreement with the experimental data.Comment: Proceedings of the International Nuclear Physics Conference 2010, Vancouver, BC - Canada 4-9 Jul 201

First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell {\Lambda}-Hypernuclei

Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the ratio of the two-nucleon and the one-proton induced decay widths, Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p = 0.50 +/- 0.24, and from neutron and proton coincidence spectra, Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with previously published ones. With these values, a method is developed to extract the one-proton induced decay width in units of the free Lambda decay width, Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by exploiting only experimental data, under the assumption of a linear dependence on A of the Final State Interaction contribution. This is the first systematic determination ever done and it agrees within the errors with recent theoretical calculations.Comment: 16 pages, 3 figures, 2 table

Delayed clusters accompanying nonmesonic weak decay of the Λ\Lambda-hypernuclei: a clue to nonleptonic processes

The nonmesonic decay of $\Lambda$-hypernuclei provides access to the nonleptonic weak decay process $\Lambda N \to NN$, which is achievable only through the observation of hypernuclear ground-state decays. We continue the discussion of some specific cases which make it possible to detect a few exclusive transitions, namely, the stripping of nucleon from the ground state results in a resonance state decaying via emission of two clusters. Delayed clusters accompanying weak decay of light hypernuclei give a unique information on spin dependence of the weak decay matrix elements.Comment: Presented at International Bogolyubov Conference "Problems of Theoretical and Mathematical Physics" (dedicated to the 100th anniversary of the birth of N.N.~Bogolyubov) Dubna, Russia, August 21 - 27, 200