Weak decays of 4He-Lambda

We measured the lifetime and the mesonic and non-mesonic decay rates of the 4He-Lambda hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K- beam on a liquid 4He target by the reaction 4He(K-,pi-)4He-Lambda. The 4He-Lambda lifetime was directly measured using protons from Lambda p -> n p non-mesonic decay (also referred to as proton-stimulated decay) and was found to have a value of tau = 245 +/- 24 ps. The mesonic decay rates were determined from the observed numbers of pi-'s and pi0's as Gamma_pi-/Gamma_tot = 0.270 +/- 0.024 and Gamma_pi0/Gamma_tot = 0.564 +/- 0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as Gamma_p/Gamma_tot = 0.169 +/- 0.019 and Gamma_n/Gamma_tot <= 0.032 (95% CL), respectively. The effects of final-state interactions and possible 3-body Lambda N N decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the non-mesonic branching fractions. The implications of the results of this analysis were considered for the empirical Delta I = 1/2 rule and the decay rates of the 4H-Lambda hypernucleus.Comment: 15 pages, 11 figures, published in PRC, revised content to match published versio

Vector analyzing power iT11 in pi d elastic scattering at 49 MeV

Measurements of the vector analyzing power iT11 in \u3c0d elastic scattering at 49 MeV have been performed using a dynamically polarized target and a magnetic spectrometer. Data at seven \u3c0+ laboratory scattering angles between 50\ub0 and 130\ub0 were taken together with a complementary measurement at 60\ub0 for \u3c0-d elastic scattering. In general, we find agreement with models that include the \u3c0N P11 amplitude and disagreement with models that exclude or suppress it

Role of the pi n P(11) interaction in pi d elastic scattering at 50-MeV

Measurements of the vector analyzing power iT11 in \u3c0+d elastic scattering at 50 MeV have been made at pion laboratory scattering angles between 60\ub0 and 130\ub0 using a dynamically polarized target and a magnetic spectrometer. In contrast to measurements of spin observables at higher energies, we find agreement with models that include the \u3c0N P11 amplitude and disagreement with models that exclude or suppress it