Using a large-acceptance germanium detector array (Hyperball), we measured a γ-ray spectrum in coincidence with production of 7ΛLi bound states in the 7Li(π+,K+) reaction. We observed a γ-ray peak at ...429 keV due to the transition from the first excited state of 7Be produced by the weak decay of 7ΛLi, 7ΛLi→7Be∗(1/2−,429 keV)+π−. From the yield of this γ-ray, the branching ratio of the 7ΛLi weak decay to 7Be∗(429) was obtained to be (6.0+1.3−1.6)×10−2. Compared with theoretically calculated values of the partial decay rates, the measurement indicates that the ground-state spin of 7ΛLi is 1/2 but not 3/2.
Cross sections for inelastic scattering of 635 and 715 MeV/
c K
+ from
12C are compared with DWIA calculations in order to check for possible density-dependent effects on K
+-nucleon cross sections ...within nuclei. New fits to 715 MeV/
c K
+ scattering spectra from
6Li give elastic and inelastic cross sections and permit an evaluation of the density dependence of these effects. The same DWIA methods are also used to estimate quadrupole non-central contributions to elastic K
+ scattering from the 1
+ ground state of
6Li, and these are found to be very small.
The 1H(e,e′K+)Λ reaction was studied as a function of the squared four-momentum transfer, Q2, and the virtual photon polarization, ɛ. For each of four Q2 settings, 0.52, 0.75, 1.00, and 2.00 ...(GeV/c)2, the longitudinal and transverse virtual photon cross sections were extracted in measurements at three virtual photon polarizations. The Q2 dependence of the σL/σT ratio differs significantly from current theoretical predictions. This, combined with the precision of the measurement, implies a need for revision of existing calculations. (APS)
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