Photodisintegration of 4^4He into p+t

The two-body photodisintegration of $^4$He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid $^4$He target. This is the first measurement of the photodisintegration of $^4$He above 0.4 GeV. The differential cross sections for the $\gamma$$^4$He$\to pt$ reaction have been measured as a function of photon-beam energy and proton-scattering angle, and are compared with the latest model calculations by J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. These results reinforce the conclusion of our previous study of the three-body breakup of $^3$He that demonstrated the great importance of three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22 postscrip figure

Polarized structure function sigma(\u27)(LT) for H-1((e)over-right-arrow,e(\u27)K(+))Lambda in the nucleon resonance region

The first measurements of the polarized structure function σLT\u27 for the reaction 1H(e⃗,e\u27K+)Λ in the nucleon resonance region are reported. Measurements are included from threshold up to W=2.05 GeV for central values of Q2 of 0.65 and 1.00 GeV2, and nearly the entire kaon center-of-mass angular range. σLT\u27 is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate s-channel resonances, as well as resonant and nonresonant processes. The results for σLT\u27 are comparable in magnitude to previously reported results from CLAS for σLT, the real part of the same response. An intriguing sign change in σLT\u27 is observed in the high Q2 data at W≈1.9 GeV. Comparisons to several existing model predictions are shown