Small-angle proton elastic scattering from the neutron-rich isotopes 6He and 8He, and from 4He, at 0.7 GeV in inverse kinematics

Absolute differential cross sections for elastic p(4)He, p(6)He and p(8)He small-angle scattering were measured in inverse kinematics with secondary He-4,He-6,He-8-beams at an energy near 0.7 GeV/u. The experiment was performed using beams from the heavy-ion synchrotron SIS and the fragment separator FRS of GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. Projectile scattering angles were measured with multi-wire tracking detectors. For proton scattering from the neutron-rich isotopes He-6 and He-8, differential elastic-scattering cross sections dsigma/dt were deduced in the range 0.002 < \t\ less than or equal to 0.05 (GeV/c)(2) of the four-momentum transfer squared t. For elastic p(4)He scattering, the data obtained in the t-range 0.002 less than or equal to \t\ less than or equal to 0.02 (GeV/c)(2) supplement the results from an earlier work performed in direct kinematics. From the differential cross sections the integral elastic-scattering cross sections sigma(el), the total cross sections sigma(tot), and the total reaction cross sections sigma(r) for the proton-nucleus strong interaction were evaluated. The data obtained on dsigma/dt allow the radial matter distributions in the He-6 and He-8 nuclei to be determined and the corresponding root-mean-square matter radii to be deduced. (C) 2002 Elsevier Science B.V. All rights reserved.