Experimental Cross Sections And Velocities Of Light Nuclides Produced In The Proton-Induced Fission Of $^{238}$U At 1 GeV

PACSInternational audienceLight nuclides produced in collisions of 1 A GeV 238U with hydrogen have been observed with a high-resolution forward magnetic spectrometer, the fragment separator (FRS), at GSI. Fragments were identified in A and Z and their production cross-sections measured. For each nuclide the velocity was precisely determined from the measured magnetic rigidity. This insight into the kinematics of the relativistic nuclear collisions allowed disentangling different reaction mechanisms. Thanks to the combined results on A, Z, and velocity of the fragments it was found out that all the observed isotopes, from Z=37 down the last element measured (Z=7), were formed in a binary decay process, interpreted as fission. A qualitative analysis of the cross sections revealed that the charge distribution of these light fragments, which forms a plateau around Z=15 and increases below Z=13, is in agreement with the theoretical expectations of the statistical model