FIRST MEASUREMENT OF THE EXCLUSIVE (P,E(+)E(-)) REACTION

摘要

We present the first data on the exclusive (p, e(+)e(-)) reaction in a nucleus. Cross sections for populating the ground state and first excited state in the residual nucleus are presented for the reaction B-11(p, e(+)e(-))C-12 at 98 MeV. The e(+)e(-) momentum vectors were measured with a high-resolution magnetic pair spectrometer. The distributions of the virtual photon invariant mass and of the direction of the electron in the virtual photon rest system are compared with a simple single-nucleon model. The (p, e+e-) cross sections are compared with corresponding data for the (p, gamma) reaction obtained with the same apparatus. The (p, e(+)e(-)) cross sections show substantial enhancement over what is expected from the simple model. [References: 9]