Measurements on small angle elastic scattering from p p and anti-p p collisions at the ISR

Experiment R211 was performed at the Intersecting Storage rings (ISR) of the European Center for Nuclear Research (CERN), Geneva, Switzerland. The aim was to measure, for pp and anti-p(p) scattering at high energy, the three quantities: (1) the total nuclear cross section, σ/sub n/, (2) the nuclear slope parameter, b, that describes the dependence of the differential elastic cross section on the 4- momentum transfer, t, for small absolute value of t, and (3) the ratio, rho, of the real to the imaginary part of the forward nuclear elastic scattering amplitude. These quantities were deduced from differential elastic scattering cross sections measured in the near forward direction. The measurements were made for pp scattering at √s = 30.5 GeV, 52.8 GeV and 62.5 GeV. The total cross section for both pp and anti-p(p) scattering is seen to rise in the range √s = 30.5 GeV to √s = 62.5 GeV. The rise is consistent with an asymptotic increase of σ/sub n/ as In2(s/s0), the highest rate allowed by the Froissart bound