Search for long-lived particles in 200 GeV/c proton-nucleon collisions

A search for long-lived particles (τ ≳ 10−8 sec), with changes ±23, ± 1, ±43 and ± 2, produced in 200 GeV pN collisions was performed at the CERN-SPS in a secondary beam equipped with superconducting r.f. separators. Upper limits were obtained for the production of long-lived hadrons and leptons. For charge - 1 particles the limits are at the level of 10−7 of the pions at a mass m = 0.2 GeV and reach the 10−11 level from 3 to 8 GeV. The production of light antinuclei was measured. The cross sections for 3He production are (1.3 ± 0.3) and (1.9 ± 0.3) × 10−34 cm2/sr · GeV/c at 21 and 47.4 GeV/c respectively; for t the cross section is (7.6 ± 0.9) × 10−34 cm2/sr · GeV/c at 23.7 GeV/c.