Antihelium-3 production in lead-lead collisions at 158 A GeV/c

The NA52 experiment measured particle and antiparticle yields at 0degrees production angle over a wide range in rapidity in lead-lead (Pb-Pb) collisions at 158 A GeV/c with a minimum bias trigger. Besides O(10(6)) antiprotons ((p) over bar) and O(10(3)) antideuterons ((d) over bar) a total of five antihelium-3(((3)He) over bar) were found. The resulting invariant differential (3)He production cross sections at p(t) similar or equal to 0 GeV/c turn out to be E d(3)sigma/dp(3) = (2.5 +/- 1.8) x 10(-7) bc(3) GeV(-2) at a rapidity of y = 3.4 in the laboratory system and (5.9 +/- 3.4) x 10(-8) bc(3) GeV(-2) at y = 4.0. The results are discussed in the framework of a simple coalescence model.