Kaon production in Au + Au collisions at 11.6-A-GeV/c

A systematic study of the spectra and yields of K{sup +} and K{sup {minus}} is reported by experiment E866 as a function of centrality in Au+Au collisions at 11.6A GeV/c. The invariant transverse spectra for both kaon species are well described by exponentials in m{sub t}, with inverse slope parameters that are largest at midrapidity and which increase with centrality. The inverse slopes of the K{sup +} spectra are slightly larger than the inverse slopes of the K{sup {minus}} spectra. The kaon rapidity density peaks at midrapidity with the K{sup +} distribution wider in rapidity than K{sup {minus}}. The integrated total yields of K{sup +} and K{sup {minus}} increase nonlinearly and steadily with the number of projectile participants. The yield per participant for kaons is two to three times larger than the yield from N-N collisions. This enhancement suggests that the majority of kaons in central Au+Au reactions are produced in secondary hadronic collisions. There is no evidence for an onset of additional kaon production from a possible small volume of baryon-rich quark-gluon plasma. The differences between K{sup +} and K{sup {minus}} rapidity distributions and transverse spectra are consistent with a lower phase space for K{sup {minus}} production due tomore » a higher energy threshold. These differences also exclude simple thermal models that assume emission from a common equilibrated system. {copyright} {ital 1998} {ital The American Physical Society}« less