Charged kaon and pion production at midrapidity in proton-nucleus and sulphur-nucleus collisions
- Niels Bohr Institute, DK-2100 Copenhagen (Denmark)
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
- Columbia University, New York, New York 10027 (United States)
- Hiroshima University, Higashi-Hiroshima 739 (Japan)
- CERN, CH-1211 Geneva 23 (Switzerland)
- Ohio State University, Columbus, Ohio 43210 (United States)
- State University of New York Stony Brook, Stony Brook, New York 11794 (United States)
- University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)
- Texas AM University, College Station, Texas 77843-3366 (United States)
- Brookhaven National Laboratory, Upton, New York 11973 (United States)
The NA44 Collaboration has measured charged kaon and pion distributions at midrapidity in sulphur and proton collisions with nuclear targets at 200 and 450 GeV/c per nucleon, respectively. The inverse slopes of kaons, are larger than those of pions. The difference in the inverse slopes of pions, kaons, and protons, all measured in our spectrometer, increases with system size and is consistent with the buildup of collective flow for larger systems. The target dependence of both the yields and inverse slopes is stronger for the sulphur beam, suggesting the increased importance of secondary rescattering for SA reactions. The rapidity density dN/dy of both K{sup +} and K{sup {minus}} increases more rapidly with system size than for {pi}{sup +} in a similar rapidity region. This trend continues with increasing centrality, and according to RQMD, it is caused by secondary reactions between mesons and baryons. The K{sup {minus}}/K{sup +} ratio falls with increasing system size but more slowly than the {bar p}/p ratio. The {pi}{sup {minus}}/{pi}{sup +} ratio is close to unity for all systems. From pBe to SPb the K{sup +}/p ratio decreases while K{sup {minus}}/{bar p} increases and {radical} ((K{sup +}{center_dot}K{sup {minus}})/(p{center_dot}{bar p})) stays constant. These data suggest that as larger nuclei collide, the resulting system has a larger transverse expansion and baryon density and an increasing fraction of strange quarks. {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 289079
- Journal Information:
- Physical Review, C, Vol. 59, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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