First measurement of antikaon phase-space distributions in nucleus-nucleuscollisions at subthreshold beam energies

Menzel, H Bottcher, I Debowski, M Dohrmann, F Forster, A Grosse, E Koczon, P Kohlmeyer, B Laue, F Naumann, L Oeschler, H Puhlhofer, F Schwab, E Senger, P Shin, Y Strobele, H Sturm, C Surowka, G Uhlig, F Wagner, A Walus, W

H. Menzel et al., First measurement of antikaon phase-space distributions in nucleus-nucleuscollisions at subthreshold beam energies, PHYS LETT B, 495(1-2), 2000, pp. 26-32

24

INGLESE

Article

Physics

PHYSICS LETTERS B

0370-2693 → ACNP

495

1-2

2000

26 - 32

ISI

0370-2693(200012)495:1-2<26:FMOAPD>2.0.ZU;2-Z

Differential production cross sections of K- and K+ mesons have been measur ed as function of the polar emission angle in Ni+Ni collisions at a beam en ergy of 1.93 A GeV. In near-central collisions, the spectral shapes and the widths of the rapidity distributions of K- and K+ mesons are in agreement with the assumption of isotropic emission. In non-central collisions, the K - and K+ rapidity distributions are broader than expected for a single ther mal source. In this case, the polar angle distributions are strongly forwar d-backward peaked and the nonisotropic contribution to the total yield is a bout one third both for K+ and K- mesons. The K- /K+ ratio is found to be a bout 0.03 independent of the centrality of the reaction. This value is sign ificantly larger than predicted by microscopic transport calculations if in -medium modifications of K mesons are neglected. (C) 2000 Elsevier Science B.V. All rights reserved.