First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions
A. Foerster, F. Uhlig, I. Boettcher, M. Debowski, F. Dohrmann, E. Grosse, P. Koczon, B. Kohlmeyer, F. Laue, M. Menzel, L. Naumann, H. Oeschler, W. Scheinast, E. Schwab, P. Senger, Y. Shin, H. Stroebele, C. Sturm, G. Surowka, A. Wagner, W. Walus
Abstract
Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 AGeV. The K-/K+ ratio is found to be nearly constant as a function of the collision centrality and system size. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.