First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions

First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions

Förster, A.; Uhlig, F.; Böttcher, I.; Debowski, M.; Dohrmann, F.; Grosse, E.; Koczon, P.; Kohlmeyer, B.; Laue, F.; Menzel, M.; Naumann, L.; Oeschler, H.; Scheinast, W.; Schwab, E.; Senger, P.; Shin, Y.; Ströbele, H.; Sturm, C.; Surowka, G.; Wagner, A.; Walus, W.

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 A·GeV. The K-/K+ ratio is found to be nearly constant as a function of the collision centrality. 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.

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