First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions.
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 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.
Förster
A
A
Technische Universität, Darmstadt, D-64289 Darmstadt, Germany.
Uhlig
F
F
Böttcher
I
I
Debowski
M
M
Dohrmann
F
F
Grosse
E
E
Koczoń
P
P
Kohlmeyer
B
B
Laue
F
F
Menzel
M
M
Naumann
L
L
Oeschler
H
H
Scheinast
W
W
Schwab
E
E
Senger
P
P
Shin
Y
Y
Ströbele
H
H
Sturm
C
C
Surówka
G
G
Wagner
A
A
Waluś
W
W