Kaon versus Antikaon Production at SIS Energies

Abstract

We analyse the production and propagation of kaons and antikaons in Ni + Ni reactions from 0.8--1.85 GeV/u within a coupled channel transport approach including the channels $BB\to K^{+}YN,\pi B\to K^{+}Y,BB\to NNK\bar{K},\pi B\to NK\bar{K},K^{+}B\to K^{+}B,\bar{K}B\to \bar{K}B,YN\to \bar{K}NN,\pi \pi \to K\bar{K}$ as well as $\pi Y\to \bar{K}N$ and $\bar{K}N\to \pi Y$ for the antikaon absorption. Whereas the experimental $K^{+}$ spectra can be reproduced without introducing any selfenergies for the mesons in Ni + Ni collisions from 0.8 to 1.8 GeV/u, the $K^{-}$ yield is underestimated by a factor of 5--7 at 1.66 and 1.85 GeV/u. However, introducing density dependent antikaon masses as proposed by Kaplan and Nelson, the antikaon spectra can be reasonably well described.

Comments: 16 pages, LaTeX, plus 12 postscript figures, submitted to Nucl. Phys. A