Medium effects in high energy heavy-ion collisions

Abstract

The change of hadron properties in dense matter based on various theoretical approaches are reviewed. Incorporating these medium effects in the relativistic transport model, which treats consistently the change of hadron masses and energies in dense matter via the scalar and vector fields, heavy-ion collisions at energies available from SIS/GSI, AGS/BNL, and SPS/CERN are studied. This model is seen to provide satisfactory explanations for the observed enhancement of kaon, antikaon, and antiproton yields as well as soft pions in the transverse direction from the SIS experiments. In the AGS heavy-ion experiments, it can account for the enhanced K + /π + ratio, the difference in the slope parameters of the K + and K − transverse kinetic energy spectra, and the lower apparent temperature of antiprotons than that of protons. This model also provides possible explanations for the observed enhancement of low-mass dileptons, phi mesons, and antilambdas in heavy-ion collisions at SPS energies. Furthermore, the change of hadron properties in hot dense matter leads to new signatures of the quark-gluon plasma to hadronic matter transition in future ultrarelativistic heavy-ion collisions at RHIC/BNL.

ϕ decay: A relevant source forK−production at energies available at the GSI Schwerionen-Synchrotron (SIS)?

“…This effect will also dilute any observed medium effects of K − . To extract precise information on the equation of state [8][9][10] and on the K − -nucleon potential, one should improve the statistics of such independent measurements for K − and φ, i.e., tag K − mesons according to their production mechanism. This kind of systematic measurements should be done for different systems and different beam energies.…”

“…The systematic study of K ± subthreshold production yields, phase space distributions, and flow observables in relativistic heavy-ion collisions at various beam energies and for various system sizes and centralities has attracted much attention, in particular in the context of in-medium properties of K + and K − mesons [1][2][3][4][5][6][7][8][9][10]. Corresponding experiments have been the focus of studies by the KaoS [11][12][13][14][15] and FOPI [16][17][18][19][20] Collaborations over the last two decades, following up on the pioneering experiments at Bevalac [21].…”

“…Indeed, the combined analysis of K + and K − suggests that a substantial part of the observed K − mesons is due to a strangeness exchange mechanism [33]. Furthermore K + and K − exhibit distinctively different in-medium properties, both in theoretical approaches [1][2][3][4][5][6][7][8][9][10][31][32][33][34] and in experiments [11][12][13]15,18,19,22].…”

Kaon production at subthreshold energies: what do we learn about the nuclear medium?

“…Especially the relation of the optical potential of K + and K − in the nuclear medium to experimental observables like the K − /K + ratios, mesonic in-plane flow and azimuthal distribution of kaons is subject of vivid discussions, who have triggered a lot of activities on the experimental [1,2,3,4,5,6,7,8,9,10] and theoretical side [11,12,13,14,15,16,17,18,19].…”

Kaonic modes in hyperonic matter and p-wave kaon condensation

“…Studies of kaon condensation stimulated theoretical investigations of in-medium kaon properties with reference to the kaon-nucleon scattering [18][19][20][21], kaonic atoms [22][23][24][25], and heavy-ion collisions [26][27][28][29][30]. The momentum dependence of kaon optical potentials in a nuclear medium has also been discussed, which may serve as unified understanding of these phenomena [31][32][33].…”