Eur. Phys. J. C 21, 545-555 (2001)
The strange border of the QCD phasesS. Kabana
Laboratory for High Energy Physics, University of Bern, 3012 Bern, Switzerland
(Received: 17 April 2001 / Published online: 24 August 2001 -© Springer-Verlag / Società Italiana di Fisica 2001 )
We address the flavour composition along the border between the hadronic and the quark-gluon plasma phases of QCD. The ratio of strange to up and down antiquarks () produced in particle and nuclear collisions is found to increase in collisions with an initially reached energy density ( ) up to GeV/fm3. Above this value it decreases approximately linearly and reaches its asymptotic value at zero baryon chemical potential ( ). We demonstrate that in nuclear collisions approaches its asymptotic value at -9 GeV/fm3, corresponding to -8 TeV per nucleon + nucleon pair, which will be reached at the LHC. After correcting for the difference in the chemical potentials of various colliding systems, universally saturates across the QCD phase boundary, following the temperature. Recent experimental puzzles as the increase in the ratio in Pb + Pb collisions at 40 GeV per nucleon, its different behaviour at midrapidity, the decrease of the double ratio of in nucleus-nucleus over p + p collisions with increasing s1/2, and the increase of in p+A over p + p collisions at the same s1/2, are naturally explained. We study the approach of thermodynamic observables at to the transition point and extract an estimate of the critical temperature.
© Società Italiana di Fisica, Springer-Verlag 2001