Abstract

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 (lambda (s)) produced in particle and nuclear collisions is found to increase in collisions with an initially reached energy density (epsilon (i)) up to epsilon (crit) similar to 1 GeV/fm(3). Above this value it decreases approximately linearly and reaches its asymptotic value at zero baryon chemical potential (PB). We demonstrate that lambda (s) in nuclear collisions approaches its asymptotic value at epsilon (i) similar to 8-9 GeV/fm(3), corresponding to s(1/2) similar to 3-8 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, lambda (s) universally saturates across the QCD phase boundary, following the temperature. Recent experimental puzzles as the increase in the K+/pi (+) ratio in Pb + Pb collisions at 40 GeV per nucleon, its different behaviour at midrapidity, the decrease of the double ratio of K/pi (A+A/p+p) in nucleus-nucleus over p+p collisions with increasing s(1/2), and the increase of lambda (s) in p+A over p+p collisions at the same s(1/2) are naturally explained. We study the approach of thermodynamic observables at mu (B) = 0 to the transition point and extract an estimate of the critical temperature.