Extracting Chemical Potentials Of Quarks In High Energy Nuclear Collisions

High energy heavy ion (nucleus-nucleus) collisions will not only present a colorful phenomenon, but also provide lots of information. Investigating the transverse momentum distributions of final-state relativistic particles can provide a unique opportunity for us to comprehend the strong interacting theory and nuclear reaction mechanisms. In addition, the chemical potential is a sign to mark the direction of spontaneous chemical reaction. In fact, the chemical potential is also a criterion for determining whether thermodynamic equilibrium does exist in the interacting region in relativistic collisions. Consequently, the chemical potential is one of the major problems for researching the quark-gluon plasma (QGP). But the chemical potential of quark is a quantity which cannot be measured directly in experiments. Therefore the measurement of the chemical potential of quark is very important in high energy collisions. In this paper, the transverse momentum distributions of charged particles are investigated by a multisource thermal model. Then, we present two methods to extract the chemical potentials of quarks in high energy collisions. The main work is divided as follows:Firstly, in the framework of the multisource thermal model, the transverse momentum distributions of charged particles produced in Pb-Pb, Au-Au, and d-Au collisions at the Super Proton Synchrotron (SPS) energies and the Relativistic Heavy Ion Collider (RHIC) energies with different centralities are investigated by a two-component revised Boltzmann distribution and a two-component Fermi-Dirac/Bose-Einstein distribution. The calculated results are successful in the descriptions of the PHENIX and NA49 experimental data. The results show that the multisource thermal model is well in agreement with experimental data in high energy collisions. Figures present that the source temperature increases obviously with increase of the particle mass and incident energy, but it does not show an obvious change with the collision centrality.Secondly, we present two methods to extract the chemical potentials of quarks in high energy collisions. The first method is based on the ratios of negatively/positively charged particles, and the effective temperatures extracted from the transverse momentum spectra of related hadrons are needed. The second method is based on the chemical potentials of some particles, and we also need the transverse momentum spectra of related hadrons. In this paper, the values of chemical potentials for up, down, and strange quarks can be obtained from two methods in a wide transverse momentum range. We would like to point out that the considered three types of quark chemical potentials do not show an obvious change with the increase of transverse momentum and impact centrality in nucleus-nucleus collisions, and in most cases the mean values of μu and μd are small and the mean values of μs are smaller. To extract six types of quark chemical potentials, we would like to propose experimental collaborations to measure simultaneously not only the transverse momentum spectra of p, p, K-, K+, π-,and π+, but also those of D-,D+,B-, and B+(even those of Δ++, Δ-, and Ω-) in high energy nuclear collisions at the RHIC and the Large Hadron Collider (LHC).