Chemical potentials of light hadrons and quarks from yield ratios of negative to positive particles in high energy $pp$ collisions

Abstract

We describe the transverse momentum spectra of $\pi^\pm$, $K^\pm$, $p$, and $\bar{p}$ produced in proton-proton ($pp$) collisions at different collision energies by using a Tsallis-Pareto-type function, and obtain the yield ratios, $k_{\pi}$, $k_{K}$, and $k_{p}$, of negative to positive particles from the fitting results of transverse momentum spectra and the extracted normalization constants. The transverse momentum dependent and energy dependent chemical potentials of light hadrons ($\pi$, $K$, and $p$) and quarks ($u$, $d$, and $s$) in $pp$ collisions are then extracted successively from the yield ratios. The six types of transverse momentum dependent chemical potentials show the trend of being close to zero in low-$p_T$ region and away from zero in high-$p_T$ region. Meanwhile, the energy dependent chemical potentials seem to decrease slightly with the increase of the collision energy, and the limiting values of the six types of chemical potentials are zero at very high energy in $pp$ collisions, which confirms that the partonic interactions possibly play an important role at RHIC and LHC, especially at LHC.