Abstract
We collected the transverse momentum (mass) spectra of charged hadrons ( π − , π + , K − , K + , p ¯ , and p ) produced in collisions over a center-of-mass energy range from 2.70 to 200 GeV (per nucleon pair). The modified Tsallis–Pareto-type function (the TP-like function) with average transverse flow velocity is used to describe the contribution of participant or constituent quarks to transverse momentum of considered hadron. The experimental spectra of π ∓ and K ∓ (or p ¯ and p ) are fitted by the convolution of two (or three) TP-like functions due to the fact that two (or three) constituent quarks are regarded as two (or three) energy resources in the formation of considered hadron. From the reasonable fits to the spectra, the thermal freeze-out parameters are extracted, and the pseudoentropy is newly defined and extracted. Some parameters quickly change in the energy range of less than 7.7 GeV, and slowly change in the energy range of greater than 7.7 GeV, indicating the variation of collision mechanism at around 7.7 GeV.
Highlights
As the basic gauge field theory [1,2,3] which is used for describing strong interactions, quantum chromodynamics (QCD) predicts that under the condition of high temperature and high density [4], partons can be released from the confined hadron phase to form a new form of substance that is called quark-gluon plasma (QGP) [5,6,7,8]
The particular system composed by this kind of substance is usually described by the QCD phase diagram [9, 10]
The symbols represent the experimental data measured by the STAR Collaboration in the RHIC-beam energy scan (BES) project [33, 34] and rescaled by different amounts marked in the panels for clarity
Summary
As the basic gauge field theory [1,2,3] which is used for describing strong interactions, quantum chromodynamics (QCD) predicts that under the condition of high temperature and high density [4], partons can be released from the confined hadron phase to form a new form of substance that is called quark-gluon plasma (QGP) [5,6,7,8]. The RHIC-BES program including its fixed target experiments is able to vary the collision energy over a wide range in low energy region, thereby achieving an extensive range of baryon chemical potential, further expanding the search objective. The transverse momentum spectra of π−, π+, K−, K+, p, and p produced at midrapidity (mid-y) in gold-gold (Au-Au) collisions with different centralities at the RHIC and its BES energy [33,34,35] are collected. The transverse mass spectra of the mentioned charged hadrons produced at mid-y in central Au-Au collisions at the AGS energy [36,37,38] are collected, though the spectra of p are not available due to low energy These spectra are used to extract the thermal freeze-out parameters and the pseudoentropy.
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