Energy density at kinetic freeze-out in Pb–Pb collisions at the LHC using the Tsallis distribution
M D Azmi, T Bhattacharyya, J Cleymans, M Paradza
Abstract
Abstract The thermodynamic parameters like energy density, pressure, entropy density, temperature and particle density are determined from the transverse momentum distributions of charged hadrons in Pb–Pb collisions at the LHC. The results show a clear increase with the centrality and the beam energy in all parameters. It is determined that in the final freeze-out stage the energy density reaches a value of about 0.039 GeV fm −3 for the most central collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msqrt> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">NN</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>5.02</mml:mn> <mml:mspace width="0.25em"/> <mml:mspace width="0.25em"/> <mml:mi>TeV</mml:mi> </mml:math> . This is less than that at chemical freeze-out where the energy density is about 0.36 GeV fm −3 . This decrease approximately follows a T 4 law. The results for the pressure and entropy density are also presented for each centrality class at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msqrt> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">NN</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>2.76</mml:mn> </mml:math> and 5.02 TeV.