Deciphering QCD dynamics in small collision systems using event shape and final state multiplicity at the Large Hadron C
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Regular Article -Theoretical Physics
Deciphering QCD dynamics in small collision systems using event shape and final state multiplicity at the Large Hadron Collider Suman Deb1 , Sushanta Tripathy1,2 , Golam Sarwar1, Raghunath Sahoo1,a , Jan-e Alam3 1
Discipline of Physics, Indian Institute of Technology Indore, Simrol, Indore 453552, India Present Address Instituto de Ciencias Nucleares, UNAM, Deleg. Coyoacán, Ciudad de México 04510, Mexico 3 Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700064, India
2
Received: 13 July 2020 / Accepted: 21 September 2020 / Published online: 6 October 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Communicated by Tamas Biro
Abstract The high-multiplicity pp collisions at the Large Hadron Collider energies with various heavy-ion-like signatures have warranted a deeper understanding of the underlying physics and particle production mechanisms. It is a common practice to use experimental data on the hadronic transverse momentum ( pT ) spectra to extract thermodynamical properties of the system formed in heavy-ion and high multiplicity pp collisions. The non-availability of event topology √ dependent experimental data for pp collisions at s = 13 TeV on the spectra of non-strange and strange hadrons constrains us to use the PYTHIA8 simulated numbers to extract temperature-like parameters to study the event shape and multiplicity dependence of specific heat capacity, conformal symmetry breaking measure (CSBM) and speed of sound. The observables show a clear dependence on event multiplicity and event topology. Thermodynamics of the system is largely governed by the light particles because of their relatively larger abundances. In this regards, a threshold in the particle production, Nch (10–20) in the final state multiplicity emerges out from the present study, confirming some of the earlier findings in this direction. As for heavier hadrons with relatively small abundances, a similar threshold is observed for Nch 40 hinting towards formation of a thermal bath where all the heavier hadrons are in equilibrium.
1 Introduction To reveal the nature of the Quantum Chromodynamics (QCD) phase transition and to get a glimpse of how matter behaves at extreme conditions of temperature and energy density, experiments like Relativistic Heavy Ion Collider (RHIC) at BNL, USA and Large Hadron Collider (LHC) at a e-mail:
[email protected] (corresponding author)
CERN, Geneva, Switzerland have got prime importance. A deconfined state of quarks and gluons, also known as Quark Gluon Plasma (QGP), is believed to be produced for very short lifetime in heavy-ion collisions in these experiments. In the QGP phase, the relevant degrees of freedom are quarks and gluons rather than mesons and baryons, which are confined color neutral states [1]. In a baffling development, the experiments at LHC discovered QGP-like properties such as strangeness enhancement [2], double-ridge structure [3] etc. in smaller collision systems like prot
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