Pseudorapidity dependence of the bulk properties of hadronic medium in pp collisions at 7 TeV

Abstract

The measured charged particle $$p_T$$ p T spectra in proton-proton collisions obtained by the CMS experiment at CERN is compared with the simulation results of EPOS–LHC and Pythia8.24 models at 7 TeV center-of-mass energy. The Pythia8.24 model describes the experimental data very well, particularly in the high $$p_T$$ p T region. The model also predicts the $$p_T$$ p T spectra for $$|$$ | $$\eta $$ η $$|$$ | < 2.4 at 0 $$\le $$ ≤ $$p_T$$ p T $$\le $$ ≤ 6 $$\text {GeV/}c$$ GeV/ c . The EPOS–LHC model underpredicts the $$p_T$$ p T spectra from 0.1 to 2 $$\text {GeV/}c$$ GeV/ c in all $$\eta $$ η bins for about 20% and the $$p_T$$ p T spectrum from 0.1 to 4.2 $$\text {GeV/}c$$ GeV/ c for $$|$$ | $$\eta $$ η $$|$$ | < 2.4 by about 15% while reasonably predicts well for $$p_T$$ p T > 4.2 $$\text {GeV/}c$$ GeV/ c within the experimental errors. Furthermore, to get information about collective properties of the hadronic matter, modified Hagedorn function with embedded transverse flow velocity and thermodynamically consistent Tsallis distribution functions are used to fit the experimental data and simulated results. The values of $$\chi ^2/ndf$$ χ 2 / n d f show that the functions fit the data and simulation results well. The parameter extracted by the functions: $$\beta _T$$ β T , $$T_0$$ T 0 , and $$T_{eff}$$ T eff decreases with increasing $$\eta $$ η . The decrease in $$\beta _T$$ β T with increasing $$\eta $$ η is due to the large energy deposition in lower rapidity bins producing rapid expansion due to large pressure gradient resulting quick expansion of the fireball. Similarly, large energy transfer in the lower pseudo-rapidity bin results in higher degree of excitation of the system which results larger values of $$T_0$$ T 0 and $$T_{eff}$$ T eff . The values of the fit constant $$N_0$$ N 0 increase with $$\eta $$ η where the values of $$N_0$$ N 0 extracted from Pythia8.24 are closer to the data than the EPOS–LHC model. The Pythia8.24 model has better prediction than the EPOS–LHC model which might be connected to its flow-like features and color re-connections resulting from different Parton interactions in the initial and final state.

Charged Particles Transverse Momentum and Pseudorapidity Distribution in Hadronic Collisions at LHC Energies

“…Such parameters are key observables to distinguish general properties of the collision that are more significant for higher collision energies [ 7 , 8 ]. Similar studies showing models’ prediction compared to experimental data at different energies are given in the references [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. The data at 0.9 and 2.36 TeV are taken from [ 4 ] and 7 TeV from [ 5 ].…”

Systematic analysis of the pp collisions at LHC energies with Tsallis function

“…-The collision of relativistic nuclei produces hot and dense matter, similar to the conditions prevailing in the early universe, called Quark Gluon Plasma (QGP) [1][2][3][4][5], where quarks and gluons have asymptotic freedom. One of the primary aims of experimental particle physicists at the Large Hadron Collider (LHC) and Relativistic Heavy Ion Collider (RHIC) is to create this state of matter and to investigate its behaviour and different kinds of properties which include space-time evolution of the medium, variation of thermal effects, flow effects, size of the medium with varying collision energy [6][7][8], the centrality of the colliding nuclei [7], rapidity [9,10] and size of the colliding nuclei [11]. During its evolution, the QGP comes across two main stages, the chemical freezeout stage and the kinetic or thermal freezeout stage.…”

Analyses of pp, Cu–Cu, Au–Au and Pb–Pb Collisions by Tsallis-Pareto Type Function at RHIC and LHC Energies

“…The present work is a continuation of our work published in [ 16 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ] using different statistical fit functions to extract parameters relevant to the collective properties of the hadronic medium.…”