# Multiplicity-dependent ${p}_{T}$ distributions of identified particles in $pp$ collisions at 7 TeV within the HIJING/$B\overline{B}$ v2.0 model

Topor Pop, V. (Physics Department, McGill University, Montreal H3A 2T8, Canada) (National Institute for Physics and Nuclear Engineering-Horia Hulubei Hadron Physics Department R-077125, Bucharest, Romania) ; Petrovici, M. (National Institute for Physics and Nuclear Engineering-Horia Hulubei Hadron Physics Department R-077125, Bucharest, Romania)

10 December 2018

Abstract: Effects of strong longitudinal color fields (SLCF) on the identified (anti)particle transverse momentum (${p}_{T}$) distributions in $pp$ collision at $\sqrt{s}=7\phantom{\rule{0.16em}{0ex}}\mathrm{TeV}$ are investigated within the framework of the HIJING/$B\overline{B}$ v2.0 model. The comparison with the experiment is performed in terms of the correlation between mean transverse momentum ($〈{p}_{T}〉$) and multiplicity (${N}_{\mathrm{ch}}^{*}$) of charged particles at central rapidity, as well as the ratios of the ${p}_{T}$ distributions to the one corresponding to the minimum bias (MB) $pp$ collisions at the same energy, each of them normalized to the corresponding charged particle density, for high multiplicity (HM, ${N}_{\mathrm{ch}}>100$) and low multiplicity (LM, ${N}_{\mathrm{ch}}<100$) class of events. The theoretical calculations show that an increase of the strength of color fields (as characterized by the effective values of the string tension $\kappa$), from $\kappa =2$ to $\kappa =5\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/\mathrm{fm}$, from LM to HM class of events, respectively, led to a ratio at low and intermediate ${p}_{T}$ (i.e., 1 GeV/$c<{p}_{T}<6$ GeV/$c$), consistent with recent data obtained at the Large Hadron Collider by the ALICE Collaboration. These results point out the necessity of introducing a multiplicity (or energy density) dependence for the effective value of the string tension. Moreover, the string tension $\kappa =5\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/\mathrm{fm}$, describing the ${p}_{T}$ spectra of identified particles (anti)particle in $pp$ collisions at $\sqrt{s}=7\phantom{\rule{0.16em}{0ex}}\mathrm{TeV}$ for high charged particle (HM) multiplicity event classes, has the same value as the one used in describing the ${p}_{T}$ spectra in central Pb-Pb collisions at $\sqrt{{s}_{NN}}=2.76\phantom{\rule{0.16em}{0ex}}\mathrm{TeV}$. Therefore, we can conclude that at the LHC energies the global features of the interactions could be mostly determined by the properties of the initial chromoelectric flux tubes, while the system size may play a minor role.

Published in: Physical Review C 98 (2018)