Event patterns (particle scatter plots) extracted from charged particle spectra in $pp$ and Pb-Pb collisions at 2.76 TeV

Abstract

The transverse momentum ($p_T$) and pseudorapidity ($\eta$) spectra of charged particles produced in proton-proton ($pp$) and lead-lead (Pb-Pb) collisions at the large hadron collider (LHC) are described by a hybrid model. In the model, the $p_T$ spectrum is described by a two-component distribution which contains an inverse power-law suggested by the QCD (Quantum Chromodynamic) calculus and an Erlang distribution resulted from a multisource thermal model. The $\eta$ spectrum is described by a Gaussian rapidity ($y$) distribution resulted from the Landau hydrodynamic model and the two-component $p_T$ distribution, where the conversion between $y$ and $\eta$ is accurately considered. The modelling results are in agreement with the experimental data measured by the ATLAS Collaboration in $pp$ collisions at center-of-mass energy $\sqrt{s}=2.76$ TeV and in Pb-Pb collisions at center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=2.76$ TeV. Based on the parameter values extracted from $p_T$ and $\eta$ or $y$ spectra, the event patterns or particle scatter plots in three-dimensional velocity and momentum spaces are obtained.