Analysis of multiplicity distributions in proton-proton collisions at LHC up to $\sqrt {s}$ = 7 TeV in quantum statistical approach

Abstract

Proton-proton collisions at new high energies ($\sqrt {s}=$2.36 and 7 TeV) at LHC resulted into a greater mean multiplicities ($<e n >$) of charged particles in the mid-rapidity region than estimated $< n >$s by different models and event generators. Another significant observation in multiplicity data is a change in slope in the distribution of primary charged hadrons in pseudorapidity intervals $|\eta|<2.4$ at $\sqrt{s} = 7$ TeV. These new observations merit further studies. We consider a two-component model of particle production to analyze the multiplicity distributions of charged hadrons from the proton-proton collisions at centre-of-mass energies $\sqrt{s} = 0.9$ TeV, $\sqrt{s} = 2.36$ TeV and $\sqrt{s} = 7$ TeV in pseudorapidity intervals $|\eta|$ of increasing width around the centre-of-mass pseudorapidity $\eta_{cm} =0$. The model, based on quantum statistical formalism, considers one chaotic and another coherent source of particle productions. The LHC data has been found to be consistent with characteristic features of the model. The analysis provides a reasonable explanation to the observed change in slope in the distribution and suggests a possible reason for underestimations of mean multiplicities by the event generators. In addition, an interesting revelation is the deviation from a scaling law, involving information entropy in quantum statistical viewpoint, derived as a function of chaotic multiplicity obtained from the two-component model.