Indication of Collective flow and Transparency in p-p Collisions at LHC.

Abstract

. The mid-rapidity transverse momentum spectra of various hadrons and the available rapidity distributions of some strange hadrons produced in p-p collisions at LHC energy √s NN = 7.0 TeV have been studied using a Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in good agreement with the experimental data. The theoretical fits of the transverse momentum spectra using the model calculations provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different hadronic species. The study reveal the presence of significant collective flow and a well defined temperature in the system thus indicating the formation of a thermally equilibrated hydrodynamic system in p-p collisions at LHC. Moreover, the fits to the available experimental rapidity distributions data of strange hadrons show the effect of almost complete transparency in p-p collisions at LHC. The transverse momentum distributions of protons and kaons produced in p-p collisions at √s NN = 200 GeV and √s NN = 2.76 TeV have also been reproduced successfully. The model incorporates longitudinal as well as a transverse hydrodynamic flow. The contributions from heavier decay resonances have also been taken into account. We have also imposed the criteria of exact strangeness conservation in the system.

Particle Ratios from Strongly Interacting Hadronic Matter

“…By studying the spectra of hadrons, one can in principle comment on some of the properties of the strongly interacting hadronic matter. For example, by studying / ratio, it has been argued that transparency effects in case of high energy heavy-ion collisions may become operative [2]. Recently, it has been found that particle ratios of some of the hadrons, for example, + / + , − / − , and Λ/ − , show a sudden rise for a specified range of center of mass energy √ in case of heavyion collisions [3][4][5][6].…”