Strong color fields effects and baryon/meson anomaly in p+p and central Pb+Pb collisions at L H C energies(*).

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Théâtre National (Centre Bonlieu)

Théâtre National

Centre Bonlieu

Board: 69
Poster Pre-equilibrium and initial state physics


VASILE TOPOR POP (McGill University, Montreal, Canada)


With the HIJING/BBar v2.0 event generator, we explore the phenomenological consequences of the suppression of perturbative quantum chromo-dynamics (pQCD) mini-jet production and of enhanced "in medium" strong longitudinal color field. Nuclear effects like shadowing and parton energy loss ("jet quenching") are included. This analysis focuses on p+p collisions at centre of mass energy (sqrt(sNN)) 0.900, 2.36 and 7 TeV, and on central Pb+Pb collisions at sqrt(sNN) = 2.76 TeV, where recent data have been reported by LHC Collaborations (ALICE, ATLAS, CMS). The effective energy-dependent string tension values are constrained by p+p data from Relativistic Heavy Ion Collider (RHIC), the Tevatron, and recent Large Hadron Collider (LHC) runs. The pQCD cut-off value p0(s) is constrained by Au+Au collisions data from RHIC. Data on charged hadron multiplicity and charged hadron nuclear modification factor (RAA) in central (0-5%) Pb+Pb collisions from the ALICE experiment at the LHC are used to constrain the main parameters of the "jet quenching" phenomena (energy loss and mean free path of initial parton-parton interactions). Predictions for the energy and centrality dependence of rapidity densities (2dNch/dy/Npart) and the hadron flavor dependence(mesons and baryons) of the nuclear modification factor RAA are presented. By studying baryon/meson ratios, we show that the jet quenching in central collisions suppresses the hard pQCD component of the particle spectra, thereby exposing a novel component of baryon dynamics that we attribute to (gluonic) baryon-anti-baryon junctions (JJbar). We predict that a baryon/mesons anomaly at intermediate transverse momentum values will persist at LHC energies, with a moderate centrality dependence. (*) This work is being supported by NSERC (Canada) and by the US Department of Energy.

Primary author

VASILE TOPOR POP (McGill University, Montreal, Canada)


Charles Gale (McGill University, Montreal, Canada) Jean Barrette (McGILL UNIVERSITY, MONTREAL, CANADA) Miklos Gyulassy (Columbia University, New York, USA)

Presentation materials