Effects of Shower Partons on Soft and Semihard hadrons Produced in Pb-Pb Collisions at 2.76 TeV

The production of all identified hadrons at the CERN Large Hadron Collider (LHC) is studied with emphasis on the $p_T$ distributions up to 20 GeV/c in central collisions. In the framework of the recombination model we find that the shower partons (due to the fragmentation of semihard partons) play an important role in the formation of hadrons in the low- and intermediate-$p_T$ regions. Parameters that control the energy loss of minijets are determined by fitting the upper half of the $p_T$ range of the pion distribution. The resultant soft shower partons are then found to dominate over the thermal partons in the non-strange sector, but not in the strange sector. Since the data on the $p_T$ spectra of all observed hadrons are well reproduced, there is no way out of the implication that any alternative dynamical model on particle production would be incomplete if it does not consider the effects of minijets even at very low $p_T$. Hydrodynamics that relies on rapid equilibration without accounting for the delayed thermalization effects of the hard and semihard partons copiously produced at LHC is an example of such models. The difference between the densities of shower partons produced at LHC and at BNL Relativistic Heavy-Ion Collider (RHIC) is quantified and discussed.