Multihadron Production and Inclusive Photon Measurement in ALICE Experiment at the LHC
ABSTRACT :
The inclusive photon measurements (dominated pi0 decays) are complementary to the charged particle measurements. We report the measurements of multiplicity and pseudorapidity distributions of inclusive photons using the ALICE Photon Multiplicity Detector (PMD) at forward rapidities (2.3 < η < 3.9) in Pb+Pb collisions at 2.76 TeV. The collision energy and the centrality dependence of the global observables, measured in heavy-ion collisions are investigated in the entire available range of the collision energy of a few GeV to a few TeV per nucleon up to the latest LHC measurements within the Participant Dissipating Energy (PDE) approach. This approach relates multihadron production in different types of collisions by combining, under the proper scaling of the collision energy, the constituent quark picture with the Landau relativistic hydrodynamics. Within the PDE approach, the energy dependence of the studied observables, obtained in the most central nuclear collisions, are shown to be well described based on the measurements in hadron interactions pointing to a universality in the multihadron production. In addition, the PDE approach allows to describe the full pseudorapidity spectra in central collisions. In the meantime, the study of the pseudorapidity spectra from the non-central collisions reveal a new scaling, named as Energy Balanced Limiting Fragmentation scaling, which provides an explanation of the RHIC “puzzle" of the difference between the centrality independence of the mean multiplicity vs the monotonic decrease of the midrapidity pseudorapidity density with centrality increases.