Abstract
Measurements of multiplicity and pseudorapidity distributions of particles produced in pp collisions are important for the study of particle production mechanisms and to obtain baseline distributions to be compared with those from heavy-ion collisions. The inclusive photon measurements (dominated by π0 decays) are complementary to the charged particle measurements. The present work focuses on the forward rapidity region with comparisons to different models such as PYTHIA and PHOJET.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 pp collisions at = 0.9, 2.76 and 7 TeV. It is observed that the photon multiplicity distributions are well described by negative binomial distributions (NBD). Multiplicity distributions are studied in terms of KNO variables for each energy. It is shown that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and power law dependence. The results are compared to different model predictions. These models reproduce experimental results at lower energy while they are not accurate at higher energies.
Highlights
The increase in particle production at midrapidity with increasing center-of-mass energy in pp collisions has been studied in detail by the ALICE experiment [1, 2] at the CERN LHC
We report the measurement of inclusive photon production in the forward pseudorapidity reg√ion (2.3 < η < 3.9) with the ALICE experiment for pp collisions at center-of-mass energies of s = 0.9 TeV, 2.76 TeV and 7 TeV
PHOJET reproduces the data at s = 0.9 TeV while PYTHIA is closer to data at all the energies
Summary
The increase in particle production at midrapidity with increasing center-of-mass energy in pp collisions has been studied in detail by the ALICE experiment [1, 2] at the CERN LHC. As the particle production mechanism could be different in different regions of pseudorapidity, it is interesting to see how particle production varies with center-of-mass energy at forward rapidity. We report the measurement of inclusive photon production in the forward pseudorapidity reg√ion (2.3 < η < 3.9) with the ALICE experiment for pp collisions at center-of-mass energies of s = 0.9 TeV, 2.76 TeV and 7 TeV. Multiplicity and pseudorapidity distributions of photons are measured using the Photon Multiplicity Detector (PMD) [4, 5], which has been designed to measure the multiplicity of inclusive photons in the forward rapidity region. The results are compared to different tunes of PYTHIA [6] and PHOJET [7, 8] generators
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