Inclusive photon production at forward rapidities in proton-proton collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV

B. Abelev , G. Conesa Balbastre (1) , J. Faivre (1) , C. Furget (1) , R. Guernane (1) , S. Kox (1) , J.S. Réal (1) , C. Silvestre (1) , R. Vernet (2) , I. Belikov (3) , B. Hippolyte (3) , C. Kuhn (3) , A. Maire (3) , L. Molnar (3) , C. Roy (3) , X. Sanchez Castro (3) , Laurent Aphecetche (4) , Guillaume Batigne (4) , H. Delagrange (4) , B. Erazmus (4) , Magali Estienne (4) , Marie Germain (4) , A. Lardeux (4) , Gines Martinez Garcia (4) , J. Martin Blanco (4) , A. Mas (4) , L. Massacrier (4) , D.A. Moreira De Godoy (4) , A. Morreale (4) , Philippe Pillot (4) , L. Ronflette (4) , Y. Schutz (4) , Alexandre Shabetai (4) , Diego Stocco (4) , M. Wang (4) , J. Zhu (4) , C. Cheshkov (5) , B. Cheynis (5) , L. Ducroux (5) , J.-Y. Grossiord (5) , Maxime Guilbaud (5) , R. Tieulent (5) , A. Uras (5) , Y. Zoccarato (5) , Z. Conesa Del Valle (6) , I. Das (6) , B. Espagnon (6) , C. Hadjidakis (6) , I. Lakomov (6) , C. Suire (6) , J. D. Tapia Takaki (6) , L. Valencia Palomo (6)

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 CC-IN2P3 - Centre de Calcul de l'IN2P3
3 IPHC - Institut Pluridisciplinaire Hubert Curien
4 SUBATECH - Laboratoire SUBATECH Nantes
5 IPNL - Institut de Physique Nucléaire de Lyon
6 IPNO - Institut de Physique Nucléaire d'Orsay

The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities ($2.3 < \eta < 3.9$) in proton-proton collisions at three center-of-mass energies, $\sqrt{s}=0.9$, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2% $\pm$ 0.3% (stat) $\pm$ 8.8% (sys) and 61.2% $\pm$ 0.3% (stat) $\pm$ 7.6% (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

B. Abelev, G. Conesa Balbastre, J. Faivre, C. Furget, R. Guernane, et al.. Inclusive photon production at forward rapidities in proton-proton collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV. European Physical Journal C: Particles and Fields, 2015, 75, pp.146. ⟨10.1140/epjc/s10052-015-3356-2⟩. ⟨in2p3-01085327⟩