Abstract
The differential cross sections for inclusive neutral pions as a function of transverse and longitudinal momentum in the very forward-rapidity region have been measured at the LHC with the LHC forward detector in proton-proton collisions at s=2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of sNN=5.02 TeV. Such differential cross sections in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. Comparing proton-proton with proton-lead collisions, we find a sizable suppression of the production of neutral pions in the differential cross sections after subtraction of ultraperipheral proton-lead collisions. This suppression corresponds to the nuclear modification factor value of about 0.1–0.3. The experimental measurements presented in this paper provide a benchmark for the hadronic interaction Monte Carlo simulation codes that are used for the simulation of cosmic ray air showers.16 MoreReceived 31 July 2015DOI:https://doi.org/10.1103/PhysRevD.94.032007This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.© 2016 CERN, for the LHCf CollaborationPhysics Subject Headings (PhySH)Research AreasCosmic rays & astroparticlesHadron-hadron interactionsPhysical SystemsPionsParticles & Fields
Highlights
Observations of high-energy cosmic rays with energy above 1014 eV provide key information for a yet unestablished origin(s) and acceleration mechanism(s) for cosmic rays
In order to grasp the experimental signature of the source of ultrahigh-energy cosmic rays (UHECRs) and to understand a consistent picture of transition from the galactic component around 1014 eV, many extensive air-shower experiments, including ongoing UHECR observatories (i.e., Auger [5] and Telescope Array [6]) have collected the data on the energy spectrum, mass composition, and arrival direction of UHECR high-energy cosmic rays over the past few decades [7,8,9]
It is important to note that critical parts of the analysis still depend on Monte Carlo (MC) simulations of airshower development that are sensitive to the choice of hadronic interaction models
Summary
Observations of high-energy cosmic rays with energy above 1014 eV provide key information for a yet unestablished origin(s) and acceleration mechanism(s) for cosmic rays. Extrapolation from the LHC energy range to a higher energy range can be achieved by using a scaling law in the forwardrapidity region One possibility for such a scaling law is the hypothesis of limiting fragmentation [12,13,14], which specifies that the secondary particles will approach a limiting distribution of rapidity in the rest frame of the target hadron. In this case, the fragmentation of a colliding hadron would occur independently of the center-of-mass energy, and the differential cross sections as a function of rapidity (hereafter, rapidity distributions) in the fragmentation region, namely the forward-rapidity region, would form a limiting distribution.
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