Measurement of forward neutral pion transverse momentum spectra fors=7  TeVproton-proton collisions at the LHC

Abstract

The inclusive production rate of neutral pions in the rapidity range greater than y = 8.9 has been measured by the Large Hadron Collider forward (LHCf) experiment during √ s = 7 TeV protonproton collision operation in early 2010. This paper presents the transverse momentum spectra of the neutral pions. The spectra from two independent LHCf detectors are consistent with each other and serve as a cross-check of the data. The transverse momentum spectra are also compared with the predictions of several hadronic interaction models that are often used for high-energy particle physics and for modeling ultra-high-energy cosmic-ray showers.

Parametrization of gamma-ray production cross sections forppinteractions in a broad proton energy range from the kinematic threshold to PeV energies

“…Different validations of the MC codes against the π 0 and γ-ray experimental data at the LHC energies (see e.g. [101][102][103][104]) show that none of the MC models is able to explain fully all the available experimental data. It is for this reason that we parametrize different models which are representative of different descriptions of hadronic interactions.…”

Transverse-momentum distribution and nuclear modification factor for neutral pions in the forward-rapidity region in proton-lead collisions atsNN=5.02TeV

“…The former is defined as having a single photon in each of the two calorimeter towers only, while a multihit π 0 event is defined as a single π 0 accompanied by at least one additional background particle (usually a photon or a neutron) in one of the two calorimeters. In the analysis presented here, events having two particles within the same calorimeter tower (multihit events) are rejected when the energy deposit of the background particle is above a certain threshold [29]. Mostly then, only single-hit π 0 events are considered in this analysis.…”

The performance of the LHCf detector for hadronic showers

“…This effect is called shower leakage-in as some of the energy leaking out from one calorimeter leaks in to the neighbor one. While leakage-in has a significant effect on the measurements of π 0 mesons [4], it also has some effect on the neutron measurements. The right panel of figure 9 shows the fraction of neutron energy deposited in the large calorimeter of the Arm2 detector as a function of the X and Y coordinates of a neutron incident on the small tower of the Arm2 detector.…”

“…It is designed to measure particles emitted in the very forward region (pseudorapidity η > 8.4) of the LHC. We have already published photon and π 0 spectra at 7 TeV protonproton collisions [3,4] and photon spectra at 0.9 TeV proton-proton collisions [5]. Forward neutron measurement is also important to verify the hadronic interaction models.…”