Measurement of inclusive forward neutron production cross section in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV with the LHCf Arm2 detector

Abstract

In this paper, we report the measurement relative to the production of forward neutrons in proton-proton collisions at √ s = 13 TeV obtained using the LHCf Arm2 detector at the Large Hadron Collider. The results for the inclusive differential production cross section are presented as a function of energy in three different pseudorapidity regions: η > 10.76, 8.99 < η < 9.22 and 8.81 < η < 8.99. The analysis was performed using a data set acquired in June 2015 that corresponds to an integrated luminosity of 0.194 nb −1. The measurements were compared with the predictions of several hadronic interaction models used to simulate air showers generated by Ultra High Energy Cosmic Rays. None of these generators showed good agreement with the data for all pseudorapidity intervals. For η > 10.76, no model is able to reproduce the observed peak structure at around 5 TeV and all models underestimate the total production cross section: among them, QGSJET II-04 shows the smallest deficit with respect to data for the whole energy range. For 8.99 < η < 9.22 and 8.81 < η < 8.99, the models having the best overall agreement with data are SIBYLL 2.3 and EPOS-LHC, respectively: in particular, in both regions SIBYLL 2.3 is able to reproduce the observed peak structure at around 1.5-2.5 TeV.

Open Questions in Cosmic-Ray Research at Ultrahigh Energies

“…Understanding the scaling of the forward particle distributions at collider energies is the key to extrapolating to higher interaction energies. LHCf (Adriani et al, 2018) is a good example that such detectors can be built even though there are large technical challenges and limitations.…”

Measurement of energy flow, cross section and average inelasticity of forward neutrons produced in $$ \sqrt{s} $$ = 13 TeV proton-proton collisions with the LHCf Arm2 detector

“…Because of the key role that forward baryons have in the development of the air showers and in the abundance of the muonic component [24], a large activity of the LHCf collaboration is dedicated to neutron measurements. A first result relative to the inclusive differential production cross section of very forward neutrons+antineutrons (hereafter simply called neutrons) produced in p-p collisions at √ s = 13 TeV was already published [25]. Here this analysis is extended from three to six pseudorapidity regions, in order to have enough data points to derive three important quantities that are directly connected to EAS development: neutron energy flow, cross section and average inelasticity.…”

“…Monte Carlo simulations with the same experimental configuration used for LHC data taking are necessary for four different purposes: estimation of correction factors and systematic uncertainties, validation of the whole analysis procedure, energy spectra unfolding, and data-model comparison. A description of all the simulation data sets, detailing how they were generated, which models were used and which effects were considered, can be found in [25]. Here it is important to remind that, depending on the purpose, a given sample is generated taking into account one or more of the following steps: hadronic collision, transport of secondary products from IP1 to TAN, and detector interactions.…”

“…Apart from small refinements, event reconstruction algorithms and event selection criteria are similar to the ones described in [25]. The incident energy is reconstructed from the total energy deposit in the calorimeter, properly weighting the release in each scintillator layer for the energy lost in the corresponding front tungsten layer and applying position dependent correction factors for shower lateral leakage and light collection efficiency.…”

Systematic differences due to high energy hadronic interaction models in air shower simulations in the 100 GeV-100 TeV range

“…Finally, hadron simulations are required to estimate the sensitivity of future gamma-ray observatories, such as the Cherenkov Telescope Array (CTA) [13], the Southern Gamma-ray Survey Observatory (SGSO) [14], and the Large High Altitude Air Shower Observatory (LHAASO) [15] which could be affected by the choice of models. The advent of LHC measurements has provided large amounts of data at never before probed energies [16] and at extreme rapidities [17,18]. This data glut promises improvements to hadronic interaction models by facilitating model tuning in energy ranges not before possible and has resulted in the creation of a new generation of air shower focused hadronic interaction models [19][20][21] tuned to this data set.…”