Abstract
In this paper, we report the measurement relative to the production of forward neutrons in proton-proton collisions at sqrt{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.
Highlights
Has been designed to measure the distributions of neutral particles produced in the very forward region in p-p and p-nucleus collisions
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
Distributions are expressed in terms of the inclusive differential production cross section dσn/dE, which was corrected for the limited coverage of the azimuthal angle
Summary
The LHCf experiment consists of two detectors [14], Arm and Arm, placed in two regions on the opposite sides of LHC Interaction Point 1 (IP1). These regions, called Target Absorber Neutral (TAN), are located at a distance of 141.05 m from IP1, after the dipole magnets that bend the two proton beams. Apart from the energy, measured using the 16 scintillator layers, the transverse position is reconstructed from the transverse profile of the showers, measured using 4 xy imaging layers These imaging layers, placed at different depths in the calorimeter, consist of 160 μm read-out pitch silicon microstrip detectors. For hadrons between 1 and 6.5 TeV, detection efficiency ranges from about 52% to 72%, energy resolution from 28% to 38%, and position resolution from 300 μm to 100 μm
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