Large Hadron Collider Forward Research Articles

Measurement of the forward η meson production rate in p-p collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{\ extrm{s}} $$\\end{document} = 13 TeV with the LHCf-Arm2 detector

The forward η mesons production has been observed by the Large Hadron Collider forward (LHCf) experiment in proton-proton collision at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV. This paper presents the measurement of the inclusive production rate of η in pT< 1.1 GeV/c, expressed as a function of the Feynman-x variable. These results are compared with the predictions of several hadronic interaction models commonly used for the modelling of the air showers produced by ultra-high energy cosmic rays. This is both the first measurement of η mesons from LHCf and the first time a particle containing strange quarks has been observed in the forward region for high-energy collisions. These results will provide a powerful constraint on hadronic interaction models for the purpose of improving the understanding of the processes underlying the air showers produced in the Earth’s atmosphere by ultra-energetic cosmic rays.

Total π+p cross section extracted from the leading neutron spectra at the LHC

We use the very forward neutron energy spectra measured by the Large Hadron Collider forward (LHCf) experiment at 7 TeV to extract the $\pi^+ p$ total cross section at centre-of-mass energies in the range 2.3$-$3.5 TeV. To do this we have to first isolate the $\pi$-exchange pole in forward neutron production in $pp$ collisions, by evaluating other possible contributions. Namely, those from $\rho$ and $a_2$ exchange, from both eikonal and enhanced screening effects, from migration, from neutron production by $\Delta$-isobar decay and from diffractive nucleon excitations. We discuss the possible theoretical uncertainties due to the fact that the data do not exactly reach the $\pi$ pole. We choose the kinematical domain where the pion contribution dominates and demonstrate the role of the different corrections which could affect the final result.

Performance study for the photon measurements of the upgraded LHCf calorimeters with Gd2SiO5 (GSO) scintillators

The Large Hadron Collider forward (LHCf) experiment was motivated to understand the hadronic interaction processes relevant to cosmic-ray air shower development. We have developed radiation-hard detectors with the use of Gd2SiO5 (GSO) scintillators for proton-proton √s = 13 TeV collisions. Calibration of such detectors for photon measurement has been completed at the CERN SPS T2-H4 line in 2015 using electron beams of 100–250 GeV and muon beams of 150–250 GeV . After the channel-by-channel absolute energy calibration, the energy resolution of the calorimeters is confirmed to be better than 3% for electrons with energy above 100 GeV . The position dependence of the energy scale of the calorimeters was reduced to the level of 1% after the corrections for scintillator nonuniformity and the shower leakage effect. The position resolution of the new shower imaging detector, a GSO-bar hodoscope interleaved in the calorimeter, was 100 μm for 200 GeV electrons. The experimental results are well explained by Monte Carlo simulations. We have confirmed that the new detectors meet the requirement of the LHCf experiment at √s = 13 TeV.

The performance for the TeV photon measurement of the LHCf upgraded detector using Gd2SiO5 (GSO) scintillators

The Large Hadron Collider forward (LHCf) experiment measures the forward particle production at the LHC to verify hadronic interaction models used in air shower experiments. We have upgraded very small sampling and imaging calorimeters using GSO scintillators to measure the most energetic particles generated in s=13TeV p–p collisions at the zero-degree region of the LHC. Upgraded detectors were calibrated at the SPS North area facility in CERN and it was confirmed that the detector can measure electro-magnetic showers with energy resolution of 3% and position resolution of better than 123μm for 100GeV electrons. The operation of LHCf in 13TeV p–p collisions has been successfully completed with integrated luminosity of 5nb−1. Reconstructed π0 peak with the mass resolution of 3.7% and stability less than 1% during the operation implies that our measurement was stable enough in the high irradiation condition.

First indication of LPM effect in LHCf, an LHC experiment

The Large Hadron Collider forward (LHCf) experiment is dedicated to the measurement of very forward neutral particle production in the high energy hadron-hadron collisions at LHC. The aim of the experiment is to improve the cosmic ray air shower development models and its setup gives an important opportunity to directly measure the Landau Pomeranchunk Migdal (LPM) effect in heavy absorber. This work presents the analysis for LPM effect on data taken in 2010 and 2013 at √ s = 7 TeV and √ s NN = 5.02 TeV respectively. We study the interactions of gamma, mainly produced by π 0 decay, in one of the calorimeter pairs of LHCf. This is composed by 16 Tungsten layers as absorbers and 16 plastic scintillators for energy measurements (Arm2). We use three parameters to describe the mean shower profile with respect the photon mean energy. The results are compared with Epics MonteCarlo simulation with LPM active and inactive models, shows a first evidence of LPM effect.

Measurement of very forward neutron energy spectra for 7 TeV proton–proton collisions at the Large Hadron Collider

The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC s=7 TeV proton–proton collisions with the pseudo-rapidity η ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results, and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However, no model perfectly explains the experimental results over the entire pseudo-rapidity range. The experimental data indicate a more abundant neutron production rate relative to the photon production than any model predictions studied here.

The performance of the LHCf detector for hadronic showers

The Large Hadron Collider forward (LHCf) experiment has been designed to use the LHC to benchmark the hadronic interaction models used in cosmic-ray physics. It measures neutral particles emitted in the very forward region of the LHC p-p or p-N collisions. In this paper, the performances of the LHCf detectors for hadronic showers was studied with MC simulations and beam tests. The detection efficiency for neutrons varies from 70% to 80% above 500 GeV. The energy resolutions are about 40% and the position resolution is 0.1 to 1.3 mm depending on the incident energy for neutrons. The energy scale determined by the MC simulations and the validity of the MC simulations were examined using 350 GeV proton beams at the CERN-SPS.

LHCf DETECTOR PERFORMANCE DURING THE 2009–2010 LHC RUN

Large Hadron Collider forward (LHCf) has successfully completed the operation during the LHC 2009–2010 period and the detectors were removed in July 2010. The event trigger, data analysis and background have been intensively studied in order to derive inclusive single photon and π0 spectra. In this paper, the details of these intensive studies are described.

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

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 proton-proton 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 ultrahigh-energy cosmic ray showers.3 MoreReceived 21 May 2012DOI:https://doi.org/10.1103/PhysRevD.86.092001This 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.© 2012 CERN, for the LHCf Collaboration

Measurement of zero degree inclusive photon energy spectra for [formula omitted] proton–proton collisions at LHC

The inclusive photon energy spectra measured by the Large Hadron Collider forward (LHCf) experiment in the very forward region of LHC proton–proton collisions at s=900GeV are reported. The results from the analysis of 0.30 nb−1 of data collected in May 2010 in the two pseudorapidity regions of η>10.15 and 8.77<η<9.46 are compared with the predictions of the hadronic interaction models DPMJET 3.04, EPOS 1.99, PYTHIA 8.145, QGSJET II-03 and SIBYLL 2.1, which are widely used in ultra-high energy cosmic ray experiments. EPOS 1.99 and SIBYLL 2.1 show a reasonable agreement with the spectral shape of the experimental data, whereas they predict lower cross-sections than the data. The other models, DPMJET 3.04, QGSJET II-03 and PYTHIA 8.145, are in good agreement with the data below 300 GeV but predict harder energy spectra than the data above 300 GeV.The results of these comparisons exhibited features similar to those for the previously reported data for s=7TeV collisions.

Revised production cross-section of γ-rays in p–p collisions with LHC data for the study of TeV γ-ray astronomy

We present the production cross-section of γ-rays based on data of p–p collisions at the Large Hadron Collider (LHC), revising the previous semi-empirical formula mainly for (1) the inelastic cross-section in p–p collisions, σpp(E0), and 2) the inclusive γ-ray spectrum in the forward region, σpp→γ(E0,Eγ). We find that the previous cross-section gives a significantly softer spectrum than found in the data of LHC. In this paper, we focus our interest mainly upon the LHC forward (LHCf) experiment, giving γ-ray spectra in the very forward region with the pseudo-rapidity η∗≳8.8 in the center of mass system (CMS), which have not been reported so far. We also give the pseudo-rapidity distribution of charged hadrons with -3⩽η∗⩽3 obtained by ALICE and TOTEM experiments, both with LHC. We find that the revised cross-section reproduces quite well the accelerator data over the wide energy range from GeV to 30PeV for projectile protons, corresponding approximately to 100MeV to 3PeV for secondary γ-rays. The production cross-section of γ-rays produced in the forward region is essential for the study of γ-ray astronomy, while not important are those produced in the central region in CMS, and of much less importance in the backward. We discuss also the average transverse momentum of γ-rays, p¯t, and the average inelasticity transferred to γ-rays, k¯γ∗, obtaining that the former increases very slowly with p¯t=100∼220MeV/c for E0=1GeV∼26PeV, and the latter is almost independent of E0, with k¯γ∗≈1/6, while we cannot exclude the possibility of a small increase of k¯γ∗.

Luminosity determination in √s = 7 TeV proton collisions using the LHCf Front Counter at LHC

In the Large Hadron Collider forward (LHCf) experiment, the luminosity is determined with the counting rates of detectors called Front Counter.During the LHCf physics operation at √s = 7 TeV in 2010, two series of calibration run in the conversion factors from the counting rate to the luminosity were carried out on 26th of April and 9th of May.Using the luminosities determined in the April and May scans with 5 % and 4 % accuracy, the conversionfactors were determined with 5.0 % accuracy,providing the luminosity determination at the LHCf experiment with this accuracy.

Measurement of zero degree single photon energy spectra for [formula omitted] proton–proton collisions at LHC

In early 2010, the Large Hadron Collider forward (LHCf) experiment measured very forward neutral particle spectra in LHC proton–proton collisions. From a limited data set taken under the best beam conditions (low beam-gas background and low occurrence of pile-up events), the single photon spectra at s=7 TeV and pseudo-rapidity (η) ranges from 8.81 to 8.99 and from 10.94 to infinity were obtained for the first time and are reported in this Letter. The spectra from two independent LHCf detectors are consistent with one another and serve as a cross check of the data. The photon spectra are also compared with the predictions of several hadron interaction models that are used extensively for modeling ultra-high energy cosmic-ray showers. Despite conservative estimates for the systematic errors, none of the models agree perfectly with the measurements. A notable difference is found between the data and the DPMJET 3.04 and PYTHIA 8.145 hadron interaction models above 2 TeV where the models predict higher photon yield than the data. The QGSJET II-03 model predicts overall lower photon yield than the data, especially above 2 TeV in the rapidity range 8.81<η<8.99.

Performance of the Arm#1 Detector for LHCf Experiment

The Large Hadron Collider forward (LHCf) experiment will provide the energy and transverse momentum spectra of neutral particles produced in the very forward region of p-p collision at 7+7 TeV, corresponding to a laboratory frame energy of 10 17 eV. The LHCf apparatus is composed of two independent detectors installed at zero degree collision angle from the ATLAS interaction point. To assess performance of LHCf detectors, we carried out a beam test in 2007 at the CERN SPS H4 beamline. We report results of the Arm#1 detector, using scintillating fibers for measuring shower positions, obtained from electron primary beams of 50–200 GeV, and proton primary beams of 150–350 GeV and muon primary beams of 150–200 GeV. We obtained energy resolution of electrons as a function of the primary energy . The position resolution of shower axis is obtained by using a position determined with the Si microstrip detectors. We also reconstructed the real geometry of each SciFi by the use of muon primary beams. Finally, we re...