M. Nakai

Measurement of zero degree single photon energy spectra for s=7 TeV proton–proton collisions at LHC

Abstract 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 .

Early results of the LHCf experiment and their contribution to ultra-high-energy cosmic ray physics

LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward region of LHC collisions. The physics goal is to provide data for calibrating hadron interaction models that are used in the study of Extremely High-Energy Cosmic-Rays. The LHCf experiment acquired data from April to July 2010 during commissioning time of LHC operations at low luminosity. Production spectra of photons and neutrons emitted in the very forward region (

First year results from LHCf

\eta>

The performance of the LHCf detector

8.4) have been obtained. In this paper preliminary results of the photon spectra taken at

Study of GSO scintillator for the LHCf upgrade

\sqrt{s}

Data analysis techniques for LHCf

= 7TeV are reported.

The LHCf experiment at LHC

We give a brief description of the purpose of the LHCf experiment, detectors and their performance, and what has been done in the first year experiment. A short summary of results at s = 900 GeV is given although the energy is not an “intrinsic” LHC energy. Since detailed results at s = 7 TeV will appear soon elsewhere, here we limit ourselves to giving also a brief account of what will come in that paper.

Energy spectrum of neutral pion at LHC proton-proton collisions measured by the LHCf experiment

The LHCf experiment is designed to measure energies and transverse momenta of neutral particles emitted in the forward region of s = 14 TeV p‐p collision at ±140 m away from the interaction point1 (IP1) of LHC. The energy resolution is confirm to be within 5% and the position resolution is better than 0.2 mm for gamma‐rays with energies from 100 GeV to 200 GeV by the test beam results at the CERN‐SPS. LHCf has taken data at 2009 and 2010 at s = 900 GeV and 7 TeV collision. A brief summary of LHCf operation at LHC is also reported here.

The status and preliminary results of the LHC forward experiment: LHCf

The GSO scintillator has a very excellent radiation resistance, fast decay time and large amounts of light yield. Because of these features, GSO will be used to upgrade the current LHCf detector. We examined the features of GSO by using heavy ion beam at Heavy Ion Medical Accelerator in Chiba (HIMAC) Japan. The linearity of PMT R7400 for the large light yield of GSO with a 132Xe beam and the radiation hardness with a 12C beam were measured. As a result, GSO scintillator showed a good linearity up to the signal corresponding to 6 TeV EM‐shower maximum in the LHCf detector, and a good radiation hardness up to 7×105 Gy. For the LHCf Arm1 detector, small scaled GSO crystals (GSO bars), have been fabricated for the position determination detector. 5 GSO bars have been manufactured and its performance have been evaluated using 12C beam. Its light yield and position dependency have been evaluated.

LHCf: calibration of hadron interaction models for high energy cosmic‐ray physics at the LHC energy

Analysis techniques in LHCf are presented, in which all techniques are required to have a high resolution and efficiency in order to overcome the severe situation, small lateral aperture and longitudinally short length of the detector. In this paper, methods for reconstructing an energy of electromagnetic shower are discussed following the data flow of measured data and Monte Carlo simulations.