The performance of LHCf calorimeter was tested at CERN SPS in 2007. For electron of 50-200 GeV, the energy resolution is < 5% and the position resolution is <200um (<60um) for Arm1 (Arm2), respectively. These results are in good agreement with the MC simulation. The LHCf experiment took data in 2009 and 2010 at 900GeV and 7TeV. The total event numbers are 100K and 400M, respectively. The luminosity was estimated by FCs and it correspond to ATLAS results. The 0 mass reconstruction shows clear peak. The time validation of 0 mass shows the radiation damage of scintillator. LHCf is already removed and upgrading for 14TeV collision at 2013.

Tsuyoshi Mase, STEL Nagoya Universityfor the LHCf collaboration

The performance of the LHCf detector

The uncertainty of the hadron interaction model causes systematic errors of air shower simulations in high-energy region. To solve the problem, the LHCf experiment measures energies and transverse momenta of neutral particles emitted in the forward region of 14TeV p-p collision at LHC. Two LHCf detectors, consisting of sampling & imaging calorimeters, are installed at zero degree collision angle at ±140m from the interaction point 1 (IP1). The energy resolution is confirmed as to be <5% and the position resolution <0.2mm for gamma-rays with energies from 100GeV to 200GeV by test beam results at the CERN SPS.LHCf took data at 2009 and 2010 at 900GeV and 7TeV collision.

Abstract

What is the LHCf experiment?

The LHCf DetectorLHCf has two independent detectors named Arm1 and Arm2. Both detectors have two sampling and imaging calorimeters. The front counters is also located in front of the detectors. Detectors are installed 140m away from the Interaction Point 1 and covered almost 0 degree.Front Counter (FCs) are inserted in front of Arm1 and Arm2 detector. FC is composed of 4 plastic scintillators and a copper plate. The aperture of FC is 64cm2. This is maximum size within the limit of the space of the TAN slot.

The targets are gamma-rays >100GeV and neutrons >1TeV. The size of the detector is W90mm x L280mm x H620mm. LHCf detectors are consisted from 16layers of scintillator and tungsten (44 total r.l. and 1.7 λ). The size of each calorimeters are 20mm&40mm for Arm1 and 25mm&32mm for Arm2. The detector also have position sensitive layers: SciFi for Arm1 and silicon strip for Arm2

The performance of the LHCf detectorThe performance of the LHCf detectors was tested at the CERN SPS North Area T2-H4 beamline from 24 Aug to 11 Sep 2007. . Data acquisition was triggered using external trigger scintillators . Signal of calorimeters and position sensors were recorded in each event . Particle incident position was measured with an external silicon strip detector (ADAMO) placed in front of the LHCf calorimeters.

[Energy Resolution]RMS of ∑dEi is defined as energy resolution. (dEi :energy deposit of i’th calorimeter layer). The result for the 25mm calorimeter is shown. Experiment and MC show good agreement for different PMT gains. ('450V' or '600V')

The designed energy and position resolutions of <5% and <200μm, respectively, at >100GeV for gamma rays were confirmed with the beam test. These performances are well explained with the MC simulation. The result was summarized in Table1 with other features.

}Silicon tracker (ADAMO)

LHCf detector

Movable stage

trigger scinti

Beam

Setup of the SPS test

[Position Resolution] The deviation RMS of the shower positions determined by Position sensor and ADAMO was defined as the position resolution. Experiment and MC show a good agreement. result of Arm is shown.

Arm1 Arm2

ΔE (for >100GeV) <5%

Δx <200um <60um

linearity <5%@7TeV

trigger threshold >100GeV

pseudo-rapidity ∞>η>8.4

The ultra high energy cosmic rays(UHECRs) are the key to understand the mechanism of propagation, direction and acceleration of cosmic rays. Therefore, they are observed by many air shower experiments, for example, Auger, HiRes, AGASA and TA. The way to know the information of a primary CR is reconstruction of the information of secondaries in the air shower by Monte Carlo simulation with hadron interaction model. However, there is uncertainty of model causes systematic errors of air shower simulations in high energy region. The LHCf physics goal is to provide crucial calibration point for the hadron interaction models used in the cosmic-ray physics.

<Table1. summary of the LHCf performance for γ>

Arm2

Arm1

Summary

Structure of detector

[Energy][Position]

←LHC energy

Energy spectrum of cosmic-ray

LHC:7TeV + 7TeV->10x1017eV@Lab Sys

The status at LHC measurements

0 Candidates

Candidates

preliminary

25mm 32mm

Silicon strip-X view

m 140=

R

I.P.1

1(E1

)

2(E2)

140mR

3%

LHCf Front Counter

LHCf Calorimeter

BRAN-IC

ZDC type1

IP1

ZDC type2

Beam pipe

TANNeutral particles

Side view

BRAN-Sci

yxbrevbrevNNnfA

NNnfL 2

2121

The LHCf experiment corrected data with stable beam run at 900GeV and 7TeV in 2009 and 2010. With Stable Beam at 900GeV

•Total of 42 hours for physics•About 105 showers events in Arm1+Arm2

With Stable Beam at 7TeV•Total of 150 hours for physics with different setups

•Different vertical position to increase the accessible kinematical range•Runs with or without beam crossing angle

•4·108 shower events in Arm1+Arm2•106 0 events in Arm1+Arm2

σx χ2

FC1 60.0±0.3m

36.9

FC2 60.3±0.3m

53.8

FC1&2 59.1±0.4m

34.2

Event display

Luminosity 0 reconstruction

Radiation damage

The sample of event display for gamma-ray with 900GeV collision. The transition curve can be found in 20mm calorimeter and the particle incident position is able to see with SciFi.

L = frevnbN1N2A

= f revnbN1N22ps xs y

The absolute luminosity can measure to use the Front Counters. The beam size was measured by the VdM scan. The Luminosity L is given by next formulation.

0’s are a main source of electromagnetic secondaries in high energy collisions. The mass peak is very useful to confirm the detector performances and to estimate the systematic error of energy scale.

The LHCf detectors were exposed the hard radiation condition. The reconstruct 0 mass was shifted after irradiated.

LHCf detector 96mm

ADAMO

Detector

Trigger Scintillator

DAQ

p,e-,mu

Front counter

Event display (gamma, pi-zero)

Total event number, data taking period

Radiation damage measured by pi-zero