The LHCf experiment Hiroaki MENJO INFN Firenze on behalf for the LHCf collaboration at 29 March 2010, MC4LHC

Outline What is the LHCf experiment ? - LHCf is one of forward experiments at LHC, with calorimeters covering  Why does LHCf look at the very forward region ? - To measure the most energetic secondaries which make an important role in air shower developments of cosmic rays. What can LHCf measure ? - E nergy spectra and P T distribution of neutral particles, gamma-rays, neutrons and  . LHCf = “LHC forward”

ATLAS LHCb CMS/TOTEM ALICE - LHCf collaboration - 6 countries 12 institutes 31 members LHCf

Location ATLAS 140m LHCf Detector(Arm#1) LHCf Detector (Arm#2) 96mm 140m 96mm IP TAN Detector Inside of TAN -Neutral particle absorber- The detector has been installed in 96mm gap of the beam pipes. Neutral particles charged particles Detectors at zero degree of collisions

The Main Calorimeters 40mm 20mm Schematic view of the calorimeters in Arm#1 Sampling Calorimeter W 44 r.l, 1.7λ I Scintilator x 16 Layers Position Detector Scifi x 4 (Arm#1) Silicon strip detector x 4 (Arm#2) Expected Performance: Energy resolution (> 100GeV) < 5% for photons 30% for neutrons Position resolution < 200μm (Arm#1) 40μm (Arm#2) 25mm 32mm Schematic view of the calorimeters in Arm#2 Two independent calorimeters allow to reconstruct π 0

Arm#1Arm#2 280mm 92mm 90mm 620mm

Beam test at SPS Energy Resolution for electrons with 20mm cal. Position Resolution (Scifi) Position Resolution (Silicon) Detector p,e-,mu σ=172 μm for 200GeV electrons σ=40 μm for 200GeV electrons - Electrons 50GeV/c – 200GeV/c - Muons 150GeV/c - Protons 150GeV/c, 350GeV/c

10m Fixed Target Acrylic or Carbon Arm#1 Detector   reconstruction at a beam test   mass was reconstructed from gamma-ray pair measured by the both two calorimeters Calibration over SPS energy Light Intensity(MIPs) ADC counts(0.025pC) 70,000 MIPs eq. Response of all PMTs for large amount of light over SPS energy upto 70,000 MIPs eq. (7TeV elemag shower) has been calibrated by a fast N 2 laser.

Sub detectors -Front Counter- Thin scintillators with 8x8cm 2 acceptance, which have been installed in front of each main detector. To monitor beam condition. For background rejection of beam-residual gas collisions by coincidence analysis Schematic view of Front counter

Movable detectors Shadow of beam pipes between IP and TAN neutral beam axis Transverse projection of Arm#1 calorimeters at zero-crossing angle. neutral beam axis η ∞ 8.7 Shadow of beam pipes between IP and TAN Transverse projection of Arm#1 calorimeters at crossing angle of 140urad. η ∞ 8.4 Shadow of beam pipes between IP and TAN neutral beam axis

Detectors in LHC Detectors in slots of TAN located 140m far from IP1 IP1,ATLAS

= Why the very forward region = The motivation comes from observations of Ultra High Energy Cosmic-Rays (UHECRs). AGN etc. ~10 20 eV Depth[g/cm 2 ] Proton Fe Photons E=10 19 eV X MAX AGASA HiRes AUGER TA -Experiments- [g/cm 2 ] Proton Iron eV10 18 eV : one of indicators for cosmic-ray composition Phys. Rev. Lett., 2010, 104, EPOS QGSJET2

= Why the very forward region = Uncertainty of hadron interaction models induces effective systematic error, especially for composition study of UHECRs. But now we have LHC to calibrate interaction models at 7+7TeV pp, equivalent to eV in lab. !! Key parameters Total cross section ↔ TOTEM, ATLAS(ALFA) Multiplicity ↔ Central detectors Inelasticity/Secondary spectra ↔ Forward calorimeters LHCf, ZDCs

Rapidity distributions at 7+7TeV pp In forward region (  ), Quite Low multiplicity, but Covering > 50% of total energy flux. = Multiplicity == Energy Flux = Calculated with DPMJET3, dashed line: neutral particles

η> 8.4 X F η> 8.7 Spectra of Secondary gamma-rays Ratio Detectable/All Most of all energetic neutral particle (X F >0.1) are detectable by LHCf

What LHCf can measure Energy spectra and Transverse momentum distribution of Gamma-rays (E>100GeV,  E/E a few 100 GeV,  E/E~30%) Neutral Pion (E>700GeV,  E/E<3%) at psudo-rapidity range >8.4 LHCf can measure only inclusive spectra !! LHCf trigger is completely independent on ATLAS trigger. However it is possible to identify coincidence events with ATLAS event by offline, and to analyze with center region (ATLAS) in future. = What can LHCf measure ? =

MC model discrimination at 14TeV  n at 7TeV + 7TeV pp 10 6 collisions ↔ 2min cm -2 s -1 n w/o resolution

Reconstruction of   MC model discrimination at 14TeV Expected Measurement spectrum by Arm1 = P T distribution =  10 7 collisions ↔ 20min cm -2 s -1

MC model discrimination at 7TeV at 3.5TeV + 3.5TeV pp  n Energy spectra with 30% energy resolution 1.5 x 10 6 collisions ↔ 3min cm -2 s -1 with 5% energy resolution We will see 7TeV collisions tomorrow !!

MC model discrimination at 900GeV at 450GeV + 450GeV pp  n w/o resolution DPMJET3 QGSJET2 QGSJET1 SYBILL Expected energy spectra with the 20x20mm calorimeter at 10 7 collisions We took data in 2009 Backgrounds w/o resolution

Preliminary resaults at 900GeV In last year, LHCf took 6,000 shower events at 900GeV collisions. ↔ > 10 6 collisions at all IPs. Shadow of beam pipes Red: colliding bunch = collision + BG Blue: single bunch = BG only Presented at 18-Dec-2009

Preliminary resaults at 900GeV MC with DPMJET3 Data in 2009 preliminary can say nothing about hadron results for the moment ! Checking detector response for hadrons carefully by beam test data. Analysis is ongoing, and we will get more statistic soon !! Presented at LHCC 17-Feb-2009 Not calibrated yet

Operation Plan 2009 Took data at 900GeV collision. ~6,000 shower events 2010 Take data at 900GeV again. Operation at TeV till 2 pb -1. Then remove detectors and upgrade them Install detectors again. Operation at 7+7TeV + we want to measure at intermediate energy ~ TeV, if LHC has. + we want to measure at light Ions+Ions collisions. We will take data in LHC commissioning phases with low luminosity at every collision energy.

Summary The LHCf experiment is one of forward experiments at LHC, with calorimeters covering  LHCf looks at very forward region to measure the most energetic secondaries which play an important role in air shower developments of cosmic rays. LHCf can measure energy spectra and P T distribution of neutral particles, gamma-rays, neutrons and  .

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Arm1  event

Arm2  event

Arm2 neutron event Transition curve in the calorimetric towers is used to discriminate between  and n  : L 90% <20 X 0 n: L 90% >20 X0