LHCf: very forward measurement of neutral particles at LHC SAKO Takashi (for the LHCf collaboration) Solar-Terrestrial Environment Laboratory, Nagoya University, Japan HERA and the LHC @ CERN 28-May-2008

Outline HECR observations and interaction models The LHCf experiment GZK energy (absolute energy scale, composition) Galactic cosmic-rays (composition) The LHCf experiment Experiment setup Model discrimination

Energy spectrum of CRs Knee; acceleration limit of galactic CRs? GZK cutoff; Propagation limit due to CMB Engel, Nuclear Phys. B (Proc. Suppl.) 151 (2006) 437-461

Berezinsky, ICRC 2007 Systematics of AGASA Total ±18% AGASA X0.9 HiRes X1.2 Yakutsk X0.75 Auger X1.2 (not enough) Systematics of AGASA Total ±18% Hadron interaction (QGSJET, SIBYLL) ~10% (Takeda et al., 2003)

Composition (Auger) Xmax favors heavy primary 4 Composition (Auger) Xmax favors heavy primary Anisotropy favors light primary (if accept AGN correlation)

Composition of Galactic CRs (KASCADE) QGSJET01 SIBYLL 2.1

Energy spectrum of CRs LHC pp collision Knee; acceleration limit of galactic CRs? GZK cutoff; Propagation limit due to CMB LHC pp collision Engel, Nuclear Phys. B (Proc. Suppl.) 151 (2006) 437-461

Transverse energy flow Pseudo rapidity in LHC LHCf Energy flow Transverse energy flow The CMS and TOTEM diffractive and forward physics working group pseudorapidity：　 = - ln (tan /2)

LHCf interaction point 1 140m 96mm Arm#1 Arm#2

Installation of the detectors in the TAN absorbers at 140m from IP1 LHCf 96 mm

LHCf (ZDCs) Acceptance η> 8.4 η> 8.7 XF 0.1 1.0 ~10cmX10cm at 140m away from collision point (5cm/140m ~ 300 urad)

The LHCf experiment K.Fukui, Y.Itow, T.Mase, K.Masuda, Y.Matsubara, H.Menjo, T.Sako, K.Taki, H.Watanabe Solar-Terrestrial Environment Laboratory, Nagoya University, Japan K.Yoshida Shibaura Institute of Technology, Japan K.Kasahara, M.Mizuishi, Y.Shimizu, S.Torii Waseda University, Japan T.Tamura Kanagawa University, Japan Y.Muraki Konan University M.Haguenauer Ecole Polytechnique, France W.C.Turner LBNL, Berkeley, USA O.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, M.Grandi, P.Papini, S.Ricciarini, G.Castellini, A. Viciani INFN, Univ. di Firenze, Italy A.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain D.Macina, A-L.Perrot CERN, Switzerland

Double Arm Detectors Arm#1 Detector Arm#2 Detector 290mm 90mm

Double Arm Detectors Arm#1 Detector 20mmx20mm+40mmx40mm 4 XY SciFi+MAPMT Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors

Model dependence in LHCf θ~ 0 radian θ~ 270 μradian Gamma-ray spectra expected in a 1000 sec operation of LHCf at very low LHC luminosity（1029cm-2s-1）

π0 spectra QGSJETII ⇔ DPMJET3χ2= 106 (C.L. <10-6) Pi zero produced at collision can be extracted by using gamma pair events Powerful to eliminate beam-gas BG QGSJETII ⇔ DPMJET3χ2= 106 (C.L. <10-6) ⇔ SIBYLL χ2= 83 (C.L. <10-6) DPMJET3 ⇔ SIBYLL χ2= 28 (C.L.= 0.024) 107events DOF = 17-2=15

Neutron spectra Energy spectra at detector front Resolution included spectra

New models (PICCO, EPOS) Proton New models (PICCO, EPOS) Drescher, Physical Review D77, 056003 (2008) Pi0 Neutron

LPM effect ○ w/o LPM ■ w/ LPM Transition curve of a 1 TeV photon w/ and w/o LPM to be measured by LHCf

Run schedule LHCf runs will be carried out during the LHC commissioning with low luminosity L<1030cm-2s-1 Data taking at 10TeV collisions in 2008 and 14TeV collisions in 2009 Dedicated run with beam crossing angle in under discussion (pseudo-rapidity limit 8.7 => 8.4) Future runs during ion collisions in study

Summary Interpretation of CR observation data in 1015-1020eV strongly depends on the interaction model used in the analysis. LHCf will set a crucial calibration point at 1017eV for the interaction models. LHCf can measure E, p spectra of gamma-rays, π0 and neutrons at η>8.7 (8.4). LHCf can clearly discriminate existing/proposed models with a short operation under very low luminosity condition.

Backup

Knapp, Shower curve 大気深さ シャワー粒子数

Calorimeter 44 radiation lengths, 1.7 hadron interaction lengths n, gamma 44 radiation lengths, 1.7 hadron interaction lengths 16 sampling scintillators 4 position layers (2 for EM, 2 for hadron) 100-7000GeV gammaに対して <5%の分解能

Manipulator DC motorによる駆動 光学エンコーダ（放射線に弱い!）による位置測定 リニアポテンシオメータ（可変抵抗）値による位置測定 名大理学部装置開発室と共同開発　 全て200m先の control roomから制御が必要

Energy resolution (gamma-rays) 5% 1TeV ↑　MC simulation <7TeV ← SPS beam test <200GeV

Position resolution