LHCf Measurements of Very Forward Particles at LHC Takashi SAKO (Solar-Terrestrial Environment Laboratory, Nagoya University, Japan) For the LHCf Collaboration XVI International Symposium on Very High Energy Interactions, 28 Jun-3 Jul 2010, Fermilab

Air shower experiments 2 Astrophysical parameters - source type - source distribution - source spectrum - source composition - propagation Image from “The Daily Galaxy” Air shower development - interaction - atmosphere Observations - lateral distribution - longitudinal distribution - particle type - arrival direction

Uncertainty in Hadron Interaction Auger, PRL (2010) Experimental data at highest energy hadron collider is indispensible => LHC

The Ｌarge Ｈadron Ｃollider Collider of 7TeV proton + 7TeV proton 1017eV @ labo. System Heavy ion collisions ATLAS / LHCf LHCb CMS / TOTEM ALICE

What to be measured at colliders multiplicity at LHC 14TeV collisions pseudo-rapidity; η= -ln(tan(θ/2)) Multiplicity All particles neutral Most of the collision products are emitted in the central region

What to be measured at colliders multiplicity and energy flux at LHC 14TeV collisions pseudo-rapidity; η= -ln(tan(θ/2)) Multiplicity Energy Flux All particles neutral Most of the energy flows into very forward

LHCf Experiment To measure very forward (η>8.4; including 0 degree) neutral particles at LHC p-p (ion-ion) collisions International collaboration of Japan-Europe-USA (36 members) ATLAS / LHCf LHCb CMS / TOTEM ALICE LHCf LHCf

The LHCf experiment K.Fukatsu, Y.Itow, K.Kawade, T.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, K.Noda, T.Sako, K.Suzuki, K.Taki Solar-Terrestrial Environment Laboratory, Nagoya University, Japan K.Yoshida Shibaura Institute of Technology, Japan K.Kasahara, M.Nakai, Y.Shimizu, T.Suzuki, 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, H.Menjo, P.Papini, S.Ricciarini, G.Castellini INFN, Univ. di Firenze, Italy G.Sinatra, A.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain D.Macina, A-L.Perrot CERN, Switzerland

Detector Location ATLAS 96mm LHCf Detector(Arm#1) Two independent detectors at either side of IP1 ( Arm#1, Arm#2 ) 96mm 140m 96mm LHC IP TAN Detector TAN -Neutral Particle Absorber- transition from one common beam pipe to two pipes 　　Slot : 100mm(w) x 607mm(H) x 1000mm(T)

ATLAS & LHCf

LHCf Detectors ＊Imaging sampling shower calorimeters ＊Two independent calorimeters in each detector (Tangsten 44r.l., 1.7λ, sample with plastic scintillators) Arm#1 Detector 20mmx20mm+40mmx40mm 4 XY SciFi+MAPMT Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors

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

Transverse projection of Arm#1 IP1,ATLAS Arm2 η ∞ 8.7 Shadow of beam pipes between IP and TAN 8.4 This is photos of our detectors installed in the LHC ring. The red one is the surface of TAN located 140m far from IP1. we can see our electronics boxes on TAN but detector were completely in experimental slots of TAN. Behind of our detectors, Luminosity monitor BRAN and ATLAS ZDC has been installed. ∞ @ 140mrad crossing angle neutral beam axis Transverse projection of Arm#1 @ zero crossing angle

Expected Results at 14 TeV collisions (assuming 0.1nb-1 statistics) Detector response not considered

Original Plan 34 32 Log(Luminosity [cm-2s-1]) 30 28 26 0.45 1.2 3.5 5 7 Beam energy (TeV) Log(Luminosity [cm-2s-1]) LHCf ideal LHCf removal LHC nominal

Real Life Original target >=2013 May-2010 Mar-2010 Dec-2009 34 32 30 28 26 0.45 1.2 3.5 5 7 Original target LHCf Removal End of June-2010 Log(Luminosity [cm-2s-1]) LHCf Ideal >=2013 May-2010 Mar-2010 Dec-2009 Beam energy (TeV)

Results at LHC

2009 Operation at 900GeV Collisions With stable beams at 900GeV, 06.Dec. – 15.Dec 2.6 hours for commissioning 27.7 hours for physics ~2,800 shower events in Arm1 ~3,700 shower events in Arm2 ~5x105 collisions at IP1 Expected spectra with each hadron interaction model Gamma-ray like @ Arm2 Hadron like @ Arm2 with 107 col.

First Events at 900GeV collisions Longitudinal development Lateral (X) Distribution Lateral (Y) Arm1 (SciFi)

First Events at 900GeV collisions Arm2 (Silicon) Longitudinal development Lateral (X) Distribution Lateral (Y) Distribution Energy scale is calibrated at SPS below 200GeV

Particle Identification A transition curve for Gamma-ray A transition curve for Hadron Thick for E.M. interaction (44X0) Thin for hadronic interaction(1.7l) L90% @ 20mm cal. of Arm1 Definition of L90% MC (QGSJET2) Data Preliminary Criteria for gamma-rays 16 r.l. + 0.002 x SdE Gamma-ray like

Both detectors give same spectra Comparison between calorimeter towers of Arm2 Gamma-ray like Hadron like Blue: including 0 degree Red: off axis No angular dependence Comparison between two Arms Blue: Arm2 Red: Arm1 Preliminary Preliminary Both detectors give same spectra

Spectra Comparison with MC (QGSJET2) prediction Conservative systematic error is assigned x15 statistics was obtained in the 2010 operation

7 TeV (3.5TeV+3.5TeV) Operation First collision on 31-March 2010 Already accumulated about 14 nb-1

Have you ever seen TeV showers? (except CRs) Gamma pair from TeV pi0 TeV gamma

Pi-zero (10% of full data) Arm1 Arm2

Energy spectra from first 1% data Hit map Very low BKG Angular dependence is seen Stronger 0 degree concentration in hadron candidates

What’s next Operation Analysis LHC started crossing angle run last week LHCf can enlarge the PT coverage Due to radiation damage LHCf removes the detectors in this summer Detector will be upgrated to rad-hard by 14TeV collisions (2013 earliest) Analysis 15 times more statistics in 900GeV data >100 time statistics in 7TeV data Systematics study rather than statistics Conversion to production spectra (cross section) Comparison with MC

Not only highest energy, but energy dependence… 7 TeV 10 TeV 14 TeV QGSJET2 7 TeV 10 TeV 14 TeV　(1017eV@lab.) SIBYLL Note: LHCf detector taken into account (biased) Secondary gamma-ray spectra in p-p collisions at different collision energies (normalized to the maximum energy) SIBYLL predicts perfect scaling while QGSJET2 predicts softening at higher energy Qualitatively consistent with Xmax prediction

Summary LHCf is a dedicated experiment to measure very forward neutral particles at LHC LHCf successfully started (and almost finished) data taking at 900GeV and 7TeV collisions We have sufficient statistics and started careful study in systematics to test hadron interaction models We will remove the detectors soon and come back at 14TeV collisions with upgraded detectors

Backup

Light Nuclei collisions (Note: Not planned in LHC!!) Energy flux in Nitrogen collisions Still strong concentration in the forward region

Expected spectra in N-N collisions Assuming to measure at the LHCf installation location Gamma spectra at <1cm from 0 degree clear difference in QGSJET2 and DPMJET3 Neutron spectra at <1cm from 0 degree dominated by fragmentation neutron Neutron spectra at 1-2cm (off center) clear difference in high energy part

Beam test at SPS p,e-,mu σ=172μm σ=40μm Detector Energy Resolution for electrons with 20mm cal. - Electrons 50GeV/c – 200GeV/c Muons 150GeV/c Protons 150GeV/c, 350GeV/c Position Resolution (Silicon) Position Resolution (Scifi) The detector performance was checked by beam tests at SPS. We had exposed the detectors in electron, muon and protons beams with a few hundreds GeV. This is energy resolution of one of the calorimeters as a function of gamma-ray energy. It is in a very good agreement with simulation results and good resolution of 5% for more than 100GeV. And bottom figures show position resolution of scintillating fibers of Arm1 and silicon detectors of Arm2 for 200GeV electrons. σ=172μm for 200GeV electrons σ=40μm for 200GeV electrons