LHCf Measurements of Very Forward Particles at LHC

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 Air shower development - interaction - atmosphere Image from “The Daily Galaxy” 2

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

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

What to be measured at colliders multiplicity at LHC 14 Te. V 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 14 Te. V 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 ALICE LHCb Japan-Europe-USA (36 members) ATLAS / LHCf CMS / TOTEM 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 J. Velasco, A. Faus D. Macina, A-L. Perrot INFN, Univ. di Catania, Italy IFIC, Centro Mixto CSIC-UVEG, Spain CERN, Switzerland

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

ATLAS & LHCf

LHCf Detectors ＊Imaging sampling shower calorimeters ＊Two independent calorimeters in each detector (Tangsten 44 r. l. , 1. 7λ, sample with plastic scintillators) Arm#1 Detector 20 mmx 20 mm+40 mmx 40 mm 4 XY Sci. Fi+MAPMT Arm#2 Detector 25 mmx 25 mm+32 mmx 32 mm 4 XY Silicon strip detectors

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

Arm 1 IP 1, ATLAS Arm 2 η Shadow of beam pipes between IP and TAN 8. 4 8. 7 ∞ ∞ is x a m a e b neutral @ 140 mrad crossing angle Transverse projection of Arm#1 @ zero crossing angle 13

Expected Results at 14 Te. V collisions (assuming 0. 1 nb-1 statistics) Detector response not considered

Original Plan Log(Luminosity [cm-2 s-1]) 34 LHC nominal 32 LHCf removal 30 LHCf ideal 28 26 0. 45 1. 2 3. 5 5 7 Beam energy (Te. V)

Real Life 34 Log(Luminosity [cm-2 s-1]) Original target 32 LHCf Removal End of June-2010 30 LHCf Ideal 28 26 May-2010 Mar-2010 Dec-2009 0. 45 1. 2 >=2013 3. 5 5 7 Beam energy (Te. V)

Results at LHC

2009 Operation at 900 Ge. V Collisions With stable beams at 900 Ge. V, 06. Dec. – 15. Dec 2. 6 hours for commissioning 27. 7 hours for physics ~5 x 105 collisions ~2, 800 shower events in Arm 1 ~3, 700 shower events in Arm 2 at IP 1 Expected spectra with each hadron interaction model Gamma-ray like @ Arm 2 Hadron like @ Arm 2 with 107 col.

First Events at 900 Ge. V collisions Arm 1 (Sci. Fi) Longitudinal development Lateral (X) Distribution Lateral (Y) Distribution

First Events at 900 Ge. V collisions Arm 2 (Silicon) Longitudinal development Lateral (X) Distribution Lateral (Y) Distribution Energy scale is calibrated at SPS below 200 Ge. V

Particle Identification A transition curve for Gamma-ray A transition curve for Hadron Thick for E. M. interaction (44 X 0) Thin for hadronic interaction(1. 7 l) L 90% @ 20 mm cal. of Arm 1 MC (QGSJET 2) y r a Data n i m i l e Gamma-ray like Pr Criteria for gamma-rays 16 r. l. + 0. 002 x Sd. E Definition of L 90%

Comparison between calorimeter towers of Arm 2 Gamma-ray like Hadron like Blue: including 0 degree Red: off axis No angular dependence Comparison between two Arms Pr ry a n i elim im l e Pr ry a in Blue: Arm 2 Red: Arm 1 Both detectors give same spectra

Spectra Comparison with MC (QGSJET 2) prediction Ø Conservative systematic error is assigned Ø x 15 statistics was obtained in the 2010 operation

7 Te. V (3. 5 Te. V+3. 5 Te. V) Operation Ø First collision on 31 -March 2010 Ø Already accumulated about 14 nb-1

Have you ever seen Te. V showers? (except CRs) Gamma pair from Te. V pi 0 Te. V gamma

Pi-zero (10% of full data) Arm 1 Arm 2

Energy spectra from first 1% data Hit map Ø Very low BKG Ø Angular dependence is seen Ø Stronger 0 degree concentration in hadron candidates 27

What’s next • Operation – 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 14 Te. V collisions (2013 earliest) • Analysis – – – 15 times more statistics in 900 Ge. V data >100 time statistics in 7 Te. V data Systematics study rather than statistics Conversion to production spectra (cross section) Comparison with MC

Not only highest energy, but energy dependence… SIBYLL 7 Te. V 10 Te. V 14 Te. V (1017 e. V@lab. ) QGSJET 2 7 Te. V 10 Te. V 14 Te. V No int te: L o a HC cc f ou det e nt (bi ctor as ed taken ) Secondary gamma-ray spectra in p-p collisions at different collision energies (normalized to the maximum energy) SIBYLL predicts perfect scaling while QGSJET 2 predicts softening at higher energy Qualitatively consistent with Xmax prediction

Summary Ø LHCf is a dedicated experiment to measure very forward neutral particles at LHC Ø LHCf successfully started (and almost finished) data taking at 900 Ge. V and 7 Te. V collisions Ø We have sufficient statistics and started careful study in systematics to test hadron interaction models Ø We will remove the detectors soon and come back at 14 Te. V 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 Ø Gamma spectra at <1 cm from 0 degree • clear difference in QGSJET 2 and DPMJET 3 Ø Neutron spectra at <1 cm from 0 degree • dominated by fragmentation neutron Ø Neutron spectra at 1 -2 cm (off center) • clear difference in high energy part

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