Contents 1. Experimental purposes 2. Experiment details

1. The First Results from the LHCf experimentand Cosmic-Ray PhysicsYasushi Muraki Department of physics, Konan University, Kobe, JapanOn behalf of the LHCfcollaboration Contents • 1. Experimental purposes • 2. Experiment details • 3. The first result of the highest energy photon spectrum obtained by the highest energy accelerator • 4. Impact on the cosmic-ray physics • Presentation @ CRIS2010, September 17th, 2010

2. The LHCf Collaboration 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, Japan 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 A.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain D.Macina, A-L.Perrot CERN, Switzerland

3. preface • One of the main problems of cosmic-ray study is the energy determination. • Castagnoli method • Calorimeter method • Shower method • We have developed many techniques like Transition radiation detector, NKG function, etc • Still it is a problem of the balloon flight to use a shallow depth calorimeter, e.x., RUN-job, JACEE etc, fluctuation is sooo large. • Chudakov proposed to launch a satellite for fixing the mass composition • Problem at Moscow cosmic ray conference in 1987 to fix the problems around the knee region. We have been called by Chdakov and assembled in a room in the together with VIPS of Academician like Ginzburg. • But Soviet Union collapsed and this idea have never been realized.

4. 1. The experimental Purpose • The main purpose of this experiment is to establish the production cross-section of pions at the very forward region in proton-proton interactions at the highest energy region, using the highest energy accelerator in the world. It has been dream of cosmic ray physicists for a long time. • To realize above purpose, we propose to install a compact calorimeter in front of the beam intersection at 140m away. It would be the smallest experiment using the largest accelerator in the world. We require a rather low luminosity operation, say 1028 -1029 and rather small bunches in a ring, say ~23 in a circle. ( In fact it was a few bunches) • By this experiment, we will be able to establish a very important data point, which will be very useful to understand for not only the highest energy cosmic ray problems, but also for establishing the forward code of the GEANT 4 program. • @ 17th Rencontre de Blois, 5/16/2005 and LHCC

5. Experimental Purpose Prepared by TOKO san in 2006

6. Present status : TA results appearedVery good talks have been given in this conference by B. Dawson and J. Matthews

7. The position of shower maximum Knapp et al, Astroparticle Physics, 19(2003) 77 LHCf Fe incidence UA7

8. Why Very Forward? xF<0.05 The right side curve shows when we measure only the particles emitted into the Feynman XF <0.05, we only measure half of the energy flow into the showers. So the measurement of the very forward direction will be very important. xF<0.1

9. Why forward? Why near the beam pipe? • To understand cosmic ray problems, • it is necessary to measure the differential cross-section of the particles emitted into the very forward cone, • While accelerator people love to measure heavy particles emitted at the central region θ≈ 90o

10. To realize this idea, we have proposed to install a small calorimeters inside the small gap at 140m away from the interaction point. In the region heavy iron material, TAN is located in order to absorb strong high-energy neutron beam produced by the pp collisions. Technical Report on the CERN LHCf experiment 12 Oct. 2005 Measurement of Photons and Neutral Pions in the Very Forward Region of LHC O. Adriani(1), L. Bonechi(1), M. Bongi(1), R. D’Alessandro(1), D.A. Faus(2), M. Haguenauer(3), Y. Itow (4), K. Kasahara(5), K. Masuda(4), Y. Matsubara(4), H. Menjo(4), Y. Muraki(4), P. Papini(1), T. Sako(4), T. Tamura(6), S. Torii(7), A. Tricomi(8), W.C. Turner(9), J. Velasco(2) , K. Yoshida(6) 1. Review of experimental purpose 2. The results of the test experiment 3. Trigger, Beam condition, Schedule, Concluding remarks

11. Y Chamber Detector location

12. 2. Experimental Details Arm1 and Arm2 detectors • The calorimeters are composed of the tungsten material with the total 44 radiation length , and 1.6 interaction mean free path. • 4 layers are prepared for the identification of the shower center by using either the scintillation fiber (Arm1) or the silicon strip detector (Arm2). • This guarantees not only the cross-check of the measurement but also it makes possible the single diffractive events and double diffractive events. • To obtain the large acceptance ( PT range) to the photons , the calorimeter can be lifted up and down by the remote manipulator.

13. Examples of simulated events for g and n

14. Configuration of the two calorimeters in the beam pipe44 radiation length or 1.6 interaction mean free path

15. Detector vertical position and acceptance Data taking mode with different position to cover PT gap Viewed from IP G • Remotely changed by a manipulator( with accuracy of 50 mm) Distance from neutral center Beam pipe aperture N Neutral flux center L All g from IP 7TeV collisions L Collisions with a crossing angle lower the neutral flux center to enlarge PT acceptance N

16. Beam pipe Side view Neutral particles TAN Actual setup in IP1-TAN (side view) BRAN-IC BRAN-Sci ZDC type2 LHCf Calorimeter LHCf Front Counter ZDC type1 IP1

17. Performance of the LHCf calorimeters • Energy resolution ≈ 2.8% @ 1TeV • Position resolution 160μm for Arm1 and 49 μm for Arm2 • PMT response to the showers from 1 particle (muon) to 105 particles (induced by 1 TeV photon) (no saturation) • Particle Identification (PID) ( γ/n, quite well separated ) • Leakage correction from the edge of the calorimeter tower ( confirmed by the SPS experiment). We only use the showers that hit 2mm inside from the edge.

18. Actual data-taking 108 events =100Mevents

19. Total number of events collected (1nb-1 ~ 108 collisions ~ 107 showers) 7TeV, without crossing angle, normal HV with crossing angle

20. Arm1 Gamma-ray like Hadron like preliminary preliminary Arm2 Gamma-ray like Hadron like preliminary preliminary Measured Spectra at 7TeV Very high statistics !! only 2% of all data Comparisons with MC are on-going.

21. The energy spectrum of photons by Arm1 and Arm2 detectors Red : Arm1 Blue : Arm2:the same rapidity region has been chosen only adjusted by the detection time Energy scale is preliminary about±2%

22. 7TeV results: Reconstruction of h p0Candidate Preliminary ηCandidate Another good energy calibration point. Production yield of h much differs among the models.

23. p0 reconstruction An example of p0 events measured energy spectrum @ Arm2 25mm 32mm preliminary Silicon strip-X view Reconstructed mass @ Arm2 ΔM/M=2.3% • Pi0’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. preliminary

24. Examples of simulated events for g and n

25. The particle identification (PID) between photons and neutrons by Nakai

26. When we insist the efficiency to squeeze photons as constant, hadrons will be involved at the highest energy region

27. When we make a criterion that the 90% energy of photons must be involved in the 18 layers from the beginning, the rate of gamma-rays increases but the catching efficiency of photons will go down. Neutrons will be involved.

28. The energy spectrum of photons at √s=7TeV by different criterion of PID @ L=5.5×1028/cm2sec

29. However if we can make appropriate correction to each criterion, we can reduce the photon spectrum.

30. Matters to be checked before publication • Linearity of photo-tubes (PMT)  • Leakage from the corner  • Energy resolution ( ~2%@1TeV)  • Particle identification  • Multi-hit correction • Beam-gas contamination(<0.1%?) • pile-up effect ( <0.7% depends on the luminosity) • Energy flow from the other calorimeter in multi-hit (5-7%) • Absolute energy calibration ( ±2%) • So still results are preliminary but things go to good direction.

31. The next target of the LHCf • The differential cross-section of photons at 7TeV A promise from the LHCf • Until the time that we must submit our paper for the • proceeding, we will be able to fix several problems. • Details should be asked toOscar Adriani (Firentze) or • Alessia Tricomi (Catania) a few weeks later.

32. The effect of our results to cosmic-ray physics(a personal view 1) • Tibet AS array with Water (prospect) • The Ne-Nμ spectrum Gamma/hadron separation

33. The effect of our results to cosmic-ray physics(a personal view 2) New data of TA and relation between Auger, Hi-Res and AGASA Preliminary

34. advertisements • There will be held an international conference in related with the highest energy cosmic rays and LHCf at Nagoya international conference hall in Dec. 10-12, 2010. • The convenient air lines are LH and Air Fin, direct flight to Nagoya (central Japan airport). • From central Japan airport, 30 minutes by the train.

35. You can down load a comic from this web citehttp://www.stelab.nagoya-u.ac.jp/

36. Italian version is ready!

37. Acknowledgements We thank to the organizers for a beautiful conference!

38. A brief history of the LHCf experiment • May. 2004 Letter of Intent • Oct. 2005 Technical report • Feb. 2006 Technical Design Report • Jun. 2006 LHCC approved • July 2007 construction starts • Aug. 2007 SPS beam test • Jan. 2008 SPS installation • Sep. 2008 First beam at LHC • Dec. 2009 900 GeV run • Mar. 2010 7TeV run • July 2010 Removal of the LHCf detector from IP1