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 @ CERN LHCC, September 22nd, 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. 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. • From 17th Rencontre de Blois, 5/16/2005 and LHCC

4. Experimental Purpose: an examination of the MC code by the experiment Prepared by Tokonatu Yamamoto of Auger collaboration in 2007

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

6. 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

7. 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

8. Y Chamber Detector location

9. 2. Experimental Details The 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.

10. Examples of simulated events for g and n

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

12. 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

13. 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

14. 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.

15. Actual data-takingIntegrated shower events at 3.5 TeV 108 events =100Mevents LHCf removal Number of pi-zero ≈ 1 Mevents

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

17. The energy spectrum of photons by Arm1 and Arm2 detectors Red : Arm1 Blue : Arm2 selected the same rapidity region, adjusted only by the running time LHCf preliminary

18. Reconstruction of p0 measured energy spectrum @ Arm2 An example of π0 events 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 the energy scale. preliminary

19. 7TeV results: Reconstruction of h p0Candidate h Candidate Preliminary Another good energy calibration point. Production yield of h much differs among the models.

20. Examples of simulated events for g and n

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

22. 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.

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

24. The energy spectrum of photons at √s=7TeV by different criterion of PID LHCf preliminary

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

26. Matters to be checked before publication • Linearity of photo-tubes (PMT)  • Leakage from the corner (~10%)  • Energy resolution ( ~2.8%@1TeV)  • Particle identification (~2%)  • Radiation damage and stability of the system (laser, pi-zero mass <3%)  • Beam position measurement (±0.5mm) • Luminosity measurement (Van der Meer method(~1%)  • Multi-hit correction • Beam-gas contamination(<0.1%?) • pile-up effect ( <0.07% depends on the luminosity) • Energy flow from other calorimeter in multi-hit (3-6%) • Absolute energy calibration ( ±2.5%) • So our results involve still preliminary in some parts but things go to a good direction.

27. Acknowledgements We acknowledge the LHC and SPS crew for successful operation of the LHC machine and We thank Carsten Niebuhr, Michelangelo Mangano and Mario Calvetti for valuable discussions and suggestions for the early time of the LHCf experiment. End of an official talk • From now, please listen my talk as rather a personal view of myself on near future. • Every scientist has a freedom to describe his image.

28. Back up slides

29. The effect of our results to cosmic-ray physics(a personal remark 1) • Tibet AS array with Water (prospect) • The Ne-Nμ spectrum Gamma/hadron separation Remark 1: The showers induced by photons normally involve small number of muons. The main background will come from the neutral pions emitted at very forward region by proton-carbon interactions. Our results indicate that this separation will be made efficiently.

30. 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

31. On your question: Why we do not show today the slide which we compared the data with the MC predictions? • The question may be very natural, but… • Because for the fairness of the each MC code; QGS jet model, DPM jet model, Sybil, Epos, etc.. • Because we have not yet obtained the differential cross-section. • Because we want to avoid to make a confusion in scientific society. • Please wait for a month to fix them.

32. The next target and jobs of LHCf • Please expect the next LHCC on November 17th • The differential cross-section of photons at 7TeV • New MC results on super high energy cosmic rays • Preparation for 14 TeV collisions continues