1. Forward particle production measured by LHCf; testing hadronic interaction models for CR physics Takashi SAKO (Solar-Terrestrial environment Laboratory/Kobayashi- Maskawa Institute, Nagoya University, Japan) On behalf of the LHCf Collaboration 11-Feb-2013 IV Workshop on Air Shower Detection at High Altitude@Napoli

2. Forward particle production measured by LHCf; testing hadronic interaction models for CR physics Takashi SAKO (Solar-Terrestrial environment Laboratory/Kobayashi- Maskawa Institute, Nagoya University, Japan) On behalf of the LHCf Collaboration 21-Feb-2013 IV Workshop on Air Shower Detection at High Altitude@Napoli

3. Outline Quick reminder for the CR and interaction Important collider observables The LHCf experiment – Experimental setup and status – Results from 900GeV and 7TeV p-p collisions – Impact on air shower – Future Summary 3

4. CR and Interaction 4

5. Uncertainty in hadronic interaction 5 PROTON IRON 10 19 10 18 0g/cm 2 Xmax Proton shower and nuclear shower of same total energy Pierre Auger Observatory Deep in the atmosphere Players: EPOS, QGSJET, SIBYLL, DPMJET models

6. 6 (Kampert and Unger, Astropart. Phys., 2012) Lower energy also… QGS1 QGSII SIBYLLEPOS

7. Collider observables 7

8. 8 Leading baryons Multi meson production What to be measured at accelerators? proton / neutron π0π0 π+π+ π-π- γ 1. Inelastic cross section （ interaction mean free path ） 3. Nuclear effect elasticity (E baryon /E 0 ) baryon spectrum inelasticity (E meson /E 0 = 1-elasticity) multiplicity meson spectrum 2. Particle production Note: √s=14TeV E lab =10 17 eV

9. Where 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 particles produced into central, Most of the energy flows into forward 9

10. 10 result @ 7TeV The TOTEM Collaboration, CERN-PH-EP-2012-353 R.Ulrich et al., PRD, 83 (2011) 054026 Before LHC After LHC

11. multiplicity@central 11 D.D’Enterria et al., Astropart. Phys., 35 (2011) 98-113

12. Forward Energy Flow (Hadronic Forward Calorimeter) 12 The CMS Collaboration, JHEP, 11 (2011) 148

13. LHCf 13

14. T.Iso, Y.Itow, K.Kawade, Y.Makino, K.Masuda, Y.Matsubara, E.Matsubayashi, G.Mitsuka, Y.Muraki, T.Sako Solar-Terrestrial Environment Laboratory, Nagoya University, Japan H.Menjo Kobayashi-Maskawa Institute, Nagoya University, Japan K.Yoshida Shibaura Institute of Technology, Japan K.Kasahara, Y.Shimizu, T.Suzuki, S.Torii Waseda University, Japan T.Tamura Kanagawa University, Japan 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 INFN, Univ. di Firenze, Italy A.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain A-L.Perrot, D.Pfeiffer CERN, Switzerland The LHCf collaboration

15. The LHC forward experiment 15 ATLAS 140m LHCf Arm#1 LHCf Arm#2 Two independent detectors at either side of IP1 (Arm#1, Arm#2 ) Charged particles (+) Beam Charged particles (-) Neutralparticles Beam pipe 96mm All charged particles are swept by dipole magnet Neutral particles (photons and neutrons) arrive at LHCf 0 degree is covered

16. LHCf Detectors Arm#1 Detector 20mmx20mm+40mmx40mm 4 XY SciFi+MAPMT Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors Imaging sampling shower calorimeters Two calorimeter towers in each of Arm1 and Arm2 Each tower has 44 r.l. of Tungsten,16 sampling scintillator and 4 position sensitive layers 16

17. 17 Which E-p T range LHCf sees ? pp 7TeV, EPOS      

18. Summary of 2009-2010 run and current status With Stable Beams at √s = 900 GeV  Total of 42 hours for physics  About 10 5 shower events in Arm1+Arm2 With Stable Beams at √s = 7 TeV (E lab = 2.5x10 16 eV)  Total of 150 hours for physics with different setups Different vertical position to increase the accessible kinematical range Runs with or without beam crossing angle  ~ 4x10 8 shower events in Arm1+Arm2  ~ 10 6 π 0 events in Arm1 and Arm2 Status  Photon spectra at 900 GeV and 7 TeV, π 0 spectra at 7TeV are published  Taking data at 4TeV/Z p-Pb collision NOW  Upgrade to more rad-hard detectors for 14TeV in 2015 18

19. Observed event Energy & PID Position & multihit ID Longitudinal development Lateral development Silicon X Silicon Y

20. Particle Identification 20 (L 90% indicates the depth of shower) Photon event Hadron event (Adriani et al., PLB, 2011) + ; data Histograms; MC 90%

21. 21 Photon spectra @ 7TeV (Data vs. Models) DPMJET 3.04 QGSJET II-03 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 Adriani et al., PLB, 703 (2011) 128-134 Around 0 degree (On axis) Off axis

22. Photon spectra @ 900GeV 22 Adriani et al., PLB, 715 (2012) 298-303

23. small-η = Large tower big-η =Small tower 900GeV vs. 7TeV Normalized by # of evnetsX F > 0.1 Statistical error only X F spectra : 900GeV data vs. 7TeV data Good agreement of X F spectrum shape between 900 GeV and 7 TeV. Preliminary Data 2010 at √s=900GeV (Normalized by the number of entries in X F > 0.1) Data 2010 at √s=7TeV (η>10.94) LHCf coverage in X F -p T plane (X F = E/E beam ) 900GeV vs. 7TeV with the same PT region 900 GeV Small+large tower 23

24. π 0 analysis π 0 candidate 599GeV & 419GeV photons in 25mm and 32mm tower, respectively M = θ√(E 1 xE 2 ) 24 Longitudinal development Lateral development Silicon X Silicon Y Small Cal. Large Cal. I.P.1 θ γ 1 (E 1 ) γ 2 (E 2 ) 140m R

25. 25 Adriani et al., PRD, 86, 092001 (2012) π 0 p T distribution in different rapidity (y) ranges

26. π 0 26 comparison with UA7 at 630GeV (Pare et al., PLB, 242, 531 (1990)) y beam - y

27. x F = E/E 0 Playing a game with air shower (effect of forward meson spectra) 27 DPMJET3 always overpredicts production Filtering DPMJET3 mesons according to an empirical probability function, divide mesons into two with keeping p T Fraction of mesons escape out of LHCf acceptance This process Holds cross section Holds elasticity/inelasticity Holds energy conservation Changes multiplicity Does not conserve charge event-by-event E=E 1 +E 2 E1E1 E2E2 x F = E/E 0 pTpT

28. An example of filtering 28 π 0 spectrum photon spectrum DPMJET3+filter 2.5x10 16 eV proton ~30g/cm 2

29. Future Neutron spectra in 7TeV p-p … analysis on going 4TeV/Z p-Pb … data taking on going Joint analysis with ATLAS … data ready 14 TeV p-p in 2015 … detector upgrade on going Light nuclei at LHC, RHIC??? … possibility in discussion 29

30. Neutron Spectra at 7TeV pp (models) 30 Model predictions Model predictions smeared by the LHCf energy resolution

31. 31 p-Pb collisions Photon spectrum at the p remnant Neutron spectrum at the p remnant (energy resolution taken into account) 1 st collider experiment pA (dA done at RHIC) LHCf triggers ATLAS to take common events with central

32. 32 Leading baryons Multi meson production What to be measured at accelerators? proton / neutron π0π0 π+π+ π-π- γ 1. Inelastic cross section （ interaction mean free path ） 3. Nuclear effect elasticity (E baryon /E 0 ) baryon spectrum inelasticity (E meson /E 0 = 1-elasticity) multiplicity meson spectrum 2. Particle production Note: √s=14TeV E lab =10 17 eV

33. Summary 33  Experiments at LHC provide useful data to calibrate CR interaction models  LHCf is a dedicated experiment to measure forward particles effective to the air shower development  LHCf completed operation at 900GeV and 7TeV p-p collisions and published photon and π 0 spectra  None of the models perfectly describe the LHCf results, but models well bracket the experiment (this is generally true for the other LHC results).  No sizable collision energy dependence is so far found  Forward meson spectra is effective in  LHCf is proceeding more analysis, takes more data with p-Pb collisions and 14TeV p-p collisions, and more…

34. 34 Cosmic-ray spectrum & Colliders LHC 14TeV Tevatron LHC 0.9TeV LHC 7 TeV SppS RHIC ISR 10 10 20 eV Knee: end of galactic proton CR End of galactic CR and transition to extra-gal CR Ankle (GZK) cutoff: end of CR spectrum Perfect (or best at least) understanding up to 10 17 eV helps CR physics

35. Backup 35

36. LHC ｆカロリーメータ構造 n, gamma 全発光量からエネルギーを、形状から粒子を判定 <7TeV の入射粒子に対して、（特に電磁）シャワーは理解されている

37. 37

38. 38 Rapidity vs Forward energy spectra η=8.40 η=8.77 η=8.40 η=8.77 η ∞ 8.7 θ [μrad] 0 310 Projected edge of beam pipe Viewed from IP1 (red:Arm1, blue:Arm2)