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Very forward measurement at LHC for U ltra -H igh E nergy C osmic -R ay physics

Very forward measurement at LHC for U ltra -H igh E nergy C osmic -R ay physics. SAKO Takashi for the LHCf collaboration (Solar-Terrestrial Environment Laboratory & Kobayashi- Maskawa Institute, Nagoya University). RIKEN seminar, 21-Jul-2011. Outline. Current UHECR observations

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Very forward measurement at LHC for U ltra -H igh E nergy C osmic -R ay physics

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  1. Very forward measurement at LHC for Ultra-High Energy Cosmic-Ray physics SAKO Takashi for the LHCf collaboration (Solar-Terrestrial Environment Laboratory & Kobayashi-Maskawa Institute, Nagoya University) RIKEN seminar, 21-Jul-2011

  2. Outline • Current UHECR observations • Forward emission in hadronic interaction • LHCf • Experiment overview • Analysis of single photon at √s=7TeV pp collisions • Impact on UHECR (on going work) • Future

  3. Frontier in UHECR Observation • What limits the maximum observed energy of Cosmic-Rays? Time? Technology? Cost? Physics? • GZK cutoff (interaction with CMB photons) >1020eV was predicted in 1966 • Acceleration limit

  4. Observations (10 years ago and now) GZK Cutoff mechanism Proton at rest 100MeV photon 3K CMB 1020eV proton • GZK cutoff prediction at 1020eV • Debate in AGASA, HiRes results in 10 years ago

  5. Observations (10 years ago and now) • Auger, HiRes (final), TA indicate GZK-like cutoff • Absolute values differ between experiments and between methods

  6. Estimate of Particle Type (Xmax) 0g/cm2 • Xmax gives information of the primary particle • Results are different between experiments • Interpretation relies on the MC prediction and has model dependence Xmax Auger TA HiRes Proton and nuclear showers of same total energy

  7. Summary of Current CR Observations • Cutoff around 1020eV seems exist. • Absolute energy of cutoff, sensitive to particle type, is still in debate. • Particle type is measured using Xmax, but different interpretation between experiments. • (Anisotropy of arrival direction also gives information of particle type; not presented today) Still open question : Is the cutoff due to GZK process of protons or heavy nuclei, or acceleration limit in the source? • Both in the energy determination and Xmax prediction MC simulation is used and they are one of the considerable sources of uncertainty. Experimental tests of hadron interaction models at accelerators are indispensable.

  8. ① Inelastic cross section If large s rapid development If small s deep penetrating ④ 2ndary interactions ② Forward energy spectrum If softer shallow development If harder deep penetrating ③ Inelasticity k (1-Eleading)/E0 If large k rapid development If small k deep penetrating

  9. What should be measured at collidersmultiplicity and energyflux at LHC 14TeV collisionspseudo-rapidity; η= -ln(tan(θ/2)) Multiplicity Energy Flux All particles neutral Most of the energy flows into very forward

  10. The LHCf experiment

  11. The LHCf Collaboration K.Fukatsu, T.Iso, Y.Itow, K.Kawade, T.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, Y.Muraki, T.Sako, K.Suzuki, K.TakiSolar-Terrestrial Environment Laboratory, Nagoya University, Japan H.MenjoKobayashi-Maskawa Institute, Nagoya University, Japan K.YoshidaShibaura Institute of Technology, Japan K.Kasahara, Y.Shimizu, T.Suzuki, S.Torii Waseda University, Japan T.TamuraKanagawa University, Japan M.HaguenauerEcolePolytechnique, France W.C.TurnerLBNL, Berkeley, USA O.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, M.Grandi, P.Papini, S.Ricciarini, G.Castellini INFN, Univ. di Firenze, Italy K.Noda, A.TricomiINFN, Univ. di Catania, Italy J.Velasco, A.FausIFIC, Centro Mixto CSIC-UVEG, Spain A-L.Perrot CERN, Switzerland

  12. ATLAS 96mm Detector Location √s=14TeV ] Elab=1017eV LHCf Detector(Arm#1) 140m Two independent detectors at either side of IP1( Arm#1, Arm#2 ) Protons Charged particles(+) Neutral particles Beam pipe Charged particles(-) TAN -Neutral Particle Absorber- transition from one common beam pipe to two pipes Slot : 100mm(w) x 607mm(H) x 1000mm(T)

  13. Arm#1 Detector 20mmx20mm+40mmx40mm 4 XY SciFi+MAPMT Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors LHCfDetectors • Imaging sampling shower calorimeters • Two independent calorimeters in each detector(Tungsten 44r.l., 1.6λ, sample with plastic scintillators)

  14. LHCf as EM shower calorimeter • EM shower is well contained longitudinally • Lateral leakage-out is not negligible • Simple correction using incident position • Identification of multi-shower event using position detectors

  15. BABY SIZE DETECTOR! 64cm 62cm *photo: two years ago. She is now larger than LHCf and difficult to control

  16. η θ [μrad] 8.7 310 ∞ 0 Calorimeters viewed from IP 0 crossing angle • Geometrical acceptance of Arm1 and Arm2 Projected edge of beam pipe

  17. Expected Results at 14 TeV Collisions(MC assuming 0.1nb-1 statistics) Detector response not considered

  18. Operation at LHC 2009-2010

  19. Summary of Operations in 2009 and 2010 • With Stable Beam at 900 GeV • Total of 42 hours for physics • About105 showers events in Arm1+Arm2 • With Stable Beam at 7 TeV • 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 • ~ 4·108 shower events in Arm1+Arm2 • ~ 106p0 events in Arm1+Arm2 • Status • Completed program for 900 GeV and 7 TeV • Removed detectors from tunnel in July 2010 • Post-calibration beam test in October 2010 • Upgrade to more rad-hard detectors to operate at 14TeV in 2014

  20. 2009-2010 run summary (7TeV) High luminosity (L=3~20e29cm2s-1) (1e11ppb, b*=3.5m,Nb=1~8) 100mrad crossing Low luminosity (L=2~10e28cm2s-1) (1~2.5e10ppb, b*=2m,Nb=1~4) No crossing angle Integrated showers at 7TeV 900GeV 108 # of showers 107 Detector removed 106 5/27 7/22 4/1 1000K Arm1 p0 stat. # of p0 500K 4/4 7/25 5/30

  21. Analysis for single photon spectra arXiv:1104.5294v2 PLB Received (Photons are mostly decay products of π0 and η)

  22. Data Set for this analysis • Data • Date : 15 May 2010 17:45-21:23 (Fill Number : 1104) except runs during the luminosity scan. • Luminosity : (6.3-6.5)x1028cm-2s-1 (not too high for pile-up, not too low for beam-gas BG) • DAQ Live Time : 85.7% for Arm1, 67.0% for Arm2 • Integral Luminosity (livetime corrected): 0.68 nb-1 for Arm1, 0.53nb-1 for Arm2 • Number of triggers : 2,916,496 events for Arm1 3,072,691 events for Arm2 • With Normal Detector Position and Normal Gain • MC • About 107pp inelastic collisions with each hadron interaction model,QGSJET II-03, DPMJET 3.04, SYBILL 2.1, EPOS 1.99 and PYTHIA8.145 Only PYTHIA has tuning parameters. The default parameters were used

  23. Event Sample (π0 candidate) Event sample in Arm2 Longitudinal development Small calorimeter Large calorimeter Note : • A Pi0 candidate event • 599GeV gamma-ray and 419GeV gamma-ray in 25mm and 32mm tower respectively. Lateral development Silicon X Silicon Y

  24. Analysis • Step.1 : Energy reconstruction • Step.2 : Single-hit selection • Step.3 : PID (EM shower selection) • Step.4 : π0 reconstruction and energy scale • Step.5 : Spectra reconstruction

  25. Analysis Step.1 • Energy reconstruction: Ephoton = f(Σ(dEi)) (i=2,3,…,13) ( dEi = AQi determined at SPS. f() determined by MC. E : EM equivalent energy) • Impact position from lateral distribution • Position dependent corrections • Light collection non-uniformity • Shower leakage-out • Shower leakage-in (in case of two calorimeter event) Shower leakage-in Light collection non-uniformity Shower leakage-out

  26. Analysis Step.2 • Single event selection (multi-hit cut) • Single-hit detection efficiency • Multi-hit identification efficiency (using superimposed single photon-like events) Small tower Large tower Arm1 Double hit in a single calorimeter Arm2 Single hit detection efficiency Double hit detection efficiency

  27. Analysis Step.3 • PID (EM shower selection) • Select events <L90%threshold and multiply P/ε ε(photon detection efficiency) and P (photon purity) • By normalizing MC template L90% to data, ε and P for certain L90% threshold are determined. hadron photon

  28. Analysis Step.4 • π0 identification from two tower events to check absolute energy • Mass shift observed both in Arm1 (+7.8%) and Arm2 (+3.7%) • No energy scaling applied, but assigned the shifts in the systematic errorin energy Arm2 Measurement 1(E1) Arm2 MC R 140m  2(E2) I.P.1 M = θ√(E1xE2)

  29. Analysis Step.5 • Spectra in Arm1, Arm2 common rapidity • Energy scale error not included in plot (maybe correlated) • Nine = σine ∫Ldt (σine = 71.5mb assumed)

  30. Spectral deformation • Suppression due to multi-hit cut at medium energy • Overestimate due to multi-hit detection inefficiency at high energy (mis-identify multi photons as single) • No correction applied, but same bias included in MC to be compared TRUE/MEASURED TRUE MEASURED True: photon energy spectrum at the entrance of calorimeter

  31. Systematic errors • Major sources of systematic error • Absolute energy • PID • Multi-hit detection efficiency • Beam position

  32. Comparison with Models

  33. Comparison with Models DPMJET 3.04 QGSJET II-03 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145

  34. DPMJET 3.04 QGSJET II-03 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 • None of the models perfectly agree with data. • DPMJET3, PYTHIA8: good agreement in 0.5-1.5TeV at η>10.94 but large difference >2TeV. • QGSJET-II gives overall lower photon yield, especially in small η. • SIBYLL2 shows good spectral shape >0.5TeV atη>10.94 but only half yield

  35. Impact on CR physics

  36. π0 spectrum and air shower • Artificial modification of meson spectra and its effect to air shower • Importance of E/E0>0.1 mesons • Is this modification reasonable? • What happens at LHC energy? => On-going QGSJET II original Artificial modification X=E/E0 Ignoring X>0.1 meson π0 spectrum at Elab = 1019eV Longitudinal AS development 30g/cm2

  37. Future

  38. Next step • Analysis • π0 energy spectrum • Fundamental in EM component of air shower • PT spectrum for photon and π0 • Extrapolation to the non-observable phase space • Hadron (neutron) analysis • Elasticity in the air shower development • Analysis for 900GeV collision data • Energy dependence of the interaction • Measurements • 14 TeV p-p collisions at LHC after 2014 • Study for p-Pb data taking at LHC (2012)? • Detector upgrade for 14TeV run • Measurements at other accelerators?

  39. Measurements at other colliders?-hadron collider is not only LHC- • Systematic forward measurements for different types of collision using the LHCf detectors • p-p collision at lower energy • No dedicated forward measurement since UA7 at SppS (√s=630GeV) • Lower energy but wide acceptance required (LHC 900GeV is not appropriate) • Ion collisions to understand p-p to A-A • In CRs, p-N, N-N, Fe-N are important (N; Nitrogen) • p-Pb collisions at LHC

  40. LHCf stands forLong-island Hadron Collider forward?? • Potential Advantages • Having ZDC installation slots close to IP • possible wide rapidity coverage • π0->2γ pair detectable • √s=500GeV p-p collision. Equivalent to UA7, but more data available with LHCf detectors. • Ion collisions; essential for CR physics • excellent if light ions are available η = -ln(tan(θ/2)) When θ= (415mm/2)/(9.8m+14.3m) = 8.6 mrad => η = 5.44

  41. π0 energy and photon opening angle • Feasibility to test the existing models is under study by MC • Detail input of the geometry (crucial to know the rapidity coverage) is necessary

  42. Summary • LHCf has successfully finished first measurements at LHC for √s=0.9 and 7 TeV p-p collisions. • First analysis result of single photon spectra is published. • Impact of LHCf results on CR physics is in investigation. • Further measurements at LHC 14TeV p-p collisions is programmed after 2014. • LHC p-Pb run in study. • Measurements at other acceleratorsin study.

  43. Backup

  44. Uncertainty in Step.2 • Fraction of multi-hit and Δεmulti, data-MC • Effect of multi-hit ‘cut’ : difference between Arm1 and Arm2 Effect of Δεmulti to single photon spectra Single / (single+multi), Arm1 vs Arm2

  45. Uncertainty in Step.3 (Small tower, single & gamma-like) • Imperfection in L90% distribution Original method Template fitting A ε/P from two methods Artificial modification in peak position(<0.7 r.l.) and width (<20%) (ε/P)B/(ε/P)A Template fitting B

  46. Beam Related Effects • Pile-up (7% pileup at collision) • Beam-gas BG • Beam pipe BG • Beam position (next slide) MC w/ pileup vs w/o pileup Crossing vs non-crossing bunches Direct vs beam-pipe photons

  47. Where is zero degree? Beam center LHCf vs BPMSW LHCf online hit-map monitor Effect of 1mm shift in the final spectrum

  48. Model uncertainty at LHC energy • On going works • Air shower simulations with modified π0 spectra at LHC energy • Try&Error to find artificial π0 spectra to explain LHCf photon measurements • Analysis of π0 events Very similar!? Forward concentration of x>0.1 π0 π0 energy at √s = 7TeV

  49. Last forward experiment at hadron collider – UA7 - • No sizable violation of Feynman scaling in forward • √s = 630GeV, Elab = 2x1014eV

  50. π0 energy flow at 500GeV p-p collisions predicted by PYTHIA8 Geometrical acceptance and rapidity coverage 50mm/20m (2.5mrad acceptance) 200mm/25m (8mrad acceptance) 400mm/20m (20mrad acceptance)

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