Forward photon spectrum in 7 TeV pp collisions measured by the LHCf - PowerPoint PPT Presentation

Forward photon spectrum in 7 TeV pp collisions measured by the LHCf experiment Koji Noda (INFN Catania) on behalf of the LHCf collaboration Workshop on Multi-Parton Interactions at the LHC 25 Nov. 2011, DESY, Hamburg

Contents • “A collider experiment for cosmic ray physics” • LHCf detector and operation • Analysis for single photon spectra at 7 TeV • Discussions & prospects • Summary

Very-high-energy cosmic ray spectrum Cosmic ray spectrum SPS Tevatron LHC M Nagano New Journal of Physics 11 (2009) 065012 AUGER SPS Tevatron LHC (UA7) cm energy at LHC (7+7TeV) <=> 10^17eV CR (fixed target) >10^15eV: detected with air-showers , but many unknowns

4 Air-shower 1. Inelastic cross section development If large σ rapid development If small σ deep penetrating 4. 2ndary interactions 2. Forward energy spectrum If softer rapid development If harder deep penetrating 3. Inelasticity k (1-E leading )/E 0 If large k rapid development If small k deep penetrating

5 Impact of air-shower development uncertainty on E-scale & composition • E-scale uncertainty Composition error SD E-scale • Surface detector: large error #of particles (AGASA claims 20%) • Florescence: OK (a few %), but FD  SD problem • Composition uncertainty AUGER alt. AUGER ICRC09 Atm. depth J.Knapp Astropart. Phys.19 (2003) 77 Model dependence must be decreased by measurements!

6 What should be measured? sqrt(s)=14TeV multiplicity and energy flux at LHC 14TeV collisions pseudo-rapidity; η = -ln(tan( θ /2)) E lab =10 17 eV Multiplicity Energy Flux All particles neutral Most of the energy flows into very forward

7 Recent input from LHC data Inelastic cross section Charged hadron multiplicity Missing part: spectra of forward neutral particles

The LHCf Collaboration 8 K.Fukatsu, T.Iso, Y.Itow, K.Kawade, T.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, Y.Muraki, T.Sako, K.Suzuki, K.Taki 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, P.Papini, S.Ricciarini, G.Castellini INFN, Univ. di Firenze, Italy K.Noda, A.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain A-L.Perrot CERN, Switzerland

9 Detector Location 140m

10 LHCf Detectors Imaging sampling shower calorimeters  Two independent calorimeters in each detector (Tungsten 44r.l., 1.6 λ , sampling with plastic scintillators)  4 position sensitive layers distributed in the calorimeters Arm#1 Detector 20mmx20mm+40mmx40mm 4 XY SciFi+MAPMT Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors

Detector photos 2 2 9 9 0 0 m m m m 90mm 90mm Arm#2 Detector Arm#2 Detector Arm#1 Detector Arm#1 Detector

12 ATLAS & LHCf 12

13 ATLAS & LHCf 13

14 Event category of LHCf Single hadron event Single photon event Pi-zero event (photon pair)

15 Expected Results at 14 TeV Collisions (MC assuming 0.1nb -1 statistics) Single photon at different η Single photon Detector response not considered Single neutron π 0

16 Brief history of LHCf Jul 2006 • May 2004 LOI Jan 2008 Assembling Installation • Feb 2006 TDR • June 2006 LHCC approved Aug 2007 SPS beam test Sep 2008 Mar 2010 1 st LHC beam 1 st 7TeV run Dec 2009 1 st 900GeV run Jul 2010 Detector removal

17 Summary of Operations in 2009 and 2010 With Stable Beam at 900 GeV Total of 42 hours for physics About 100 k shower events in Arm1+Arm2 With Stable Beam at 7 TeV Total of 150 hours for physics with different setups Different vertical position & with beam crossing angle for a wide kinematical range Arm1 π 0 events ~ 400 M shower events in Arm1+2 ~ 1 M π 0 events in Arm1+2 Arm1 π 0 stat. Status Completed program for 900 GeV and 7 TeV Removed detectors from tunnel in July 2010 Post-calibration beam test in October 2010 Upgrade on-going to more rad-hard detectors for 14TeV in 2014

18 EM shower and π 0 example Event sample by Arm2 • neutral pion candidate Longitudinal development • 599GeV & 419GeV photons in 25mm Large Small Cal. Cal. and 32mm tower, respectively • M = θ x sqrt(E 1 xE 2 ) Lateral development Silicon X Silicon Y Publication (w/ MC) coming soon Invariant mass of photon pairs

‘new’ neutral pion analysis Original New Analysis! Idea Type-II BG reduction still to be optimized

20 Single photon energy spectra O. Adriani et al., PLB 703 (2011) 128-134 • DATA ▫ 15 May 2010 17:45-21:23 (#Fill 1104), Low Luminosity (6.5-6.3)x10 28 cm -2 s -1 , no beam crossing angle ▫ 0.68 nb-1 for Arm1, 0.53nb-1 for Arm2 • MC ▫ DPMJET3.04, QGSJETII03, SYBILL2.1, EPOS1.99, PYTHIA 8.145 ▫ 10 7 inelastic p-p collisions by each model • Analysis ▫ Particle identification using longitudinal shower development ▫ multi-hit rejection ▫ Acceptance cut: two common η ranges (small tower: η>10.94, large: 8.81<η<8.9) = No correction for geometrical acceptance Arm2 Arm1 ▫ systematic errors

21 Particle ID EM and hadronic showers are separated with a method based on a difference of the longitudinal shower development beam direction # Response of detectors to hadrons is in study. N photon /N hadron ratio will give a good information for model discrimination For other details in the photon analysis, please refer to the publication: O. Adriani et al., PLB 703 (2011) 128-134

22 Obtained photon spectra  Normalized by number of inelastic collisions N ine = σ ine * ∫Ldt  σ ine = 71.5mb assumed; consistent with recent ATLAS result +1.8 (c.f. 73.5±0.6 . mb by TOTEM ) -1.3 => Combined & compared with MC models

23 Comparison between Models Magenta hatch: MC Statistical errors Gray hatch : Systematic Errors DPMJET 3.04 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 QGSJET II-03 • None of the models nicely describe the LHCf data in the whole energy range (100 GeV – 3.5 TeV). • Very big discrepancy in the high energy region • Significant improvement of the models is possible by model developers

24 Impact on CR physics  Artificial modification of meson spectra -> How does it affect?  ∆ Xmax (p-Fe) ~ 100 g/cm 2  The effect ~30 g/cm 2

Discussions & prospects • LHCf for multi-parton physics? ▫ very forward = low-x parton scattered by high-x parton ▫ In small-x, gluon is dominant, but its density begins to saturate with increasing energy How much is the non-linear saturation effect? soft hard semi-hard reality

Discussions & prospects • LHCf for multi-parton physics? ▫ very forward = low-x parton scattered by high-x parton ▫ In small-x, gluon is dominant, but its density begins to saturate with increasing energy How much is the non-linear saturation effect? soft hard semi-hard reality • What’s next to be analyzed or measured? ▫ neutral pion: already mentioned ▫ 900GeV photon : E-scale of the non-linear effect? ▫ 7 TeV photon Pt: support for the photon spectrum result ▫ 7 TeV hadron spectra: inelasticity for CR physics ▫ pA run (in 2012 ): larger effect? ▫ 14 TeV run (in 2014 ): larger effect, but upgrade needed

Studies for pA run (foreseen in 2012) photon spectra by Arm2 in p-Pb run (p-remnant side) Model dependence would be larger than in 7 TeV pp run We hope LHCf will come back to CERN in 2012

28 Upgrade for 14TeV for rad-hardness higher luminosity is expected in the 14TeV runs Kawade+ (2011) for improvement of energy reconstruction Silicon layer positions in Arm2 detector MC X,Y X,Y X,Y X,Y X,Y X,Y X Y X Y Energy reconstruction with the Si layers is also useful

E rec. only with Si Si data Method for the obtained data: ▫ Correction esp. for high-E events (fitting with a peak shape) ▫ ADC count -> energy deposit gain (by test beam) -> incident energy reconstruction func. (by MC) E only by Si vs. E by scinti. E reconstruction E resolution (w/ corr.) 0.9~1.1TeV only with Si data: mean ~5%, E reso. ~15% (~10% will be achieved with the upgrade) # This is a good news for separation of multi-hit events (type-II neutral pions) scinti. energy (GeV)

Summary • LHCf: a collider experiment for cosmic ray physics • DAQ for 900GeV & 7 TeV pp collision completed • Single photon spectra show a discrepancy from the MC simulation models • It will be a guideline for improvement of the non- linear effect implementation in the models • Now following analyses for pi-zero & 900GeV photon spectra etc. are underway • Studies for pA run in 2012 and upgrade works for 14 TeV pp run are also on-going

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33 By Ostapchenko

Physics of MCs s ( Physics of MC ( K. Werner, EDS09, CERN)

Nonlinear effects in MCs Nonlinear effects in MCs Non-linear effects are implemented in a phenomenological manner all slides are by K. Werner, EDS09, CERN