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Lorenzo Bonechi ( INFN – Firenze) on behalf of the LHCf Collaboration

CSN1 22 September 2011, Bari. LHCf : s tatus and perspectives . Lorenzo Bonechi ( INFN – Firenze) on behalf of the LHCf Collaboration. Outline. Overview of LHCf Cosmic rays in the atmosphere and hadronic interaction models Detection of neutral particles at low angle at LHC

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Lorenzo Bonechi ( INFN – Firenze) on behalf of the LHCf Collaboration

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  1. CSN1 22 September 2011, Bari • LHCf: status and perspectives Lorenzo Bonechi(INFN – Firenze) on behalf of the LHCf Collaboration

  2. Outline • Overview of LHCf • Cosmic rays in the atmosphere and hadronic interaction models • Detection of neutral particles at low angle at LHC • Description of detectors • Data analysis • Published results for single  in7 TeVpp interactions • On-going analysis for  at 7 TeV and single  at 900 GeV • Simulation of p-Pb interactions • Upgrade of detectors for new measurements • Summary L.Bonechi, CSN1, Bari

  3. LHC Purpose of the experiment • Experimental measurement: • Precise measurement of neutral particle (g,p0 and n) spectra in the very forward region at LHC • 7 TeV + 7 TeV in the c.m. frame  1017 eV in the laboratory frame: • We are simulating in the biggest’s world laboratory what happens in nature when a Very High Energy Cosmic Ray interacts in the atmosphere • Why in the very forward region? • Because the dominant contribution to the energy flux in the atmospheric shower development is carried on by the very forward produced particles L.Bonechi, CSN1, Bari

  4. Protons Charged particles Neutral particles Beam pipe The LHCf location Recombination Chamber Detectors are located Inside the TANs (absorbers for neutral particles) Detectors measure energy and impact point of g from p0decays e.m. calo tracking layers • Two independent detectors on both • sides of IP1 • Redundancy • Background rejection (esp. beam-gas) 96mm L.Bonechi, CSN1, Bari

  5. Details of the detectors Arm1 Sampling and imaging E.M. calorimeters • Absorber: W (44 r.l , 1.55λI ) • Energy measurement: plastic scintillator tiles • 4 tracking layers for imaging: XY-SciFi(Arm#1) and XY-Silicon strip(Arm#2) • Each detector has two calorimeter towers, which allow to reconstruct p0 40mm 20mm Performances Energy resolution (> 100GeV): < 5% for photons and  30% for neutrons Position resolution for photons:< 200μm (Arm#1) and  40μm (Arm#2) Arm2 32mm Front Counters • thin scintillators 80x80 mm • monitoring of beam condition • Van der Meer scan 25mm L.Bonechi, CSN1, Bari

  6. 290mm Arm#1 Detector 90mm Arm#2 Detector L.Bonechi, CSN1, Bari

  7. Summary of data taking 2009-2010 • Data taking with Stable Beams at (450 + 450) GeV • Dec 6th – Dec 15th 2009 and May 2nd – May 27th 2010 • 42 hours for physics • Data taking with Stable Beams at (3.5 + 3.5) TeV • Mar 30th – Jul 19th 2010 • 150 hours for physics with different setups • Different vertical positions to increase the accessible kinematical range • Runs with or without 100 rad beam crossing angle L.Bonechi, CSN1, Bari

  8. Analysis of (3.5+3.5) TeV data • Clean sub-set of data (nominal config., no beam crossing angle, low luminosity) • Nominal config., no beam crossing angle • Low luminosity (measured by front counters) • Particle IDentification • Study of longitudinal energy deposit (L90% is the depth in calorimeter for containment of 90% of the total released energy) • Selection of single gamma events • Study of transverse energy deposit • Energy reconstruction • Based on total energy deposit in scintillator tiles • Common pseudo-rapidity region for Arm1/2 • η>10.94 and 8.81<η<8.9 Distribution of L90% Multiple hit event (seen on one silicon layer) Arm1 Arm2 L.Bonechi, CSN1, Bari

  9. Published results for single  at 7 TeV Adriani et al., Physics Letters B 703 (2011) 128–134 (small tower) (large tower) DPMJET 3.04 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 QGSJET II-03 Magenta hatch: MC Statistical errors Gray hatch : Systematic Errors L.Bonechi, CSN1, Bari

  10. Further analysis • s  7 TeV • : energy and pt (or ) distribution (in progress) • Single  : pt (or ) distribution • s  900 GeV • : no • Single : energy and pt (or ) distribution (in progress) • Lower priority: hadrons (n) L.Bonechi, CSN1, Bari

  11. Neutral pionsat 7 TeV • 0’s are the main source of electromagnetic secondaries in high energy collisions • The mass peak is very useful to check the detector performances and to estimate the systematic error on the energy scale Selected data (2010 May 15, 17:45-21:23, Fill# 1104) No crossing angle, pile up is negligible (~0.2%) Low luminosity : (6.3-6.5)x1028cm-2s-1 DAQ Live Time : 85.7% (Arm1), 67.0% (Arm2) Integrated lumi : 0.68 nb-1 / 0.53nb-1 (Arm1/2) MC simulations DPMJET 3.04, QGSJET II-03, SYBILL 2.1, EPOS 1.99and PYTHIA8.145 Propagation in beam pipe and detector response are considered. In each model 107 collisions are generated. 1(E1) 25 mm tower 32 mm tower R 140m Silicon -strip X-view  2(E2) I.P.1 Silicon -strip Y-view L.Bonechi, CSN1, Bari

  12. Neutral pionsat 7 TeV (Arm1) (2) Type-I event Type-II event 1 1 Large tower Large tower 2 2 Small tower Small tower • This has been dealt with so far. • It can cover wide opening angle. • Thus this type dominates in low energy region. • While due to unavoidable gap between each tower, sensitivity in high energy is rather worse. • Now it is possible to analyze this type of events thanks to the improvement of multi-hit reconstruction. • Tight opening angle(~high E) can be detected by this type of π0. • Mass peak is still wide. 22 September 2011 L.Bonechi, CSN1, Bari

  13. Neutral pionsat 7 TeV (Arm1) (3) LHCf-Arm1Data 2010(Large tower) LHCf-Arm1Data 2010 PRELIMINARY Blue solid : TotalBlue dashed : SignalCyan : BackGroundYellow : Fitting error PRELIMINARY No acceptance correction No acceptance correction For ref, values in DPMJET3<Mγγ> = 135.2MeV σ = 4.9MeV (Data-MC)/MC~7.8% (due mainly to energy scale) Type-II has a peak around 135MeV, but BG reduction is biggest homework L.Bonechi, CSN1, Bari 22 September 2011

  14. Single photons at 900 GeV • This analysis is in a raw preliminary status for Arm1: • Under development • Energy reconstruction function is new • special one for low energy region: • PID threshold • PID criteria is same as 7TeV • Threshold is updated • Multi-hit cut • Not yet included (future plan) • Systematic error • Luminosity normalization • All other corrections • For Arm2 we are generating Monte Carlo events (one month needed to complete the generation for all models) L.Bonechi, CSN1, Bari

  15. Future measurements: proton – lead ion The study of proton interactions with nuclei in the forward region is important for cosmic ray physics, because strictly related to the interactions of primary cosmic rays with the atmosphere. Ideally we would like to measure the interaction of protons with Nitrogen ions (to reproduce real atmospheric showers) or at least with light ions. Anyway the study of proton – heavy ion interaction in the forward region can be important to study the scaling properties of cross sections with respect to the pp case ( nuclear modification factors andparton density saturation) Interaction  p-Pb @ LHC in 2012 (3.5 TeV protons). We are studying the impact of our measurement. LPCC @ CERN on 17 October 2011 (Hopefully in the near future also proton-light ion run will be feasible, for example at RHIC!!!) L.Bonechi, CSN1, Bari

  16. proton – lead ion simulation This simulation is based on the EPOS (version 1.99) interaction model DPMJET III simulation is also under development • Simulating protons with energy Ep= 3.5 TeV • Energy per nucleon for ion is given by and results 1.38 TeV/nucl (at LHC the momentum must be the same for both beams) • Arm2 geometry considered on both sides in this simulation • Detector response not included yet Right-side or “p-remnant side” Left-side or “Pb-remnant side” 140 m 140 m p-beam Pb-beam Beam line L.Bonechi, CSN1, Bari

  17. proton – lead ion: -ray hit map Pb-remnant side p-remnant side L.Bonechi, CSN1, Bari

  18. proton – lead ion: neutron hit map p-remnant side, E > 500 GeV p-remnant side, E > 100 GeV Only the proton remnant side is considered in these plots, because on the ion-remnant side a huge peak due to the neutron fragment is found just coming along the beam line. E>100GeV E>500GeV L.Bonechi, CSN1, Bari

  19. p – Pb: multiplicities on small tower Pb –remnant side p –remnant side n Too many neutron fragments!!!  L.Bonechi, CSN1, Bari

  20. p – Pb: multiplicities on big tower Pb –remnant side p –remnant side n  L.Bonechi, CSN1, Bari

  21. p – Pb: -ray pseudo rapidity distribution Pseudo rapidity distribution All energies E>10GeV L.Bonechi, CSN1, Bari

  22. p – Pb: neutron pseudo rapidity distribution All energies E>10GeV L.Bonechi, CSN1, Bari

  23. p – Pb: energy vs pseudo-rapidity PHOTONS NEUTRONS L.Bonechi, CSN1, Bari

  24. p – Pb: energy spectra in p-remnant side PHOTONS SMALL TOWER PHOTONS BIG TOWER NEUTRONS BIG TOWER NEUTRONS SMALL TOWER L.Bonechi, CSN1, Bari

  25. Upgrade of detectors Rad-hard detectors are needed for operations at √s=14TeV √s=7TeVoperation in 2010√s=14TeV operations Dose ~ 200GyExp. Dose~2000Gy  10 We replaces some parts to radiation harder hard ones (no change to detector design) Upgraded Detector Current Detector Plastic Scintillators（Eljen TechnologyEJ260） Scintillating Fibers（KURARAY SCSF- 38） Silicon Strip Detectors GSO scintillators GSO scintillator bars (use current ones) L.Bonechi, CSN1, Bari

  26. Radiation hardness: scintillators Specification of both EJ-260(current detector)and GSO(upgraded detector) GSO Scintillators Test of GSO bar belts 1mmx1mm×20mmx5 Relative Light Yield as a function of dose. The results have been taken by irradiation of carbon beam at HIMAC* (290MeV/n) *HIMAC : Heavy Ion Medical Accelerator in Chiba L.Bonechi, CSN1, Bari

  27. Upgrade of silicon detectors SOME IMPORTANT POINTS UNDER INVESTIGATION : • Remove pedestal fluctuation (1nd level upgrade) • Reduce the saturation effect at Eg > 1 TeV (2nd level upgrade) • Very important improvement for higher energy LHC runs • It requires production of completely new silicon modules • Improve the energy resolution for the silicon system (2nd level upgrade) • Useful cross check for scintillators 1st level upgrade  before proton-lead run 2nd level upgrade  before pp at 14 TeV run L.Bonechi, CSN1, Bari

  28. Upgrade: pedestal fluctuation 1st level upgrade (minor intervention!) To avoid pedestal fluctuation (observed also for low energy photons) we will test soon some simple circuits to be installed on the LV power lines to the front-end. Then we want to decouple the powering of the two half-boards of each front-end. Silicon modules are the black ones in the picture. This modification requires opening the detector , cutting the power lines and fixing some new simple electric circuit. L.Bonechi, CSN1, Bari

  29. Upgrade: saturation effect • 2nd level upgrade • To reduce the saturation effect for high energy releases in silicon layers there are several possibilities that are under discussion and investigation. Decision are not yet fixed. Main points are: • No possibility to change the Pace3 chips with higher dynamic range preamplifiers • We should operate directly on the silicon side • Reducing the silicon depleted thickness to produce less charge • Decreasing the bias voltage (not safe) • Producing new thin silicon detectors (safer, but we loose the possobility to detect MIPs) • Reducing the charge collected by the readout strips • Connecting the floating strips to ground (we save the sensitivity to MIPs, but we loose probably in spatial resolution) We are setting up a LASER system in laboratory for detailed tests L.Bonechi, CSN1, Bari

  30. Upgrade: saturation effect • 2nd level upgrade • To reduce the saturation effect for high energy releases in silicon layers there are several possibilities that are under discussion and investigation. Decision are not yet fixed. Main points are: • No possibility to change the Pace3 chips with higher dynamic range preamplifiers • We should operate directly on the silicon side • Reducing the silicon depleted thickness to produce less charge • Decreasing the bias voltage (not safe) • Producing new thin silicon detectors (safer but we loose the possibility to detect MIPs) • Reducing the charge collected by the readout strips • Connecting the floating strips to ground (we save the sensitivity to MIPs, but we have to study how much we loose in spatial resolution) We are setting up a LASER system in laboratory for detailed tests L.Bonechi, CSN1, Bari

  31. Upgrade: saturation effect (2) The existing situation The charge collected on the floating strip is collected by capacitive coupling on the read out strip Floating Floating Floating Floating Under investigation The charge collected on the grounded strip is definitely lost! We reduce the collected charge. We can also do more complex geometries: Readout-Gnd-Gnd GND GND GND GND L.Bonechi, CSN1, Bari

  32. Upgrade: saturation effect (3) Silicon sensor Fan-out circuits Basic detection unit Modifications: New fan-out circuits New bonding scheme New thin silicon layers L.Bonechi, CSN1, Bari

  33. Upgrade: energy resolution • Our main idea: • Do not increase the number of silicon layers • Re-arrange the position of the existing 8 silicon layers inside the calorimeter, to make better use of the 4 silicon sensors currently located very deep in the calorimeter and not useful for g energy measurement • Keep anyway few ‘double layers’ to have a good matching between x and y coordinates L.Bonechi, CSN1, Bari

  34. X,Y X,Y X,Y X,Y Y X Y X Y X Y X • Upgrade: energy resolution (2) Optimization of silicon layer positions for energy reconstruction Silicon layer positions in the current Arm2 detector. Distribute 8 silicon layers Geometrical configuration of this simulation study Silicon layers are inserted at the front of all scintillator layers. For energy reconstruction, Summation of dE of all scintillator layers,2, 8 and 16 of the 16 silicon layers. L.Bonechi, CSN1, Bari

  35. Upgrade: energy resolution (3) Simulation implemented with the FLUKA simulation tool Hit Position Selection 4<x<16, 4<y<16 8 Silicon Layers 6 6 12 12 18 26 34 42 X0 Good energy resolution of the silicon layers !! L.Bonechi, CSN1, Bari

  36. Upgrade: energy resolution (4) Original configuration (2X0 thick tiles) double layers Updated configuration L.Bonechi, CSN1, Bari

  37. Summary LHCf has published the single photon spectrum in two different pseudo-rapidity intervals in the very forward region of the LHC for 7 TeV total energy pp interactions. New analysis are under development for the study of neutrons and neutral pions and for the transverse momentum distributions. Plan for the future measurements: • Proton-lead run at LHC in 2012 • Requires correction of pedestal fluctuation (test in lab with laser system) • Simulation under development (3.5 TeV proton energy) • Presentation of LOI at beginning of 2012 • Proton-proton interactions at 14 TeV • It is the main purpose of this experiment • Reduction of saturation effect (test of possible solutions and production of new silicon modules) • Study of a possible proton-light ion run at RHIC • Simulations under development • Visit at RHIC within end of 2011 L.Bonechi, CSN1, Bari

  38. Backup slides L.Bonechi, CSN1, Bari

  39. The LHCf international collaboration • O.Adriania,b, L.Bonechia, M.Bongia, G.Castellinia,b, R. D’Alessandroa,b, A.Fausn, K.Fukatsuc, M.Haguenauere, Y.Itowc,d, K.Kasaharaf, K. Kawadec, D.Macinag, T.Masec, K.Masudac, Y. Matsubarac, H.Menjoa,d, G.Mitsukac, Y.Murakic, M.Nakaif, K.Nodai, P.Papinia, A.-L.Perrotg, S.Ricciarinia, T.Sakoc,d, Y.Shimitsuf, K.Suzukic, T.Suzukif, K.Takic, T.Tamurah, S.Toriif, A.Tricomii,j, W.C.Turnerk, J.Velascom, A.Viciania, K.Yoshidal • INFN Section of Florence, Italy • University of Florence, Italy • Solar-Terrestrial Environment Laboratory, Nagoya University, Japan • Kobayashi Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya, Japan • EcolePolytechnique, Palaiseau, France • RISE, Waseda University, Japan • CERN, Switzerland • Kanagawa University, Japan • INFN Section of Catania, Italy • University of Catania, Italy • LBNL, Berkeley, California, USA • Shibaura Institute of Technology, Japan • IFIC, Centro Mixto CSIC-UVEG, Spain

  40. Open Issues on HECR spectrum Difference in the energy scale between different experiments??? M Nagano New Journal of Physics 11 (2009) 065012

  41. Data set for photon analysis (pp@3.5+3.5TeV) • Data • Date : 15 May 2010 17:45-21:23 (Fill Number : 1104) except runs during the VdM luminosity scan. • Luminosity : (6.3-6.5)1028cm-2s-1, • DAQ Live Time : 85.7% for Arm1, 67.0% for Arm2 • Integrated Luminosity : 0.68 nb-1for Arm1, 0.53nb-1 for Arm2 • Number of triggers : 2,916,496events for Arm13,072,691events for Arm2 • Detectors in nominal positions and normal gain • Monte Carlo • QGSJET II-03, DPMJET 3.04, SYBILL 2.1, EPOS 1.99 and PYTHIA 8.145: about 107 pp inelastic collisions each

  42. Luminosity • Luminosity for the analysis is calculated from Front Counter rates: • The conversion factor CF is estimated from luminosity measured during VdM scan VDM scan Beam sizes sx and sy measured directly by LHCf

  43. Particle Identification (PID) PID criteria based on transition curve L90% variable is the depth at which 90% of the signal has been released MC/Data comparison done in many energy bins • QGSJET2-gamma and -hadron are normalized to data(/collision) independently • LPM effects are switched on

  44. p0 mass and energy scale issue (II) • Disagreement in the peak position • Peak at 145.8  0.1 MeV for ARM1 (7.8% shift) • Peak at 140.0  0.1 MeV for ARM2 (3.8% shift) • No ‘hand made correction’ is applied for safety • Main source of systematic error  see later Arm1 Data Peak at 145.8 ± 0.1 MeV 7.8 % shift Many systematic checks have been done to understand the energy scale difference Arm2 Data Arm2 MC (QGSJET2) Peak at 140.0 ± 0.1 MeV 3.8 % shift Peak at 135.0 ± 0.2 MeV 3.8 % shift

  45. Multiple hit (MHIT) event rejection (I) One event with two hits in Arm2 • Rejection of MHIT events is mandatory especially at high energy (> 2.5 TeV) One event with three hits in Arm2 MHIT events are identified thanks to position sensitive layers in Arm1 (SciFi) and Arm2 (Si-mstrip)

  46. Multiple hit (MHIT) event rejection (II) Single  detection efficiency for various MC models Multi  detection efficiency for various MC models

  47. Acceptance cut for combined Arm1/Arm2 analysis For a comparison of the Arm1 and Arm2 reconstructed spectra we define in each tower a region of pseudo-rapidity and interval of azimuth angle that is common both to Arm1 and Arm2. As first result we present two spectra, one for each acceptance region, obtained by properly weighting the Arm1 and Arm2 spectra R1 = 5mm R2-1 = 35mm R2-2 = 42mm q= 20o For Small Tower h> 10.94 For Large Tower 8.81 < h< 8.99

  48. Comparison Arm1/Arm2 (small tower) (large tower) Multi-hit rejection and PID correction applied. Energy scale systematic (correlated between Arm1 and Arm2) has not been plotted to verify the agreement between the two detectors within the non correlated uncertainties. Deviation in small tower is still not clear. Anyway it is within systematic errors.

  49. Summary of systematics (I) • Uncorrelated uncertainties between ARM1 and ARM2- Energy scale (except p0 shift) : 3.5%- Beam center position : 1 mm- PID : 5% for E<1.7TeV, 20% for E>1.7TeV- Multi-hit selection: • Arm1 small tower: 1% for E<1TeV, 1%20% for E>1TeV • Arm1 large tower: 1% for E<2TeV, 1%30% for E>2TeV • Arm2 small tower: 0.2% for E<1.2TeV, 0.2%2.5% for E>1.2TeV • Arm2 large tower: 0.2% for E<1.2TeV, 0.2%4.8% for E>1.2TeV • Correlated uncertainties- Energy scale (p0 shift): 7.8% for Arm1 and 3.8% for Arm2 (asymmetric) - Luminosity : 6.1% Estimated for Arm1 and Arm2 by same methods but independently

  50. Summary of systematics (II) ` ` Multiple hit cut Beam center position ` Particle ID More details in paper Measurement of zero degree single photon energy spectra for √S=7TeV proton-proton collisions at LHC Submitted to Physics Letters B

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