Recent results on neutral particles spectra from the LHCf experiment Massimo Bongi - INFN (Florence, Italy) LHCf Collaboration 13th ICATPP Conference on Astroparticle, Particle, Space Physics and Detectors for Physics Applications Villa Olmo - Como, Oct 3 rd – 7 th, 2011

Massimo Bongi – ICATPP – 3 rd October 2011 – Como High-energy cosmic rays LHC SPS AUGER Tevatron E [eV] Recent excellent observations (e.g. Auger, HiRes, TA) but the origin and composition of HE CR is still unclear 2

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Development of atmospheric showers LHC forward (LHCf) experiment eV proton The dominant contribution to the shower development comes from particles emitted at low angles (forward region). Experimental tests of hadron interaction models are necessary LHC gives us the unique opportunity to study hadronic interactions at eV 7 TeV + 7 TeV → E lab ≈ 1 x eV 3.5 TeV TeV → E lab ≈ 3 x eV 450 GeV GeV → E lab ≈ 4 x eV  The depth of the maximum of the shower X max in the atmosphere depends on energy and type of the primary particle  Several Monte Carlo simulations (different hadronic interaction models) are used and they give different answers about composition 3

Massimo Bongi – ICATPP – 3 rd October 2011 – Como 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, T.Suzuki, S.Torii Waseda University, Japan Y.Shimizu JAXA, 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 and Universita’ di Firenze, Italy K.Noda, A.Tricomi INFN and Universita’ di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain A-L.Perrot CERN, Switzerland The LHCf collaboration 4

Massimo Bongi – ICATPP – 3 rd October 2011 – Como LHCf experimental set-up 96mm ATLAS 140m LHCf Detector (Arm1) ATLAS LHCb CMS ALICE LHCf Beam pipe Protons Charged particles (+) Charged particles (-) Neutral particles TAN 5

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Arm1 detector Scintillating Fibers + MAPMT: 4 pairs of layers (at 6, 10, 30, 42 X 0 ), 200 μm tracking measurements (resolution < 200 μm) 16 layers Plastic Scintillator: 16 layers, 3 mm thick, trigger and energy profile measurement 40mm 20mm Absorber: 22 tungsten 44 X 0, 1.55 layers, 44 X 0, 1.55 Sampling e.m. calorimeters: each detector has two calorimeter towers which allow to reconstruct  0 Front counters: thin plastic scintillators, 80x80 mm 2  monitor beam condition  estimate luminosity  reject background due to beam - residual gas collisions by coincidence analysis 6

Massimo Bongi – ICATPP – 3 rd October 2011 – Como 25mm 32mm Arm2 detector 16 layers Plastic Scintillator: 16 layers, 3 mm thick, trigger and energy profile measurement Absorber: 22 tungsten 44 X 0, 1.55 layers, 44 X 0, 1.55 Sampling e.m. calorimeters: each detector has two calorimeter towers which allow to reconstruct  0 Front counters: thin plastic scintillators, 80x80 mm 2  monitor beam condition  estimate luminosity  reject background due to beam - residual gas collisions by coincidence analysis Silicon Microstrip: 4 pairs of layers (at 6, 12, 30, 42 X 0 ), 40 μm tracking measurements (resolution ~ 40 μm) 7

Massimo Bongi – ICATPP – 3 rd October 2011 – Como ATLAS & LHCf 8

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Arm1 detector Arm2 detector 90mm 290mm 9

Massimo Bongi – ICATPP – 3 rd October 2011 – Como What LHCf can measure Energy spectra and transverse momentum distribution of:  gamma rays (E>100 GeV, dE/E<5%)  neutral hadrons (E>few 100 GeV, dE/E~30%)  π 0 (E>600 GeV, dE/E<3%) in the pseudo-rapidity range η >8.4 14TeVEnergy 14TeV Low multiplicity High energy flux Low multiplicity High energy flux (simulated by DPMJET3) η ∞ 8.5 Front view of crossing angle Projected edge of beam pipe mm 10

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Event categories leading baryon (neutron) multi meson production π0π0 photon hadron event π 0 event photon event LHCf calorimeters 11

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Summary of operations in 2009 and 2010 With stable beams at 450GeV+450GeV Total of 42 hours for physics (6 th –15 th Dec. 2009, 2 nd -3 rd,27 th May 2010) ~ 10 5 showers events in Arm1+Arm2 With stable beams at 3.5TeV+3.5TeV Total of 150 hours for physics (30 th Mar.-19 th Jul. 2010) Different vertical positions to increase the accessible kinematical range Runs with or without beam crossing angle ~ 4·10 8 shower events in Arm1+Arm2 ~ 10 6  0 events in Arm1+Arm2 Status Completed program for 450GeV+450GeV and 3.5TeV+3.5TeV Removed detectors from tunnel in July 2010 (luminosity >10 30 cm -2 s -1 ) Post-calibration beam test in October 2010 Upgrade to more rad-hard detectors to operate at 7TeV+7TeV in

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Photon energy spectra analysis EXPERIMENTAL DATA p-p collisions at √s=7 TeV, no crossing angle (Fill# 1104, 15 th May :45-21:23) Luminosity: (6.3÷6.5) x cm -2 s -1 (3 crossing bunches) Negligible pile-up (~0.2%) DAQ Live Time: 85.7% (Arm1), 67.0% (Arm2) Integrated luminosity: 0.68 nb -1 (Arm1), 0.53 nb -1 (Arm2) MONTE CARLO DATA 10 7 inelastic p-p collisions at √s=7 TeV simulated by several MC codes: DPMJET 3.04, QGSJET II-03, SYBILL 2.1, EPOS 1.99, PYTHIA Propagation of collision products in the beam pipe and detector response simulated by EPICS/COSMOS ANALYSIS PROCEDURE 1.Energy Reconstruction: total energy deposition in a tower (corrections for light yield, shower leakage, energy calibration, etc.) 2.Rejection of multi-hit events: transverse energy deposit 3.Particle identification (PID): longitudinal development of the shower 4.Selection of two pseudo-rapidity regions: Combine spectra of Arm1 and Arm2 and compare with MC expectations 13

Massimo Bongi – ICATPP – 3 rd October 2011 – Como 1 TeV π 0 candidate event 25mm tower 32mm tower scintillator layers – longitudinal development silicon layers – transverse energy Y view X view 600 GeV photon 420 GeV photon  Energy reconstruction  PID  Energy reconstruction  PID  Hit position  Multi-hit identification  Hit position  Multi-hit identification  π 0 mass reconstruction 14

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Energy reconstruction  Energy reconstruction: E photon = f( Σ E i ) (i = layer index) (E i = A x Q i determined at SPS; f() determined by MC and checked at SPS)  Impact position from lateral distribution  Position dependent corrections: light collection non-uniformity shower leakage-out (and 2 mm edge cut) shower leakage-in Light collection non-uniformity Shower leakage-in correction 2 mm Shower leakage-out 25mm tower 32mm tower 15

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Multi-hit rejection  Rejection of multi-hit events is mandatory especially at high energy (> 2.5 TeV)  Multi-hit events are identified thanks to position sensitive layers in Arm1 (SciFi) and Arm2 (Si-  strip) Arm1 Arm2 Small towerLarge tower Arm2 Multi-hit detection efficiency Single-hit detection efficiency 16

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Particle identification 500 GeV < E REC < 1 TeV photon hadron 44 X λ  L 90% : longitudinal position containing 90% of the shower energy  Photon selection based on L 90% cut  Energy dependent threshold in order to keep constant efficiency ε PID = 90%  Purity P = N phot /(N phot +N had ) estimated by comparison with MC  Event number in each bin corrected by P/ ε PID  MC photon and hadron events are independently normalized to data  Comparison done in each energy bin  LPM effects are switched on 17

Massimo Bongi – ICATPP – 3 rd October 2011 – Como π 0 mass reconstruction I.P.1   1 (E 1 )  2 (E 2 ) 140 m R m ≈ θ√(E 1 xE 2 )  Energy scale can be checked by π 0 identification  Mass shift observed both in Arm1 (+7.8%) and Arm2 (+3.7%)  Many checks have been done to understand the energy scale difference: the estimated systematic uncertainty on π 0 reconstruction is 4.2%  Conservative approach: no correction is applied to the energy scale, but an asymmetric systematic error is assigned Arm2 MC Peak : ± 0.2 MeV 18

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Comparison between the two detectors R1 = 5 mm R2-1 = 35 mm R2-2 = 42 mm R1 = 5 mm R2-1 = 35 mm R2-2 = 42 mm  We define two common pseudo-rapidity and azimuthal regions for the two detectors:8.81 < η < 8.99, Δφ = 20˚ (large tower) η > 10.94, Δφ = 360˚ (small tower)  Normalized by the number of inelastic collisions (assuming σ ine = 71.5 mb)  General agreement between the two detectors (deviation in small tower within the error) ΔφΔφ Red points: Arm1 detector Blue points: Arm2 detector Filled area: uncorrelated systematic uncertainties 19

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Combined photon spectra gray hatch: systematic error error bars: statistical error 20

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Comparison with MC gray hatch: systematic errormagenta hatch: MC statistical error DPMJET 3.04 QGSJET II-03 SYBILL 2.1 EPOS 1.99 PYTHIA

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Preliminary π 0 spectra  Mass range selection: +/- 10 MeV around the measured peak  Acceptance depends on energy and transverse momentum (lowest energy is limited by maximum angle between photons)  Comparison with MC is on-going  Extend the analysis to events with two photons in the same tower m ≈ θ√(E 1 xE 2 ) E π = E 1 +E 2 22

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Summary and outlook  Single photon analysis at 3.5 TeV TeV: first comparison of various hadronic interaction models with experimental data in a challenging phase space region very safe estimation of systematics no model perfectly reproduces LHCf data, especially at high energy new input data for model developers implications for HE CR physics under study  Neutral pion analysis at 3.5 TeV TeV is in progress: compare pion spectra with MC include events with two gammas hitting the same tower the same analysis can be extended to η and K 0 particles  Other analysis: complete the analysis at 450 GeV GeV, neutrons, transverse momentum distributions, extend pseudo-rapidity range,…  We are upgrading the detectors to improve their radiation hardness (GSO scintillators): we will come back on the LHC beam for the 7 TeV + 7 TeV runs discussion is under way to come back for possible p-Pb runs in

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Massimo Bongi – ICATPP – 3 rd October 2011 – Como AGASA Systematics Total ±18% Hadr Model ~10% (Takeda et al., 2003) AGASA Systematics Total ±18% Hadr Model ~10% (Takeda et al., 2003) Open Issues on UHECR spectrum M Nagano New Journal of Physics 11 (2009) Depth of the max of the shower X max in the atmosphere AUGER HiRes 25

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Front counters Thin scintillators with 8x8cm 2 acceptance, which have been installed in front of each main detector. To monitor beam condition. For background rejection of beam-residual gas collisions by coincidence analysis Schematic view of Front counter 26

Detector vertical position and acceptance Remotely changed by a manipulator( with accuracy of 50  m) Distance from neutral center Beam pipe aperture Data taking mode with different position to cover P T gap N L G All  from IP Viewed from IP Neutral flux center N L 7TeV collisions Collisions with a crossing angle lower the neutral flux center thus enlarging P t acceptance 27

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Expected 14 TeV collisions  n 00 Energy spectra and transverse momentum distribution of: photons (E > 100 GeV):  E/E < 5% neutral pions (E > 500 GeV):  E/E < 3% neutrons (E > few 100 GeV):  E/E ~ 30% in the pseudo-rapidity range  >

Massimo Bongi – ICATPP – 3 rd October 2011 – Como LHCf energy resolution 2.5 x 2.5 cm 2 tower2.0 x 2.0 cm 2 tower Energy resolution < 5% at high energy, even for the smallest tower 29

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Arm1 position resolution Number of event x-pos[mm] y-pos[mm] 200 GeV electrons E[GeV] σ X =172µm σ Y =159µm σ X [mm] σ Y [mm] 30

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Arm2 position resolution x-pos[mm] y-pos[mm] Alignment has been taken into account 200 GeV electrons E[GeV] σ X =40µm σ Y =64µm σ X [µm] σ Y [µm] 31

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Estimation of pile-up When the circulated bunch is 1x1, the probability of N collisions per crossing is: The ratio of the pile-up event is: The maximum luminosity per bunch during runs used for the analysis is 2.3x10 28 cm -2 s -1 So the probability of pile-up is estimated to be 7.2%, with σ=71.5mb and f rev = 11.2 kHz Taking into account our calorimeter acceptance for an inelastic collision (~0.03) only 0.2% of events have multi-hit due to pile-up 32

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Luminosity estimation Luminosity for the analysis is calculated from Front Counter rates: The conversion factor CF is estimated from luminosity measured during Van der Meer scan VDM scan Beam sizes  x and  y measured directly by LHCf 33

Massimo Bongi – ICATPP – 3 rd October 2011 – Como  0 mass vs  0 energy Arm2 data No strong energy dependence of reconstructed mass Arm2 data No strong energy dependence of reconstructed mass 34

Massimo Bongi – ICATPP – 3 rd October 2011 – Como 2  invariant mass 7 TeV Arm2 detector, all runs with zero crossing angle True η mass:547.9 MeV MC reconstructed η mass peak: ± 1.0 MeV Data reconstructed η mass peak: ± 1.8 MeV (2.6% shift) 35

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Effect of mass shift Energy rescaling NOT applied but included in energy error M inv = θ √(E 1 x E 2 ) – (ΔE/E) calib = 3.5% – Δθ/θ = 1% – (ΔE/E) leak-in = 2% => ΔM/M = 4.2% ; not sufficient for Arm1 (+7.8%) 145.8MeV (Arm1 observed) 135MeV ±7.8% flat probability ±3.5% Gaussian probability Quadratic sum of two errors is given as energy error (to allow both 135MeV and observed mass peak) 36

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Systematic uncertainties Energy reconstruction (detector response, from beam test at SPS): 3.5% Multi-hit rejection (estimated by comparing true MC and reconstructed MC spectra after MH cut): from 1% for E < 1.5 TeV to 20% at E = 3 TeV PID (by comparing 2 different approaches): 5% for E 1.7 TeV Beam center position (by comparing position measured by LHCf and by Beam Position Monitors): 5÷20 % varying with energy and pseudo-rapidity Luminosity (Front Counter measurement during Van der Meer scans): 6.1%, it causes an energy independent shift of spectra, not included in photon spectra Energy shift (π 0 mass shift, asymmetric): 7.8% Arm1, 3.7% Arm2 Total energy scale systematic:-9.8% / +1.8% for Arm1 -6.6% / +2.2% for Arm2 Systematic uncertainty on spectra is estimated from the difference between normal spectra and energy scaled spectra 37

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Background Beam-Gas backgrounds Secondary-beam pipe backgrounds 1.Pile-up of collisions in one beam crossing  Low Luminosity fill, L=2.3x10 28 cm -2 s -1  7.2% pile-up at collisions, 0.2% at the detectors. 2.Collisions between secondary's and beam pipes  Very low energy particles reach the detector (few % at 100GeV) 3.Collisions between beams and residual gas  Estimated from data with non-crossing bunches.  ~0.1% 38

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Arm1 Arm2 gamma-ray likehadron like Acceptance is different for the two arms. Spectra are normalized by # of  -ray and hadron like events. Energy spectra at 900 GeV PRELIMINARY Only statistical errors are shown 39

Massimo Bongi – ICATPP – 3 rd October 2011 – Como Radiation damage studies 30 kGy  Dose evaluation on the basis of LHC reports on radiation environment at IP1  ~ cm -2 s -1 luminosity are expected  ~ 10 kGy during few months operation lead to ~ 50% light output decrease  continuous laser calibration to monitor scintillators and correct for the decrease of light output  test of Scintillating fibers and scintillators 40