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

22 September 20112L.Bonechi, CSN1, Bari 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  in 7 TeV pp 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

22 September 20113L.Bonechi, CSN1, Bari Purpose of the experiment Experimental measurement : – Precise measurement of neutral particle (   0 and n) spectra in the very forward region at LHC 7 TeV + 7 TeV in the c.m. frame  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 LHC

22 September 20114L.Bonechi, CSN1, Bari Detectors measure energy and impact point of  from  0 decays e.m. calo tracking layers Two independent detectors on both sides of IP1 Redundancy Redundancy Background rejection (esp. beam-gas) Background rejection (esp. beam-gas) Charged particles Neutralparticles Beam pipe Protons Detectors are located Inside the TANs (absorbers for neutral particles) 96mm Recombination Chamber The LHCf location

22 September 20115L.Bonechi, CSN1, Bari Details of the detectors 40mm 20mm Performances Energy resolution (> 100GeV): < 5% for photons and  30% for neutrons Position resolution for photons: < 200μm (Arm#1) and  40μm (Arm#2) Sampling and imaging E.M. calorimeters  Absorber: W (44 r.l, 1.55λ I )  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  0 Front Counters thin scintillators 80x80 mm monitoring of beam condition Van der Meer scan Arm1 25mm 32mm Arm2

22 September 20116L.Bonechi, CSN1, Bari Arm#1 Detector Arm#2 Detector 90mm 290mm

22 September 20117L.Bonechi, CSN1, Bari Summary of data taking Data taking with Stable Beams at ( ) GeV Dec 6 th – Dec 15 th 2009 and May 2 nd – May 27 th hours for physics Data taking with Stable Beams at ( ) TeV Mar 30 th – Jul 19 th hours for physics with different setups Different vertical positions to increase the accessible kinematical range Runs with or without 100  rad beam crossing angle ShowerGammaHadron Arm146,8004,10011,527 Arm266,7006,15826,094 ShowerGammaHadronπ0π0 Arm1172,263,25556,846,874111,971,115344,526 Arm2160,587,30652,993,810104,381,748676,157

22 September 20118L.Bonechi, CSN1, Bari Analysis of ( ) 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

22 September 20119L.Bonechi, CSN1, Bari Published results for single  at 7 TeV Adriani et al., Physics Letters B 703 (2011) 128–134 Gray hatch : Systemati c Errors Magenta hatch: MC Statistical errors DPMJET 3.04 SIBYLL 2.1 EPOS 1.99 PYTHIA QGSJET II-03 (small tower) (large tower)

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

22 September L.Bonechi, CSN1, Bari I.P.1   1 (E 1 )  2 (E 2 ) 140m R  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 25 mm tower32 mm tower Silicon  -strip X-view Silicon  -strip Y-view Selected data ( 2010 May 15, 17:45-21:23, Fill# 1104) No crossing angle, pile up is negligible (~0.2%) Low luminosity : ( )x10 28 cm -2 s -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 1.99 and PYTHIA8.145 Propagation in beam pipe and detector response are considered. In each model 10 7 collisions are generated. Neutral pions at 7 TeV

L.Bonechi, CSN1, Bari Large tower Small tower Type-I event 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. 11 22 22 September 2011 Large tower Small tower Type-II event 11 22 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 π 0. Mass peak is still wide. Neutral pions at 7 TeV (Arm1) (2) 12

L.Bonechi, CSN1, Bari22 September 2011 Neutral pions at 7 TeV (Arm1) (3) 13 LHCf-Arm1 Data 2010 (Large tower) Blue solid : Total Blue dashed : Signal Cyan : BackGround Yellow : Fitting error LHCf-Arm1 Data 2010 PRELIMINARY (Data-MC)/MC~7.8% (due mainly to energy scale) Type-II has a peak around 135MeV, but BG reduction is biggest homework For ref, values in DPMJET3 = 135.2MeV σ = 4.9MeV No acceptance correction

Single photons at 900 GeV 22 September L.Bonechi, CSN1, Bari 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)

22 September L.Bonechi, CSN1, Bari 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 and parton density saturation) Interaction  LHC in 2012 (3.5 TeV protons). We are studying the impact of our measurement. CERN on 17 October 2011 (Hopefully in the near future also proton-light ion run will be feasible, for example at RHIC!!!)

22 September L.Bonechi, CSN1, Bari proton – lead ion simulation Simulating protons with energy E p = 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 Beam line 140 m p-beamPb-beam Left-side or “Pb-remnant side” Right-side or “p-remnant side” This simulation is based on the EPOS (version 1.99) interaction model DPMJET III simulation is also under development

22 September L.Bonechi, CSN1, Bari proton – lead ion:  -ray hit map Pb-remnant sidep-remnant side

22 September L.Bonechi, CSN1, Bari 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

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

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

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

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

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

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

22 September L.Bonechi, CSN1, Bari Upgrade of detectors Rad-hard detectors are needed for operations at √s=14TeV √s=7TeV operation in 2010 √s=14TeV operations Dose ~ 200Gy Exp. Dose ~2000Gy  10 We replaces some parts to radiation harder hard ones (no change to detector design) Plastic Scintillators （ Eljen Technology EJ260 ） Scintillating Fibers （ KURARAY SCSF- 38 ） Silicon Strip Detectors GSO scintillators GSO scintillator bars (use current ones) Upgraded Detector Current Detector

22 September L.Bonechi, CSN1, Bari Radiation hardness: scintillators GSO Scintillators Test of GSO bar belts 1mmx1mm×20mmx5 EJ-260GSO Radiation hardness (Gy) Density (g/cm 3 ) X 0 (cm) Decay time (ns) Light yield （ NaI=100 ） Specification of both EJ-260(current detector) and GSO(upgraded detector) 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

22 September L.Bonechi, CSN1, Bari Upgrade of silicon detectors 1.Remove pedestal fluctuation (1 nd level upgrade) 2.Reduce the saturation effect at E  > 1 TeV (2 nd level upgrade) – Very important improvement for higher energy LHC runs – It requires production of completely new silicon modules 3.Improve the energy resolution for the silicon system (2 nd level upgrade) – Useful cross check for scintillators 1 st level upgrade  before proton-lead run 2 nd level upgrade  before pp at 14 TeV run SOME IMPORTANT POINTS UNDER INVESTIGATION :

22 September L.Bonechi, CSN1, Bari Upgrade: pedestal fluctuation 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. 1 st 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.

22 September L.Bonechi, CSN1, Bari Upgrade: saturation effect 2 nd 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 1.Reducing the silicon depleted thickness to produce less charge a.Decreasing the bias voltage (not safe) b.Producing new thin silicon detectors (safer, but we loose the possobility to detect MIPs) 2.Reducing the charge collected by the readout strips a.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

22 September L.Bonechi, CSN1, Bari Upgrade: saturation effect 2 nd 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 1.Reducing the silicon depleted thickness to produce less charge a.Decreasing the bias voltage (not safe) b.Producing new thin silicon detectors (safer but we loose the possibility to detect MIPs) 2.Reducing the charge collected by the readout strips a.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

22 September L.Bonechi, CSN1, Bari Upgrade: saturation effect (2) Floating GND The charge collected on the floating strip is collected by capacitive coupling on the read out strip 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 The existing situation Under investigation

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

22 September L.Bonechi, CSN1, Bari 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  energy measurement Keep anyway few ‘double layers’ to have a good matching between x and y coordinates

22 September L.Bonechi, CSN1, Bari Upgrade: energy resolution (2) 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. Silicon layer positions in the current Arm2 detector. X,Y XYXYXYX Y Distribute 8 silicon layers Optimization of silicon layer positions for energy reconstruction

22 September L.Bonechi, CSN1, Bari Upgrade: energy resolution (3) Good energy resolution of the silicon layers !! Hit Position Selection 4<x<16, 4<y<16 8 Silicon Layers X 0 Simulation implemented with the FLUKA simulation tool

22 September L.Bonechi, CSN1, Bari Upgrade: energy resolution (4) Original configuration Updated configuration double layers (2X 0 thick tiles)

22 September L.Bonechi, CSN1, Bari 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: 1.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 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) 3.Study of a possible proton-light ion run at RHIC  Simulations under development  Visit at RHIC within end of 2011

22 September L.Bonechi, CSN1, Bari Backup slides

The LHCf international collaboration O.Adriani a,b, L.Bonechi a, M.Bongi a, G.Castellini a,b, R. D’Alessandro a,b, A.Faus n, K.Fukatsu c, M.Haguenauer e, Y.Itow c,d, K.Kasahara f, K. Kawade c, D.Macina g, T.Mase c, K.Masuda c, Y. Matsubara c, H.Menjo a,d, G.Mitsuka c, Y.Muraki c, M.Nakai f, K.Noda i, P.Papini a, A.-L.Perrot g, S.Ricciarini a, T.Sako c,d, Y.Shimitsu f, K.Suzuki c, T.Suzuki f, K.Taki c, T.Tamura h, S.Torii f, A.Tricomi i,j, W.C.Turner k, J.Velasco m, A.Viciani a, K.Yoshida l a)INFN Section of Florence, Italy b)University of Florence, Italy c)Solar-Terrestrial Environment Laboratory, Nagoya University, Japan d)Kobayashi Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya, Japan e)Ecole Polytechnique, Palaiseau, France f)RISE, Waseda University, Japan g)CERN, Switzerland h)Kanagawa University, Japan i)INFN Section of Catania, Italy j)University of Catania, Italy k)LBNL, Berkeley, California, USA l)Shibaura Institute of Technology, Japan m)IFIC, Centro Mixto CSIC-UVEG, Spain 39

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

Data set for photon analysis Data – Date : 15 May :45-21:23 (Fill Number : 1104) except runs during the VdM luminosity scan. – Luminosity : ( )  cm -2 s -1, – DAQ Live Time : 85.7% for Arm1, 67.0% for Arm2 – Integrated Luminosity : 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 – 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 10 7 pp inelastic collisions each 41

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  x and  y measured directly by LHCf 42

Particle Identification (PID) PID criteria based on transition curve L 90% 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 43

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

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

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

Acceptance cut for combined Arm1/Arm2 analysis R1 = 5mm R2-1 = 35mm R2-2 = 42mm  = 20 o For Small Tower  > For Large Tower 8.81 <  < 8.99 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 47

Comparison Arm1/Arm2 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. (small tower) (large tower) 48

Summary of systematics (I) Uncorrelated uncertainties between ARM1 and ARM2 - Energy scale (except  0 shift) : 3.5% - Beam center position : 1 mm - PID : 5% for E 1.7TeV - Multi-hit selection : Arm1 small tower: 1% for E 1TeV Arm1 large tower: 1% for E 2TeV Arm2 small tower: 0.2% for E 1.2TeV Arm2 large tower: 0.2% for E 1.2TeV Correlated uncertainties - Energy scale (  0 shift): 7.8% for Arm1 and 3.8% for Arm2 (asymmetric) - Luminosity : 6.1% Estimated for Arm1 and Arm2 by same methods but independently 49

` ` Summary of systematics (II) Beam center position Multiple hit cut ` 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 50

What do we expect from LHCf? γ n π0π0 Energy spectra and transverse momentum distribution of  (E  100GeV,  E  E  5%) Neutrons (E> few 100 GeV,  E  E  30%)  0 (E  500GeV,  E  E  3%) in the pseudo-rapidity range 

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 52

Linearity of PMTs (Hamamatsu R7400) PMTs R7400 are used in current LHCf system coupled to the scintillator tiles Test of linarity was held at HIMAC using Xe beam PMT R7400 showed good linearity within 1% up to signal level corresponding to 6TeV showerMAX in LHCf. 53

Accumulated events in events!LHCf removal 54

Pile-up events When the configuration of beams is 1x1 interacting bunches, 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 of 71.5mb Taking into account the calorimeter acceptance (~0.03) only 0.2% of events have multi-hit due to pile-up. It does not affect our results 55

 0 mass versus  0 energy Arm2 Data No strong energy dependence of reconstructed mass 56

2  invariant mass and  mass Arm2 detector: all runs with zero crossing angle True  Mass:547.9 MeV MC Reconstructed  Mass peak: ± 1.0 MeV Data Reconstructed  Mass peak: ± 1.8 MeV (2.6% shift)  candidate (  50 events)  0 candidate 57

Analysis of 900 GeV Event Arm1 Event Arm2 58

Beam-gas 900 GeV Very big reduction in the Beam Gas contribution!!!! Beam gas  I, while interactions  I 2 59

Beam SPS Energy Resolution for electrons with 20mm cal. Position Resolution (Scifi) Position Resolution (Silicon) Detector p,e-,mu σ=172 μm for 200GeV electrons σ=40 μm for 200GeV electrons - Electrons 50GeV/c – 200GeV/c - Muons 150GeV/c - Protons 150GeV/c, 350GeV/c 60

Energy SPS Difference of energy reconstruction at SPS between data and MC is < 1%. Systematic error for gain calibration factor layer by layer is 2% 61

Particle and energy flow vs rapidity Low multiplicity !! High energy flux !! simulated by DPMJET3 62

Radiation damage 30 kGy Expected dose: 100 Gy/day at cm -2 s -1 Expected dose: 100 Gy/day at cm -2 s cm -2 s -1 : 10 kGy cm -2 s -1 : 10 kGy 50% light output 50% light output Continous monitor and calibrationwith Laser system!!! Continous monitor and calibrationwith Laser system!!! Scintillating fibers and scintillators 1 kGy 63

Uncertainty on the energy scale Two components: - Relatively well known: Detector response, SPS => 3.5% - Unknown:  0 mass => 7.8%, 3.8% for Arm1 and Arm2. Please note: - 3.5% is symmetric around measured energy - 7.8% (3.8%) are asymmetric, because of the  0 mass shift - No ‘hand made’ correction is applied up to now for safety Total uncertainty is -9.8% / +1.8% for Arm1 -6.6% / +2.2% for Arm2 Systematic Uncertainty on Spectra is estimated from difference between normal spectra and energy shifted spectra. 64

Uncertainty on the beam center Error of beam center position is estimated to be 1 mm from comparison between our results and the BPM results The systematic errors on spectra were estimated from the difference between spectra with 1 mm shift of acceptance cut area. 5% to 20% linear rise from 100 GeV to 3.6 TeV Arm1 Results - true single gamma events 100 GeV<E<3.5 TeV : 5% 65

Uncertainty from PID Template fitting A: 1 degree of freedom: - Absolute normalization Template fitting B: 3 degrees of freedom: - Absolute normalization - Shift of L90% distribution - Width of L90% distribution Efficiency and purity are estimated with two different approaches Hatched : data Red : true-gamma Blue : true-hadron Green : Red+Blue Systematic error from PID are assumed: 5% for 100GeV < E < 1.7TeV 20% for E > 1.7TeV Both on small and large tower Arm1 Hatched : data Red : true-gamma Blue : true-hadron Green : Red+Blue 66

Uncertainty from Multiple Hit corrections ARM1 ARM2 67