Physics results of the LHCf experiment

Transcription

1 Univesity & INFN Catania Physics motivation and the LHCf detector Forward spectra at s = 7 TeV and 900 GeV p-p collisions p-pb run Detector upgrade Prospects for new data taking EPS-HEP 2013, July , Stockholm, Sweden

2 p-p interactions in the very forward region 2 LHC gives a unique opportunity to calibrate the hadronic intection models up to Motivation Verify the hadron interaction models used in air shower simulations by the 6.5TeV+6.5TeV most powerful and E lab = energetic ev hadron 3.5TeV+3.5TeV accelerator : LHC E lab = 2.6x10 16 ev 450GeV+450GeV E lab = 2x10 14 ev p-p " s = 14 TeV ev Forward region is very effective on air Key shower Parameters development Key Inelastic Parameters Cross Section Inelastic! TOTEM, Cross ATLAS, Section CMS,ALICE Forward TOTEM, Energy ATLAS, CMS,ALICE Spectrum Forward! LHCf, Energy ZDC Spectrum and etc. Inelasticity LHCf, ZDC and k= 1-plead/pbeam etc. Inelasticity! LHCf, k= ZDC 1-plead/pbeam and etc. Secondary LHCf, ZDC and interactions etc. Secondary interactions P. 4

3 LHCf: location and detector layout 3 Detector I Tungsten Scintillator Scintillating fibers Detector II INTERACTION POINT Tungsten IP1 (ATLAS) Scintillator Silicon mstrips Front Counter Front Counter 140 m 140 m γ 8 cm 6 cm n π 0 γ 44X 0, 1.6 l int Arm#1 Detector 20mmx20mm+40mmx40mm 4 X-Y SciFi tracking layers Arm#2 Detector 25mmx25mm+32mmx32mm 4 X-Y Silicon strip tracking layers

4 LHCf: a brief photo-history 4 May 2004 LOI Jul 2006 construction Jan 2008 Installation Feb 2006 TDR June 2006 LHCC approved Dec st 900GeV run Mar st 7TeV run Aug 2007 SPS beam test Dic 2012 ARM2 re-installation Jul 2010 Detector removal Gen-Feb 2013 p-pb run April 2013 Detector removal and upgrade

5 5 Single photon spectra at 7 TeV p-p DPMJET 3.04 SIBYLL 2.1 EPOS 1.99 PYTHIA QGSJET II-03 No Model able to reproduce LHCf data especially in the high-energy region Magenta hatch: MC Statistical errors Gray hatch : Systematic Errors

6 Photons : 900GeV vs 7TeV spectra 6 Coverage of the photon spectra in the plane Feynman-X vs P T XF spectra : 900GeV data vs. 7TeV data Preliminary 900GeV vs. 7TeV with the same P T region 900 GeV Small+large tower Data 2010 at s=900gev (Normalized by the number of entries in X F > 0.1) Data 2010 at s=7tev (η>10.94) Normalized by the number of entries in X F > 0.1 No systematic error is considered in both collision energies. Good agreement of X F spectrum shape between 900 GeV and 7 TeV. weak dependence of <pt> on ECMS

7 /Data /Data /Data Events/ (1MeV) 1/ 1/ 1/ 3 3 s inel Ed s/dp MC/Data 3 3 s inel Ed s/dp 3 3 s inel Ed s/dp -2 [GeV ] Ratio (MC/Data) MC/Data MC/Data -2 [GeV ] -2 [GeV ] 1/ 1/ 1/ 3 3 s inel Ed s/dp 3 3 s inel Ed s/dp 3 3 s inel Ed s/dp -2 [GeV ] -2 [GeV ] -2 [GeV ] 2 ¼ Xn X Nobs i¼1 a¼1 a;i ð1þ S a;iþ N comb A þ 2 penalty ; (7) a;i where the index i represents the p T bin number running from 1 to n (the total number of p T bins), Na;i obs is the number of events, and a;i is the uncertainty of the 2 penalty term 2 penalty ¼ X6 7 TeV π 0 analysis j ¼1 ðj" j Arm1 j2 þ j" j Arm2 j2 Þ: (9) The 0 productionratesfor thecombineddataof LHCf are summarized in Tables IV, V, VI, VII, VIII, and IX. Note 7 R 1 (E 1 ) 2 (E 2 )! 0! -1 2! 10 IP LHCf s R = 140mò m 10! " -3 10! # I.P.1 PYTHIA MEASUREMENT OF FORWARD p[gev] NEUTRAL PION... p[gev] PHYSICAL REVIEW p[gev] D 86, (20 T Reconstructed Mass O. ADRIANI et al. PHYSICAL REVIEW D 86, (2012) LHCf s LHCf s =7TeV LHCf p 0 s=7tev p LHCf s LHCf p s=7tev MC/Data =7TeV 0 9.6<y< <y<1.0 LHCf-Arm1s 48.9<y< <y< <y<9.4 MC/Data 9.0<y< ò Data2010 DPMJET3.04 QGSJETI-03 SIBYL2.1 EPOS1.9 =7TeV 8.9<y<9.0 p 0-1 Ldt= nb =7TeV LHCf p 0 s=7tev p 0 DPMJET <y<9.6-1 =7TeV, ò Ldt=2.53nb QGSJETI Ldt= nb SIBYL2.1 Ldt= nb ò EPOS1.9 PYTHIA8.145 PT spectra =7TeV p 9.0<y< Ldt= nb LHCf s 9.0<y<9.2 T ò9.0<y<9.2 ò ò -1 Ldt= nb -1 Ldt= nb LHCf s=7tev p 9.2<y< Ldt= nb T -1 ò9.2<y<9.4 ò Ldt= nb ò p 0-1 Ldt= nb p [GeV] p [GeV] p [GeV] T Reconstructedm [MeV] 4.5 LHCf s=7tev p 0 FIG. 4 (color online). Reconstructed invariant mass distribution within therapidity 4rangefrom <y<9.6 to 9.2. Solid curveshows the best-fit composite 3.5 physics model to-1the invariant mass Ldt= nb distribution. Dashed curveindicatesthebackground ò component. Solid and dashed curves 3 indicate the signal and background windows, respectively T T Same 5 conclusions as for photons 5 Similar as Photon results results P No model LHCf able s=7tev to p reproduce LHCf data LHCf s=7tev 4 9.6<y< <y<1.0 Best overall agreement with EPOS Ldt= nb ò ò gg FIG. 7 (color online). Combined p T spectra of the Arm1 and Arm2 detectors (black dots) and the total uncertainties (shaded p rectangles) compared with the predicted spectra by hadronic interaction models Ldt= nb

8 8 LHCf <p T > distribution Courtesy P. LIPARI Three different approaches used to derive the average transverse momentum, p T 1. by fitting an empirical function to the p T spectra in each rapidity range (exponential distribution based on a thermodynamical approach) 1. by fitting a gaussian distribution 2. by simply numerically integrating the p T spectra Results of the three methods are in agreement and are compared with UA7 data and hadronic model predictions

9 T 9 Playing a game with air shower (effect of forward meson spectra) DPMJET3 always over-predicts production Filtering DPMJET3 mesons according to an empirical probability function, divide mesons into two with keeping p T Fraction of mesons escape out of LHCf acceptance This process Holds cross section Holds elasticity/inelasticity Holds energy conservation Changes multiplicity Does not conserve charge event-by-event E 1 E 2 E=E 1 +E 2 x F = E/E 0 x F = E/E 0

10 10 An example of filtering DPMJET3+filter Vertical Depth (g/cm 2 ) photon spectrum π 0 spectrum ~30g/cm 2 2.5x10 16 ev proton AUGER, ICRC 2011

11 Entries S[VEM] Entries de/dx[pev/g/cm 2 ] Motivations Inelasticity measurement k = 1-pleading/pbeam Muon excess at POA. (T. Pierog and K. Warner PRL 101, , 2008) Performance for for neutrons Efficiency ~70% Energy Res % Position Res. a few mm ( +30% than MC) Details were presented by K.Kawade (ID:850) yesterday Forward baryon production Neutron spectra N e u t r o n A n a ly s is Motivations; Forward b r Motivations Neutron spectra predicted Motivations: Inelasticity measurement Inelasticity k=1-p measurement by interaction Expected models neutron leading Neutron /p beam spectra 1 0 predicted Very Muon excess at k Pierre = large diffeence in neutral 1-pleading/pbeam Auger Observatory by interaction 9 0 models p-p, " s= 7TeV Energy: (13.8+_0.7) PYTHIA EeV EPOS baryon spectra among the 8 0 Small QGSJET2 30 Tower Zenith: (56.5+_0.2 EPOS predicts Muon more excess muons at POA. o ) DPMJET3 due to larger X 7 0 (T. Pierog and K. Warner PRL 101, baryon production models is ((T. expected Pierog and p-p, , K. " s= 2008) 7TeV Max :(752+_9) SYBIL g/cm Warner PRL 101, , 2008) Small Tower => importance Performance of baryon for measurement neutrons Direct measurement of inelasticity 2 0 Efficiency ~70% Muon Energy excess Res % Position Res. a few mm Muon excess in CR Details were presented observation is found relative by K.Kawade (ID:850) yesterday to the MC predictions P Energy[GeV] LHCf Smal tower PYTHIA EPOS QGSJET2 DPMJET3 SYBIL P. 12 Depth[g/cm

12 events/n inel /GeV events/n /GeV inel Neutron spectra 12 Small Tower Smal tower -6! Norapidityselection Noefficiencycorection Onlystatistical eror Data EPOS QGSJET2 PYTHIA SYBIL LHCf Preliminary Large Tower hdata! Norapidityselection Noefficiencycorection Onlystatistical eror Data EPOS QGSJET2 PYTHIA SYBIL LHCf Preliminary Only Arm1 Large small beam center ReconstructedEnergy[GeV] ReconstructedEnergy[GeV] Estimations of systematic uncertainties LHCf Smal tower LHCf Largetower Estimations of systematic uncertainties } Study of unfolding } On Study of unfolding of the spectra are going ARM2 analysis ongoing

13 Operation in Jan-Feb IP2 Pb Arm2 IP1 p IP8 p-pb/pb-p operation One arm (Arm2) observation p-remnant side (little Pb remnant) Common trigger with ATLAS 2.76 TeV p-p operation

14 14 Physics in p-a p-p p-n p-pb QGSJET II-04 All η 8.81<η<8.99 η>10.94 Photon spectra at different η in p-p, p- N and p-pb collisions Enhancement of suppression for HI (Courtesy of S.Ostapchenko) Nuclear effect in the forward particle production Photon spectra for different impact parameters

15 15 LHCf p-pb run: Photon spectra 4+202) 3+, / ) ( ) 0!%&*,!i!89- :- /(18+0:,<' ( B'. CC(:- L +,( YDE(:- L +,( Alessia FG!@' Tricomi 025, +!HI FF! Physics results =8?2) of, the ' #&W!=4CCW!CL` LHCf experiment a! G!

16 Reinstall Reinst 16 LHCf Future PLANS LHC TeV 2011/ shutdown TeV Jul LHCf I Detector upgrade LHCf-HI Detector upgrade : Detector upgrade for 13 TeV run Replaced plastic scintillators with Rad Hard GSO Modify the silicon layers positions to improve silicon-only energy resolution and improve the dynamic range of silicon Test beam at SPS to calibrate ARM1/2 Re-installation of the detector 2015: run at 13 TeV p-p collision at LHC 2016 Operation at RHIC, p-p at s=500gev, p-n at s NN =200GeV (proposal presented at BNL PAC) 2019??? Run at LHC in p-light A EJ260 LHCf II 8 Silicon Layers X

17 17 Conclusions The first LHCf data taking at LHC was very successful 7 TeV and 900 GeV inclusive photon spectra and p 0 p T spectra published First comparison of various hadronic interaction models with experimental data in the most challenging phase space region (8.81 < h < 8.99, h > 10.94) Large discrepancy especially in the high energy region with all models Comparisons with models gives important hints for HECR and soft QCD Physics Neutron spectra in p-p and photon spectra in p-pb analyses are ongoing We have clearly demonstrated the imortance of a calibration of hadronic interaction models used in HECR Physics Implications of our data in UHECR Physics under study in strict connection with relevant theoreticians and model developer We are upgrading the detectors to improve their radiation hardness We are also planning a possible run at RHIC with lighter ions (2016?) and waiting for LHC p-light A(2019?) And of course We are looking forward for the 13 TeV run with upgraded detector!!!

18 Backup slides Some additional material

19 Single photon spectra at 900 GeV p-p 19 Results in agrrement with 7 TeV spectra No Model able to reproduce LHCf data especially in the high-energy region

20 R 1 (E 1 ) 2 (E 2 ) R = 140m 140m I.P.1 7 TeV π 0 analysis Mass, energy and transverse momentum are reconstructed from the energies and impact positions of photon pairs measured by each calorimeter M E P p p 0 T p 0 0 E 1 P E T 1 1 E E 2 2 P 2,, T 2 Analysis Procedure Standard photon reconstruction Event selection - one photon in each calorimeter - reconstructed invariant mass Background subtraction by using outer region of mass peak Unfolding for detector response. Acceptance correction. 20 Dedicated part for π 0 analysis

21 7 TeV p 0 spectra 21 dpmjet 3.04 & pythia show overall agreement with LHCf data for 9.2<y<9.6 and p T <0.25 GeV/c, while the expected p 0 production rates by both models exceed the LHCf data as p T becomes large sibyll 2.1 predicts harder pion spectra than data, but the expected p 0 yield is generally small qgsjet II-03 predicts p 0 spectra softer than LHCf data epos 1.99 shows the best overall agreement with the LHCf data. behaves softer in the low p T region, p T < 0.4GeV/c in 9.0<y<9.4 and p T <0.3GeV/c in 9.4<y<9.6 behaves harder in the large p T region.

22 Muon excess at Pierre Auger Obs. 22 Pierre Auger Collaboration, ICRC 2011 (arxiv: ) Auger hybrid analysis event-by-event MC selection to fit FD data (top-left) comparison with SD data vs MC (top-right) muon excess in data even for Fe primary MC EPOS predicts more muon due to larger baryon production => importance of baryon measurement Pierog and Werner, PRL 101 (2008)

23 Neutron at LHCf phase-space 23 By Tanguy Pierog, Modelists waiting for LHCf!!

24 Neutron Detection Efficiency and energy 24 linearity Linear fit Parabolic fit % Efficiency at the offline shower trigger Flat efficiency >500GeV

25 Energy and Position Resolution 25 X Y We are trying to improve the energy resolution by looking at the electromageticity of the event Neutron incident at (X,Y) = (8.5mm, 11.5mm) ~1mm position resolution Weak dependence on incident energy

26 26 LHCf GeV & 7 TeV With Stable Beam at 900 GeV Dec 6 th Dec 15 th 2009 With Stable Beam at 900 GeV May 2 nd May 27 th 2010 Shower Gamma Hadron Arm1 46,800 4,100 11,527 Arm2 66,700 6,158 26,094 With Stable Beam at 7 TeV March 30 th - July 19 th 2010 We took data with and without 100 μrad crossing angle for different vertical detector positions Shower Gamma Hadron Arm1 172,263,255 56,846, ,971, ,526 Arm2 160,587,306 52,993, ,381, ,157

27 Data Set for inclusive photon spectrum analysis at 7 TeV 27 Data Date : 15 May :45-21:23 (Fill Number : 1104) except runs during the luminosity scan. Luminosity : ( )x10 28 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 PYTHIA8.145: about 10 7 pp inelastic collisions each

28 Tower 32mm 25mm 28 Systematic Uncertainties Main systematic uncertainty due to energy scale Energy scale can be checked by π 0 identification from two tower events. Mass shift observed both in Arm1 (+7.8%) and Arm2 (+3.7%) No energy scaling applied, but shifts assigned in the systematic error in energy Uncorrelated uncertainties between ARM1 and ARM2 - Energy scale (except p 0 error) - Beam center position - PID - Multi-hit selection R 1 (E 1 ) 2 (E 2 ) R = 140m 140 m M = θ (E 1 xe 2 ) 25 mm tower I.P.1 Silicon layers 32 mm tower Correlated uncertainty - Energy scale (p 0 error) - Luminosity error Scintillator layers

29 An example of p 0 events 25mm p 0 reconstruction measured energy Arm2 32mm preliminary 29 Silicon strip-x view R 1 (E 1 ) = 140m R 140m Reconstructed Arm2 2 (E 2 ) I.P.1 p 0 s are the main source of electromagnetic secondaries in high energy collisions. The mass peak is very useful to confirm the detector performances and to estimate the systematic error of energy scale.

30 30 Calorimeters viewed from IP θ [μrad] η 0 crossing angle 100urad crossing angle η Projected edge of beam pipe Geometrical acceptance of Arm1 and Arm2 Crossing angle operation enhances the acceptance

31 31 Luminosity measurement Luminosity for the analysis is calculated from Front Counter rates: L = CF R FC The conversion factor CF is estimated from luminosity measured during Van der Meer scan I I L = n f 1 2 VDM b rev 2ps s x y Beam sizes s x and s y measured directly by LHCf BCNWG paper VDM scan

32 32 Pile-up estimation When the circulated bunch is 1x1, the probability of N collisions per Xing is The ratio of the pile up event is R pileup = P(N) = ln exp[-l] N! P(N ³ 2) P(N ³1) = 1- (1+ l)e-l 1- e -l l = L s f rev 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

33 33 p T distribution dependence Courtesy P. LIPARI Interplay of LHCf data with HECR Physics Workshop, Catania, July

34 34 Backgrounds 1. Pileup of collisions in one beam crossing Low Luminosity fill, L=6x10 28 cm -2 s -1 7% pileup 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% Beam-Gas backgrounds Secondary-beam pipe backgrounds

35 35 Systematic error from Energy scale Two components: - Relatively well known: Detector response, SPS => 3.5% - Unknown: p 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 p 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.

36 p 0 Mass 36 Arm1 Data Peak at ± 0.1 MeV 7.8 % shift Disagreement in the peak position No hand made correction is applied for safety Main source of systematic error see later Many systematic checks have been done to understand the energy scale difference Arm2 Data Peak at ± 0.1 MeV Arm2 MC (QGSJET2) Peak at ± 0.2 MeV 3.8 % shift

37 p 0 mass vs p 0 energy 37 Arm2 Data No strong energy dependence of reconstructed mass

38 Signal window : [-3σ, +3σ] Sideband : [-6σ, -3σ] and [+3σ, +6σ] Preliminary 7 TeV π 0 analysis Remaining background spectrum is estimated using the sideband information, then the BG spectrum is subtracted from the spectrum made in the signal window. 38 Validity check of unfolding method Measured EPOS True EPOS Unfolded(by π 0 +EPOS) Unfolded(by π 0 +PYTHIA) LHCf-Arm1 s=7tev 9.0<y<11.0 Acceptance for π 0 at LHCf-Arm1 Detector responses are corrected by an unfolding process that is based on the iterative Bayesian method. (G. D Agostini NIM A 362 (1995) 487) Detector response corrected spectrum is proceeded to the acceptance correction.

39 900GeV 7TeV DATA-MC : comp. 900GeV/7TeV 39 η> <η<8.9

40 40 LHCf p-pb run: Neutron spectra 4+202) 3+, / ) ( ) 0!%&*,!i!/+<:,- /(18+0:,<' ( B'. CC(:- L +,( YDE(:- L +,( 3Q4 (FT FS] J (SFBc!R6gc T (gb( #c T BgZ FSFZ (gt (6" FBF(*!c 6B(( Alessia FG!@' Tricomi 025, +!HI FF! Physics results =8?2) of, ' the #&W!=4CCW!CL` LHCf experiment a! ^!

41 41 h Mass Arm2 detector, all runs with zero crossing angle True h Mass: MeV MC Reconstructed h Mass peak: ± 1.0 MeV Data Reconstructed h Mass peak: ± 1.8 MeV (2.6% shift)

42 EJ260 (HIMAC* Carbon beam) 10% decrease of light yield after exposure of 100Gy GSO (HIMAC Carbon beam) No decrease of light yield even after 7*10^5Gy exposure, BUT increase of light yield is confirmed The increase depend on irradiation rate (~2.5%/[100Gy/hour]) Comparison of EJ260 and GSO -Radiation Hardness- 42 *HIMAC : Heavy Ion Medical Accelerator in Chiba