LHC forward experiment : LHCf
Hiroaki MENJO (KMI, Nagoya University, Japan) On behalf of the LHCf collaboration
HESZ2013, Nagoya Univ., Japan, 02 -04 March Contents Large Hadron Collider q Introduction -The most powerful accelerator on the earth- q The LHCf experiment -An LHC forward experiment- Ultra High Energy Cosmic Rays What is the most powerful accelerator in the Universe ? q Recent results - Forward photon energy spectra at 900GeV and 7TeV p-p - - Forward π0 spectra SppS Tevatron q Recent & Future Operation LHC q Summary The LHCf collaboration
T.Iso, Y.Itow, K.Kawade, Y.Makino, K.Masuda, Y.Matsubara, E.Matsubayashi, G.Mitsuka, Y.Muraki, T.Sako 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, M.Grandi, 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 Introduction HECRs Extensive air shower observation • longitudinal distribution • lateral distribution • Arrival direction Air shower development Astrophysical parameters • Spectrum • Composition • Source distribution
Xmax distribution measured by AUGER
Xmax the depth of air shower maximum. An indicator of CR composition
Uncertainty of hadron interaction models > 1018 1019 Error of
③ Inelasticity k= 1-plead/pbeam If large k (π0s carry more energy) rapid development If small k ( baryons carry more energy) deep penetrating
5 (relevant to Nµ ) The Large Hadron Collider (LHC)
17 pp 7TeV+7TeV è Elab = 10 eV 2014- 16 pp 3.5TeV+3.5TeV è Elab = 2.6x10 eV 14 pp 450GeV+450GeV è Elab = 2x10 eV
Key parameters for air shower developments q Total cross section CMS/TOTEM ↔ TOTEM, ATLAS, CMS q Multiplicity ↔ Central detectors q Inelasticity/Secondary spectra ↔ Forward calorimeters ALICE LHCf, ZDCs LHCb/MoEDAL ATLAS/LHCf
6 The LHCf experiment LHCf Detector(Arm#1) ATLAS
140m Two independent detectors at either side of IP1 ( Arm#1, Arm#2 ) Beam pipe Protons Charged particles (+)
Neutral particles Charged particles (-) TAN -Neutral Par cle Absorber- 96mm transi on from one common beam pipe to two pipes Slot : 100mm(w) x 607mm(H) x 1000mm(T) 7 The LHCf Detectors Sampling and Positioning Calorimeters • W (44 r.l , 1.7λI ) and Scintillator x 16 Layers • 4 positioning layers XY-SciFi(Arm1) and XY-Silicon strip(Arm#2) • Each detector has two calorimeter towers, which allow to reconstruct π0 Expected Performance Energy resolution (> 100GeV) 32mm < 5% for photons Arm2 25mm 30% for neutrons Position resolution < 200µm (Arm#1) 40µm (Arm#2) Front Counter • thin scintillators with 80x80mm2 • To monitor beam condition. 40mm • For background rejection of beam-residual gas collisions 20mm by coincidence analysis 8 Arm1 Arm1
Arm2
IP1,ATLAS
92mm 90mm
9 LHCf can measure Front view of calorimeters @ 100µrad crossing angle η Energy spectra and beam pipe shadow Transverse momentum distbu on of 8.5 • Gamma-rays (E>100GeV,dE/E<5%) • Neutral Hadrons (E>a few 100 GeV, dE/E~30%) • π 0 (E>600GeV, dE/E<3%) at pseudo-rapidity range >8.4 ∞
Mul plicity@14TeV Energy Flux @14TeV
Low multiplicity !! High energy flux !!
10 simulated by DPMJET3 Results from √s = 900 GeV and 7 TeV p-p data
“ Measurement of zero degree single photon energy spectra for √s = 7 TeV proton-proton collisions at LHC “ O. Adriani, et al., PLB, Vol.703-2, p.128-134 (09/2011)
“Measurement of zero degree inclusive photon energy spectra for √s = 900 GeV proton-proton collisions at LHC“ O. Adriani, et al., Submitted to PLB.,CERN-PH-EP-2012-048
“Measurement of forward neutral pion transverse momentum spectra for √s = 7TeV proton-proton collisions at LHC” O. Adriani, et al., Submitted to PRD, arXiv:1205.4578
Operation in 2009-2010
At 450GeV+450GeV p-p • 06 Dec. –15 Dec. in 2009 27.7 hours for physics, 2.6 hours for commissioning ~2,800 and ~3,700 shower events in Arm1 and Arm2 • 02 May – 27 May in 2010 ~15 hours for physics ~44,000 and ~63,000 shower events in Arm1 and Arm2 At 3.5TeV+3.5TeV p-p • 30 Mar. – 19 July in 2010 ~ 150 hours for physics with several setup With zero crossing angle and with 100µrad crossing angle. ~2x108 and ~2x108 shower events in Arm1 and Arm2
Operation at √s = 900GeV and 7TeV has been completed successfully. The detectors has been removed from the LHC tunnels at July 2010, and will be upgraded for the future operations.
12 Event sample
Longitudinal development measured by scintillator layers 25mm Tower 32mm Tower Total Energy deposit è600GeV è420GeV èEnergy photon photon Shape èPID
Lateral distribution measured by silicon detectors X-view
Hit position, Multi-hit search. Y-view
π0 mass reconstruction from two photon. Systematic studies
Mπ 0 = Eγ1Eγ 2 ⋅θ Photon spectra at √s = 7 TeVLHCf Collaboration / Physicsp-p Letters B 703 (2011) 128–134 129
8.81<η<8.9 q Pseudo-rapidity, η>10.94 and 8.81<η<8.9 q The spectra of two detectors are η>10.94 consistent within the errors. Arm1 Arm2
Fig. 1. Cross sections of the calorimeters seen from IP1, left for Arm1 and right for Arm2. The origin of the coordinates is defined as the zero degree collision angle in the ideal case while the stars indicate the actual zero degree found in the experimental data. The shaded area over Y 40 mm is behind the projection of the beam pipe in = case of 0 beam crossing angle where the calorimeters are insensitive to the collision products. Dashed lines in the calorimeters indicate the boarder of the 2 mm edge cut as described in Section 3.1 and the dark areas indicate common rapidity ranges of the two Arms selected to obtain the final spectra.
measure the neutral particle production cross sections at very for- MC predictions of several hadron interaction models in Section 5 ward collision angles of LHC proton–proton collisions, including and summarized in Section 6. zero degrees. When the LHC reaches its designed goal of 14 TeV collision energy, the energy in the equivalent laboratory frame will 2. Data be 1017 eV, a factor of one thousand increase compared to previ- ous accelerator data in the very forward regions [8,9]. Data used in this analysis was obtained on 15 May 2010 dur- Two detectors, called Arm1 and Arm2, have been installed in ing proton–proton collisions at √s 7TeVwithzerodegreebeam = the instrumentation slots of the TANs (Target Neutral Absorbers) crossing angle (LHC Fill 1104). The total luminosity of the three 28 2 1 located 140 m from the ATLAS interaction point (IP1) and at crossing bunches in this fill, L (6.3–6.5) 10 cm− s− ,pro- Arm1 detector± = × zero degree collision angle. Inside a TAN the beam vacuum cham- vided ideal operating conditions as discussed in Section 4.Thedata ber makes a Y shaped transition from a single common beam tube that were taken during a luminosity optimization scan were elimi- Arm2 facingdetector the IP to two separate beam tubes joining to the arcs of nated from the analysis. The trigger for LHCf events was generated LHC. Charged particles from the IP are swept aside by the in- at three levels. The first level trigger (L1T) was generated from ner beam separation dipole D1 before reaching the TAN so only beam pickup signals (BPTX) when a bunch passed IP1. A shower neutral particles are incident on the LHCf detectors. This unique trigger was generated when signals from any successive 3 scintil- location covers the pseudo-rapidity range from 8.7 (8.4 in case of lation layers in any calorimeter exceeded a predefined threshold. the operation with the maximum beam crossing angle) to infin- Then the second level trigger for shower events (L2TA) was issued ity (zero degrees). Each detector has two sampling and imaging when the data acquisition system was armed. The threshold was calorimeters composed of 44 radiation lengths (1.55 hadron in- chosen to achieve >99% efficiency for >100 GeV photons. Data teraction lengths) of tungsten and 16 sampling layers of 3 mm were recorded with the third level trigger (L3T) when all the other thick plastic scintillators. The transverse sizes of the calorime- types of second level triggers (pedestal, laser calibration, etc.) were ters are 20 mm 20 mm and 40 mm 40 mm in Arm1, and combined. Examples of the longitudinal and lateral development of × × 25 mm 25 mm and 32 mm 32 mm in Arm2. The smaller electromagnetic showers observed in the Arm2 detector are shown × × 0 calorimeters cover the zero degree collision angle. The cross sec- in Fig. 2.Inthiscasetwoelectromagneticshowersfromπ decay tions of the calorimeters seen from IP1 are illustrated in Fig. 1. into two photons are shown, with each photon striking a differ- Four X–Y layers of position sensitive detectors (scintillating fiber, ent calorimeter of the Arm2 detector. The generation of the L2TA SciFi, belts in Arm1 and silicon micro-strip sensors in Arm2; 1 mm and L3T triggers, and hence the data recording, were performed and 0.16 mm readout pitches, respectively) are inserted in order independently for the Arm1 and Arm2 detectors. Data acquisition to provide transverse positions of the showers. The LHCf detec- was carried out under 85.7% (Arm1) and 67.0% (Arm2) average live- tors have energy and position resolutions for the electromagnetic times ("DAQ ). The livetimes were defined as "DAQ NL2TA/Nshower = showers better than 5% and 200 µm, respectively, in the energy where Nshower and NL2TA are the number of counts in the shower range >100 GeV. More detail on the scientific goals, construction and L2TA triggers, respectively. and performance of the detectors can be found in previous reports The integrated luminosities ( Ldt)correspondingtothedata [10–15]. used in this Letter are 0.68 nb 1 (Arm1) and 0.53 nb 1 (Arm2) −! − This Letter describes the first analysis results of LHCf data. Sin- after the data taking livetimes are taken into account. The ab- gle photon energy spectra are reported for √s 7TeVproton– solute luminosity is derived from the counting rate of the Front = proton collisions. In Section 2 the data set used in the analysis is Counters (FC) [11].FCsarethinplasticscintillatorsfixedinfront introduced. In Section 3 the analysis process and experimental re- of the LHCf main calorimeters and covering a wide aperture of sults are presented. Beam related background and uncertainties are 80 mm 80 mm. The calibration of the FC counting rates to the × discussed in Section 4.Theexperimentalresultsarecomparedwith absolute luminosity was made during the Van der Meer scans on Photon spectra at √s = 7 TeV p-p
Data Sys.+Stat .
DPMJET 3.04 QGSJETII-03 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145
• No model can reproduce the LHCf data perfectly. • DPMJET and PYTHIA are in good agreement Eγ<1.5TeV, but harder in E>1.5TeV. • QGSJET and SIBYLL shows reasonable agreement of shapes in high-η but not in low-η • EPOS has less η dependency against the LHCf data. Photon spectra at √s = 900 GeV p-p
Data Sys.+Stat .
DPMJET 3.04 QGSJETII-03 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 MC/Data
• Both of Data and MC show little η dependency. • The tendencies of MC against Data are very similar to one of 7 TeV in η > 10.94. DATA : Comp. 900GeV/7TeV
XF spectra : 900 GeV data vs. 7 TeV data Coverage of 900GeV and 7TeV results in Feynman-X and P T Preliminary 900GeV vs. 7TeV Arm1-Data Arm1-EPOS with the same PT region Preliminary Preliminary
Data 2010 at √s=900GeV (NormalizedData 2010 by at the √ s=7TeVnumber of(η entries>10.94) in XF > 0.1) DataData 2010 2010 at √ats=7TeV √s=900GeV (η>10.94) Small tower : 22.6% Large tower : 77.4% Scaling factor : 0.1
Good agreement of X spectrum Note : No systematic error is considered F in both collision1 energies.d 21% of the luminosity 1 d shape between 900 GeV and 7TeV. determination error allows vertical shift. pT dpT èweak dependence of
15 π0 analysis
Mass, energy and transverse momentum are R reconstructed from the energies and impact γ (E ) θ = 1 1 140 m positions of photon pairs measured by each R calorimeter 2 M 0 E E , 140m π = γ 1 γ 2θ
E 0 = E + E , θ π γ 1 γ 2 γ (E ) 2 2 I.P.1 PT 0 = PT + PT π γ 1 γ 2 6 7 7
Mass reconstructed from photon pairs ticallyAcceptance significant Rapidity difference was- PT found. A chi-square testscintillator with a 337 nm UV laser pulse [6, 19]. The 1 1 scintillator with a 337 nm UV laser pulse [6, 19]. The ) 500 2 1 of the corrected spectra1 based on the default responsedifference between linear and non-linear reconstructions -2 10-2 -1 0.9 10-2 0.9 -2 difference between linear and non-linear reconstructions LHCf-Arm1 s=7TeV, Ldt=2.53nb 0.9 LHCfLHCffunction Arm1Arm1 against10 the0.9 true spectraLHCfLHCf ensuresArm2 Arm2 the10 chi-square [GeV/c] [GeV/c] for 3 TeV photons is only 0.5 % at maximum, nevertheless T T ∫ [GeV/c] [GeV/c] for 3 TeV photons is only 0.5 % at maximum, nevertheless T T p 0.8 p 0.8 9.0 < y < 9.2 E=3TeV E=3TeV 400 p 0.8 probability is greaterp 0.8 than 60 %. Thus it is concluded E=3TeV E=3TeV thethe measured measured non-linear non-linear response response functions functions have have been been ap- ap- 0.70.7 that with the method0.70.7 used in this analysis there is no -3 -3 plied in the analysis. -3 -310 plied in the analysis. 300 0.60.6 significant bias and1010 the0.60.6 statistical uncertainty is10 correctly 0.5 E=2TeVE=2TeV quoted. 0.5 E=2TeVE=2TeV TheThe second second source source is is estimated estimated using using the the recon- recon- Events / (1 MeV/c 0.5 0.5 structedstructedπ0π0mass.mass. Although Although the the reconstructed reconstructed in- in- 200 0.40.4 0.40.4 -4 -4 0.30.3 1010-4 0.30.3 10-410 variantvariant masses masses of of the the MC MC simulations simulations reproduce reproduce the the E=1TeVE=1TeV E=1TeVE=1TeV 0 0 0.20.2 0.20.2 restrest mass mass of of the theπ s,π s, those those of theof the experimental experimental data data 100 2 2 2 2 0.10.1 0.10.1 areare 145.8 145.80.10.1 MeV/ MeV/c c(Arm1)(Arm1) and and 139.9 139.90.1 MeV/0.1 MeV/c c ± ± 2 2 ± ± -5 E.10 -5 Acceptance correction 10-5 -5 (Arm2) where 0.1 MeV/c uncertainties are statistical. 0 00 10 00 10 (Arm2) where 0.1 MeV/c uncertainties are statistical. 80 100 120 140 160 180 99 9.5 9.5 10 10 10.5 10.5 11 99 9.5 9.5 10 10 10.5 10.5 11 11 ± ± Rapidity RapidityRapidity AA portion portion of of the the 8.1% 8.1% and and 3.8% 3.8% invariant invariant mass mass excess excess Reconstructed m [MeV/c2] Rapidity Rapidity γγ comparedcompared to to the theπ0 πmass0 mass can can be be explained explained by the by the sys- sys- The apertures of the LHCf calorimeters0 0 do not cover FIG.FIG. 5: 5: (color (colorthe online). online). full 2π Theazimuthal acceptance acceptance angle over map map the of of the entire theππ rapiditydetec-detec- rangetematictematic uncertainty uncertainty in indetermining determining the the opening opening angle angle of of FIG. 4: (color online). Reconstructed invariant masstion distr ini- the LHCf detectors: Arm1 (left) and Arm2 (right). bution within the rapidity range from 9.0 to 9.2. Solidtion curvein the LHCfthat is detectors: sampled. Arm1 A correction (left) and for this Arm2 must (right). be appliedaa photon photon pair pair and and the the uncertainty uncertainty of the of the absolute absolute en- en- Fiducial area cut and energy threshold (Ephoton > 100 GeV) shows the best-fit composite model to data. DashedFiducial curve areato cut the and data energy before threshold it can be (E comparedphoton > with100 GeV) theoreticalergyergy scale, scale, as as formulated formulated in Eq.in Eq. (1). (1). However, However, since since the the indicates the background component of the compositeareare model. taken taken into into account. account. Z-axis indicates indicates the the detection detection effi effi- - 0 expectations. typicaltypical uncertainty uncertainty in in opening opening angle angle is estimated is estimated to be to be ciencyciency of of ππ0 events.events. Dashed curves curves indicate indicate the the energy energy for for The correction is done using the rapidity and p phaselessless than than 1 % 1 % by by the the position position determination determination resolution resolution eacheach phase phase space, space, EE =1TeV,2TeVand3TeV. T space. Correction coefficients are determined as follows.andand the the alignment alignment of theof the position position sensitive sensitive detectors, detectors, the the First, using a toy MC simulation, a single π0 is generateduncertainty of the absolute energy scale is completely de- duced above. Note that the π0 kinematics that are simu- uncertainty of the absolute energy scale is completely de- at IP1 and the decay photons are propagated to the LHCftermined by the invariant mass excess. Indeed the energy lated within the allowed phase space are independent of 0 termined by the invariant mass excess. Indeed the energy detectors. The energy-momentum0 4-vector of the π sarescaling correction is applied both for Arm1 and Arm2 ac- the particular interaction model that is being used. On F. Multi-hit π 0 correction scaling correction is applied both for Arm1 and Arm2 ac- randomlyF. Multi-hit chosen soπ thatcorrection they cover the rapidity rangecording to each mass shift. the other hand background particles are simulated by that the LHCf detectors are able to measure. The beamcording to each mass shift. an interaction model which is discussed later, since the The total energy scale uncertainty is calculated by The detectedpipe events shadow have on the been calorimeter distinguished and the according actual detector The total energy scale uncertainty is calculated by amount of background particles is not directly measuredThe detected events have been distinguished according quadratically adding the standard deviations of two com- to whether theyposition have are a single taken intophoton account hit (single-hit using surveyπ0 data.) in quadratically adding the standard deviations of two com- by the LHCf detector. 0 ponents. The uncertainty estimated by the calibration toeach whether of the they calorimeters have a single of the photon Arm1 or hit Arm2 (single-hit detectorsπ or) in ponents. The uncertainty estimated by the calibration The detector response to π0 events depends on the ra- Next fiducial area cuts in the transverse X-Y plane areis assumed to follow a Gaussian probability distribu- each of the calorimeters of the Arm10 or Arm2 detectors or is assumed to follow a Gaussian probability distribu- multiple photonapplied hits to (multi-hit eliminate particlesπ 0) in one that or do both not fall of the within thetion with the standard deviation of 3.5 %, and the ab- pidity and pT spectrum, since the performance ofmultiple the par- photon hits (multi-hit π ) in one or both0 of the calorimeters.acceptance In this analysis, of the calorimeters. only single-hit In theπ fiducialevents area cut,tion with the standard deviation of 3.5 %, and the ab- ticle identification algorithm and the selectioncalorimeters. efficiency In this analysis, only single-hit π0 events solute energy scale after the energy scale correction is of events with a single photon hit in both calorimetersare considered. of a systematic shift of the proton beam axis is consideredsupposedsolute energy to be normally scale after uncertain the energy within scale [0.0% correction, 8.1%] is are considered. 0 an Arm1 or Arm2 detector (single-hit) depend uponThe the loss ofaccording multi-hit to theπ events beam-axis is corrected reconstruction with during the LHCandsupposed [0.0%, 3 to.8 %] be with normally the standard uncertain deviation within of [0 8.1/2.0%, %8.1%] The loss ofoperation. multi-hit Inπ addition0 events a cut is iscorrected applied to with eliminate the pho- energy and the incident position of a particle.help The dis- of event generators. A range of ratios of multi-hit andand 3.8/2% [0.0%, for3.8 Arm1 %] with and the Arm2, standard respectively. deviation Then of 8.1/2 the % 0 tons with energy less than0 100GeV. This corresponds to tributions of the reconstructed rapidity and pThelpspectrumπ events of event relative generators. to single-hit A rangeπ events of ratios is estimated of multi-hit us- and 3.8/2% for Arm1 and Arm2, respectively. Then the 0 the treatment of the actual0 data to reduce contaminationtotal energy scale uncertainties are assigned with respect for given true rapidity and pT spectrum leadsπ toing theevents several re- relative hadronic to single-hit interactionπ models.events is The estimated observed us- total energy scale uncertainties are assigned with respect sponse function which gives the relationship between the by interactions with the residual gas molecules and theto the central value of the mass shift, 8.1 %/2 for Arm1 ingspectra several are hadronic then multiplied interaction by this models. ratio and The contribute observed 3.8to %/2 the for central Arm2. value of the mass shift, 8.1 %/2 for Arm1 measured rapidity and pT by the LHCf detector and true beam pipe. 0 spectraa systematic are then uncertainty multiplied corresponding by this ratio to and the contribute variation 3.8 %/2 for Arm2. information of π s generated in the proton-proton colli- Finally two phase space distributions are produced;The systematic shift of bin contents due to the energy aamong systematic the interaction uncertainty models. corresponding In this way to the the variation single- The systematic shift of bin contents due to the energy sion. 0 one is for all the particles generated at IP1 and the otherscale uncertainty is estimated using two energy spectra amonghit π thespectra interaction are corrected models. so they In this represent way the inclusive single- scale uncertainty is estimated using two energy spectra Finally the observed rapidity and pT spectra are0 0 cor- is for the particles accepted by the calorimeters. Theby ra- artificially scaling the energy with the two extremes rected with the response function which is equivalenthitπ πproductionspectra are spectra. corrected The p soT dependent they represent range inclusive of the quoted above. The ratios of the two extreme spectra to 0 tio of the0 distribution with fiducial cuts divided by theby artificially scaling the energy with the two extremes to the likelihood function in Bayes’ theorem.πflux Theproduction cor- of multi-hitdistribution spectra.π events without The haspT fiducialdependent been cuts estimated is thenrange the using of acceptance the thequoted non-scaled above. spectrum The ratios are assigned of the two as systematic extreme spectra shifts to qgsjet 0dpmjet 3.04 sibyll 2.1 rections are carried out iteratively whereby theflux starting of multi-hitII-03effi [30],ciency.π events Figs. 5 showhas[36], been the acceptance estimated effi[37], usingciency asin athe each non-scaled bin. spectrum are assigned as systematic shifts epos 1.99 [29] and pythia0 8.145 [34, 35], and resulted point of the current iteration is the ending pointqgsjet of theII-03function [30], dpmjet of the π 3.04rapidity[36], andsibyllpT and 2.1 dashed[37], curvesin each bin. previous iteration. Statistical uncertainty is alsoeposin 0–10 prop- 1.99 % of[29]indicate the and flux linespythia of single-hit of constant 8.145π0[34,πevents.0 energy, 35], andE =1TeV,2TeV resulted agated from the first iteration to the last. Iteration is and 3 TeV. The left and right0 panels indicate the accep- in 0–10 % of the flux of single-hit π events. B. Particle identification stopped at 4th process at maximum to obtain a regular- tance efficiency for Arm1 and Arm2, respectively. The ization of the unfolded results. B. Particle identification V.final SYSTEMATIC rapidity and p UNCERTAINTYT spectra are obtained by applying Validation of the unfolding procedure is checked by ap- the acceptance map shown in Figs. 5 to the uncorrectedSome disagreements in the L90% distribution are found plying the response function to the reference MC simula-V.data, SYSTEMATIC and the inefficiency UNCERTAINTY due to the branching ratiobetween of the data and the MC simulations. This may be Some disagreements in the L90% distribution are found tion samples. Default response function is determined the π0 decayA. Energy into two scale photons ( 1.2 %) is also takencaused by residuals of the channel-to-channel calibrations 0 ∼ between the data and the MC simulations. This may be with two photons from π decay and the low energy into account.A. Energy Note that scale the correction maps in Figs.or 5 the incomplete tuning of the LHCf detector simulation epos caused by residuals of the channel-to-channel calibrations (E<100GeV) background particles generated byThe energyare scale purely uncertainty kinematic and consists do not of depend two uponsources, the partic-to the calibration data. 1.99. Validity of the choice of epos 1.99 is tested by ular hadronic interaction model that has been used. Theor the incomplete tuning of the LHCf detector simulation one is estimated using a beam test at SPS and calibration The systematic uncertainty of L is evaluated by comparing two corrected spectra, one is by eposThe 1.99 energyuncertainty scale uncertainty of the acceptance consists map of caused two sources, by the finiteto the calibration data. 90% by a radiation source and the second is caused by the shift comparing the L distribution of the π0 candidate and another by pythia 8.145 [34, 35] instead.one No statis- is estimatedstatistics using of a MC beam simulation test at isSPS negligibly and calibration small. The systematic90% uncertainty of L is evaluated by in the π0 mass distribution as mentioned in Sec. IV B. events of the observed data with the MC90% simulation. The by a radiation source and the second is caused by the shift comparing the L distribution of the π0 candidate The first source is evaluated to be 3.5 % and is domi- observed L is increased90% by at most 1 r.l. The system- in the π0 mass distribution as mentioned in Sec. IV B. 90% nated by the uncertainties in factors converting± measured aticevents shifts of of the bin observed contents data are taken with the from MC the simulation. ratio of two The The first source is evaluated to be 3.5 % and is domi- observed L90% is increased by at most 1 r.l. The system- charge to deposited energy [20]. Note that the linearity spectra with artificial shifts of L90% by relevant value to nated by the uncertainties in factors converting± measured atic shifts of bin contents are taken from the ratio of two of each PMT was carefully tested before detector assem- the spectra without any L90% shift, and this effect may charge to deposited energy [20]. Note that the linearity spectra with artificial shifts of L by relevant value to bly over a wide range of signal amplitude by exciting the distort the observed spectra by 0–20%90% depending on pT. of each PMT was carefully tested before detector assem- the spectra without any L90% shift, and this effect may bly over a wide range of signal amplitude by exciting the distort the observed spectra by 0–20% depending on pT. 0 π spectra at √s = 7 TeV p-p 11 ] ] ] 3 3 3 c c c
-2 0 -2 0 -2 0 1 LHCf s=7TeV π 1 LHCf s=7TeV π 1 LHCf s=7TeV π 8.9 < y < 9.0 9.0 < y < 9.2 9.2 < y < 9.4 [GeV [GeV [GeV 3 Ldt=2.53+1.90nb-1 3 Ldt=2.53+1.90nb-1 3 Ldt=2.53+1.90nb-1
/dp 10-1 ∫ /dp 10-1 ∫ /dp 10-1 ∫ σ σ σ 3 3 3 Ed Ed Ed inel inel inel
σ 10-2 Data 2010 σ 10-2 σ 10-2 1/ 1/ 1/ DPMJET 3.04 QGSJET II-03 10-3 SIBYLL 2.1 10-3 10-3 EPOS 1.99 PYTHIA 8.145 -4 -4 -4 10 0 0.1 0.2 0.3 0.4 0.5 0.6 10 0 0.1 0.2 0.3 0.4 0.5 0.6 10 0 0.1 0.2 0.3 0.4 0.5 0.6 p [GeV/c] p [GeV/c] p [GeV/c] T T T ] ] ] 3 3 3 c c c
-2 0 -2 0 -2 0 1 LHCf s=7TeV π 1 LHCf s=7TeV π 1 LHCf s=7TeV π 9.4 < y < 9.6 9.6 < y < 10.0 10.0 < y < 11.0 [GeV [GeV [GeV 3 Ldt=2.53+1.90nb-1 3 Ldt=2.53+1.90nb-1 3 Ldt=2.53+1.90nb-1
/dp 10-1 ∫ /dp 10-1 ∫ /dp 10-1 ∫ σ σ σ 3 3 3 Ed Ed Ed inel inel inel
σ 10-2 σ 10-2 σ 10-2 1/ 1/ 1/
10-3 10-3 10-3
10-4 10-4 10-4 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 p [GeV/c] p [GeV/c] p [GeV/c] T T T • EPOS1.99 show the best agreement with data in the models. FIG.• 7: DPMJET (color online). and Combined PYTHIApT spectra have of harder the Arm1 spectra and Arm2 detectorsthan data (black (“popcorn dots) and the model”) total uncertainties (shaded triangles) compared with the predicted spectra by hadronic interaction models. • QGSJET has softer spectrum than data. (only one quark exchange is allowed)
upper Rapidity p pT Total uncertainty The values of pT obtained in Table II and Table III T ! " are in reasonable! agreement." When a specific value of [GeV/c][MeV/c][MeV/c] [9.2, 9.4] 0.6 167.1 4.3 pT is needed the values of pT for this paper are de- ! " ! " [9.4, 9.6] 0.4 146.1 1.7 fined as pT in Table II, obtained by fitting of the expo- ! " [9.6, 10.0] 0.4 117.1 1.6 nential function. The systematic uncertainty related to a [10.0, 11.0] 0.2 76.0 1.9 possible bias of the pT extraction methods is estimated ! " by the difference of pT derived from two different ap- 0 ! " TABLE III: Average transverse momentum of π derived by proaches: fitting an exponential function and numerical numerical integration of the pT spectra for the rapidity range integration. The estimated systematic uncertainty is 5 %. 9.2 The pT predicted by hadronic interaction models are ! " The values of pT that have been obtained in this anal- shown by open circle (sibyll 2.1), open box (qgsjet II- ysis are compared! in" Fig. 10 with the results from UA7 at 03) and open triangle (epos 1.99). sibyll 2.1 typically 0 LHCf π PT spectra at 7TeV (data/MC) DPMJET 3.04 QGSJETII-03 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 EPOS gives the best agreement both for shape and yield. MC/Data 0 PT[GeV] 0.6 0 PT[GeV] 0.6 0 PT[GeV] 0.6 MC/Data 20 0 PT[GeV] 0.6 0 PT[GeV] 0.6 0 PT[GeV] 0.6 0 pT spectra vs best-fit function Average pT vs ylab PLB 242 531 (1990) YBeam=6.5 for SPS YBeam=8.92 for7 TeV LHC ylab = ybeam - y 1. Thermodynamics (Hagedron, Riv. Nuovo Cim. 6:10, 1 (1983)) • Systematic uncertainty of LHCf data is 5%. • Compared with the UA7 data (√s=630GeV) and MC simulations (QGSJET, SIBYLL, EPOS). • Two experimental data mostly appear to lie along a common curve → no evident dependence of 10000 Small tower 4000 Large tower q Big discrepancy 9000 PYTHIA PYTHIA true energy EPOS MC3500 EPOS 8000 QGSJET2 QGSJET2 between models. DPMJET3 3000 DPMJET3 7000 (0% smeared) SYBILL SYBILL 2500 6000 es i true energy 5000 2000 ntr E Entries 4000 q Performance 1500 (0% smeared) 3000 1000 for neutrons 2000 500 o 70% Efficiency 1000 0 0 0 1000 2000 3000 4000 5000 6000 0 1000 2000 3000 4000 5000 6000 Energy[GeV] Energy[GeV] o 35% Eres Detector performance o 1mm Position Res. 10000 Small tower 4000 Large tower 9000 PYTHIA PYTHIA @ 1.5TeV n EPOS 3500 EPOS 8000 QGSJET2 QGSJET2 DPMJET3 3000 DPMJET3 Detector performance 7000 SYBILL SYBILL 2500 6000 es is also interaction 35% smeared i 35% smeared 5000 2000 ntr E Entries 4000 model dependent. 1500 3000 1000 2000 500 1000 0 0 0 1000 2000 3000 4000 5000 6000 0 1000 2000 3000 4000 5000 6000 Energy[GeV] Energy[GeV] Operation in 2013 and future prospects. Resent and Future operations p-Pb operation (Jan-Feb. 2013) Install the one of the LHCf detector. Nuclear effect at the proton remnant side. LOI, O.Adriani, et al.CERN-LHCC-2011-2015 Done p-p at 13TeV (2015) Future Measurement at the LHC design energy. Energy scaling by comparison with √s = 900 GeV and 7 TeV data TDR, O.Adriani, et al. CERN-LHCC-2006-004 p-light ions (O, N) (2019?) Collisions as high energy cosmic-rays and atmospheric nuclei. Operations at RHIC ( Sako’s talk tomorrow) Lower collision energy, ion collisions. Starting discussion with RHIC people. LHCf p – Pb runs at √sNN= 5 TeV Pb IP1 IP2 Arm2 IP8 p l 2013 Jan-Feb for p-Pb/Pb-p collisions. ¡ Install only Arm2 at one side (Si good for multiplicity) ¡ Data both at p-side (20Jan-1Feb) and Pb-side (1fill, 4Feb) One of the LHCf detector (Arm2) has been installed into the LHC tunnel again in Dec. 2012. Arm2 detector 25 LHCf p-Pb runs q L = 1x1029 – 0.5x1029cm-2s-1 q β* =0.8m, 145µrad crossig angle q 338p+338Pb bunches (min.ΔT=200ns), 296 colliding at IP1 q 10-20kHz trig rate downscaled to ~700Hz q 20-40Hz ATLAS common trig. Coincidence seems successful Statistic in Operation 2013 p-remnant side Pb-remnant side Beam reversal #Events (Millions) 20 Jan 27 Jan. 01 Feb. 26 Operation at Pb-remnant side Pb-remnant side p IP1 IP2 Arm2 IP8 Pb +4.0MC cm (Pb-remnant)shift from beam spot 3.5cm, 4.0cm A high multiplicity event (Pb-side) 27 Operations in 2013 q Proton-Proton Collision at √s = 2.76 TeV. o 4 hours operation on 14 Feb. 2013 successfully done. è Energy Scaling by comparing with 7TeV and 900GeV data q CommonJoint operation Data Taking with ATLAS in 2013 LHCf won't be in ATLAS readout (no ROD/ROB for LHCf) Strategyo is ATLASto record events was independently triggered events by and prescaled then merge them LHCf at triggers ( 20-40 Hz) offline level (cf https://edms.cern.ch/document/930829/1 ) → Write ATLAS LVL1ID in LHCf よって生じているかを推定するのは容易ではない。 event Common analysis with ATLAS LHCf検出器が設置されている衝突点（IP1）にcan help to study the mechanisms は、ATLAS検出器が設置されている。ATLASとof forward particle production. LHCfによって広いラピディティ（η）領域をカバー L1ID etc... èCentral information. した測定を行うことにより、陽子衝突事象の分類が èZDC 可能になる。図３は、ATLASとLHCf検出器のラピ L1 ティティ範囲と特徴的な事象での生成粒子の分布を 示した。Diffractive事象では、中心領域には粒子生L1_LHCf Raw Raw 成がなく、ATLAS検出器を使うことでNon- Reco Diffractive事象と明瞭に区別することができる。図Merging Reco ４には、ハドロン相互作用モデルEPOS1.99LHC4)を 用いて計算した14TeV陽子衝突での最前方中性子ス Merged D3PD (?) ペクトルを示す。中心領域 (|η|<5)に粒子生成がゼ To have a substantial overlap between ATLAS and LHCf, ATLAS should record events when LHCf triggerロであり、高エネルギー陽子の有無により、Single/ fires Not clear at which level of dataDouble format Diffractive will be merged 事象選別したものを破線で示す。 → Useful to discuss 3 with physics group and Data Preparation Diffractive事象による中性子は、高エネルギー側に 寄った分布を持っており、３TeVー７TeVの領域では 約半分を占めている。このように、ATLASのデータ を用いて事象分類することにより、物理過程に沿っ た測定を行うことが可能となる。 ②研究期間で明らかにすること 図３、ATLAS検出器とLHCf検出器の 本研究では、2014年の次期LHCf実験測定にむけ ラピディティ範囲（上）と、特徴的な て、ATLAS実験との共同測定を行うためのLHCf検出 事象での生成粒子の分布。 器の新トリガーシステムの構築を行うことを 目的とする。新しいボードを導入し、トリ ガーシステムを高性能化する。これを用い て、ATLASグループと共同測定システムを構 築する。 ③本研究の意義 本研究によってATLAS実験との共同データ 取得および解析を行うことで、最前方領域事 象の物理過程の理解が可能となる。LHCエネ ルギーでの同様の研究は他に世界で唯一の結 果となり、相互作用モデルの改良に非常に有 用なデータとなる。 参考文献 1. B.R. Dawson, AIPC 1367 (2011), 11-16. 2. O. Adriani, et al., PLB 207, P128-134,2011 図４、最前方中性子エネルギースペクト 3. O. Adriani, et al., arXiv:1205.4578 ル。破線が、ATLAS検出器の測定結果を用い 4. K. Werner, et al, PR. C74,044902 (2006) てDiffractive事象を選別した結果。 名古屋大学 Data list of LHCf γ, n π0 With ATLAS p-p, √s=900GeV, 2010 ✔ (event flags) p-p, √s=2.76TeV, 2013 ✔ LHCf triggers è p-p, √s=7TeV, 2010 ✔ ✔ (event flags) p-p, √s=13 TeV, (2015) ✔ ✔ LHCf triggers è Future operations p-N,O, (>2019) ✔ ✔ LHCf triggers è p-Pb, √s =5TeV, 2013 ✔ ✔ LHCf triggers è NN p-p 400GeV, p-A ✔ ✔ è PHENIX, STAR at RHICH (???) Data list of LHCf γ, n π0 With ATLAS p-p, √s=900GeV, 2010 ✔Higher Energy(event flags) - Energy Scaling p-p, √s=2.76TeV, 2013 ✔ LHCf triggers è - Larger PT Coverage (event flags) p-p, √s=7TeV, 2010 ✔ PT = (√s/2)✔ XF θ p-p, √s=13 TeV, (2015) ✔ Heavier✔ LHCf triggers Ion è - Nuclear effect p-N,O, (>2019) ✔ ✔ LHCf triggers è ✔ ✔ LHCf triggers è p-Pb, √sNN=5TeV, 2013 Extend our Physics - Diffraction p-p 400GeV, p-A ✔ ✔ è PHENIX, STAR at RHICH (???) Summary q LHCf has measured the energy and transverse momentum spectra at the very forward region of √s = 900GeV and √s =7TeV p-p collisions in 2010. q We showed the spectra of very forward photons at √s = 900 GeV and 7 TeV p-p collisions and π0s at √s = 7 TeV p-p collisions. No model can produce data perfectly but the data are located in the middle of the model predictions. q Many analyses are ongoing, o Hadron analysis o PT spectrum of photons q Recent and Future operations will provide many data. o p-Pb collisions (Successfully done in 2013) o p-p collisions at √s = 7TeV (2015) o p-Light ion (O,N) (>2019) o operations at RHIC q Analysis with the central data (ATLAS) o Trigger exchange between LHCf and ATLAS Backup slides Photos ATLAS 620mm η Shadow of beam pipes between IP and TAN 8.7 280mm 90mm Pseudo-rapidity range. ∞ η > 8.7 @ zero crossing angle η > 8.4 @ 140urad neutral beam axis 7TeV π0 analysis 7TeV photon spectra by LHCf PT threshold PT threshold PT threshold PT threshold (Phys. Lett. B 703 128-134 (2011)) • Photon analysis and π0 analysis compensate each missing information. 0 - High energy photon originates from large PT π events. Photon PT analysis can - Photon spectrum includes a contribution from other hadrons/baryons. connect each measurement. Photons on the p-remnant side q Photon energy distrib. in different η intervals at √sNN = 7 TeV q Comparison of p-p / p-N / p-Pb q Enhancement of suppression for heavier nuclei case QGSJET II-04 SIBYLL 2.1 p-p p-N p-Pb All ηs 8.81<η<8.99 η>10.94 Courtesy of S. Ostapchenko 35 Event sample Longitudinal development measured by scintillator layers 25mm Tower 32mm Tower Total Energy deposit è600GeV è420GeV èEnergy photon photon Shape èPID Lateral distribution measured by silicon detectors X-view Hit position, Multi-hit search. Y-view π0 mass reconstruction from two photon. Systematic studies Mπ 0 = Eγ1Eγ 2 ⋅θ 900GeV photon analysis Cross section of LHCf detectors Beam pipe shadow Beam pipe shadow Two pseudo-rapidity ranges • - η>10.15 - 8.77<η<9.46 Arm1 and Arm2 data show an overall good agreement Arm1 Arm2 within their systematic uncertainties. Arm1 data vs Arm2 data 12 5 5 5 DPMJET 3.04 4.5 LHCf s=7TeV π0 4.5 LHCf s=7TeV π0 4.5 LHCf s=7TeV π0 QGSJET II-03 MC/Data 4 8.9 < y < 9.0 SIBYLL 2.1 MC/Data 4 9.0 < y < 9.2 MC/Data 4 9.2 < y < 9.4 EPOS 1.99 3.5 Ldt=2.53+1.90nb-1 3.5 Ldt=2.53+1.90nb-1 3.5 Ldt=2.53+1.90nb-1 ∫ PYTHIA 8.145 ∫ ∫ 3 3 3 2.5 2.5 2.5 2 2 2 1.5 1.5 1.5 1 1 1 0.5 0.5 0.5 0 0 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 p [GeV/c] p [GeV/c] p [GeV/c] T T T 5 5 5 4.5 LHCf s=7TeV π0 4.5 LHCf s=7TeV π0 4.5 LHCf s=7TeV π0 MC/Data 4 9.4 < y < 9.6 MC/Data 4 9.6 < y < 10.0 MC/Data 4 10.0 < y < 11.0 3.5 ∫ Ldt=2.53+1.90nb-1 3.5 ∫ Ldt=2.53+1.90nb-1 3.5 ∫ Ldt=2.53+1.90nb-1 3 3 3 2.5 2.5 2.5 2 2 2 1.5 1.5 1.5 1 1 1 0.5 0.5 0.5 0 0 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 p [GeV/c] p [GeV/c] p [GeV/c] T T T FIG. 8: (color online). Ratio of the combined pT spectra of the Arm1 and Arm2 detectors to the predicted pT spectra by hadronic interaction models. Shaded areas indicate the range of total uncertainties of the combined pT spectra. 0 gives harder π spectra, namely larger pT ,andqgsjet has a poor agreement with LHCf data for 8.9 VIII. CONCLUSIONS Acknowledgments The inclusive production of neutral pions in the ra- We thank the CERN staff and the ATLAS collabo- pidity range larger than y =8.9hasbeenmeasuredat ration for their essential contributions to the successful the LHCf experiment in LHC proton-proton collisions in operation of LHCf. We also thank Tanguy Pierog for early 2010. Transverse momentum spectra of neutral pi- numerous discussions. This work is partly supported by ons have been measured by two independent LHCf detec- Grant-in-Aid for Scientific research by MEXT of Japan tors, Arm1 and Arm2, and give consistent results. The and by the Grant-in-Aid for Nagoya University GCOE combined Arm1 and Arm2 spectra have been compared ”QFPU” from MEXT. This work is also supported by with the predictions of several hadronic interaction mod- Istituto Nazionale di Fisica Nucleare (INFN) in Italy. A els. dpmjet 3.04, epos 1.99 and pythia 8.145 agree with part of this work was performed using the computer re- the LHCf combined results in general for the rapidity source provided by the Institute for the Cosmic-Ray Re- range 9.0