LICE The ALICE detector A LargeIonColliderExperiment Gert-Jan Nooren Bachelor Introduction 10 February 2010

10 FEB 10bachelor introThe ALICE detectorGJN22 in search of the Quark Gluon Plasma collide heaviest ions at largest accelerator to make quark-gluon-plasma

10 FEB 10bachelor introThe ALICE detectorGJN326 JUN 09The ALICE detectorGJN3

10 FEB 10bachelor introThe ALICE detectorGJN4 Simulated event

10 FEB 10bachelor introThe ALICE detectorGJN5Fysisch Colloquium 31 maart some signatures of QGP thermal photons –black body radiation, however pions are produced copiously and  0     requires photon detector heavy quark production –short lifetimes, only decay detectable D 0 (cū) ―> K - π + cτ = 0.1 mm requires precision vertex detector π + cτ = 7.8 m K - cτ = 3.7 m

10 FEB 10bachelor introThe ALICE detectorGJN66 some signatures of QGP thermal photons –black body radiation, however pions are produced copiously and  0     requires photon spectrometer heavy quark production –short lifetimes, only decay detectable D 0 (cū) ―> K - π + cτ = 0.1 mm requires secondary vertex detector properties of hot dense matter –jet quenching –flow requires 2π azimuthal coverage

10 FEB 10bachelor introThe ALICE detectorGJN77 general layout of a LHC detector  define point of collision or the vertex  measure momentum –magnetic field –inner tracking system –general tracking device  particle identification –hadron detectors –photon detectors –muon detector

10 FEB 10bachelor introThe ALICE detectorGJN8 8 ALICE detector design Due to high number of particles cannot follow all –incomplete reconstruction of collision –no ‘hermetic’ detector –subdetectors do not cover full angular ranges what we need: –detectors for event characterisation spectators -> ZDC multiplicity -> V0, FMD –heavy quark detectors e.g. charm –J/ψ -> dimuonspectrometer –D 0 -> vertex detector –photons -> PHOS, EMCAL

10 FEB 10bachelor introThe ALICE detectorGJN9 magnet B = 0.5 T

10 FEB 10bachelor introThe ALICE detectorGJN10 10 ITS The Inner Tracking System The main tracking device of ALICE is the TPC, but the ITS is the heart of the ALICE tracking system –needed to get reasonable momentum resolution at higher p T –needed to reconstruct secondary vertices –needed to track low momentum particles being at the centre: –do not disturb the particles for the outer detectors scattering energy loss / secondary particle production –cope with high particle density: 10 4 tracks simultaneously  main features –low mass / radiation thickness –high granularity –all silicon, various techniques

10 FEB 10bachelor introThe ALICE detectorGJN11 11 ITS The Inner Tracking System all silicon, 6 layers low mass: 8 % X 0 SPD 2.3 % SDD 2.4 % SSD 1.7 % structure 1.3 % layer typeR [cm] area [m 2 ] chan- nels occu- pancy _R_R_Z_Z 1 pixels SPD M  m100  m M0.6 3 drift SDD k  m25  m k1 5 double sided strip SSD M4 20  m830  m M3.3

10 FEB 10bachelor introThe ALICE detectorGJN1226 JUN 09GJN1212 ITS The Inner Tracking System pixel, drift, strip 1698 double sided strip sensors 73 * 40 mm um thick 768 strips on each side 35 mrad stereo angle 260 silicon drift sensors 70 * 70 mm um thick collection anodes field cathodes Z R RR 240 silicon pixel sensors 13 * 68 mm um thick 256 * 160 cells 5 pixelchips per sensor E = 600 V/cm E ~ 200 V/cm

10 FEB 10bachelor introThe ALICE detectorGJN13

10 FEB 10bachelor introThe ALICE detectorGJN14 TPC Time Projection Chamber ionising particle creates free electrons electric field pulls them towards endplates with read-out chambers  particle track is projected onto endplate position sensitive detectors record: –position: R and φ –arrival time –charge drift time determines Z 3 D track reconstruction [1 mm] continuous energy loss measurement [5 %]  slow E B φ Z R

10 FEB 10bachelor introThe ALICE detectorGJN1526 JUN 09GJN1515 outer Field Cage inner drift gas 90% Ne 10% CO 2 HV electrode 90 m 3 5 m dia/length 100 kV 558k channels 90 MB/event ALICE TPC, largest ever

10 FEB 10bachelor introThe ALICE detectorGJN16

10 FEB 10bachelor introThe ALICE detectorGJN17 TRD TransitionRadiationDetector principle: –radiation is emitted when a fast particle traverses a EM discontinuity –electron is fast enough to produce X-rays in the radiator, pion is not radiator fibre+foam: many transitions driftchamber to detect X-ray photons –also sensitive to charge particles –2-D read-out six layers of these (638 m 2 ) –tracking! TRD Electrons Pions

10 FEB 10bachelor introThe ALICE detectorGJN18

10 FEB 10bachelor introThe ALICE detectorGJN19 TOF Time Of Flight measure traveling time between two detectors –start detector T0 quartz Cherenkov radiator with fast Photomultiplier -> 37 ps –stop detector TOF at R= 3.8 m MultigapResistivePlateChamber -> 40 ps 13 kV 141 m 2 of these!

10 FEB 10bachelor introThe ALICE detectorGJN20

10 FEB 10bachelor introThe ALICE detectorGJN21SAP1EXP21 E.M. cascades X0X0 2X 0 3X 0 bremsstrahlung annihilation pair creation electron Compton positronphoton continues down to ~10 MeV 2R moliere

10 FEB 10bachelor introThe ALICE detectorGJN22 22 ECAL ElectroMagneticCALorimeter Lead-scintillator sampling calorimeter Shashlik fiber geometry Avalanche photodiode readout ‘towers’

10 FEB 10bachelor introThe ALICE detectorGJN23

10 FEB 10bachelor introThe ALICE detectorGJN24 PHOton Spectrometer PbWO 4 crystals: clear as glass, denser than steel Avalanche photodiode read out Charged particle veto needed: MWPC 3854 crystals

10 FEB 10bachelor introThe ALICE detectorGJN25 photon detectors granularity PHOS’ better resolution can separate 2 photons from  0 decay PHOSEMCAL depth [X 0 ] 20 energy resolution in plot10%/√E width / R M [cm] 2.2/2.26/3.2    m 0 = 135 MeV/c 2 PHOS (9 m 2 )

10 FEB 10bachelor introThe ALICE detectorGJN26

10 FEB 10bachelor introThe ALICE detectorGJN27 HMPID High-MomentumParticleIdentificationDetector Particle identification at momenta beyond the range of ITS, TPC, TOF Ring Imaging Čerenkov detector n = 1.3 ( = 175 nm)  > 0.77 p > 1.21 mc

10 FEB 10bachelor introThe ALICE detectorGJN28

10 FEB 10bachelor introThe ALICE detectorGJN29 dimuon spectrometer muon pair produced by decay of J/ψ and Y front absorber to filter muons >4 GeV/c dipole 0.7 T, 3 Tm with 5 tracking chambers special trigger plus filter to reduce low p T muons from π and K decay front absorber: 10 int 60 X 0 carbon, concrete, steel beam shield: W, Pb, Fe filter: 7 int Fe

10 FEB 10bachelor introThe ALICE detectorGJN30The ALICE detectorGJN30 V0 Two arrays of scintillators on each side of the interaction point –plastic scintillator –photomultiplier read-out via fibres combinations yield triggers: –minimum bias –multiplicity –centrality –beam / gas V0A (z=3.3 m) V0C (z=-0.9 m) delay from interaction point

10 FEB 10bachelor introThe ALICE detectorGJN3126 JUN 09The ALICE detectorGJN31 ZDC ZeroDegreeCalorimeter three types: proton, neutron, EM ZNZPZEM dimensions [cm 3 ]7*7*10012*22*1507*7*20 absorber tungsten alloybrasslead 17.6 g/cm g/cm g/cm 3 length 251 X X 0 35 X int 8.2 int 1.1 int

10 FEB 10bachelor introThe ALICE detectorGJN32 trigger controls the read-out of subdetectors –prepare detectors –control sequences, like sampling or digitising –busy: if any is not ready, no new trigger is allowed –past-future protection select interesting events –adjust datastream to available bandwidth –reduces data volume for analysis input from key detectors –T0 and V0: time and position of interaction –ZDC: centrality –pixels –Muontrigger –PHOS and EMCAL: photons

10 FEB 10bachelor introThe ALICE detectorGJN33 Trigger, DAQ and HLT 1.25 GB/s to mass storage, 1 PB/y 25 GB/s HLT why HighLevelTrigger? even with good trigger all subdetectors produce 25 GB/s processorfarm can reconstruct events  refined selection

10 FEB 10bachelor introThe ALICE detectorGJN34 tracking tracking from 0.1 to 100 GeV/c –small material budget: < 10% X 0 vertex  end of TPC main tracking subdetectors –ITS 6 layers ~30 um 6 cm < R < 45 cm stand-alone tracking at low p T –TPC continuous ~1 mm 85 cm < R < 247 cm –TRD 6 layers ~1 mm 2.9 m < R < 3.7 m

10 FEB 10bachelor introThe ALICE detectorGJN35 ITS performance Beam spot at 2.36 TeV ITS measures primary vertex with ~ 100  m resolution (only rough alignment)

10 FEB 10bachelor introThe ALICE detectorGJN36 determine momentum in B field bonus: charge determine mass via by measuring β and γ: –energy loss via Bethe-Bloch 36 PID techniques for Particle IDentification

10 FEB 10bachelor introThe ALICE detectorGJN37 energy loss signals ITS 900 GeV p+p data  ITS (SDD + SSD)  TPC

10 FEB 10bachelor introThe ALICE detectorGJN38 determine momentum in B field bonus: charge determine mass via by measuring β and γ: –energy loss via Bethe-Bloch ITS, TPC –beta Time of flight Čerenkov –gamma: transition radiation 38 PID techniques for Particle IDentification

10 FEB 10bachelor introThe ALICE detectorGJN39 velocity signals from TOF velocity  = v/c Protons Kaons Pions all plots: preliminary calibration & alignment ! 900 GeV

10 FEB 10bachelor introThe ALICE detectorGJN40 determine momentum in B field bonus: charge determine mass via by measuring β and γ: –energy loss via Bethe-Bloch ITS, TPC –beta Time of flight TOF Čerenkov HMPID –gamma: transition radiation TRD neutral particles –exclude charged particles, then measure energy PHOS, EMCAL –via decay into charged particles short lived particles via decay to measured particles –J/ψ via dimuonspectrometer –others via displaced vertex 40 PID techniques for Particle IDentification

10 FEB 10bachelor introThe ALICE detectorGJN41 Decay examples PDG: MeV K 0 s  PDG: MeV  p     PDG: MeV All from ~300k p+p 900 GeV – Physics analysis ongoing PDG: MeV  p Λ cτ = 7.9 cm K 0 cτ = 2.7 cm

10 FEB 10bachelor introThe ALICE detectorGJN42 First interactions 11 th September.. then, on 19 Sep … Circulating beam 2 on 11 Sep: stray particle interacts in SPD  ITS has 7 tracks reconstructed with common vertex first alignment and calibration is ok ALICE is ready for beam

10 FEB 10bachelor introThe ALICE detectorGJN43 High-multiplicity event

10 FEB 10bachelor introThe ALICE detectorGJN44