The Alice Experiment Felix Freiherr von Lüdinghausen

Transcription

1 The Alice Experiment Felix Freiherr von Lüdinghausen

2 Alice, who is Alice? Alice is A Large Ion Collider Experiment. Worldwide hit in 1977 for the band Smokie Alice is the dedicated heavy ion experiment at the LHC Alice 2

3 Where is Alice? Alice 3

4 The home of Alice This is the former magnet of the L3 experiment at the LEP and now the home of the Alice detectors at the LHC. It provides a magnetic field of 0.5 tesla Alice 4

5 What is Alice made of? Size: 16x 16x 25m³ Weight: 1000t Alice 5

6 What kind of detector's exist? Alice 6

7 Where is the ITS? Alice 7

8 What is the ITS? The Inner Tracking System is the vertex detector of Alice. It consists of the Silicon Pixel Detector (SPD), Silicon Drift Detector (SDD) and Silicon Strip Detector(SSD) Alice 8

9 What is the ITS? Silicon Pixel Detector (SPD): 3.3M channels first layer + 6.6M channels second layer Silicon Drift Detector (SDD): 43k channels first layer + 90k channels second layer Busy time: ~800μs Samplerate: ~1kHz for whole Alice Detector Silicon Strip Detector(SSD): 1.1M channels first layer + 1.5M channels second layer All three detectors together have a total area of 6,74m² Alice 9

10 What is the ITS doing? Vertex finding in the ITS for an event of a Proton-Proton collision Alice 10

11 ITS performance Alice 11

12 Where are the Forward Detectors? Alice 12

13 What are the Forward Detectors: FMD, T0, V0? FMD: five rings of silicon strip detectors T0: Two arrays of Cherenkov radiators + detectors V0: Two rings of plastic scintillators Part of Level 0 trigger multiplicity information in forward and backward regions ( η > 1.5) Alice 13

14 Where is the TPC? Alice 14

15 What is the TPC? The Time Projection Chamber is the main tracking device in Alice, which is also used for particle identification. It consist of two chambers with 2,5 m length and 2,8 m radius, which have together a volume of 88m³ filled with a gas micture of 90% argon and 10% carbon-dioxide Alice 15

16 What is the TPC? pads in total Drift length: 2,5m Drift velocity 2,7cm/μs Resolution in z: 1100μm ~90μs drift time over the detector length-> ~11kHz Alice 16

17 TPC performance Betheblochformula Alice 17

18 Where is the TRD? Alice 18

19 What is the TRD? The Transition Radiation Detector is the main electron detector in Alice. It will cover a total area of ~736m² in six layers with 1.12 Mio channels when completly installed. The chambers are filled with a gas mixture of 85% Xenon and 15% carbon-dioxide. Size: 7m length x 3,7m radius Alice 19

20 What is the TRD? Electrons and pions are distinguished by the additional Signal from the transition radiation at the end of the pulse. Drift velocity: 1.6cm/μs, timebin: 0.1μs Alice 20

21 TRD performance Here is shown the difference in rejecting pions in the TOFspectra with the TRD compared to without the TRD at 2 GeV/c Alice 21

22 Where is the TOF? Alice 22

23 What is the TOF? The Time of Flight detector is dedicated to charged particle identification over a very large part of phase space and a rapidity acceptance from 0.5 GeV/c to 2.5 GeV/c with an timeresolution of less than 120 ps, it's radius is roughly 4m Alice 23

24 What is the TOF? The TOF is coupled with the T0 detector as start trigger and the TOF for the stop signal. While being a gas detector the TOF is not a drift chamber to it's need of high time resolution (~100ps) Alice 24

25 TOF performance Alice 25

26 Where is the HMPID? Alice 26

27 What is the HMPID? The High Momentum Particle Identification detector enhances the PID capability of ALICE beyond the momentum range allowed by ITS, TPC and by the TOF to the range of: up to 3 GeV/c for p and K up to 5 GeV/c for p (on a track-by-track basis) Alice 27

28 What is the HMPID? Cherenkov photons, emitted in the layer of liquid C6F14, are detected by a photon counter onto the pad cathode of a multiwire proportional chamber (MWPC) Alice 28

29 Where is the EMCAL? Alice 29

30 What is the EMCAL? The Electro Magnetic Calorimeter consists out of Pb-scintillators, it's main function is the study of jet quenching (interaction of energetic partons with dense matter) Alice 30

31 Where is the PHOS? Alice 31

32 What is the PHOS? The Photon Spectrometer is used for detection of high energetic photons. It consists of 3584 Leadtungsten crystals which work as calorimeter and cover an area of ~8m² Alice 32

33 Where is the Muon arm? Alice 33

34 What is the Muon arm? The muon spectrometer covers a pseudo-rapidity from -4 < η < -2.5, which corresponds to an polar angular of Due to the large Absorber needed to reduce the flux of hadrons only muons with momenta above 4GeV/c could be detected Alice 34

35 Where is the PMD? Alice 35

36 What is the PMD? The Photon Multiplicity Detector is a forward detector on the opposite side of the Muon arm. It provides charged-particle multiplicity information in the pseudo-rapidity range from -3.4 < η < -1.7 and 1.7 < η < Alice 36

37 Where is the ZDC? Alice 37

38 What is the ZDC? The Zero Degree Calorimeters are used to mesure the energy of the spectator nucleons to determine the centrality of the event. They are located 115 meters away from the interaction point on both sides along the beam line. The ZDCs are made by a stack of heavy metal plates grooved to allocate a matrix of quartz fibres Alice 38

39 What is this all good for? Alice 39

40 Eventdisplay LHC10e run In the Eventdisplay you can see all the detected signals combined into tracks with particle-identification, charge, mass, impulse and so on. Than this is used for analysis over a huge number of events by just applying cuts, filters and special criterias just like needed Alice 40

41 Eventdisplay LHC10e run Alice 41

42 Short look at heavy ions Alice 42

43 Short look at heavy ions Alice 43

44 Centrality in Pb-Pb Alice 44

45 dnch/dη in central Pb-Pb at 2.76Tev dnch/dη = 1584 ± 4 (stat.) ± 76 (syst.) Correction for detector acceptance: dn ch dn = 1 tracklet, with = 2 ; = 0.14 d d Alice 45

46 Bibliography The Alice Experimen at the CERN LHC( Alice Status Report , Andrea Dainese ( Physics Performance Report, Volume I+II ( Alice 46