The Alice Experiment Felix Freiherr von Lüdinghausen

The Alice Experiment Felix Freiherr von Lüdinghausen

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. 25.11.2010 Alice 2

Where is Alice? 25.11.2010 Alice 3

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. 25.11.2010 Alice 4

What is Alice made of? Size: 16x 16x 25m³ Weight: 1000t 25.11.2010 Alice 5

What kind of detector's exist? 25.11.2010 Alice 6

Where is the ITS? 25.11.2010 Alice 7

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). 25.11.2010 Alice 8

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. 25.11.2010 Alice 9

What is the ITS doing? Vertex finding in the ITS for an event of a Proton-Proton collision. 25.11.2010 Alice 10

ITS performance 25.11.2010 Alice 11

Where are the Forward Detectors? 25.11.2010 Alice 12

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) 25.11.2010 Alice 13

Where is the TPC? 25.11.2010 Alice 14

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. 25.11.2010 Alice 15

What is the TPC? 570132 pads in total Drift length: 2,5m Drift velocity 2,7cm/μs Resolution in z: 1100μm ~90μs drift time over the detector length-> ~11kHz 25.11.2010 Alice 16

TPC performance Betheblochformula 25.11.2010 Alice 17

Where is the TRD? 25.11.2010 Alice 18

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 25.11.2010 Alice 19

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 25.11.2010 Alice 20

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. 25.11.2010 Alice 21

Where is the TOF? 25.11.2010 Alice 22

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. 25.11.2010 Alice 23

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). 25.11.2010 Alice 24

TOF performance 25.11.2010 Alice 25

Where is the HMPID? 25.11.2010 Alice 26

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) 25.11.2010 Alice 27

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). 25.11.2010 Alice 28

Where is the EMCAL? 25.11.2010 Alice 29

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). 25.11.2010 Alice 30

Where is the PHOS? 25.11.2010 Alice 31

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. 25.11.2010 Alice 32

Where is the Muon arm? 25.11.2010 Alice 33

What is the Muon arm? The muon spectrometer covers a pseudo-rapidity from -4 < η < -2.5, which corresponds to an polar angular of 171-178. Due to the large Absorber needed to reduce the flux of hadrons only muons with momenta above 4GeV/c could be detected. 25.11.2010 Alice 34

Where is the PMD? 25.11.2010 Alice 35

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 < 5. 25.11.2010 Alice 36

Where is the ZDC? 25.11.2010 Alice 37

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. 25.11.2010 Alice 38

What is this all good for? 25.11.2010 Alice 39

Eventdisplay LHC10e run 130844 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. 25.11.2010 Alice 40

Eventdisplay LHC10e run 130844 25.11.2010 Alice 41

Short look at heavy ions 25.11.2010 Alice 42

Short look at heavy ions 25.11.2010 Alice 43

Centrality in Pb-Pb 25.11.2010 Alice 44

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 25.11.2010 Alice 45

Bibliography The Alice Experimen at the CERN LHC(http://iopscience.iop.org) Alice Status Report 17.11.2010, Andrea Dainese (http://indico.cern.ch) Physics Performance Report, Volume I+II (http://iopscience.iop.org) http://www.lhc-facts.ch/index.php?page=alice 25.11.2010 Alice 46