March 3, 2008E. Scapparone INSTR081 Particle identification in ALICE E. Scapparone(INFN/CERN) on behalf of the ALICE Collaboration INSTR08, March 3, 2008 Outline - Experimental layout and status of the main subdetectors; - Detector performance; - Example of ALICE phsycs potential. March 3, 2008E. Scapparone INSTR0822 ALICE: A Large Ion Collider Experiment at CERN-LHC Size: 16 x 26 meters Weight: 10,000 tonnes p-p (L=10 31 cm -2 s -1 ), Pb-Pb (L= cm -2 s -1 ) March 3, 2008E. Scapparone INSTR083 Life in Pb-Pb interactions was never easy. NA49 At RHIC became harder.. ALICE simulated central event !..also more RHIC STAR March 3, 2008E. Scapparone INSTR084 6 layers, three technologies (keep occupancy at a few % for max multiplicity) SPD: silicon pixels (0.2 m 2, two layers, 9.8 M channels) SDD: silicon drift (1.3 m 2, two layers, 133 k channels) SSD: double-sided silicon strips (4.9 m 2, two layers, 2.6 M channels ) R out =43.6 cm SPD SSD SDD ITS(Inner Tracking System) L out =97.6 cm Material Budget: 1% X 0 per layer ! March 3, 2008E. Scapparone INSTR085 Challenge: track densities at r = 4 cm (1st layer): up to 100 / cm2 SPD (0.2 m 2 ) Cell size (r z : 50 m x 425 m space resolution(r ) : 12 m space resolution(z): 100 m ITS SDD (1.3 m 2 ) cell size (r ,z): 294 x 150 m2 space resolution (r , z) : 35 m space resolution(z): 23 m SSD (4.9 m 2 ) cell size (r ,z): 95 x 4200 m2 space resolution (r ): 20 m space resolution (z); 830 m 40 m m 75 mm 42 mm 6 chips March 3, 2008E. Scapparone INSTR0866 Inner Tracking System ~ 10 m 2 Si detectors, 6 layers Pixels, Drift, double sided Strips Strips SSD Drift SDD Pixels Inner Silicon Tracker Pixels SPD March 3, 2008E. Scapparone INSTR087 TPC SSD/SDD SPD March 3, 2008E. Scapparone INSTR0888 Optimized for dN/d 8000 l = 5 m, = 5.6m, 88 m3, 570,000 channels x 500 time bins, up to 80 Mbytes/event (after 0 suppression) Features: lightweight: 3% X 0 total material for perpendicular tracks novel digital electronics (ALTRO) highly integrated, digital shaping; tail cancellation;0-suppression; Baseline restoration Powerful laser calibration system TPC Drift gas:Ne (86) / CO 2 (9.5) / N 2 (4.5) (dE/dx) 5.5 to 6.5 %, depending on multiplicity (measurements and simulations) March 3, 2008E. Scapparone INSTR0899 ALICE TPC: 5 years construction March 3, 2008E. Scapparone INSTR0810 Cosmics recorded in Commissioning with Cosmics and Laser tracks Spatial resolution and Electronics noise in experiment according to specifications Status: installed and being commissioned March 3, 2008E. Scapparone INSTR0811 e/ separation in central barrel p>1 GeV/c fast trigger for high momentum particles (hadrons, electrons)+ tracking 540 detectors ~ 760m 2 18 super modules length: 7m X/X 0 ~ 22 % 28 m 3 Xe/CO 2 (85/15) 1.2 million channels Transition Radiation Detector (TRD) Status: partially installed; being commissioned TRD March 3, 2008E. Scapparone INSTR0812 TRD - Signal Generation & Processing Average pulse heigth (mV) e-) = 90 % March 3, 2008E. Scapparone INSTR0813 TRD Installation March 3, 2008E. Scapparone INSTR0814 TOF requirements: Large array to cover the ALICE barrel (~150 m 2 ) Time resolution < 100 ps High efficiency, > 95% High segmentation: few thousands of particles per unit of rapidity expected in Pb-Pb collision at s = 5.5 TeV/nucleon pair ALICE choice: a detector based on MRPC, segmented in ~157,000 channels, (3.5 x 2.5) cm2 area March 3, 2008E. Scapparone INSTR0815 TOF 2 crates /side pads, total sensitive area: ~150 m 2 18 Supermodules, each made of 5 modules: 2 external (19 strips), 2 intermediate (19 strips), 1 central (15 strips) 7.4 m Readout performed by two VME Crates/Side March 3, 2008E. Scapparone INSTR0816 Cross section of a double-stack MRPC strip 2 rows of 48 readout pads (3.5 x 2.5 cm 2 ) Active strip length = 120 cm Differential signal to FEA card 10 gaps 250 m March 3, 2008E. Scapparone INSTR0817 Test beam of single strips Efficiency Time resolution( ps) > 99.9 % average ~ 50 ps Gas mixture: C 2 F 4 H 2 (90%) SF 6 (5%) C 4 H 10 (5%) Similar results obtained when strips are inserted inside the modules March 3, 2008E. Scapparone INSTR0818 M = p ((t2 c2 /L2 )-1)1/2 TOF = 80 ps ; B = 0.5 T March 3, 2008E. Scapparone INSTR SMs installed ; next 4 SMs to be installed next week; being commissioned March 3, 2008E. Scapparone INSTR0820 December 2007 cosmic run Event display of a muon crossing the TOF detector March 3, 2008E. Scapparone INSTR0821 Proximity Focused RICH 11 m 2 active detector area 7 modules - 0.6< < 0.6; = 58 deg CsI Photocathode read by pads Threshold momentum = 1.21* (Particle Mass) PID optimization for 1 GeV < p < 6 GeV High Momentum Particle Identifier: HMPID March 3, 2008E. Scapparone INSTR0822 HMPID (Sept 06) HMPID: Installed; being commissioned March 3, 2008E. Scapparone INSTR0823 Example of a high multiplicity event as seen by the HMPID dN/d =6000 March 3, 2008E. Scapparone INSTR stations of high granularity pad tracking chambers, over 1 million channels Complex absorber/small angle shield system (~10 I ) to minimize background (90 cm from vertex) RPC Trigger Chambers MUON spectrometer set-up 0.7 T, bending power 3 Tm 4 MW power, 800 tons Worlds largest warm dipole Trigger pt cut on single : ~1 GeV/c March 3, 2008E. Scapparone INSTR0825 Lepton Acceptance ATLAS & CMS present a large lepton acceptance | |