A Large Ion Collider Experiment Future Upgrade and Physics Perspectives of the ALICE TPC Taku Gunji On behalf of the ALICE Collaboration Center for Nuclear Study, The University of Tokyo 1

A Large Ion Collider Experiment Outline ALICE upgrade after Long Shutdown 2 (LS2) ALICE TPC upgrade with micro-pattern gaseous detectors Status of R&D activities Summary and Outlook 2 ALICE TPC Upgrade Technical Design Report (submitted in 2013)

A Large Ion Collider Experiment ALICE Physics Program in Run3 Detailed characterization of the QGP at the highest LHC energy Main Physics topics. Uniquely accessible with ALICE after LHC luminosity and detector upgrade. –Heavy-flavors (charm, beauty): Diffusion coefficient – azimuthal anisotropy and R AA In-medium thermalization and hadronization – meson-baryon –Low-mass and low–pt di-leptons: Chiral symmetry restoration – vector meson spectral function Space-time evolution and thermodynamical properties – radial and elliptic flow of emitted radiation –Quarkonia (J/ ,  ’,  ) : Charm and bottom thermalization, regeneration – R AA, flow –Jet quenching and fragmentation: Energy loss, transport properties vs. Q 2 – R AA, flow –Heavy-nuclei, exotic hadrons: Confinement, Coalescence, quasi-state in QGP – R AA, flow 3 ALICE Upgrade LoI:

A Large Ion Collider Experiment ALICE Upgrade Strategy Operate ALICE at high rate, record all MB events –Goal: 50kHz in Pb-Pb (~10nb -1 in Run3 and Run4) Upgrade detectors and electronics during Long Shutdown 2 (2018) –New Inner Tracking Systems Improved vertexing, tracking at low p T, and improved rate capability –GEM TPC with continuous readout High rate capability, preserve PID and tracking performance –Muon Forward Tracker –Electronics, Trigger, online-offline upgrade Talk by S. Siddhanta (172) 4 Posters by L. V. Palomo(M-29), A. Uras(F-56) Posters by R. Romita(M-23), C. Terrevoli(M-27), J. Stiller(M-26)

A Large Ion Collider Experiment Example: Low Mass Di-electrons High statistics + Dalitz, conversion and charm rejection in new ITS, TPC+TOF for eID Reduced systematic uncertainties from charm decay 5 ALICE Simulation TPC Current rate New ITS B= 0.2T ALICE Simulation TPC High rate New ITS B=0.2T dedicated low-field run

A Large Ion Collider Experiment ALICE TPC 114cm 50cm 5m E E Readout chamber Central Electrode (-100kV) Diameter: 5 m, length: 5 m Acceptance: |  |<0.9,  =2  Readout Chambers: total = 72 –Outer (OROC): 18 x 2 –Inner (IROC): 18 x 2 –Pad size Inner: 4×7.5 mm 2, Outer: 6×10&15 mm 2 –Pad channel number = 557,568 Gas: Ne-CO 2 (90-10) (in Run1) at drift field = 400V/cm –  T ~  L ~0.2mm /√cm, v d ~2.7cm/  s Total drift time: 92  s MWPC + Gating Grid Operation –Rate limitation < 3.5kHz 6 OROC IROC

A Large Ion Collider Experiment GEM TPC upgrade Operation of MWPC w/o Gating Grid in 50 kHz Pb-Pb would lead to massive space-charge distortion due to back-drifting ions. Continuous readout with GEMs –GEM has advantages in: Reduction of ion backflow (IBF) High rate capability No ion tail –Requirement IBF < 1% at Gain =2000 dE/dx resolution < 12% for 55 Fe Stable operation under LHC condition 7 Standard GEM Pitch=140  m Hole  =70  m

A Large Ion Collider Experiment Space Charge Distortions Ions from 8000 events pile up in the drift volume in 50kHz Pb-Pb collisions (t ion =160ms) 1% of IBF at Gain = 2000 (  =20) –At small r and z, dr=20cm and dr  = 8cm For the largest part of drift volume, dr<10 cm –Corrections to a few are required for final resolution (  r  ~ 200um) 8

A Large Ion Collider Experiment GEM TPC R&D Program Extensive studies started in –Technology choice Baseline: GEM stacks of standard (S) and large-pitch (LP) COBRA-GEM 2 GEM + MicroMegas(MMG) –Ion backflow –Gain stability –Discharge probability –Large-size prototype Single mask technology –Electronics R&D –Garfield simulations –Physics and Performance simulations Collaboration with RD51 at CERN 9 280um

A Large Ion Collider Experiment 4 GEM setup with S and LP foils IBF and Resolution studies for baseline solution –Different foil configurations, V GEM, transfer field E T IBF optimized setting = high E T1 & E T2, and low E T3, V GEM1 ~V GEM2 ~V GEM3 <<V GEM4 – % IBF at  (5.9keV)~12% 10 4 GEM S-LP-LP-S 140um pitch280um pitch

A Large Ion Collider Experiment Garfield Simulations Garfield++/Magboltz simulations –Field calculation by ANSYS –IBF quantitatively well described by simulations based on Garfield GEM1(S) GEM2(LP) GEM3(LP) GEM4(S)

A Large Ion Collider Experiment dE/dx studies with 3 GEM Prototype 12 G= Prototype IROC was built in With 3 single-mask GEMs Beam test at PS (e/  /p) in 2012 Good e/  separation  dE/dx / ~ 10.5% Comparable to the current TPC resolution (~9.5% with IROC)

A Large Ion Collider Experiment Alternative: 2 GEM + MicroMegas IBF and Resolution studies –V Mesh, V GEM, transfer field E T –It is possible to reach < 0.2% IBF at  (5.9keV)~12%. 13 Large-scale solution and operational stability still to be verified Ne-CO 2 (90-10) Gain~ U MMG U GEM

A Large Ion Collider Experiment Electronics New ASIC “SAMPA” –Integration of the functionality of the present preamp/shaper and ALTRO ADC+DSP Both polarity, Continuous/Triggered RO SAR ADC (10M or 20MSPS) –First MWP submission in April 14 Upgrade of ALICE Electronics & Trigger System (Technical Design Report)

A Large Ion Collider Experiment Reconstruction Scheme Two stage reconstruction scheme: –Cluster finding and cluster-to-track association in the TPC Data compression by x20 : 1 TB/s  50 GB/s Scaled average space-charge distortion map –Full tracking with ITS-TRD matching High resolution space-charge map (time interval~5ms) for full distortion calibration 15

A Large Ion Collider Experiment Expected Performance Space charge fluctuations (~3%) are taken into account. (N evt,dN ch /d ,etc) ITS-TPC track matching and p T resolution are practically recovered after 2 nd reconstruction stage. 16

A Large Ion Collider Experiment Summary and Outlook The ALICE program after LS2 requires an upgrade of the TPC. MWPC-based readout chambers will be replaced by detectors employing micro-pattern detectors including GEMs to allow TPC operation in continuous mode. Extensive R&D of the GEM TPC upgrade –4 GEMs, 2GEM+MMG IBF<1%, Resolution for 55 Fe<12% –Performance of the present TPC will be maintained in 50kHz Pb-Pb collisions. –Stability, discharge probability under study –Beam test of IROCs at PS and SPS in 2014 Construction (GEM, FEE) from

A Large Ion Collider Experiment Backup slides 18

A Large Ion Collider Experiment IBF with conventional GEMs Measurement at CERN(RD51)/TUM/FRA/Tokyo. –3 or 4 standard GEM settings –standard and/or large pitch foils –X-ray from top or side, –current readout from each electrode 19

A Large Ion Collider Experiment Other options COBRA-GEM –SciEnergy, 400um pitch 2 GEM + MicroMegas 20

A Large Ion Collider Experiment Calculator Parameterization of collection, extraction, gain, resolution, and IBF vs. V GEM, E d, E t, E ind, S/LP 21 Collection vs. E d /U GEM1 Extraction vs. E T /U GEM2

A Large Ion Collider Experiment Calculator Parameterization of collection, extraction, gain, resolution, and IBF vs. V GEM, E d, E t, E ind, S/LP 22 RMS/Gain vs. Total Multiplication*sqrt(collection) # of ions in drift/Effective Gain vs. E d /U GEM1

A Large Ion Collider Experiment Space-charge fluctuation Source of space-charge fluctuations –The number of pile up events, Multiplicity –Charge of the tracks, Granularity 23 At 8000 ion pile up events, space-charge fluctuation is 2-3%. Dominant source: N evt fluctuation Multiplicity fluctuation Need take into account these fluctuations for distortion corrections.

A Large Ion Collider Experiment Space-charge map Study of space-charge distortions based on real Pb-Pb data 24 50kHz Pb-Pb collisions pileup events in ion drift time=160msec Overlapped 130k events are used to estimate time-averaged space- charge distortion.

A Large Ion Collider Experiment Space-charge fluctuation Time shifted space-charge map 25 Simulation inputs: Use fluctuating space- charge map for track distortion and Correction Use time-shifted map ~5msec is the time-scale to update the space-charge map during the online-calibration procedure

A Large Ion Collider Experiment Distortion correction in 2 nd stage Simulate statistics of typical calibration interval (~5msec. 250Hz) –Pre-reconstruct by scaled average SC map Then, use ITS-TRD track interpolation –Map residual local distortions and 2-D correction analysis to get (dr, dr  ) 26 Spatial Patterns of dr and dr  are well reproduced.

A Large Ion Collider Experiment IROC Prototype Large-size GEM foils by CERN using single mask technology. 3 standard GEM foils in prototype 27

A Large Ion Collider Experiment TPC Operation without GG MWPC without GG –Best estimate: ion back flow (IBF) rate of ~5% at gain = 6000 –Simulation shows a large distortion in electric field  impossible Tolerable limit –IBF rate of 1% at gain 2000; ~20 back flow ions per electron 28

A Large Ion Collider Experiment Front-end Electronics Comparison of FEE parameters for RUN 1 and 3 Data rates and bandwidth requirements

A Large Ion Collider Experiment Current TPC Performance 98% tracking efficiency in pp. 1-3% lower for central Pb-Pb Momentum resolution ~ 1% at 1GeV, 5% at 50GeV dE/dx resolution= 5.5% in pp and 7% in Pb-Pb 30

A Large Ion Collider Experiment Gating Grid Operation 31 GG close 100us after collisions GG closed for 180us (ion arrival time to the GG) IBF<10 -4 but event rate < 3.5kHz GG open results in 5-8% IBF

A Large Ion Collider Experiment Gain Stability 3 stacked GEMs with 90 Sr for Ne/CO 2 (90/10) –Single-wire chamber as a reference for correction of the gain fluctuation due to P/T 32 Gain Variation within 0.5% at gain=1800

A Large Ion Collider Experiment Prototype Beamtest at PS in 2012 IROC Prototype (3 standard GEMs) beamtest at CERN-PS T10 –e, , p: 1-3 GeV for negative, 1&6 GeV for positive –PCA16 + ALTRO Readout from LCTPC collaboration –dE/dx resolution for standard and IBF setting 33

A Large Ion Collider Experiment Garfield Simulations Garfield++ simulations –Field calculation by ANSYS –Mis-alignment of GEMs –Measurements are understood. 34

A Large Ion Collider Experiment IBF and Energy Resolution Systematic studies for 4 GEM –different foil configurations, V GEM, transfer field E T IBF optimized setting = high E T1 & E T2, and low E T3, V GEM1 <V GEM2 <V GEM3 <V GEM4 – % IBF and  (5.9keV)=11-12% 35 4 GEM S-LP-LP-S

A Large Ion Collider Experiment Space-charge distortion correction 36

A Large Ion Collider Experiment Occupancy Average pileup = 5 MB events –2500 tracks in average –~7500 tracks is maximum Maximum occupancy : 70% at IROC 37