Particle identification. RHIC, LHC (ALICE) (status and future) N.Smirnov. Physics Department, Yale University JLab, Detector workshop, June 4-5, 2010.

STAR Detector 2 m B = 0.5 T

ALICE Detector ALICE Detector 3 ITS TPC TRD TOF PHOS HMPID EMCAL

STAR; dE/dx at low pT On-line TPC track reconstruction Time Projection Chamber: STAR: 45 padrow, 2 meters (radius),  dE/dx)  8.2%, ALICE: 160 padrow, 2.5 meter (radius), σ (dE/dx)  ( )% -1< 

PiD, Topology and Mass Reconstruction (STAR) Topology analysis (V0s,Cascades,  -conversion, “kink”-events…) limitation in low pT, and stat. TPC

Gas detector (TPC) simulation. Tracking and dE/dX performance -- FVP approach *) -- Monte-Carlo program was prepared to simulate number of interactions (and position along the particle track), and a transfer energy in each interaction as a function of a gas mixture parameters and particle momentum (βγ). -- GEANT3, detail and careful detector response simulation *) All details can be found: -- H. Bichsel, NIM A562 (2006)

Detector response simulation GEANT3 was used to describe experiment geometry as realistic as possible, and to simulate a particle track. One particle per event, 0.5 T magnetic field, “decay” and “nuclear interaction” – OFF. For each TPC pad-row “input” and “output” points in space (Local Coordinate System) and particle momentum were saved (“HIT”). For each HIT number of ionization electrons and there position in space were simulated including long range (delta-) electrons using energy losses approach stressed earlier.

Detector response simulation For each electron: -- drift, absorption, diffusion, anode wire selection steps were simulated. -- Gas amplification (Polya distribution). -- An induction charge on read-out pads was calculated. FEE response using an “arrival” time for each electron, “noise” and “cross-talk” parameters. Cluster finding (“efficiency” parameter); q in a cluster. Truncated procedure. dE/dX and PID analysis – in “N σ “ for {log(q / )/σ+9}.

STAR TPC; experiment – simulation comparison ( dE/dX and PID analysis – in “Nσ“ for {log(q / )/σ+9}.) Data from O. Barannikova, Proc. 21 st Winter Workshop on Nuclear Dynamics (2005). Simulation: Try to be ACAP with number of Hits / track; and use the same Truncated approach. NσNσ π π p p K K

STAR TPC; experiment – simulation comparison Pt, GeV/c (Nσ, K - Nσ, π) (Nσ, p - Nσ, π) { experiment *) / simulation } / / / / / / / / Conclusion: Simulation approach reproduced experimental data ( STAR, P10). *) Yichun Xu, … arXiv: v1, 27 July 2008

Simulation result for ALICE TPC; the same approach, but 90% cluster finding efficiency and “optimal” truncated procedure dE/dX as a function of βγdE/dX as a function of momentum P, GeV/c βγ π K p

ALICE TPC; PiD performance (on a “track level”) Particle momentum – 4. GeV/c NσNσ p π K Proton identification: Efficiency – “purity” Cut parameter For 70% efficiency – 70% “purity”

ALICE TPC; PiD performance (on a “track level”) Particle momentum – 10. GeV/c p π K NσNσ Proton identification: Efficiency – “purity” Cut parameter For 70% efficiency – 70% “purity”

ALICE TPC; PiD performance (on a “track level”) NσNσ Particle momentum – 15. GeV/c π p K Proton identification: Efficiency – “purity” For 70% efficiency – 70% “purity” Cut parameter

Preliminary conclusion (personal opinion) ALICE TPC PiD performance is not good enough to get high Pt (>10 GeV/c ) Proton identification on a “track level”. Most probable – simulation results are too optimistic In “real” experiment: -- cluster finding and track reconstruction is not easy busyness. It is never can be done perfect because of track overlaps, background, distortions. -- gas amplification and noise have “additional” variations (along wire, wire-to-wire, P/T, …) and should be careful calibrated and under control. My forecast is “60 – 60”. But the first run will demonstrate.

r ~ 235cm, s~1.1m 2 |  |<0.3 and   CERN-STAR Ring Imaging Čerenkov Detector STAR Detectors Prototype (ALICE, small acceptance) STAR Time Projection Chamber run II 200 GeV dE/dx pions kaons protons deuterons electrons dE/dx PID range:  (dE/dx) =.08] p  ~ 0.7 GeV/c for K /   ~ 1.0 GeV/c for p/x |  |<1.5 and  

1)Charged particle through radiator 2)MIP and photons detection 3) Ring reconstruction RICH Identification RICH PID range: 1 ~3 GeV/c for Mesons 1.5 ~4.5 GeV/c for Baryons STAR preliminary Liquid C6F14 Cluster charge, ADC counts, experimental data 4) Response simulation

Cherenkov distribution and Fitting: integrated method Cherenkov angle distribution in momentum bins 3 Gaussians fit:  8 (= 9-1 constraint) parameters.  constraint: integral = entries.  fixing parameters with simulation pions kaons protons  Separate species for each momentum slice:

Identified particle p T spectra 9 such detectors are working in ALICE

Read out pad size ： 3.15cm×6.3cm Gap: 6×0.22mm 95% C 2 H 2 F 4 5% Iso-butane Multigap Resistive Plate Chamber MRPC Technology developed at CERN MRPC Technology developed at CERN 3800 modules, 23,000 readout chan. to cover TPC barrel Multi-gap Resistive Plate Chamber TOFr: 1 tray (~1/200),  (t)=85ps

TOF R&D Accomplished in FY03-04 TOF R&D Accomplished in FY03-04 HV was on for the entire run – no failuresHV was on for the entire run – no failures SF 6 is NOT required in the gas mixSF 6 is NOT required in the gas mix Noise rate ~200Hz from OR of 72 chan.Noise rate ~200Hz from OR of 72 chan. TPC track matching doneTPC track matching done Calibrations (t-zero, slewing, TDC nonlinearity, …) are all performedCalibrations (t-zero, slewing, TDC nonlinearity, …) are all performed 85 ps MRPC timing resolution demonstrated for a small system in the RHIC/STAR environment85 ps MRPC timing resolution demonstrated for a small system in the RHIC/STAR environment 95% MRPC efficiency demonstrated in the RHIC/STAR environment95% MRPC efficiency demonstrated in the RHIC/STAR environment PID capability demonstratedPID capability demonstrated Electron tagging demonstratedElectron tagging demonstrated Physics publication submittedPhysics publication submitted

Hadron identification: STAR Collaboration, nucl-ex/ ToF + dE/dX: “e / hadron PID” Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!! electrons nucl-ex/

ALICE experiment ALICE has a unique capability, among the LHC experiments, of charged particle identification, due to the exploiting of different types of detectors:  ITS + TPC : low p T identification (up to p = 600 MeV/c).  TOF : covers intermediate p T region.  TRD : electrons identification.  HMPID : high p T region (1÷5 GeV/c) p (GeV/c) TPC + ITS (dE/dx)  /K /K/K K/ p e /  HMPID (RICH) TOF p (GeV/c) TRD e /  /K/K K/ p High-p T Physics at LHC, 17 March 2008 G. Volpe with TOF data

Definition of “high Pt” Experience from RD26; HMPID R&D, construction and utilization in STAR and ALICE Experience to work with micro-pattern gas detectors RICH R&D results from BRAHMS, LHCb and COMPAS Experiment Radiator Gas and Length UV detector Pad size BRAHMS C4F10 (+) 150 cm Ph. Tubes 1.1x1.1 cm 2 COMPAS C4F cm MWPCH+CsI 0.8x0.8 cm 2 LHCb (RICH 1) C4F10 + AG 85 cm HPDs.25 x.25 cm 2 (HERMES)  Reliable Detector response simulation  Gas quality and Index of refraction controls

ALICE VHMPID design constraints Charged hadrons ( , K, p) identification in GeV/c  Focusing RICH with gaseous radiator  High Pt trigger Limited available space in ALICE  Filling factor (acceptance), radiator length Limited time for R&D and (possibly) detector construction  HMPID heritage and know-how: CsI, MWPC, FEE,… 07/05/2010A. Di Mauro - RICH2010, Cassis25

Radiator gas CF4 (n ≈ , γ th ≈ 31.6) has the drawback to produce scintillation photons (Nph ≈ 300/MeV), that increase the background. C4F10 (n ≈ , γ th ≈ 18.9) C5F12 (n ≈ 1.002, γ th ≈ 15.84) this gas has been used in the DELPHI RICH detector

07/05/2010 Detector principle scheme Focusing RICH, C 4 F 10 gas radiator L~ 80 cm Photon detector a la HMPID, baseline option: MWPC with CsI pad (8x8 mm) segmented photocathode; alternative: CsI- TGEM or GEM Spherical (or parabolic) mirror, composite substrate, Al/MgF2 coating FEE based on HMPID Gassiplex chip, analogue readout for localization via centroid measurement 27A. Di Mauro – RICH2010, Cassis CaF 2

11 12 Integration in ALICE 07/05/2010A. Di Mauro – RICH2010, Cassis Free slot for prototype ~ ½ supermodule  7% acceptance wrt TPC  12% wrt TPC in |η | < 0.5 (jet fully contained) TPC TRD

Expected performance The detector consists of 9 modules of 1.4 m 2 corresponding to an acceptance of ~ 10% Signal (GeV/c) Absence of signal (GeV/c)  4-16 K11-16 p PID performance from Cherenkov angle resolution studied in ALIROOT overlapping single particle Cherenkov events to HIJING background

PID performance: ID range Signal (GeV/c) Absence of signal (GeV/c)  4-24 K11-24 p /10/0930ALICE Upgrade Forum Lower limit: Cherenkov threshold Upper limit: 3  separation

HIJING generator dN ch /d  = 4000 at mid rapidity: maximum foreseen Simulation results: Pb-Pb background High-p T Physics at LHC, 17 March 2008 G. Volpe

Option I; PID for π One particle / event With Central Pb+Pb HJ as a background Particle was identified as π (Blue), k - Red, p – Green, No PID - black ~ 15 %

One particle / event With Central Pb+Pb HJ as a background Particle was identified as π (Blue), k - Red, p – Green, No PID - black Option I; PID for K

One particle / event With Central Pb+Pb HJ as a background Particle was identified as π (Blue), k - Red, p – Green, No PID - black Option I; PID for p

Proposed option II. Three detectors in the same space available RICH with CF4 and windowless GEM+CsI pad read-out Gas micro-pattern tracking detector with pad-readout. Threshold Cherenkov detector with C4F10 + quartz window + GEM pad-readout

Option II; Two detectors (RICH with CF4 and Cherenkov with C4F10) plus additional tracking detector. Spherical UV Mirror CF4 gas C4F10 gas SiO2 Window Tracking Detector, 5x5 mm 2 pads GEM detector with CsI and 5x5 mm 2 pads MWPCh or GEM detector with CsI and 5x5 mm 2 pads 70 cm 35 cm Particle track & UV photons It is useful for high Pt trigger

Option II; PID for π One particle / event With Central Pb+Pb HJ as a background Particle was identified as π (Blue), k - Red, p – Green, No PID - black

One particle / event With Central Pb+Pb HJ as a background Option II; PID for K Particle was identified as π (Blue), k - Red, p – Green, No PID - black

With Central Pb+Pb HJ as a background One particle / event Option II; PID for p Particle was identified as π (Blue), k - Red, p – Green, No PID - black

Option II; detector response ( cluster charge) for UV photons and MIPs; and High Pt trigger possibility Cluster charge, pC Blue – UV photons; Red – MIPs Green – No FEE Noise Three reconstructed MIP hits were matched as a track, Line fit in (XY) and (RZ) DCA to (0., 0.) in (XY), cm Pt, GeV/c With cuts selected to get 98% efficiency for “one high Pt track / event” -for Central HIJING event the probability to get false trigger ( “DCAxy < 15. cm”) is smaller than 4% / detector

Beam tests of CsI coated TGEM (Nov 2009) 10x10 cm prototype layout: Triple Thick GEM with CsI coated top element, CaF 2 window Cherenkov radiator, pad readout Goals of the tests: - Gas mixture % optimization (Ne/CH 4 ) - HV settings/gain optimization - FEE setting for readout of e - induced signal - Response of CsI layer evaporated on TGEM - Prove working principle: simultaneous detection of single UV photons (Cherenkov radiation) and MIPs

The PHENIX Hadron Blind Detector (HBD) Proximity Focused Windowless Cherenkov Detector Radiator gas = Working gas Gas volume filled with pure CF 4 radiator 24 Triple GEM Detectors (12 modules per side) Area = 23 x 27 cm 2 Mesh electrode Top gold plated GEM for CsI Two standard GEMS Kapton foil readout plane One continuous sheet per side Hexagonal pads (a = 15.6 mm) Cherenkov blobs e+e+ e-e-  pair opening angle ~ 1 m

Concluding Slides Detector design for best possible hadron PID *) Must include: dE/dX ToF TRD Cherenkov and RICH with liquid, aerogel, and gas radiator working inside of B-field (CsI + GEMs, TGEMs, MWPCH). High quality track finding and momentum reconstruction Trigger *) based on working detectors and R&D results at RHIC and LHC

P, GeV/c π/K/p dE/dx + ToF p π A1 A1+A2+RICH RICH K A1+ToF A1+A2 RICH ToF A1+A2 RICH Performance of Hadron PID And a good quality e, μ,  -identification A1, A2 – aerogel Cherenkov detectors with different n-index

Conclusion Cherenkov Detectors at RHIC and LHC are working and will be used in upgraded and new experimental setups.

STAR Upgrades R&D Proposal The broad strategy for upgrading the STAR Detector includes: “Improve the high-rate tracking capability and develop the technology for eventual replacement of the Time Projection Chamber.” STAR tracking issues that need to be addressed and solved ( at upgraded RHIC luminosity ) TPC Event pile up TPC Space Charge Additional tracking, PID Detectors Trigger power improvement Increase data rate

Possible solution. Future STAR tracking / PID set up (TPC replacement )  16 identical miniTPC’s with GEM readout; “working” gas: fast, low diffusion, UV transparent. dR = cm, dZ=+/-45 cm, maximum drift time – 4.5 μs. with enhanced e+/- PID capability (Cherenkov Detector in the same gas volume)  3-4 layers of Pad Detectors on the basis of GEM technology: needed space resolution, low mass, not expensive, fast (∆t ~ 10 ns )  Allows consideration to use the space for more tracking ( Forward Direction), PID Detectors (TRD, Airogel Ch, …..)

High precision Vertex Detector ( c-, b- decay identification) High resolution inner vertex detector, better than 10  m resolution, with better than 20  m point-back accuracy at the primary vertex. CMOS Active Pixel Sensor (APS) technology – can be very thin, allows some readout to be on same chip as detector. Develop high speed APS technology for second generation silicon replacement (LEPSI/IReS, and LBNL+UC Irvine) Required Areas of development: APS detector technology Mechanical support and cabling for thinned silicon Thin beam pipe development Calibration and position determination Data stream interfacing

100 MeV e - 20 cm 55 cm 70 cm CsI Photocathode Fast, Compact TPC with enhanced electron ID capabilities 2 x 55. cm 16 identical modules with 35 pad-rows, double (triple) GEM readout with pad size: 0.2x1. cm². Maximum drift: cm. “Working” gas: fast, low diffusion, good UV transparency.

STAR tracking, proposed variant Pad Detector III Pad Detector II Pad Detector I Beam Pipe and Vertex Detectors miniTPC ToF EMC Magnet y x R z

HBD PID, step 1 (for “low” Pt tracks)  For all found in miniTPC tracks dE/dX analysis/ selection were done;  then some number of tangents to selected tracks were calculated and “crossing” points with Pad Det (if it was possible) were saved,  “search corridor” was prepared. Pad Det with CsI (GEM ?!) y x Z, cm φ, rad

HBD PID, step 2, (for “high” Pt e+/-) For tracks that crossed Pad Detector I, a matching procedure was done ( TPC track – Pad Det Hit ), and an analysis took place to check the number of UV- photons hits inside of cut values (which are the function of Pt, Pz) e- miniTPC hits Pad Det I hits

Pad Detector response simulation, and e+/- PID Central Au+Au event (dNch/dY~750), simulated using HIJING event generator with “full scale” detectors response simulation, Reconstructed hit positions, Z-Rphi, cm MIP – blue points UV – red points 1640 MIP hits  8200 act. Pads 790 UV hits  1185 act. Pads Pad size = 0.6x0.6 cm2 Number of pads = Occupancy = 7.0% Rφ, cm Z, cm

HBD performance (preliminary) For “central” HIJING events, CH4, 0.5 T:  the lepton PID efficiency ( all found tracks in TPC) – 90.8%.  The number of wrong hadron identifications – 1.5 tracks/event. Number of reconstructed UV photons/track ( 9 or more TPC hits ) Mean 7.4 RMS 2.83