Particle identification in STAR (status and future) R.Majka, N.Smirnov. Yale University (for the STAR experiment) 5 th International Workshop on Ring Imaging Cherenkov Detectors. Playa del Carmen, Mexico, Nov. 30 – Dec. 5, STAR Detector at RHIC, BNL was designed primarily for measurements of hadron production over a large solid angle, featuring detector systems for high precision tracking, momentum reconstruction and particle identification. The hadron identification was done using dE/dX data, and topological identification of decaying particles by secondary vertices finding and/or reconstructing invariant masses. The CERN-STAR RICH Detector extended the particle identification capabilities for charged hadrons at mid-rapidity. ToF Detector (MRPC technology) construction and installation is in a progress. First results are available and will be presented. The simulated performance of a fast, compact TPC in combination with a Cherenkov CsI Pad Detector for enhanced e+/- identification will be discussed as a possible variant of a STAR upgrade

STAR Detector 2 m B = 0.5 T

dE/dx at low pT On-line TPC track reconstruction Time Projection Chamber: 45 padrow, 2 meters (radius),  dE/dx)  8%, -1< 

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

Statistical Model Strangeness Enhancement Resonance Suppression STAR Preliminary

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

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: “Hadron-Blind Detector” Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!! electrons nucl-ex/

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

carbon composite (75  m) Young’s modulus 3-4 times steel aluminum kapton cable (100  m) silicon chips (50  m) 21.6 mm 254 mm Mechanical and integration issues are being addressed: Existing Silicon Two Layers of APS Integration volume and rapid insertion/removal being studied using modern 3-D modeling tools. Features of First Generation Design: 2 layers 2 layers Inner radius ~1.8 cm Inner radius ~1.8 cm Active length 20 cm Active length 20 cm Readout speed 4 ms (generation 1) Readout speed 4 ms (generation 1) MIMOSA-5  LEPSI/IReS MIMOSTAR MIMOSA-5  LEPSI/IReS MIMOSTAR Number of pixels 130 M ( 20 x 20 μm² pixel size) Number of pixels 130 M ( 20 x 20 μm² pixel size)

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, …..)

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

Expression of Interest - A Comprehensive New Detector at RHIC II P. Steinberg, T. Ullrich (Brookhaven National Laboratory) M. Calderon (Indiana University) J. Rak (Iowa State University) S. Margetis (Kent State University) M. Lisa, D. Magestro (Ohio State University) R. Lacey (State University of New York, Stony Brook) G. Paic (UNAM Mexico) T. Nayak (VECC Calcutta) R. Bellwied, C. Pruneau, A. Rose, S. Voloshin (Wayne State University) and H. Caines, A. Chikanian, E. Finch, J.W. Harris, M. Lamont, C. Markert, J. Sandweiss, N. Smirnov (Yale University) EoI Document at

Comprehensive New Detector at RHIC II Large magnetic field (B = 1.3T) < |  | < 3.4 inside magnet –Tracking –PID out to 20 – 30 GeV/c –EM/hadronic calorimetry –  chambers –Triggering 4  acceptance 3.5 <  < 4.8 forward spectrometer –External magnet –Tracking –RICH –EM/hadronic calorimetry –Triggering Quarkonium physics Quarkonium physics Jet physics Jet physics Forward low-x physics Forward low-x physics Global observables in 4  Global observables in 4  Spin Physics Spin Physics HCal and  -detectors Superconducting coil (B = 1.3T) RICH HCal &  -dets Aerogel EM Calorimeter ToF Forward spectrometer: (  = ) magnet tracking RICH EMCal (CLEO) HCal (HERA)  -absorber |  |  1.2  = 1.2 – 3.5 Central detector (|   3.4) HCal and  -detectors Superconducting coil (B = 1.3T) Vertex tracking RICH HCal and  -detectors Aerogel EM Calorimeter ToF Tracking: Si, mini-TPC(?),  -pad chambers PID: RICH ToF Aerogel Forward tracking: 2-stage Si disks Forward magnet (B = 1.5T) Forward spectrometer: (  = ) RICH EMCal (CLEO) HCal (HERA)  -absorber |  |  1.2  = 1.2 – 3.5 Central detector (|   3.4) SLD magnet

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 Hadron PID And a good quality e, μ,  -identification

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