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Particle identification in STAR (status and future)

Particle identification in STAR (status and future). 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.

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Particle identification in STAR (status and future)

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  1. Particle identification in STAR(status and future) 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 R.Majka, N.Smirnov. Yale University (for the STAR experiment) 5th International Workshop on Ring Imaging Cherenkov Detectors. Playa del Carmen, Mexico, Nov. 30 – Dec. 5, 2004.

  2. STAR Detector B = 0.5 T 2 m 2 m

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

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

  5. Resonance Suppression Strangeness Enhancement Statistical Model 200 GeV pp 200 GeV Au+Au STAR Preliminary

  6. dE/dx kaons protons deuterons pions electrons STAR Detectors run II Au+Au @ 200 GeV STAR Time Projection Chamber |h|<1.5 and Df = 360o CERN-STAR Ring Imaging Čerenkov Detector dE/dx PID range: [s (dE/dx) = .08] p  ~ 0.7 GeV/c for K/  ~ 1.0 GeV/c for p/x Prototype (ALICE, small acceptance) r ~ 235cm, s~1.1m2 |h|<0.3 and Df = 20o

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

  8. pions kaons protons Cherenkov distribution and Fitting: integrated method Cherenkov angle distribution in momentum bins • 3 Gaussians fit: • a8 (= 9-1 constraint) parameters. • constraint: integral = entries. • fixing parameters with simulation a Separate species for each momentum slice:

  9. Identified particle pT spectra

  10. Multigap Resistive Plate Chamber MRPC Technology developed at CERN Read out pad size： 3.15cm×6.3cm gap：6×0.22mm 95% C2H2F4 5% Iso-butane 3800 modules, 23,000 readout chan. to cover TPC barrel Multi-gap Resistive Plate Chamber TOFr: 1 tray (~1/200), s(t)=85ps

  11. ToF + dE/dX: “Hadron-Blind Detector” Hadron identification: STAR Collaboration, nucl-ex/0309012 nucl-ex/0407006 electrons Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!!

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

  13. 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

  14. 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 = 20-50 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, …..)

  15. Fast, Compact TPC with enhanced electron ID capabilities CsI Photocathode 100 MeV e- 2 x 55. cm 20 cm 55 cm 70 cm 16 identical modules with 35 pad-rows, double (triple) GEM readout with pad size: 0.2x1. cm². Maximum drift: 40-45 cm. “Working” gas: fast, low diffusion, good UV transparency .

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

  17. HBD PID, step 1 (for “low” Pt tracks) Pad Det with CsI (GEM ?!) • 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. y x Z, cm φ, rad

  18. 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

  19. 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 Rφ, cm 1640 MIP hits  8200 act. Pads 790 UV hits  1185 act. Pads Pad size = 0.6x0.6 cm2 Number of pads = 133632 Occupancy = 7.0% Z, cm

  20. HBD performance (preliminary) Number of reconstructed UV photons/track ( 9 or more TPC hits ) 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. Mean 7.4 RMS 2.83

  21. 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 http://www.bnl.gov/henp/docs/pac0904/bellwied_eoi_r1.pdf

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

  23. Hadron PID π/K/p dE/dx + ToF A1 A1+A2+RICH π RICH A1+ToF A1+A2 K RICH ToF A1+A2 p RICH 1. 2. 3. 4. 5. 6. 7. 8. 9. 10 12. 14. 16 18. P, GeV/c And a good quality e, μ, -identification

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

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