Particle identification in STAR(status and future)

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.

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 DetectorSTAR Detector

2 m

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~1.1m2

||<0.3 and

CERN-STAR Ring Imaging Čerenkov Detector

STAR Detectors

Prototype (ALICE, small acceptance)

STAR Time Projection Chamber

run II Au+Au @ 200 GeV

dE/dx

pion

s

kaons

pro

tons

deute

rons

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 radiator2) MIP and photons detection

3) Ring reconstruction

RICH Identification

RICH PID range:1 ~3 GeV/c for Mesons1.5 ~4.5 GeV/c for Baryons

STAR preliminaryLiquid 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

kaonsprotons Separate species for each momentum slice:

Identified particle pT spectra

Read out pad sizeRead out pad size ：：3.15cm×6.3cm3.15cm×6.3cm

gapgap ：： 6×0.22mm6×0.22mm

95% C95% C22HH22FF44

5% Iso-butane5% Iso-butane

Multigap Resistive Plate Chamber Multigap Resistive Plate Chamber MRPCMRPC Technology developed at CERN Technology developed at CERN

3800 modules, 23,000 readout chan. to cover TPC barrel3800 modules, 23,000 readout chan. to cover TPC barrel

Multi-gap Resistive Plate Chamber TOFr: 1 tray (~1/200), (t)=85ps

Hadron identification: STAR Collaboration, nucl-ex/0309012

ToF + dE/dX: “Hadron-Blind Detector”

Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!!

electrons

nucl-ex/0407006

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 Mechanical and integration issues are integration issues are being addressed:being addressed:

Existing SiliconExisting Silicon

Two Two Layers of Layers of APSAPS

Integration volume and rapid Integration volume and rapid insertion/removal being studied insertion/removal being studied using modern 3-D modeling using modern 3-D modeling tools.tools.

Features of First Generation Design:Features of First Generation Design:

• 2 layers2 layers

• Inner radius ~1.8 cmInner radius ~1.8 cm

• Active length 20 cmActive length 20 cm

• Readout speed 4 ms (generation 1) Readout speed 4 ms (generation 1)

• MIMOSA-5 MIMOSA-5 LEPSI/IReS MIMOSTAR LEPSI/IReS MIMOSTAR

• Number of pixels 130 M ( 20 x 20 Number of pixels 130 M ( 20 x 20 μμm² pixel size)m² 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 = 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, …..)

100 MeV e-

20 cm

55 cm70 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: 40-45 cm. “Working” gas: fast, low diffusion, good UV transparency .

STAR tracking, proposed variant

Pad Detector III

Pad Detector II

Pad Detector I

Beam Pipe andVertex 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

xZ, 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 pointsUV – red points

1640 MIP hits 8200 act. Pads790 UV hits 1185 act. PadsPad size = 0.6x0.6 cm2Number of pads = 133632Occupancy = 7.0%

Rφ, cm

Z, cm

HBD performance (preliminary)

0

200

400

600

800

1000

1200

1400

1 6 11 16 21

N photons

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 7.4RMS 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 http://www.bnl.gov/henp/docs/pac0904/bellwied_eoi_r1.pdf

Comprehensive New Detector at RHIC II

Large magnetic field (B = 1.3T)

- 3.4 < || < 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 physicsQuarkonium physics• Jet physicsJet physics• Forward low-x physicsForward low-x physics• Global observables in 4Global observables in 4• Spin PhysicsSpin Physics

HCal and -detectors

Superconducting coil (B = 1.3T)

RICH

HC

al &

-d

ets

Aerogel

EM Calorimeter

ToF

Forward spectrometer: ( = 3.5 - 4.8) 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

HC

al a

nd

-det

ecto

rs

Aerogel

EM Calorimeter

ToFTracking: Si, mini-TPC(?), -pad chambers

PID: RICH ToF Aerogel

Forward tracking: 2-stage Si disks

Forward magnet (B = 1.5T)

Forward spectrometer: ( = 3.5 - 4.8) RICH EMCal (CLEO) HCal (HERA)-absorber

|| 1.2

=

1.2 – 3.5

Central detector (| 3.4)

SLD magnet

1. 2. 3. 4. 5. 6. 7. 8. 9. 10 12. 14. 16 18.

P, GeV/c

π/K/p dE/dx + ToF

p

πA1 A1+A2+RICH

RICH

KA1+ToF A1+A2

RICH

ToF A1+A2RICH

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.