performance of prototype mrpc detector for star frank geurts (rice univ.) for the star tof...
TRANSCRIPT
Performance of Prototype MRPC
Detector for STAR
Frank Geurts (Rice Univ.)
for the
STAR TOF collaboration
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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Outline
STAR Time of Flight MRPC Prototype: TOFr TOFr at AGS
test results TOFr at RHIC (STAR)
physics results Summary
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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Solenoidal Tracker At RHIC
Great interest in large acceptance PID over an extended pT range full TOF replaces the existing Central
Trigger Barrel. covers the TPC tracking detector
based on Multi-gap Resistive Plate Chambers (MRPC) prototype detector: TOFr
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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STAR Time of Flight STOP detector:
future: barrel of MRPCs prototype single tray of MRPCs: TOFr
START detector dedicated detector, close to the beam line run II – IV: pseudo-Vertex Position
Detectors particle trajectories and momentum:
TPC tracker σ(p)/p ~ 1-2%, σ(s)/s~0.2%
Requirements: total time resolution σ(t)~100ps
MRPC resolution ~80ps detector segmentation to limit occupancy to
10-15% fit into integration envelope for present
CTB operate in 0.5T magnetic field operate at particle fluxes ~200Hz/cm2
inexpensive safe not impair performance of other
subsystems (interaction material, gas containment)
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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STAR MRPC Tests at BNL
AGS testnear E949 exp.
STARdetector
Brookhaven National LabUpton, NY
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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MRPC Moduledimensions: 21.8 x 8.4 cm2
sensitive area: 20.0 x 6.1 cm2
6 gas gaps spacing 220 micron outer glass thickness: 1.1 mm inner glass thickness: 0.54 mm
6 Copper pick-up pads 6.1 x 3.4 cm2
0.3 cm spacing
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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Tray Layout form factor: Central Trigger
Barrel tray 241 x 21.6 x 8.9 cm3
TOFr single tray 28 modules installed
168 channels two HV busses
full TOF 120 trays in two barrels different tray design φ-coverage: 60 x 6˚ z-coverage: 2 x (Δη=1) 32 modules/tray
192 channels
η=1 sideη=0 side
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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TOFr Tray Construction
FEEs installed
η~1 side
η~0 side
all MRPC modules installed
February 2002Rice Univ., Houston TX
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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TOFr at the AGS close to E949 experiment
no test beam, but radiation area significant non-relativistic
momentum spread significant radiation during the spills
in-spill (2s) dark current: 60nA out-spill (3s): 30nA no AGS operation: 10nA
measurements Optimal FEE threshold voltages Optimal high voltage gas mixtures
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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8 PMTs’ coincident signal as TDC start and ADC gate.
AGS Trigger Set-up
in-beam view
4 x 19 cm2 covered area by scintillators
along-beam viewtray
FE
E
beamdirection
tray
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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AGS TOFr Analysis strict cuts on all PMT trigger pedals strict cuts on single MRPC pad signals
no neighboring hits ADC signal < (μped + 1.5*σped)
effectively select on central hits eliminate edge effects (5ps effect)
T-A (slewing) corrections reference PMTs MRPCs
(Shao Ming et al.)
CE
RN
T1
0 d
ata
AGS – MRPC slewing
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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AGS TOFr Analysis (cont’d) Time resolution for one MRPC pad (t) ~70 ps after PMT T-A
correction no accurate position information:
remaining position smearing 45 ps/cm propagation time < 4 cm wide
raw MRPC timing(incl. start timing)
start timing(based on 8
PMTs)
0 -18˚ ~30˚ σ(t) distributions for different
incident angles 12 modules at η=0
0-18˚ 4 modules at η=1
~30˚
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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AGS: HV & FEE Threshold
90% Freon + 5% iso-butane + 5% SF6 FEE threshold voltages:
1.2, 2.2 and 2.7 V High voltages: 13.25 – 16 kV typical noise rates (mod.#2)
Vthres=1.2V, HV=14.5kV: 7 - 8Hz caveat:
no control over the beam quality possible time dependent spread
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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AGS: Gas Mixtures
module #2 tested at various HVs all other modules at fixed HVs (table) Vthres = 1.2 V start time corrected σ(t) SF6: stronger quenching, higher HV larger primary ionization for iso-butane similar efficiencies for A and B mixtures
HV
[kV]
efficiency
[%]
σ(t)
[ps]
A. freon + iso-butane + SF6 15 96.4 72.4
B. freon + iso-butane 14 97.2 76.8
C. freon 14.5 96.1 87.0
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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TOFr in STAR
run II (2001/2): Au+Au, p+p start: pVPD stop: TOFp (PMT+scintillators)
run III (2003): d+Au, p+p start: pVPD stop: TOFp + TOFr
TOFr tray
East-TPC
TOFp TOFr
x
y
54˚
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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TOFr Operations in STAR High voltage at 14kV Vthres = 1.2V gas mixture: 95% freon + 5% iso-butane 72 digitized out of 168 available channels
2 dead channels noise rate for 70 channels: ~240 Hz
Δφ=6°, Δη~0.4 only ~0.3% TPC coverage
large data sets, dedicated TOFr trigger 25M STAR minimum bias events
6.6M pVPD events 0.7M TOFr hits 0.1 hits per pVPD physics event
2.5M STAR TOFr trigger events 2.0M pVPD events 2.4M TOFr hits 1.22 hits per pVPD physics event.
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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start time: pVPD coincidence 3 detector elements per pVPD coverage
19% solid angle 4.43 < η < 4.94
start timing resolution is multiplicity dependent Au+Au (run II): σ(t) ~ 24ps d+Au (run III): σ(t) ~ 80ps p+p: σ(t) ~ 120ps
path length and momentum TPC track extrapolation to TOFr tray
primary tracks only, i.e. must originate from the primary collision vertex
at least 15 out of maximum 45 hits in the TPC tracker
match tracks to TOFr hits calibration
T0 correction T-A slewing correction local z-position correction MRPC stop timing resolution ~80ps
consistent for d+Au and p+p data
STAR: TOFr Analysis
TPC
pVPDeast
pVPDwest
Aud
TOFx
STAR TOFrp+pσ(total)~162ps
STAR TOFrp+pσ(start)~139ps
(Lijuan Ruan et al.)
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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STAR: TOFr Analysis (cont’d)
• 1/β vs. momentum for π±, K± and p(pbar) from 200 GeV d+Au collisions.
• insert shows m2=p2(1/β2-1) for 1.2 < pT <1.4 GeV/c
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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STAR: TPC tracking and TOFr matching efficiencies
TPC trackingefficiency for pbar
TPC-TOFr matchingefficiency for pbar
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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STAR: TOFr Results other corrections:
particle feed-down and contamination trigger background and biases energy loss
invariant cross sections for π±, K± and p(pbar) in 200GeV/c d+Au and p+p collision
(p+pbar)/h ratios measured by TOFr compared with other measurements similar for d+Au at 200GeV/c, and p+pbar
at 1.8TeV/c and p+p at 23.8GeV/c ratio for Au+Au at 130GeV/c twice that of
d+Au Final state rescattering, Cronin effect can
not explain this.
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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STAR: TOFr Physics!nucl/ex-0309012, submitted to PRL
RPC2003 -- Oct. 20, 2003 F.Geurts -- Performance of Prototype MRPC Detector for STAR
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Summary prototype TOF detector build in Feb.2002 tested at the AGS for various Vthres, HVs and gas settings
optimal running conditions for STAR HV=14kV Vthres=1.2V gas mixture: 95% Freon + 5% Iso-butane
STAR d+Au and p+p run very successful large data set dedicated trigger very stable operations
fast and relevant physics results important push for full MRPC-based STAR TOF proposal