star collaboration meeting, nantes, july2002 svt analysis/status update jun takahashi – university...
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STAR Collaboration Meeting, Nantes, July2002
SVT Analysis/Status UpdateJun Takahashi – University of Sao Paulo
STAR Collaboration Meeting - Nantes- July 2002
SVT Hardware Status• In the 2001 run:
– Full SVT was installed.– 90% of the readout channels were operational.– During Au+Au run, we had ~1800e- rms noise.– Fixed the HV Power Supply ground.– During p+p, we had ~1200e- rms noise.
• For next RHIC run:– SVT is being repaired at the moment to increase active area.– Expect installation in STAR by mid-August.– Water system being modified to improve temperature control.– New thermal switch in RDO box to avoid magnetic field effects.– New RDO code being loaded which includes Level2
abort/accept.
STAR Collaboration Meeting - Nantes- July 2002
SVT – EST, Track to hit matching
• Projects TPC track to the outer barrel in the SVT and searches for a hit.
• Refits the track with the found hit to project and search next SVT barrel hit.
• Performs gradual search from high pt -> low pt tracks, eliminating hits.
• Performs a final track kalman fit considering TPC+SVT hits.
• In p+p, there is a maximum 70% matching efficiency.
STAR Collaboration Meeting - Nantes- July 2002
Primary Matching “efficiency”
Efficiency is defined as thenumber of tracks with SVT hits added (2 or more)
p-p
p-pFlat in pt
Peaked around center of SVT
If you go to ±30cm average effic is 45%
STAR Collaboration Meeting - Nantes- July 2002
Simulating mis-alignments
Drift residual- No shift
Drift residual-With shift(x=2mm, y=0.8mm,z=1.4mm)
Barrel 1 Barrel 2 Barrel 3
STAR Collaboration Meeting - Nantes- July 2002
Drift Residuals vs Wafer
Before Alignment
After Alignment
Magnitudes agree with survey results
Shifted to x=-0.276cm y=-0.82cm z=-0.192cm
STAR Collaboration Meeting - Nantes- July 2002
Hit Residuals with respect to projection in the drift
direction
T0 wrong by~3 timebins
STAR Collaboration Meeting - Nantes- July 2002
Anode Residuals vs pt
Au-AuAfter correction
Remember!!!
This residual includes the projection momentum resolution too!!!
STAR Collaboration Meeting - Nantes- July 2002
More anode residuals
BUT!!!
Tilt would have to be 0.1 radians!
Could be that separation of wafers is not correct but that requires a squeezing of 300 microns!!
Still investigating why!!!
Wafer 4Wafer 2
Wafer 6
STAR Collaboration Meeting - Nantes- July 2002
Impact Parameter Improvement3D impact parameters global track associated to
primary
Mean 0.89->0.86 cmRMS 0.77->0.76 cm
Mean 0.7->0.51 cmRMS 0.59->0.48 cm
Au+Au
TPC+SVTTPC only
p+p
TPC+SVTTPC only
Better DCA resolution for primaries !!!
STAR Collaboration Meeting - Nantes- July 2002
Impact Parameter Improvement
3D impact paramaters global track associated to primary
p-p
TPC+SVT(|z|<30cm )TPC only
(|z|<30cm)
Without
beamlineconstraint
With Without
beamlineconstraint
With
“Official” difference Mean 0.66->0.4cm, RMS 0.56->0.45cm
STAR Collaboration Meeting - Nantes- July 2002
Vertex Finding - Data
p-p
Stripes areThe very lowMult. Events.
Still investigating which measurement is correct!!
STAR Collaboration Meeting - Nantes- July 2002
Vertex Finding - Resolution
p-p
cmStill slight offset of 0.05cm (agrees with residuals)
Nprim>10sigma= 0.24cm
STAR Collaboration Meeting - Nantes- July 2002
dE/dx
SVT dE/dx (still someCalibrating to do!)
TPC dEdx
STAR Collaboration Meeting - Nantes- July 2002
More dE/dx
Identified Primaries
Identified Secondaries
STAR Collaboration Meeting - Nantes- July 2002
Charge vs Drift
cmCenter of wafer
Drift Drift
Some evidence of“charge loss”~20%
Probably trouble in cluster analysis.We “correct” for this currently by scaling to make flat.On ladder by ladder basis.
Should really do this detector by detector.
STAR Collaboration Meeting - Nantes- July 2002
Hit charge vs Anodes
Still need charge gain correction on the anode basis!!
STAR Collaboration Meeting - Nantes- July 2002
V0’s with the SVT
pp data. Red – SVT+TPC , Black – TPC only.
STAR Collaboration Meeting - Nantes- July 2002
V0’s with the SVT, pt distribution
pp data. Red – SVT+TPC , Blue – TPC only.
STAR Collaboration Meeting - Nantes- July 2002
Summary•Initial detector parameters (alignment/calibration) determined.
•Preliminary analysis shows good detector performance.•Matching efficiency up to 70%.
•Independent primary vertex determination.
•dE/dx measurement.
•Results show overall improvements to STAR analysis such as:
•Better resolution of Primary track impact parameter.
•Higher efficiency for low pt K0s detection.
•Still to be improved:•Fine tuning of alignment parameters.
•Drift Velocity calibration using laser measurements.
•Gain correction to improve dE/dx measurements.
•Low pt tracking.
STAR Collaboration Meeting - Nantes- July 2002
Global Matching “efficiency” 2
p-p
Effic now defined as:
Num = Hit foundDen = Track hit wafer
Hit on wafer ==Occupancy
Hit within 1cm
Hit found by EST
STAR Collaboration Meeting - Nantes- July 2002
Location of Noise hits
Noise defined as hits with r > 1cm from track
Clear ladders/Wafersthat are noisy and we should eliminate