Post on 30-Dec-2015
description
Progress and status of the SSD
Jörg Reinnarth - SUBATECH
STAR Collaboration Meeting
Warschaw, Poland
August 2005
What is the SSD • SSD = Silicon Strip Detector
• Proposed and designed to enhance the STAR tracking capabilities in the central region
• Improve reconstruction efficiency
short-lived particles such as Λ and Ω
• 20 ladders x 16 modules = 320 modules
• Double-sided silicon, 20m in r, 700m in z, -1< η < 1
SSDSVT
TPC
SSD one year ago• One year ago…
– All 20 ladders installed at STAR– Ladders were tested– Noise problems reduced– Complete MC-Geometry done– SSD added to online histogramms– Since Jan 2005 SSD in the run
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=
SSD in Run ‘05
SSD in Run ‘05• During Cu+Cu runs SSD worked very well• 74 million Cu+Cu200 TPC events; 57 million with TPC+SSD• 77% of all TPC events include the SSD; 67% SSD+SVT• 90% of the SSD were working properly (2 ladder off)
• 93% of all CuCu62 TPC events include SSD; 90% SSD+SVT
• Then in pp problems started to occur:• First: Low voltage problems on power supply side• Next: While working the SSD slowed down whole system• Air compressor was frequently infault• Finally: Major CAEN problem, no high voltage • Since middle of June the SSD is no longer in the runs• 41 million p+p events with SSD; 24% of all p+p TPC events
020406080
100120140
Eve
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30
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SSD hits with SVT and TPC CuCu200 ppCuCu62
CuCu200 HighTower
ppProduction
CuCu200 MinBias
CuCu62 MinBias
pp MinBias
CuCu200 pp
Pedestal & noise in Run ‘05
CuCu200
Cu+Cu 200
p+pCu+Cu 62Cu+Cu 200
Cu+Cu 62 p+p
Finer study to be done
Noise higher than in Run `04
Software progress
PointMakerIncorrect Clusterfinding
No MySQL database connection
DbMaker DaqMaker StSsdUtildirect database connection
Simulation chainOld and incomplete code
TrackingNever used, Code not usable
Tracking not tuned
AlignmentData behave strange
CalibrationNo gain calib., no mapping
PointMakerReady, ntuple & histo outputsMySQL database connection
DbMaker DaqMaker StSsdUtilNo more direct connection
Simulation chainCode completed
Simulated data exist
Tracking Works, first tests,
tuning on simulated dataalignment needed
AlignmentHistos and fits created
Simulated data help align
CalibrationPedestal, noise, gain done
Dead strip list needed
Still needed:Alignment
Tracking real data
FEB05
FEB05
TODAY
TODAY
Data analysis with SSD
Soon future
Progress in detail
+ Resultsobtained so far
X XX X
SSD chip calibration
H
H
L
L
X
X
X
Calibration needed for:
• particle identification (dE/dx)
• cluster matching
Cluster matching
• Package algorithm works
• 70% cluster (1 or 2 strips)
• 80% of case: package 1-n
• 20% ambiguos hits
• Cluster matching works
but: needs calibration
SSD (Landau distribution for real data)
Different individualLandau distributions
Overall gain calibrationneeded
Max = 0.78
Max = 0.9
Calibration through pulser runs
4 Channel per ladder pulsed
Pulser not working
SSD calibration
SSD (ITTF tracking with SSD)
SSD Alignment• Alignment needed to get correct SSD position• Installation and ladder exchange move the ladder and wafer
from their measured positions• Alignment software is ready • Technique: Plot residuals in x, y against , z, etc. (e.g. Residual in x: Local x track position on wafer – local x hit position = Δx)
→ Residual in x, y expected to be distributed around zero → SSD shift in one direction: residual → sinus distribution → Rotation: x-residual constantly shifted
Alignment needed for tracking
Δx Δy
SSD Alignment
φ
Global alignment after correction
Δx
φ
Ladder alignment through simulation
Δx
Δx
Δx
z
z
z
MC with Δy = 0.2 → Slope
Real data: No slope but Δx shift→ Shift ladder with Δx = 0.043
Negative slope → Shift ladder with Δy = -0.5
Different data sets, same parameters
Primary tracks: field data
Primary tracks: reversed field
Global tracks: no field
Not consistent data !
Alignment not completely from scratch
dXdY
SSD Outlook
• Alignment has to be finished• Calibration table will be implemented• Tracking will be persued
When SSD alignment and calibration is complete:• Request for the SSD in the next production• Tracking efficiency will be determined• Impact on the detection efficiency will be evaluated
SSD for upcoming runs
• In August/September ´05 a team will be at BNL• Low voltage problems• High voltage problems (exchange CAEN)• Ladder 8 (permanent high voltage problem)• Ladder 7 pedestal setting problem (board?)• Overall noise has to be reduced (like run ´04)• SSD will be opened at the EAST plattform
Alignment problem1. Did global alignment2. Do ladder by ladder alignment3. Plot and fit histogramms and compare to simulated behavior4. Correct shifts and rotations like predicted from simulated data
This does not work. Data do not behave like predicted
SSD (Number of clusters)
P side N side
SSD pedestal & noise distribution
Pedestal per Chip Mean noise per chip
/128! /128!
Simulate the alignment
Δx
Δx
φ
φ
φ
Δx
Δx
z
zMove whole barrel Δy = 0.2