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

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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

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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