SVT and pp production

1
SVT and pp production
Nothing tends so much to the advancement of
knowledge as the application of a new instrument
- Sir Humphrey Davy (1778-1829)
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Codes included in the Chain

• StSvtDaqMaker - Reads the raw data Copes
  with no SVT data
• StSvtSeqAdjMaker - Applies tighter ASIC cuts and
  locates
• sequences in time only
• StSvtClusterMaker Finds clusters
• StSvtClusterAnalysisMaker Fits clusters,
  deconvolutes,
• rejects some hits
• StSvtHitMaker Transforms in to STAR global,
  fills scs_spt table
• StSvtVertexFinderMaker Finds the Z position of
  the Primary vertex
• StEstMaker TPC Track to SVT hit matching

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The SVT Coordinate Systems
3 coordinate frames Wafer layer, ladder,
wafer, hybrid,timebucket, anode Local layer,
ladder, wafer, cm from center of WAFER in OUR
x (drift) and y (anode) frames Global x, y, z
in STAR magnet system
anode
timebucket
x
y
timebucket
anode
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Primary Vertex Finder - Simulation
Resolution 65 microns
Resolution 350 microns
Good way to check alignment between SVT and TPC
as function of time
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Primary Vertex - Simulation
Resolution 60 microns in x,y , 100 in z
(c.f 100 and 150 for year 1)
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Vertex Finding - Data
Au-Au
p-p
There is a systematic shift Between TPC and SVT
of 2mm - expected from alignment studies
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Principle of EST

• Take TPC tracks
• Using primary vertex location refit tracks
• Project to SVT layers
• Use several loops sorting by pt to match tracks
  to SVT hits increase search area each time.
• First insist on one hit on each layer then 2 hits
  total
• Using unmatched tracks search again not using
  primary vertex

IMPORTANT SVT DOES NOT CREATE TRACKS
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Primaries - Simulation
Primary tracking efficiency 3 hits in the SVT
and gt5 in the TPC Efficiency 80 Purity 90
1.5
1.5
-1.5
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Primaries - Simulation
Primary tracking efficiency 2 hits in the SVT
and gt5 in the TPC
pt
pt
0
2
0
2
Efficiency 70 Purity 85
h
1.5
-1.5
h
1.5
-1.5
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Secondaries - Simulation
Secondary leaves 3 hits in SVT and gt5hits in TPC
pt
Efficiency 40 Purity 90
h
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Tuning EST with real data
Au-Au
Au-Au
Alter search radius for adding SVT hits to try to
find optimum
Seems after 1cm start to loose hits/track
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Primary Matching efficiency
Efficiency is defined as the number of tracks
with SVT hits added (2 or more)
p-p
Flat in pt Peaked around center of SVT
p-p
If you go to 30cm average effic is 45
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Location of Noise hits
Noise defined as hits with Dr gt 1cm from track
Clear ladders/Wafers that are noisy and we should
eliminate
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Simulating mis-alignments
Drift residual - No shift

• Drift residual
• With shift
• (x2mm, y0.8mm,
• z1.4mm)

Barrel 1
Barrel 2
Barrel 3
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Drift Residuals vs Wafer
Before Alignment
After Alignment
Magnitudes agree with survey results
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Anode Residuals vs Wafer
Before Alignment
After Alignment
Slight over-shoot in correction
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Average Drift Residuals
Au-Au Mixed events Closest hit
Au-Au All hits
Au-Au Closest hit
Au-Au Closest hit After alignment
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Average Anode residuals
Au-Au Mixed events Closest hit
Au-Au All hits
Au-Au Closest hit
Au-Au Closest hit After alignment
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Drift Residuals vs pt
Au-Au Before correction
Au-Au After correction
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Anode Residuals vs pt
Au-Au Before correction
Au-Au After correction
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Residuals after refit of EST
The refit only slightly pulls the track towards
the SVT hits. Probably because we put 1mm errors
on the hits
Au-Au Before correction
Dr (cm)
z (cm)
x direction
y direction
z direction
p-p Before correction
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More detailed residuals
Select one ladder and take a closer look at
residuals
Appears to be a tilt along z
If drift velocity incorrect would expect to see
the residual get worse as function of timebucket
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Impact Parameter - Simulation
Impact parameter for global TPC only tracks
Better Discrimination!
Log10Impact
Impact (cm)
Impact parameter for global TPCSVT tracks
Log10Impact
Impact (cm)
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Impact Parameter Improvement -Data
p-p
TPCSVT (zlt20)
Au-Au
TPC only
SVTTPC
p-p
3D impact paramaters global track associated to
primary
TPC only (zlt20cm)
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Strangeness (1) -Simulation
X
With at least one track from the SVT
TPC Only
Secondary Vertex Resolution improves
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2-D DCA - Data
TPC only
SVT Matched tracks
p-p
We looked as a function of Pt but see nothing of
interest, just a random scatter still working
on this.
SVT is slightly narrower, and shifted.
cm
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Strangeness (2)- Simulation
Cut variables change so can cut tighter to
improve signal to noise and efficiency
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V0s with the SVT
TPC only
TPC SVT (40)
Au-Au
Cuts used are those from last year for TPC only
Au-Au
Hard to say. At least not really making things
worse
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dE/dx
Au-Au
SVT dE/dx (a mess!!!)
Au-Au
TPC dE/dx
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Slow Simulator

• Nearly ready to rock and roll
• Includes
• affects of coulomb repulsion and diffusion during
  drift of electrons
• pasa response and shaping (causes undershoot in
  our signals)

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Simulation vs Data (1)
Black contours SvtSlowSim
Colour contours real data
Removed with cut
Noise in system obvious as no change in peakADC
as function of drift
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Simulation vs Data (2)
Black contours SvtSlowSim
Colour contours real data
Simulation under predicts the width
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Simulation vs Data (3)
Black contours SvtSlowSim
Colour contours real data
Simulation has slightly too high peakADC
Deconvolution doesnt work well or noise from
ripple
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Simulation vs Data (4)
Simulation doesnt quite have diffusion
correct. Charge is not spread enough in either
anode or time direction