Transcript Document 7804406

MDC4 - SVT
Most of the work shown here done by:
Lilian Martin, Javier Castillo, Boris Hippolyte, Selemon Bekele
PWG Meeting - May 2001
SVT Installed
STAR detector gets new silicon heart
– CERN Courier
Radii – 5,10 15 cm
Length ±12.4 cm
± 18.6 cm
± 21.7cm
(-1 < h < 1)
91% live
6% of the detector read out
if set noise level to 4 mV
PWG Meeting - May 2001
Helen Caines
In MDC4
Ran :
Fast Simulator
Private Vertex Finder (grouping technique)
Global tracking (est)
Also have raw data reader,cluster-finder, cluster
fitter, alignment code
PWG Meeting - May 2001
Helen Caines
Slow Simulator
Nearly ready to rock and
roll
Includes:
•affects of coulomb
repulasion and diffusion
during drift of electrons
•pasa response and shaping
(causes undershoot in our
signals)
PWG Meeting - May 2001
Helen Caines
Clustering
Anode
direction
Drift time
>95% Efficient with
expected signal/noise
Drift
direction
Position Resolution:
<25 microns
Systematic shift in drift direction
due to pasa response
PWG Meeting - May 2001
Helen Caines
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
PWG Meeting - May 2001
Helen Caines
Tracking
Impact parameter
for global TPC
only tracks
Better
Discrimination!
Log10Impact
Impact (cm)
Impact parameter
for global TPC+SVT
tracks
Log10Impact
PWG Meeting - May 2001
Impact (cm)
Helen Caines
Primaries
Primary tracking
efficiency – 3
hits in the SVT
and >5 in the TPC
pt 2
0
pt 2
0
Efficiency ~80%
Purity ~ 90%
-1.5
h
1.5 -1.5
PWG Meeting - May 2001
h
1.5
Helen Caines
Primaries
Primary tracking
efficiency – 2
hits in the SVT
and >5 in the TPC
pt 2
0
pt
0
2
Efficiency ~70%
Purity ~ 85%
-1.5
h
1.5
-1.5
PWG Meeting - May 2001
h
1.5
Helen Caines
Secondaries
Secondary leaves
3 hits in SVT and
>5hits in TPC
pt
Efficiency ~40%
Purity ~90%
h
PWG Meeting - May 2001
Helen Caines
Own Primary Vertex Finder
Resolution: 350 microns
Resolution: 65 microns
Good way to check alignment between SVT and TPC as
function of time
PWG Meeting - May 2001
Helen Caines
Primary Vertex
Resolution: 60 microns in x,y , 100 in z
(c.f 100 and 150 for year 1)
PWG Meeting - May 2001
Helen Caines
Primary Vertex
Wiggle gone – Except possibly at
edges where SVT isn’t
(Mind you it never used to be
there it has “developed” over
the past year. Still not clear
what causes it.)
PWG Meeting - May 2001
Helen Caines
Strangeness
Maximum finding efficiency
– 3.5%
Find 12% of those after
cuts
Find a good
signal
X
PWG Meeting - May 2001
Helen Caines
Strangeness (2)
Associated W
Mean pt 1.8 GeV
W
Simulated with a mean pt of 1 GeV
Efficiency – 0.9% BEFORE CUTS!!
Efficiency of the
cuts tuned for year 1
is 3% of this 0.9%
PWG Meeting - May 2001
Helen Caines
Strangeness (3)
TPC Only
X
With at least one
track from the SVT
Secondary Vertex Resolution improves
PWG Meeting - May 2001
Helen Caines
Strangeness (4)
Cut variables change so can cut tighter to
improve signal to noise and efficiency
PWG Meeting - May 2001
Helen Caines
Conclusion
Worked better than expected.
All the vital pieces of code are in place
Lots of tuning to do
PWG Meeting - May 2001
Helen Caines