Physics with the HFT prototype?
J. Bouchet for the HFT-soft group
04/21/23 Star Coll. Meeting, LBNL, Nov. 2011 1
1. Motivation2. Results of simulation :
a) Acceptance optimization studies
b) Tracking efficiency studies with TPC+PXL
3. Next steps
Motivation• PIXEL detector is the inner sub-system of the HFT tracker
in STAR• 3 (or 2 or 4) PXL sectors (out of 10) will be installed in
STAR next year for Run-13 as an engineering run • Question : Which geometry is the most efficient for track
pointing and physics measurement ?
04/21/23 Star Coll. Meeting, LBNL, Nov. 2011 2
• for low Pt D0, opening angle between daughters is large.• For higher Pt D0, the openingangle decreases.Different Pt D0 regimes lead todifferent configurations of the sectors.cosine(φpion-φkaon) vs. PtD0
04/21/23 Star Coll. Meeting, LBNL, Nov. 2011 3
=0
=36
=72=108
=180
=252 =288
=324=216
=144
2 configurations studied
Triangle-shape Joined-shape
1 sector covers 36
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Simulation Setup1. Input:
– Generate 100k D0 with flat Pt in [0,5], ||<3,|Vz|<10 cm– Count :
• NN : # of D0 input
• N0 : # of D0 after Pt cut for both daughters and|| <1
• N1 : # of D0 with above cuts + TPC>10,PXL=2
• N2 : # of D0 in triangle configuration
• N3 : # of D0 in joined configuration
• Single track efficiency/ghosting• Modify the existing geometry file with
– Removal of SSD and IST– Localization of 3 pxl sectors according the patches configuration
• ~500 central AuAu Hijing events but NO PILEUP– Plus minbias AuAu hijing events for creating pile-up
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Cuts on Daughters:||<1, TPC>10,PIXL=2,
triangle(N2)
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Cuts on Daughters:||<1, TPC>10,PIXL=2,
triangle(N3)
• Can we do anything substantial here ?• Any physics with the prototype?
What physics can be achieved ?
Charm cross-section Charm Rcp04/21/23 7Star Coll. Meeting, LBNL, Nov. 2011
TPC+PXL Efficiency/ghosting studies• BFC chain reconstruction and tracking (Sti) with only pixel
prototypes geometry = no material form SSD nor IST.• 350 hijing events, no pile up.• Vertex cuts :
– |Vreco -VMC| < 0.01 cm : good reconstruction vertex– |Vreco | < 10 cm
• Tracks cuts :– Reco TPC hits >15– |η|<1
• The definition is :– effSiGoodRc = # of tracks with 2 good pixels hit / # of tracks with 2 MC
pixel hits– Ghosting = # of tracks with 2 good pixels hits / # of tracks with 2
pixel hits
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TPC+PXL TPC+SSD+IST+PXL
Hijing – NO Pile-up
Good tracking efficiency (but no pile-up yet)
Efficiency with TPC+PXL prototype
04/21/23 9Star Coll. Meeting, LBNL, Nov. 2011
Ghosting with TPC+PXL prototypehttp://www.star.bnl.gov/protected/jetcorr/kapitan/HFT/upgr15_2010/productionQA/thin/CD1/single/
Hijing – NO Pile-up
TPC+PXL TPC+SSD+IST+PXL
Low Ghosting
04/21/23 10Star Coll. Meeting, LBNL, Nov. 2011
Next steps• Include pile-up events :
– Will increase single track ghosting
• Study reconstruction of D0 in this environment– So far it looks encouraging– We have two configurations for x-section and Rcp
measurements (if everything else goes well)– Please think of what physics YOU would like to do.
We will help you run the simulation.
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Back-up
SSD+PXL
04/21/23 Star Coll. Meeting, LBNL, Nov. 2011
Note : the x-axis scale changes with the layer
Pixel outer layer Pixel inner layerSSD layer
13
PXL only
04/21/23 Star Coll. Meeting, LBNL, Nov. 2011
Note : the x-axis scale changes with the layer
Pixel outer layer Pixel inner layerSSD layer
14
comments• With SSD :
– Residuals in r/phi for the outer pixel layer is better than w/o SSD
– Residuals in r/phi for the inner pixel are slightly better than w/o SSD
– Residuals in r/phi and Z are asymetric (due to the asymetric resolution of SSD) for both outer and inner layer
• w/o SSD:– Residuals in r/phi and Z are symmetric (due to
the same resolution of the pixel)
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Some precautions to make
1. Optimization wrt TPC sectors :
•TPC has 12 sectors
•PIXEL has 10 sectors
2. TPC sectors health during a physics run : we want to avoid to place a PXL sector matching a unhealthy TPC sector
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MRPC ToF MRPC ToF barrelbarrel
100% ready for run 100% ready for run 10 (now!)10 (now!)BBC
PMD
FPD
FMS
EMC barrel EMC End
Cap
DAQ100DAQ10000
FGT
Completed
Ongoing
MTD
R&DHFT
TPC
FHC
HLT