1
Scan of DCA resolution - run 7
• MinBias
• Production2
• Issues
•Improvement for DCA resolution estimation :
•Dependence with η•Dependence with particle Id
2
Cuts, files used• get_file list used :<input URL="catalog:star.bnl.gov?
production=P08ic,trgsetupname=2007&myprod;,daynumber=&myday;,filetype=daq_reco_mudst,tpc=1,ssd=1,svt=1,sanity=1,filename~physics,storage=hpss" nFiles="1000" />
• Cuts • |zvertex |<5 cm : to have a clean sample• TPC hits> 15• || in SSD range (~ ||<1.2)• pT >0.1
• Fit function :
• Traduce the (detector+alignment) resolution and Multiple Coulomb Scattering
• Fit done for 0.2 < 1/P < 5• In the next plots, x-axis = day number (day 110 = April, 20th, day 170 =
June,19th)• DCA resolution@1GeV (for tracks with N=2,3,4) vs day number to study
stability of DCA resolution
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MinBias
4
Production2
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Issue• Not really an issue but just the way how to get the proper
estimation of the DCA resolution (using adapted cuts,etc …)
• Example : MinBias for day132
• Fit is not working for low momentum ; mostly always for SSD only
• The fit uses a gaussian distribution : for low momentum, there are tails in the DCA distribution
• (recall : my goal is to look at all tracks, but in physics analysis, we will use tracks with N silicon >1(2) to include precision from SVT)
•Reasons : 1.there is no track cuts with respect the acceptance of SSD-SVT so it’s a - yield integrated ; Tracks with large eta may degrade the resolution2. To use properly the fit function, need the beta factor ;it means to know the mass (=particle id)
DCA resolution vs η (SSD only)
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•For very low pT(yellow), the DCA resolution is not good•For low pT (<.6), we see some detector edges effect the dca resolution is degraded•For pT~1, we reach the SSD resolution uniformly in η
DCA resolution vs η (SSD+SVT(1))
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•For very low pT(yellow), the DCA resolution still presents edge effects •When increasing pT~ , the DCA resolution is uniform (flat) at ~ 500 μm
DCA resolution vs η(SSD+SVT(>1))
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•For very low pT(yellow), the DCA resolution still presents edge effects •When increasing pT~ , the DCA resolution is uniform (flat) at ~ 250 μm
1.DCA resolution vs η(SSD only)
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2.DCA resolution for pions
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• selection of π with :•|Nσπ| < 2•Rejection of K with |NσK| < 2
•The X-axis is then 1/βPThe fit is in better agreement with the data points up to 1/βP = 3.5
3.DCA resolution from datapoints
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• another solution to estimate the DCA resolution@1GeV is to take directly the data points instead of the fit•For the SSD, ~ 100 μm of difference with the fit
DATA FIT
summary• Production2 presents a better DCA resolution vs
time for the first part of the run (until day 140), only for tracks with N silicon =1 (which is the SSD point)
• Tracks with N>1 benefits from the SVT points precision : the DCA resolution vs time is stable for this cases
• DCA resolution depends (at low pT) with the pseudo rapidity
• Investigate other ways to get proper evaluation/improvements of the DCA resolution
Pdf files
• The details are here :– Minbias per run:http://drupal.star.bnl.gov/STAR/system/files/test_histo_MB_allDetails.pdf
– Production2 per run :http://drupal.star.bnl.gov/STAR/system/files/test_histo_P2_allDetails.pdf
– Minbias, day110 : DCA resolution per eta-phi slices:
http://drupal.star.bnl.gov/STAR/system/files/
Eta_Phi_histo_Allsilicon_noerrorsbar.pdf