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Scan of DCA resolution - run 7

• MinBias

• Production2

• Issues

•Improvement for DCA resolution estimation :

•Dependence with η•Dependence with particle Id

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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