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Scan of DCA resolution - run 7

Scan of DCA resolution - run 7. MinBias Production2 Issues Improvement for DCA resolution estimation : Dependence with η Dependence with particle Id. Cuts, files used. get_file list used :

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Scan of DCA resolution - run 7

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  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

  3. MinBias

  4. Production2

  5. Issue • 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) • Not really an issue but just the way how to get the proper estimation of the DCA resolution (using adapted cuts,etc …) • Reasons : • 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 resolution 2. To use properly the fit function, need the beta factor ;it means to know the mass (=particle id)

  6. DCA resolution vs η (SSD only) • 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

  7. DCA resolution vs η (SSD+SVT(1)) • For very low pT(yellow), the DCA resolution still presents edge effects • When increasing pT~ , the DCA resolution is uniform (flat) at ~ 500 μm

  8. DCA resolution vs η(SSD+SVT(>1)) • For very low pT(yellow), the DCA resolution still presents edge effects • When increasing pT~ , the DCA resolution is uniform (flat) at ~ 250 μm

  9. 1.DCA resolution vs η(SSD only)

  10. 2.DCA resolution for pions • selection of π with : • |Nσπ| < 2 • Rejection of K with |NσK| < 2 • The X-axis is then 1/βP •  The fit is in better agreement with the data points up to 1/βP = 3.5

  11. 3.DCA resolution from datapoints DATA FIT • 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

  12. 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

  13. 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

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