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Improving DCA Resolution Estimation in MinBias Production2

This study focuses on improving the estimation of DCA (Distance of Closest Approach) resolution in MinBias Production2. Information such as dependence on η, particle ID cuts, and the use of specific files are explored. The analysis includes applying cuts, examining track properties, employing fit functions, and evaluating resolution stability over time. Notable findings reveal the impact of low momentum and the need for proper track selection based on SSD and SVT points. Various factors affecting DCA resolution, along with solutions for enhancement, are investigated. Key results and comparisons offer insights into resolution variations and optimizations. For comprehensive details and data points, relevant PDF files are provided for reference.

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Improving DCA Resolution Estimation in MinBias Production2

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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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