1. 1 Scan of DCA resolution - run 7 MinBias Production2 Issues Improvement for DCA resolution estimation : Dependence with η Dependence with particle Id

2. 2 Cuts, files used get_file list used : Cuts |z vertex |<5 cm : to have a clean sample TPC hits> 15 |  | in SSD range (~ |  |<1.2) p T >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. 3 MinBias

4. 4 Production2

5. 5 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 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) 6 For very low pT(yellow), the DCA resolution is not good For low p T (<.6), we see some detector edges effect  the dca resolution is degraded For p T ~1, we reach the SSD resolution uniformly in η

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

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

9. 1.DCA resolution vs η(SSD only) 9

10. 2.DCA resolution for pions 10 selection of π with : |Nσ π | < 2 Rejection of K with |Nσ K | < 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 11 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 DATAFIT

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 p T ) 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_noer rorsbar.pdf