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FMS+FTPC Analysis Status Report

FMS+FTPC Analysis Status Report. Jim Drachenberg 2009 STAR Analysis Meeting. OUTLINE. Context: Forward Jets FMS+FTPC Correlations Understanding FTPC Tracks Moving Forward. For more info: http://www.star.bnl.gov/protected/spin/drach/Run8FMS/. Separating Sivers and Collins Effects.

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FMS+FTPC Analysis Status Report

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  1. FMS+FTPC AnalysisStatus Report Jim Drachenberg 2009 STAR Analysis Meeting OUTLINE • Context: Forward Jets • FMS+FTPC Correlations • Understanding FTPC Tracks • Moving Forward For more info: http://www.star.bnl.gov/protected/spin/drach/Run8FMS/

  2. Separating Sivers and Collins Effects Sivers mechanism:asymmetry in the forward jet or gproduction Collins mechanism:asymmetry in the forward jet fragmentation SP SP kT,q p p p p Sq kT,π Sensitive toproton spin–partontransverse motioncorrelations Sensitive to transversity To discriminate between the two effects we need to go beyond π0 detection tojetsordirect photons

  3. FMS+FTPC Jets FTPC: charged particle tracks FMS: energy deposition Look at jet asymmetries in a region with large π0 asymmetries

  4. FMS+FTPC Jets FTPC: charged particle tracks FMS: energy deposition As a first step, I look at correlations between FTPCtracks and FMS energy deposition

  5. FMS+FTPC Correlations • Obtain list of clusters from FMS • For two highest energy clusters in a module, reject if 0.055 < m< 0.215 GeV • Keep clusters with Ecluster > 5 GeV (similar studies with Ecluster < 2 GeV) • Assign to specific cell based on x-y

  6. FMS+FTPC Correlations • Obtain list of clusters from FMS • For two highest energy clusters in a module, reject if 0.055 < m< 0.215 GeV • Keep clusters with Ecluster > 5 GeV (similar studies with Ecluster < 2 GeV) • Assign to specific cell based on x-y • For each cluster, loop over west-FTPC primary tracks with pT > 0.8 GeV/c and p > 10 GeV/c

  7. FMS+FTPC Correlations • Obtain list of clusters from FMS • For two highest energy clusters in a module, reject if 0.055 < m< 0.215 GeV • Keep clusters with Ecluster > 5 GeV (similar studies with Ecluster < 2 GeV) • Assign to specific cell based on x-y • For each cluster, loop over west-FTPC primary tracks with pT > 0.8 GeV/c and p > 10 GeV/c • Approximate FTPC track projection as a straight line, out to zFMS = 734.1 cm (Spin 2008 value)

  8. FMS+FTPC Correlations • Obtain list of clusters from FMS • For two highest energy clusters in a module, reject if 0.055 < m< 0.215 GeV • Keep clusters with Ecluster > 5 GeV (similar studies with Ecluster < 2 GeV) • Assign to specific cell based on x-y • For each cluster, loop over west-FTPC primary tracks with pT > 0.8 GeV/c and p > 10 GeV/c • Approximate FTPC track projection as a straight line, out to zFMS = 734.1 cm (Spin 2008 value) • Calculate xtrack - xcluster and ytrack - ycluster

  9. FMS+FTPC Correlations The end result: clear correlations between projected FTPC track position at zFMS and FMS energy clusters • Consistent geometry • (even more?) Confidence in mapping

  10. FMS+FTPC Correlations Charge-dependent effects are also evident denontes the general trend from -+ charge Typical separation distance ~ 2 cm

  11. Understanding FTPC Tracks Now that correlations are established, focus on understanding FTPC tracks and tuning cuts First, focus on pile-up looking at  spectra

  12. Understanding FTPC Tracks Out of the box... For 9967 minbias events (low scaler rate runs), Ntracks/Nevents ~ 5.02 As a rough estimate… dN/d ~ (Ntracks/Nevents) / (avg. FTPC tracking efficiency) / (FTPC acceptance) Assume 10% loss from sector boundaries, electronics knocking out 1/6 sectors, and FTPC acceptance of ~0.7 units of … dN/d ~ (Ntracks/Nevents) / 0.52 Compare… dN/dFTPC ~ 9.65 to dN/dUA5 ~ 2 for  ~ 3.2

  13. Understanding FTPC Tracks 9065062 9065073 9066015 Run <Ratescaler> 65062 9.5k 65073 7.8k 66015 6.5k To get idea of pile-up: chose three runs with varying RICH scaler (ZDC coincidence) values from the FMS-slow data Note these are much higher in rate than previous minbias run

  14. Understanding FTPC Tracks 65062 With cuts |zvertex| < 50 cm and Nfit/Nposs > 0.59 Run: 9065062 9065073 9066015 Ratescaler: 9.5k 7.8k 6.5k Ntracks/Nevents: 15.0 13.6 12.2 dN/d: 28.9 26.1 23.4 Extrapolating to Rate = 0: ‘physics yield’ of ~6.24 tracks/event or dN/d ~ 12 (lots of pile-up!) Next, I’ll consider a cut on DCA 65073 66015

  15. Understanding FTPC Tracks I make two assumptions: 1) Ntracks = Nsignal + Nbackground 2) Nbackground = const*Ratescaler Nsignal = Nlow rate - ((Ratehigh/Ratelow)-1)-1 *(Nhigh rate - Nlow rate) Where N is, say, the eta distribution…

  16. Understanding FTPC Tracks If not rate-dependent I make two assumptions: 1) Ntracks = Nsignal + Nbackground 2) Nbackground = const*Ratescaler Nsignal = Nlow rate - ((Ratehigh/Ratelow)-1)-1 *(Nhigh rate - Nlow rate) Where N is, say, the eta distribution… Pure background

  17. Understanding FTPC Tracks I normalize the number of events passing the vertex cut Then subtract the lowrate run from the highrate run Then, scaling the pure-background distribution by the rate factor, I subtract the result from the lowrate run The result is our “signal”

  18. Understanding FTPC Tracks Looking at pT bins, I assign cuts: pT range (GeV/c) DCA cut (cm) 0.0 - 0.5 < 2.5 0.5 - 1.5 < 1.5 > 1.5 < 1.0 Looking at pT > 3 GeV/c, it appears a maximum pT cut may be appropriate

  19. Understanding FTPC Tracks 63126 With cuts |zvertex| < 50 cm, Nfit/Nposs > 0.59, and the pT-dependent DCA cut Run: 9063126 9063142 9064011 Ratescaler: 8.3k 6.3k 4.9k Ntracks/Nevents: 2.83 2.49 2.41 dN/d: 5.44 4.79 4.64 Extrapolating back to Rate = 0: ‘physics yield’ of ~1.75 tracks/event or dN/d ~ 3.4 Larger than UA5, but FMS-trigger might have something to do with it 63142 64011

  20. Understanding FTPC Tracks Minbias data also shows improvement after the DCA cut w/o Cutwith Cut Ntracks/Nevents:4.40 1.52 dN/d: 8.46 2.93 -distribution is less ‘peaked’ and - is more uniform Again, larger than UA5, but BBC condition may play role

  21. Understanding FTPC Tracks From the DCA study, it was implied a maximum pTcut may be appropriate

  22. Understanding FTPC Tracks Follow the approach from the DCA study It appears the background distribution approaches the low-rate distribution around pT ~ 2 GeV/c Perhaps a cut at pT 3 or 4 GeV/c is appropriate

  23. Moving Forward • Plenty to do! • vertex issues, e.g. deal with “bad” vertices • Reference other FTPC analyses (e.g. Run 8 d+Au FTPC-E), for more cuts that might be applicable • For FMSslow: begin to look at Deta-Dphi distributions between FTPC tracks and highest energy FMS photon cluster for hint of a jet cone • etc.

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