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Analysis of FMS and FTPC Correlations in Forward Jets for Sivers and Collins Effects

This report details the analysis conducted by Jim Drachenberg in 2009, focusing on the forward jets in the context of the STAR experiment. The aim is to differentiate between Sivers and Collins effects using FMS and FTPC correlations. This report also covers methodologies involving charged particle tracks and energy deposition, emphasizing the importance of precise measurements in understanding spin-parton transverse motion correlations. The findings suggest measurable asymmetries that advance our understanding of transversity and jet dynamics.

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Analysis of FMS and FTPC Correlations in Forward Jets for Sivers and Collins Effects

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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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