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Rapidity dependency of azimuthal correlations for pp and dAu

Rapidity dependency of azimuthal correlations for pp and dAu. Xuan Li (BNL&SDU) STAR Collaboration meeting (BNL, Nov 2010). Outline. Motivation Data analysis cluster finder introduction π 0 like events selection and data & simulation comparison Preliminary correlation results

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Rapidity dependency of azimuthal correlations for pp and dAu

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  1. Rapidity dependency of azimuthal correlations for pp and dAu Xuan Li (BNL&SDU) STAR Collaboration meeting (BNL, Nov 2010) Xuan Li

  2. Outline • Motivation • Data analysis • cluster finder introduction • π0 like events selection and data & simulation comparison • Preliminary correlation results • Summary & To do Xuan Li

  3. Motivation • To probe nuclear gluon density at low x. Rapid rise of the gluon density at low-x evident from F2(x)/lnQ2 at fixed x (Prytz relation) Can’t increase indefinitely. Saturation? Proton gluon density At a given x, nuclear (mass number A) gluon density ≈ A1/3* nucleon gluon density. And we lack data below x=0.02 for nuclear [Phys. Rev. C70 (2004)044905, hep-ph/0308248]. Xuan Li Fixed Target Experiments

  4. Motivation • How to access low X gluon. • Large rapidity p production (hp~4) probes asymmetric partonic collisions. • Mostly high-x valence quark + low-x gluon • 0.3 < xq< 0.7 • 0.001< xg< 0.1 , this is broad distribution for gluon. • If we measure two jets, we will limit the measured gluon x range. Forward di-jets are more sensitive to low x gluon. Xuan Li

  5. Motivation • Test the phase boundary at fixed Q2. τ related to rapidity of produced hadrons. Fix PT , look through different x region (Iancuand Venugopalan, hep-ph/0303204) Fix Pt at forward rapidity π0, and vary the rapidity of associated π0. Vary the Pt to study the boundary. Xuan Li

  6. Motivation • Provide direct sensitivity to gluon density at 0.001< x < 0.02. FMS-BEMC(TPC) correlation PT(FMS)>2.5GeV/c 1.5GeV/c<PT(BEMC/TPC)<PT(FMS) PT(FMS)>2.0GeV/c 1.0GeV/c<PT(BEMC/TPC)<PT(FMS) Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering. arXiv:0907.3473 Xuan Li

  7. Motivation • Provide direct sensitivity to gluon density at 0.001< x < 0.02. FMS-FMS correlation Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering. arXiv:1005.2378 Xuan Li

  8. Motivation • Provide direct sensitivity to gluon density at 0.001< x < 0.02. FMS-EEMC correlation ? Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering. Xuan Li

  9. π0 decay kinematics Proton (Gold) Proton (Deuteron) • Run8 STAR geometry π0 decay into 2 photons. Assuming the energy of π0 is 3GeV to 10GeV, then the separation of photons in EEMC is from 25.2cm to 7.6 cm. Xuan Li

  10. FMS π0 triggered event • Within the FMS triggered data, selecting events where di-photon invariant mass is less than 0.2GeV/c2 and Pt is larger than 2.5 GeV/c. For example, with pp FMS triggered data. • Primary vertex associated with BBC coincidence requirements. Xuan Li

  11. Introduction to cluster finder • BEMC (EEMC) geometry EEMC η range [1.08,2.0], BEMC η range [-1,1]. X(Y) Y Z X EEMC BEMC ϕ ϕ η η Xuan Li

  12. Event display • Run 8 pp fms triggered data. Cluster is threshold bounded group of towers. The energy threshold for the BEMC tower is 70MeV, and for EEMC is ADC pedestal plus 4sigma. Sorting the tower energy, then add in the tower near the high tower to construct cluster. cluster BEMC tower energy deposited without energy threshold. cluster EEMC BEMC Xuan Li

  13. EEMC cluster properties in pp data • Single cluster tower multiplicity, energy, η and φ. 1 2 3 4

  14. BEMC cluster properties in pp data • Single cluster tower multiplicity, energy, η and φ.

  15. π0 like event (di-cluster) • PP part for BEMC η>=0 part. (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, require cluster detector η in [0,0.9].. π0 peak in BEMC di-clusters. (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, reuire cluster detector η in [0,0.9]. (3) Ratio of leading tower energy over cluster energy > 0.9 (4) Zγγ < 0.7 leading tower energy over cluster energy in leading cluster Zγγ is energy sharing between two clusters Mass of di-clusters

  16. π0 like event (di-cluster) • PP part for EEMC (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, require cluster detector η in [1.1,1.9].. π0 peak in EEMC di-clusters. (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, reuire cluster detector η in [1.1,1.9]. (3) Ratio of leading tower energy over cluster energy > 0.9 (4) Zγγ < 0.7 leading tower energy over cluster energy in leading cluster Zγγ is energy sharing between two clusters Mass of di-clusters

  17. π0 like event (di-cluster) • dAu part for BEMC η>=0 part. (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, require cluster detector η in [0,0.9].. (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, reuire cluster detector η in [0,0.9]. (3) Ratio of leading tower energy over cluster energy > 0.9 (4) Zγγ < 0.7 π0 peak in BEMC di-clusters. Zγγ is energy sharing between two clusters leading tower energy over cluster energy in leading cluster Mass of di-clusters

  18. π0 like event (di-cluster) • dAu part for EEMC (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, require cluster detector η in [1.1,1.9].. π0 peak in EEMC di-clusters. (1) 1.25GeV/c < Pt<2.5GeV/c (2) Fiducial Volume cut, reuire cluster detector η in [1.1,1.9]. (3) Ratio of leading tower energy over cluster energy > 0.9 (4) Zγγ < 0.7 leading tower energy over cluster energy in leading cluster Zγγ is energy sharing between two clusters Mass of di-clusters

  19. π0 events in the EEMC single cluster? • Assuming the tower is zero massed, • Assuming the leading tower, sub-leading tower as the photon candidates in the EEMC single cluster, • Dγγ is defined as the separation between the photons which is projected in the EEMC detector. X(Y) Y Dγγ Dγγ γ1 γ2 X Z Xuan Li

  20. Simulated π0 decay kinematics • Projection on the EEMC, with the π0 Pt in [1.25GeV/c, 2.5GeV/c] and Zγγ<0.7 cuts. For FMS π0 events, Cuts on the single cluster is 1.25GeV/c<Pt<2.5GeV/c Zγγ < 0.7 Dγγ VS η of π0 Dγγ VS Zγγ Most of the π0 events are in EEMC single clusters. Xuan Li

  21. π0 like event (single cluster) • PP part for EEMC 1.25GeV/c < Pt<2.5GeV/c (1) 1.25GeV/c < Pt<2.5GeV/c. (2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85]. (3) Zγγ < 0.65 π0 candidates Zγγ is energy sharing between leading two towers. Leading and sub-leading tower energy over cluster energy Mass of single cluster

  22. π0 like event (single cluster) • dAu part for EEMC 1.25GeV/c < Pt<2.5GeV/c (1) 1.25GeV/c < Pt<2.5GeV/c. (2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85]. (3) Zγγ < 0.65 π0 candidates Zγγ is energy sharing between leading two towers. Leading and sub-leading tower energy over cluster energy Mass of single cluster

  23. MB data and simulation comparison • EEMC pp MB single cluster simulation. Simulation Simulation ratio is Leading and sub -leading tower energy over cluster energy. Zγγ is energy sharing between leading two towers. Data Data Xuan Li

  24. MB data and simulation comparison • EEMC pp MB single clusterpropeties. MB simulation MB data Xuan Li

  25. MB data and simulation comparison • EEMC pp MB single cluster invariant mass. Simulation Data (1) 1.25GeV/c < Pt<2.5GeV/c. (2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85]. (3) Zγγ < 0.65 scaledifferent Xuan Li

  26. MB data and simulation comparison • EEMC dAu MB single cluster invariant mass. Simulation Data (1) 1.25GeV/c < Pt<2.5GeV/c. (2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85]. (3) Zγγ < 0.65 scale different Xuan Li

  27. Azimuthal correlation (FMS-BEMC) • FMS photon pair Pt > 2.5GeV/c and mass<0.2 GeV/c2. BEMC di-cluster 1.25GeV/c < Pt < 2.5GeV/c and mass<0.2GeV/c2. Uncorrected Coincidence Probability (radian-1) Width 0.710 ± 0.030 Width 0.733± 0.041 Fms triggered pp data Fms triggered dAu data Xuan Li

  28. Azimuthal correlation (FMS-BEMC) • FMS photon pair Pt > 2.0GeV/c and mass<0.2 GeV/c2. BEMC di-cluster 1.0GeV/c < Pt < 2.0GeV/c and mass<0.2GeV/c2. Uncorrected Coincidence Probability (radian-1) Width 0.815 ± 0.019 Width 0.752± 0.031 Fms triggered pp data Fms triggered dAu data Xuan Li

  29. Azimuthal correlation (FMS-EEMC) • FMS photon pair Pt > 2.5GeV/c and mass<0.2 GeV/c2. EEMC di-cluster 1.25GeV/c < Pt < 2.5GeV/c and mass<0.2GeV/c2. Uncorrected Coincidence Probability (radian-1) Width 0.961 ± 0.127 Width 0.817 ± 0.196 Fms triggered pp data Fms triggered dAu data Xuan Li

  30. Azimuthal correlation (FMS-EEMC) • FMS photon pair Pt > 2.0GeV/c and mass<0.2 GeV/c2. EEMC di-cluster 1.0GeV/c < Pt < 2.0GeV/c and mass<0.2GeV/c2. Uncorrected Coincidence Probability (radian-1) Width 0.833 ± 0.048 Width1.032± 0.179 Fms triggered pp data Fms triggered dAu data Xuan Li

  31. Azimuthal correlation (FMS-EEMC) • FMS photon pair Pt > 2.5GeV/c and mass<0.2 GeV/c2. EEMC single cluster 1.25GeV/c < Pt < 2.5GeV/c and mass<0.2GeV/c2. Uncorrected Coincidence Probability (radian-1) Width 0.731 ± 0.021 Width 0.935 ± 0.061 Fms triggered pp data Fms triggered dAu data Xuan Li

  32. Azimuthal correlation (FMS-EEMC) • FMS photon pair Pt > 2.0GeV/c and mass<0.2 GeV/c2. EEMC single cluster 1.0GeV/c < Pt < 2.0GeV/c and mass<0.2GeV/c2. Uncorrected Coincidence Probability (radian-1) Width 0.840 ± 0.015 Width1.039± 0.053 Fms triggered pp data Fms triggered dAu data Xuan Li

  33. Summary • To find the 3rd point from FMS-EEMC azimuthal correlation to approach gluon density at low x. • BEMC di-cluster π0 like correlation results are consistent with Ermes’s correlation results. • There are π0 like hints in the EEMC tower clusters. To do • To add in ESMD information to get clearer π0 events. • Need suggestions and help for he ESMD calibration. • Work on the Xuan Li

  34. Backup Xuan Li

  35. Motivation • Provide direct sensitivity to gluon density at 0.001< x < 0.02. FMS-FMS correlation FMS-EEMC correlation FMS-BEMC(TPC) correlation Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering. Xuan Li

  36. Event display • Run 8 dAufms triggered data. EEMC BEMC Xuan Li

  37. Cluster width definition • BEMC • Unfold the barrel, and put in the Rϕ, Z plane. X(Y) Z Rϕ Small width R ϕ Large width Z Xuan Li

  38. Cluster width definition • EEMC • In xy plane. Y Y X Small width Large width X Xuan Li

  39. dAu FMS triggered data • FMS di-photon invariant mass. With FMS photon pair which has mass less than 0.2GeV/c2 and Pt larger than 2.5 GeV/c. Xuan Li

  40. EEMC cluster property in dAu data • Single cluster tower multiplicity, energy, η and φ. Xuan Li

  41. BEMC cluster property in dAu data • Single cluster tower multiplicity, energy, η and φ. Xuan Li

  42. π0 like event (single cluster) • EEMC pp fms triggered single cluster mass. Xuan Li

  43. π0 like event (single cluster) • EEMC dAufms triggered single cluster mass. Xuan Li

  44. MB data and simulation comparison • EEMC dAu MB single cluster simulation. Simulation Simulation ratio is Leading and sub -leading tower energy over cluster energy. Zγγ is energy sharing between leading two towers. Data Data Xuan Li

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