1 / 25

J/ ψ Production in p+p and d+Au Collisions at sqrt(S_NN) = 200 GeV at STAR

J/ ψ Production in p+p and d+Au Collisions at sqrt(S_NN) = 200 GeV at STAR. Chris Perkins UC Berkeley/Space Sciences Laboratory Stony Brook University For the STAR Collaboration 3/31/2009. Motivation – Mid-Rapidity | η | < 1. Possible Heavy Quarkonia production mechanism at RHIC energy

lilith
Download Presentation

J/ ψ Production in p+p and d+Au Collisions at sqrt(S_NN) = 200 GeV at STAR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. J/ψ Production in p+p and d+Au Collisions at sqrt(S_NN) = 200 GeV at STAR Chris Perkins UC Berkeley/Space Sciences Laboratory Stony Brook University For the STAR Collaboration 3/31/2009

  2. Motivation – Mid-Rapidity |η| < 1 • Possible Heavy Quarkonia production mechanism at RHIC energy • Insight into heavy flavor transport through the medium • Suppression and color screening • 2 and 3 component models and AdS/CFT model • Need Midrapidity d+Au measurements to disentangle Cold Nuclear Effects from Hot Nuclear Effects to better understand heavier systems (Au+Au, Cu+Cu) For additional details, see posters by Zebo Tang and Chris Powell Chris Perkins

  3. Motivation – Forward Rapidity • How can high-xF intrinsic heavy flavor happen? • Not from Gluon Splitting (extrinsic heavy flavor) • Heavy quarks are multi-connected to the valence quarks within a proton • Why does high-xF intrinsic heavy flavor matter? • Required for Diffractive Higgs production at the LHC • Provides a clear signal for Higgs production due to small background QED QCD • Can intrinsic heavy flavor expectations be tested experimentally? Phys.Rev. D73 (2006) 113005 • This is the first measurement of high-xF J/ψ at sqrt(s) > 62 GeV. Chris Perkins

  4. STAR Detector • J/ψ detected at both Forward and Midrapidity through its decay channel to e+e- (~6% BR). • Significant reduction in background electrons expected at Midrapidity due to material removal prior to 2008 Run. Forward Meson Spectrometer Previously occupied by SVT/SSD Chris Perkins

  5. Mid-rapidity d+AuRun 8 Chris Perkins

  6. Mid-rapidity Electron Identification • Low-pT : • dE/dx cut with TPC • p/E cut with BEMC Minbias Trigger See poster by Chris Powell • High-pT : • Higher pT electron: TPC + BEMC + BSMD • BEMC – fast trigger to enrich high-pT electron sample • BSMD – electron/hadron separation • Lower pT electron: TPC only • BEMC High-Tower Trigger • See poster by Zebo Tang Chris Perkins

  7. Low-PT Mid-rapidity J/ψ in d+Au • Efficiency corrected d+Au yield scaled by number of binary collisions and STAR p+p data • All centrality bins • Significance ~ 5.7 σ • Much better signal/background than previous low-pT J/ ψ measurements at STAR • Most central events (0-20%) • See poster by Chris Powell Chris Perkins

  8. High-PT Mid-rapidity J/ψ in d+Au • Significance = 13 σ Triggered pT Spectrum • Significant observation of signal – corrections for yield still in progress • Efficiency corrected pT spectrum still in progress • See poster by Zebo Tang Chris Perkins

  9. High-PT J/ψ -Hadron Correlations in d+Au 1) no near side correlation 2) strong near side correlation • Disentangle contributions to J/Psi production via correlations • From Monte Carlo studies, ref: PLB 200, 380(1988) and PLB 256,112(1991) • No significant near-side, high-pT J/ψ – hadron correlation in d+Au • May constrain feeddown contribution from B mesons • Can shed light on the J/ production mechanism • See poster by Zebo Tang Chris Perkins

  10. Forward Rapidity p+pRun 8 Chris Perkins

  11. Forward Meson Spectrometer (FMS) • 20x more acceptance than previous forward detectors at STAR • Full azimuthal coverage for 2.5 < η < 4 FPD FMS • Increased acceptance not only increases pion yields and kinematic range but also gives much higher geometric efficiency for high-xF J/ψ Geometric Efficiency: J/ψ xF Chris Perkins

  12. FMS Analysis Procedure • Gain Calibrations : Done iteratively on a cell-by-cell basis by associating di-photon invariant mass peak with high tower cell and adjusting to PDG value for π0 mass. • Trigger :FMS High Tower + BBC Minbias (~ 6 pb-1 Sampled Luminosity) • Reconstruction : • Resolution smeared for simulation events to match detector resolution • All other reconstruction procedures and cuts were the same for data and simulation • 3-Cluster Analysis Overview : • χC → J/ψ + γ → e+ + e- + γ • Motivated by analysis done on ω → π0 + γ presented by Andrew Gordon at Moriond (see display) • For each group of 3 clusters within an event, associate the pair with reconstructed mass closest to 3.097 GeV/c2 with the J/ψ and the remaining cluster with the γ. • Provides additional arm with which to eliminate background Chris Perkins

  13. FMS Minbias Simulations and Association Analysis • Fast J/ψ generator + full GEANT simulations • Data : • Plot includes < 1% of full data set • Simulation : • PYTHIA 6.222 + full GEANT simulations • 9.2 nb-1 Integrated Luminosity • Reconstructed quantities match generated quantities quite well • Full simulation models Mpair data very well Chris Perkins

  14. Forward p+p J/ψ – 2-Cluster Analysis Reconstructed 2-cluster invariant mass Fit with Gaussian + Polynomial Gaussian Fit Parameters: • μ = 3.083 ± 0.017 GeV/c2 • σ = 0.028 ± 0.011 GeV/c2 • χ2/d.o.f. = 24.6/25 • Significance from fit • 2.1 σ Background Simulation: • Needs more statistics • Normalized to integral of data • Cuts Applied: • E_pair > 60.0 GeV • Zγγ < 0.7 • Isolation Radius: • 0.5 Eta-Phi Chris Perkins

  15. Forward p+p J/ψ – 2-Cluster Analysis Reconstructed 2-cluster invariant mass • Fit with Gaussian + Offset • Gaussian Fit Parameters: • μ = 3.080 ± 0.020 GeV/c2 • σ = 0.082 ± 0.026 GeV/c2 • χ2/d.o.f. = 20.83/26 • Significance from fit • 4.5 σ • Cuts Applied: • E_pair > 60.0 GeV • Zγγ < 0.7 • Isolation Radius: • 0.4 Eta-Phi • pT_cluster > 1.0 GeV/c Chris Perkins

  16. Forward p+p J/ψ – 3-Cluster Analysis • Reconstructed invariant mass of candidate χC → J/ψ + γ events • Peak Counts = 8.40 ± 2.88 • 2.9 σ Significance • μ = 2.97 ± 0.025 GeV • σ = 0.070 ± 0.025 GeV • χ2/d.o.f. = 0.7 with 14 points fit. • Significance depends on background model • 2.9 σ significance with currently estimated background. Chris Perkins

  17. Summary • Mid-Rapidity : • Significant signal reported for high-pT and low-pT J/ψ in d+Au • RdAu consistent with Ncoll scaling for low-pT J/ψ • No significant near-side, high-pT J/ψ – hadron correlation in d+Au • Can constrain feeddown from B mesons • Forward Rapidity : • Significant signal reported for p+p collisions using 2-cluster analysis and new 3-cluster analysis • Provides first look at high-xFχC → J/ψ + γ feeddown • First observations of high-xF J/ψ at sqrt(s) > 62 GeV Chris Perkins

  18. Outlook • Mid-Rapidity : • High-pT : • Efficiency corrections, RdAu, constrain B meson feeddown • Low-pT : • J/ψ mass spectrum in different centrality bins • Forward Rapidity : • Further analysis needed for p+p yield measurement : • Efficiency & Luminosity corrections • d+Au : • Nuclear effects in forward direction – new territory • 500 GeV : • Measure Upsilon and compare mass scaling • Towards understanding virtual heavy quark content in the proton Chris Perkins

  19. Backup Slides Chris Perkins

  20. Mid-Rapidity Low-pT Total Efficiency Chris Perkins

  21. J/ψ Association Analysis Chris Perkins

  22. Field Effects • Does the signal survive the field? • Radial and Azimuthal fields impart impulses in the Φ direction • These impulses are small and in opposite directions (they nearly cancel each other) • Field effects on our signal are small Chris Perkins

  23. Forward p+p J/ψ – 2-Cluster Analysis Reconstructed 2-cluster invariant mass Fit with Gaussian + Polynomial Gaussian Fit Parameters: • μ = 3.083 ± 0.017 GeV/c2 • σ = 0.028 ± 0.011 GeV/c2 • χ2/d.o.f. = 24.6/25 • Significance from fit • 2.1 σ Background Simulation: • Needs more statistics • Normalized to integral of data • Cuts Applied: • E_pair > 60.0 GeV • Zγγ < 0.7 • Isolation Radius: • 0.5 Eta-Phi Chris Perkins

  24. Forward p+p J/ψ – 2-Cluster Analysis Reconstructed 2-cluster invariant mass • Fit with Gaussian + Offset • Gaussian Fit Parameters: • μ = 3.080 ± 0.020 GeV/c2 • σ = 0.082 ± 0.026 GeV/c2 • χ2/d.o.f. = 20.83/26 • Significance from fit • 4.5 σ • Cuts Applied: • E_pair > 60.0 GeV • Zγγ < 0.7 • Isolation Radius: • 0.4 Eta-Phi • pT_cluster > 1.0 GeV/c Chris Perkins

  25. Mid-rapidity Cuts • Low-pT – TPC + BEMC • pT track > 1 GeV/c • 3 < p < 4 GeV/c tracks • |nσe| < 3, |nσp| > 2.5, |nσpi| > 2.5, |nσK| > 2.5 • p/E < 2.3 • High-pT – • nσe > -2 Chris Perkins

More Related