1 / 18

STAR Heavy Flavor Capabilities in the RHIC II Era

This paper discusses the capabilities of the STAR detector at RHIC II for studying heavy flavor physics, including open charm flow, chemical equilibration, heavy quark energy loss, temperature and density effects, and PID capabilities.

gfoos
Download Presentation

STAR Heavy Flavor Capabilities in the RHIC II Era

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. STAR Heavy Flavor Capabilities in the RHIC II Era James C. Dunlop Brookhaven National Laboratory RHIC II Science Workshop, Apr. 2005

  2. Kinetic Thermalization: Open Charm Flow F. Laue et al, nucl-ex/0411007 Test mechanism for thermalization: charm heavy, so needs many collisions to reach kinetic equilibrium. Current measurements: indirect from electrons, and so suffer from large statistical and systematic errors Need direct open charm reconstruction (at low pT)! RHIC II Science Workshop, Apr. 2005

  3. Chemical Equilibration: Open Charm Yields • No thermal creation of c or b quarks; m(c) = 1.1GeV >> T • c and b quarks interact with lighter quarks  thermal recombination ? • Ds+/D0 very sensitive • J/y: suppression vs recombination ? • Precision necessary for J/y, dilepton baseline RHIC II Science Workshop, Apr. 2005

  4. Heavy Quark Energy Loss • total energy loss comparable but smaller than in the massless case Armesto, Salgado, Wiedemann, PRD69 (2004) 114003 B.W. Zhang, E. Wang, X.N. Wang, PRL93 (2004) 072301 Djordjevic, Gyulassy, NPA733 (2004) 265 Flavor dependence of coupling: Less radiation, and so less suppression, for massive objects • vacuum radiation suppressed in the dead-cone q < m/E Dokshitzer, Kharzeev, PLB 519 (2001) 199 • medium-induced radiation fills the dead-cone Armesto, Salgado, Wiedemann, PRD69 (2004) 114003 massive dI/dk2 massless dead cone k2 RHIC II Science Workshop, Apr. 2005

  5. Temperature and density: Onium RHIC • Yields and Spectra of the onium states (J/, Upsilon, and excited states) to measure the • thermodynamics of deconfinement through varying dissociation temperatures • To deeply probe the plasma through studies of (Debye) screening length l ~ 1 /gT and map in-medium QCD potential • Study vs. Pt • Study vs. centrality • Study in lighter systems • Study vs. a control ( the Upsilon) • Upsilon rate ~ 10-3 J/Y Yield in 10 weeks of AuAu running at design luminosity This physics requires luminosity upgrade 10 RHIC II Science Workshop, Apr. 2005

  6. The STAR Detector Magnet Coils Central Trigger Barrel (CTB) ZCal Time Projection Chamber (TPC) Year 2000 Barrel EM Cal (BEMC) Silicon Vertex Tracker (SVT)Silicon Strip Detector (SSD) FTPCEndcap EM CalFPD TOFp, TOFrYear 2001+ RHIC II Science Workshop, Apr. 2005

  7. STAR (Central) Coverage p Endcap EMC Barrel EMC Tracking (TPC,SVT,SSD,HFT) Tracking (TPC,SVT,SSD) Tracking (degraded) f TOF -p -1 0 1 2 h RHIC II Science Workshop, Apr. 2005

  8. Upgrades relevant to heavy flavor • Barrel Electromagnetic Calorimeter (EMC) • Current ¾ barrel will be instrumented to full azimuthal coverage, -1 < h < 1, for next RHIC run • Barrel Time of Flight (TOF) • Current prototype patches to be upgraded to full azimuth, -1 < h < 1. • Project is in President’s budget. • Forward Meson Spectrometer (FMS) • Full azimuthal EM Calorimetry 2.5 < h < 4.0 • Possibility of charm measurements in this region • Proposal submitted to NSF • Data acquisition upgrade (DAQ1000) • Upgrade TPC readout an order of magnitude, ~double effective Luminosity • Heavy Flavor Tracker (HFT) • High precision (<10 um) measurements for displaced vertices RHIC II Science Workshop, Apr. 2005

  9. PID Capabilities I: TOF and TPC Hadron identification: STAR Collaboration, nucl-ex/0309012 PRL 94 (2005) 062301 Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!! RHIC II Science Workshop, Apr. 2005

  10. PID Capabilities II: EMC • TPC as a candidate selector • dE/dX for p > 1.5 GeV/c • Electrons can be discriminated from hadrons up to >8 GeV/c • EMC • Towers • p/E for electron and hadron candidates • p is the track momentum • E is the tower energy • Peak position depends on the distance to the center of the tower • SMD (Shower Max Detector) • Shower cluster type • Type 3 = both SMD planes • Track-SMD cluster distance • Hadrons have a wider distribution • e/h discrimination power ~ 105 • TPC ~ 500 • EMC ~ 250 RHIC II Science Workshop, Apr. 2005

  11. PID Capabilities III: Direct Reconstruction PRL 94 (2005) 062301 • Direct reconstruction using Minv • Uncertainty limitation is combinatoric background TOF: cleanly identify daughters HFT: identify displaced vertices NEvents for 3s D0→Kp Signal Number of Au+Au events required for 3s signal. FOM=reduction in Nevents from TOF RHIC II Science Workshop, Apr. 2005

  12. More demanding reconstruction D0→ K p using HFT, 50M events • From only 50M events, additional rejection power of HFT leads to extremely small uncertainties in both spectra and v2 • Charm quark flow can be fully addressed with this upgrade Also: Measure Ds f + p RHIC II Science Workshop, Apr. 2005

  13. Triggering Capabilities from the EMC • EMC provides a Level 0 high-pT electron trigger • Runs for every RHIC crossing (10 MHz) • Multiple ET thresholds in prescale ladder • For this plot, 2.5 and 5 GeV • Enhancement proven to be >1000 for pT > 5 GeV/c • More sophisticated triggers: • Upsilon • Limited only by luminosity • ~15K Upsilon in 30 nb-1 • J/Psi • Needs TOF for discrimination in Au+Au RHIC II Science Workshop, Apr. 2005

  14. DAQ Limitations (and their removal) • Current limit from TPC front-end electronics is 100 Hz • Limits size of datasets • ~100M events/nominal RHIC run • Affects available luminosity • Deadtime scales linearly with rate • 50 Hz = 50% dead, i.e. 50% drop in luminosity available to rare triggers: usual compromise • Proposal to replace TPC electronics with ALICE chips to increase maximum rate by order of magnitude • Rate of events to disk increased (though timely processing of events on disk is an issue) • Removes deadtime: effective doubling of RHIC luminosity RHIC II Science Workshop, Apr. 2005

  15. Photonic Background PRC 70 (2004) 044902 • STAR reconstructs p0, g from conversions in material inside the TPC • Crucial cross-check of material budget: • Sweet spot: ~6% radiation length from vertex to TPC • Removal efficiency from low Minv cut ~60% RHIC II Science Workshop, Apr. 2005

  16. Photonic Background II • Current methods • Photonic electrons dominate below ~1 GeV/c • Clear nonphotonic signals above g e+e- Future capabilities: Large suppression by HFT Enabling technology for low-mass dilepton measurements RHIC II Science Workshop, Apr. 2005

  17. b quark measurements • B mesons accessible using semileptonic decay electrons • Issue: nonphotonic electrons will be measured, but what is the real fraction of these from B? Highly model dependent • Using displaced vertex tag may be the ONLY reliable method pT ~ 15 GeV/c: s (Au+Au) ~ 20mb/Gev 30 nb-1yields 600K b-bar pairs Non-photonic electrons in d+Au Tagging in Au+Au (w/ HFT) RHIC II Science Workshop, Apr. 2005

  18. Summary • STAR has proven capabilities for heavy flavor measurements at RHIC • Electron identification using three detector systems (TPC, TOF, EMC) from 1 to >10 GeV/c • Photonic background rejection using topological methods • Triggering capabilities to utilize full luminosity for rare probes • Direct reconstruction of charmed mesons • STAR has a clear path for improving its capabilities • Completion and extension of calorimetric coverage • Extension of TOF coverage to full azimuth for electrons and combinatoric background rejection in direct reconstruction • Upgrade of Data Acquisition to increase effective luminosity and untriggered data samples • Installation of the heavy flavor tracker for displaced vertices RHIC II Science Workshop, Apr. 2005

More Related