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Charm Production at Large Rapidities in pp and dAu Collisions at RHIC

Charm Production at Large Rapidities in pp and dAu Collisions at RHIC. Xiaorong Wang for PHENIX collaboration New Mexico State University. gold. deuteron. North Muon arm : 2.4 > h > 1.2. South Muon arm : -1.2 > h > -2.0. The PHENIX Detectors. PHENIX Preliminary. Direction. Au-going.

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Charm Production at Large Rapidities in pp and dAu Collisions at RHIC

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  1. Charm Production at Large Rapidities in pp and dAu Collisions at RHIC Xiaorong Wang for PHENIX collaboration New Mexico State University X. R. Wang, DIS2006, Tsukuba, Japan

  2. gold deuteron North Muon arm : 2.4 > h > 1.2 South Muon arm : -1.2 > h > -2.0 The PHENIX Detectors Xiaorong Wang, SQM 2006

  3. PHENIX Preliminary Direction Au-going d-going Physics Questions High pT light hadrons • Cold nuclear medium effects: • Parton distributions • gluon (anti)shadowing • CGC • Interactions with medium • Parton energy loss • QCD Power Correction • Recombination • New probes: • Charm Xiaorong Wang, SQM 2006

  4. yield y X Gluon Shadowing in Heavy Nucleus From Eskola, Kolhinen, Vogt Nucl. Phys. A696 (2001) 729-746. Universal Xiaorong Wang, SQM 2006

  5. Shadowing at Forward rapidity in dAu collisions Power correction only J. Qiu & I. Vitev • Color Glass Condense • Dynamic Multiple Scattering Power Correction D. Kharzeev & K. Tuchin hep-ph/0310358 CGC Xiaorong Wang, SQM 2006

  6. Recombination • “Explains” light hadron yields in forward and backward rapidities • Input: low pT forward /backward hadron distributions • Expect similar effects on open charm(?) • Measurement of charm yields could provide additional constrains on these models H Xiaorong Wang, SQM 2006

  7. Decay muons number of tracks Punch-through hadrons ? Prompt muons Prompt+decay muons Hadron Gap2 Gap3 Gap4 Open Charm Analysis Techniques Prompt µ background subtraction • Punch-through hadrons: Data driven method to Estimate attenuation • Decay muons: Vertex distribution analysis m decay p,K m prompt p,K punch through absorber Muon detector Xiaorong Wang, SQM 2006

  8. Comparison Prompt - pt spectrum with theory Run2pp - FONLL: Solid line and band Without scaling the charm contribution: dotted line FONLL: Fixed Order next-to-leading orderterms and Next-to-Leading-Log large pTresummation. FONLL and PYTHIA calculation under predicted PHENIX Data at forward rapidity, Xiaorong Wang, SQM 2006

  9. Prompt ’s pT spectra in dAu collisions and RdAu North Arm: d going direction; South Arm: Au going direction Xiaorong Wang, SQM 2006

  10. 1.2 1.0 RdA 0.8 0.6 0.4 0.2 0 X How about J/Psi? • _NO_ Recombination! • Gluon shadowing/saturation • Initial state parton energy loss • J/Psi final state nuclear absorption has minimal effects on the shape Xiaorong Wang, SQM 2006

  11. Shadowing or Energy Loss ? • Shadowing is not enough • Initial state energy loss? • Incoming gluons loss energy before the hard collisions • Affects low pT particle production in the FWD and BWD papidities Xiaorong Wang, SQM 2006

  12. pT broadening: Cronin Effect Broadening of J/y pT distribution suggests initial scattering (maybe also energy loss) is important Xiaorong Wang, SQM 2006

  13. Summary and Outlook • Physics at Forward and Backward Rapidity: • open charm • J/psi • Observed: heavy ~ ligh hadrons • suppression in the forward • enhancement in the backward • Causes for such effects are not very clear • Shadowing: CGC, Power correction • Initial state energy loss • recombination • Need more theoretical work • Need/Like to have: • Lower energy dAu collisions: stay away from shadowing regions • Explore { x, Q, sqrt(s) } space -> (y, pT, sqrt(s)) experimentally • Parton energy loss vs shadowing • pT evolution – shadowing vs power correction • Shadowing vs recombination • Explore QCD dynamics in details in coming years! Xiaorong Wang, SQM 2006

  14. Backup Xiaorong Wang, SQM 2006

  15. Sources of prompt muons (pT> 0.9GeV) (determined from Pythia) D±±, … , c++, charge asymmetric B±  ± ±  ± *  + - charge symmetric q q  *  + - J/,… + - , ,  + - Xiaorong Wang, SQM 2006

  16. PHENIX Preliminary PHENIX Preliminary Direction Au-going d-going Nuclear Modification Factor: RdAu(decay  from light hadrons) RdAu vs η RdAu vs pT Xiaorong Wang, SQM 2006

  17. Experimental Challenge Prompt Muons Punch-through hadrons Decay Muon Xiaorong Wang, SQM 2006

  18. PYTHIA open charm simulation gluons in Pb / gluons in p X From Eskola, Kolhinen, Vogt Nucl. Phys. A696 (2001) 729-746. PHENIX muon arms “x” coverage Particle production in the d direction (north) is sensitive to the small-x parton distribution in the Au nuclei; whereas in the gold (south) is sensitive to the large-x in Au Xiaorong Wang, SQM 2006

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