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Measurement of single muons with the PHENIX experiment at RHIC

Measurement of single muons with the PHENIX experiment at RHIC. Hot Quarks 2006, May 20. D.J Kim Yonsei University For the PHENIX Collaboration. Outline. Introduction How can we measure HF ? Background measurements to the cocktails ( 1.Free Decay[K, π ] , 2.Punch-through )

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Measurement of single muons with the PHENIX experiment at RHIC

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  1. Measurement of single muons with the PHENIX experiment at RHIC Hot Quarks2006, May 20 • D.J Kim • Yonsei University • For the PHENIX Collaboration

  2. Outline • Introduction • How can we measure HF ? • Background measurements to the cocktails ( 1.Free Decay[K,π], 2.Punch-through ) • Prompt muon results in pp. dAu • Light meson bg measurement in CuCu • Summary and Outlook

  3. Physics Motivations Why do we measure heavy quarks (charm/bottom)? • In p+p collisions: • Important test of pQCD. Can pQCD predict charm production( LO, NLO )? • Base line analysis for d+Au and Au+Au • In d+Au collisions: • Study of “cold” nuclear matter effect (Gluon Saturation/CGC,[shadowing] , Cronin effect) • In A+A collisions: • Medium modification effects (energy loss, collective flow) • Important baseline of J/ analysis

  4. Signal/Background Run04: X=0.4%, Radiation length Run02: X=1.3% (1) q_hat = 0 GeV2/fm (4) dNg / dy = 1000 (2) q_hat = 4 GeV2/fm (3) q_hat = 14 GeV2/fm Charm energy loss in Au+Au 200GeV at y~0 • Even heavy quark (charm) suffers substantial energy loss in the matter • The data provides a strong constraint on the energy loss models. • Charm/Bottom contribution ? • Radiative energy loss + Elastic energy loss with Different αs = .3 or .43 (M. G. Mustafa, Phys.Rev.C72:014905,2005) • Teaney and Moore (hep-ph/0412346) • K.J Eskola (Nucl.Phys.A747(2005) 511) • Systematics • Large in low pT because of low S/B • At higher pT, systematic error ~ statistical error • Uncertainty in pp is large • preparing the high pT RAA (up to pT = 10 GeV/c). • Run5 pp ( ~ x 10 stat ) (1-3) from N. Armesto, et al., hep-ph/0501225 (4) from M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301

  5. (η = 0) PHENIX Preliminary Phys. Rev. Lett. 88, 192303 (2002) How to measure Heavy Flavor ? • STAR • Direct D mesons hadronic decay channels in d+Au • D0Kπ • D±Kππ • D*±D0 π • Single electron measurements in p+p, d+Au • PHENIX • Single electron measurements in p+p, d+Au, Au+Au , y~0sNN = 130,200,62.4 GeV • Single muon measurements in p+p, d+Au ,1<|y|<2 sNN = 200 GeV • Experimentally observe the decay products of Heavy Flavor particles (e.g. D-mesons) • Hadronic decay channels DKp, D0p+ p- p0 • Semi-leptonic decays De(m) K ne

  6. What have we measured • Open heavy flavor (HF) • y, pT dependence (y=0,pp,dAu,AuAu, y=1.65,pp,dAu) • Centrality dependence (y=0,dAu,AuAu) • Reaction plane dependence (y=0, AuAu) • RHIC provided Cu+Cu 200GeV(~3.0 nb^-1), 62.4GeV(~0.19 nb^-1) Collisions during 2005 • Better systematic studies are possible with different √s, collision species. • better precision on the centrality measurement in the lower Npart region • Species : pp, dAu, CuCu, AuAu • √s : 200 GeV, 62.4GeV, 130GeV • Statistics : More is always better (allows reduction in statistical and systematic errors)

  7. PHENIX detector at RHIC • Electron measurements • |h|<0.35 • Two separate arms 2xDf = 900 • dp/p ~ 1% p • Electron ID • RICH (gthr=35) • e/p separation up to pT ~ 4.8 GeV/c • Muon measurements • 1.2 < |h| < 2.4 • Two separate arms in forward and backward rapidity

  8. Muon Production ; origin of muons • Origins of muons • PYTHIA p+p @ √s=200GeV • low PT: • light hadron decays • high PT: • Heavy quark decays Muon PT distribution

  9. Candidate Muon Tracks in the Muon Spectrometer The muon arms covered rapidities 1.2 < || < 2.4 Candidate Tracks: Prompt Muons Punch-through hadrons Stopped hadrons Decay muons

  10. Identifier Tracker Absorber Decay muons Average flight Distance (blue arrows) Punch-through hadrons Prompt muons Decay muons (green tracks) Positive z → Collision range Absorbers are in Red Decay muon Contribution(N_decay) The yield of decay muons depends on the collision location linearly, which also constrains the hadron production, I hadron, at the collision point.

  11. Raw Count 2 3 4 5 6 Momentum (GeV/c) Raw Count 2 3 4 5 6 Momentum (GeV/c) Tracks stopping in Gap 2 “stopping” muons and hadrons hadrons Tracks stopping in Gap 3 Muons above 2.7 GeV/c punch through the entire detector. Punch-Through hadrons ( N_punch) • Extract decay component from z-vertex slope of normalized muon yield. • Calculate punch-through component with simplified absorption model: Nuclear interaction length λ • Nuclear interaction cross section • ~ not well-known • can be resolved with large statistics run5pp, CuCu with this method!!

  12. Decay muons Punch-through hadrons Prompt muons Cocktails • Sources of  candidates • Decay  is important at all pT. • Punch-through is small, but • important due to large uncertainty. • Prompt  signal comparable to decay •  when pT ~ 2(GeV/c).

  13. PRELIMINARY Comparison to Theory ; p+p 200GeV FONLL: Fixed Order next-to-leading order terms and Next-to-Leading-Log large pT resummation. PYTHIA 6.205 parameters, tuned to describe existing s < 63 GeV p+N world data ( PDF – CTEQ5L, mC = 1.25 GeV, mB = 4.1 GeV, <kT> = 1.5 GeV, K = 3.5 ) Excess over NLO calculation. The excess gets even stronger at forward, due to the rapidity dependence of cross section ? • Total cross section for PYTHIA 6.205 • CC = 0.658 mb, BB = 3.77 b

  14. 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

  15. Prompt ’s pT spectra in dAu collisions and RdAu North Arm: d going direction; South Arm: Au going direction • For muons from open heavy flavor decay, a suppression in forward rapidity is observed. It is consistent with CGC. Results are statistically limited. • The mechanism of the observed enhancement at backward rapidity needs more theoretical investigation. Anti-shadowing and recombination could lead to such enhancement ?

  16. Decay muons ( pT) in Cu+Cu 200GeV 200GeV p+p 200GeV Cu+Cu PHENIX preliminary • consistent with run2 p+p • MinBias pT spectra in Cu+Cu 200GeV only at this moment(Online production) • Limited statistics now, Full data set will be available in the near future • CuCu 200GeV : ~ statistics x10 more

  17. Nuclear Modification Factor CuCu 200GeV • shows enhancement in higher pT in the forward rapidity • it is consistent with the mid-rapidity measurement within the errors • One of main physical background to Inclusive muons is under control

  18. Rapidity • Modest Gaussian Shape is observed • pT>1GeV/c in MinBias collisions

  19. Summary ; p+p, d+Au • FONLL and PYTHIA 6.205 under predicted prompt at forward rapidity in pp collisions at 200 GeV. • For muons from open heavy flavor decay, a suppression in forward rapidity is observed. It is consistent with CGC. Results are statistically limited. • The mechanism of the observed enhancement at backward rapidity needs more theoretical investigation. Anti-shadowing and recombination could lead to such enhancement.

  20. Perspective • Non-photonic Single electronRAA in Au+Au 200GeV collisions suggests that • Even heavy quark suffers substantial energy loss in the matter • Still systematical errors and statistical error is not sufficient to constraint energy loss models  Can be improved with better pp reference and more high pT data points AND…. • More systematic studies can be possible via different collision species, energies (Cu+Cu 200GeV, 62.4GeV), and rapidities. • stage is set, background analysis are underway • Light meson pT and RAA in Cu+Cu MB 200GeV collisions are measured at this moment in the forward rapidity. • punch-through hadrons can be calibrated with large set of tracks ( run5pp,CuCu ) with great precision • Perspectives on Cu+Cu 200GeV , 62.4GeV • Light mesons : centrality dependency can be studied with good statistics • Prompt muon signal ( charm, bottom ) • Flow

  21. RHIC History X 25

  22. 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 order terms and Next-to-Leading-Log large pT resummation. FONLL and PYTHIA calculation under predicted PHENIX Data at forward rapidity,

  23. dNg/dy=1000 Theory Comparison M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301 Disagreement with PHENIX preliminary data!

  24. dNg/dy=3500 How can we solve the problem? N. Armesto et al., Phys. Rev. D 71, 054027 (2005) Reasonable agreement, but the dNg/dy=3500 is not physical!

  25. Electrons Pions + Elastic Energy loss ? First results indicate that the elastic energy loss may be important M. G. Mustafa, Phys.Rev.C72:014905,2005 as = .3

  26. With Different αs as = .3 as = .4

  27. Rapidity dependency

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