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Measurement of single muons with the PHENIX experiment at RHIC

Explore heavy quark measurements with PHENIX Collaboration at RHIC, including charm energy loss in Au+Au collisions and systematic studies for better precision. Learn about muon production origins and detailed analyses for heavy flavor detection.

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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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