SQM06, Zhangbu Xu (BNL)1 Overview of charm production at RHIC Zhangbu Xu (BNL) Presentions: Xiaorong Wang, PHENIX (Forward muon) Yifei Zhang, STAR (mid-rapidity, muon, electron) Haibin Zhang, STAR (STAR overview) Adrew Glenn, PHENIX (PHENIX overview) Posters: Chen Zhong, STAR (Low-pt muon) H.D. Liu et al., nucl-ex/ X. Dong, thesis, nucl-ex/ All nice talks on data are Over I am offering my own view Thank the organizers
SQM06, Zhangbu Xu (BNL)2 Outline Charm Total Cross Sections Are we alone? What’s right and what’s wrong? Are lepton spectra sensitive to flow? Form Factors What scale? (30%, x3) Does it make senses? Color, flavor (dE/dx)? Is pp/FONLL off by 3—6 serious? Wild Speculations and Outlook M c 1.5 GeV>>T c, QCD, M uds M/E>>0
SQM06, Zhangbu Xu (BNL)3 Are we alone? Can we confirm or rule out Cosmic Ray experiments (Pamir, Muon, Tian Shan) under similar conditions? Data provide reference for Au+Au data and J/psi from charm coalescence STAR >3x PYTHIA,pQCD Energy dependence R and F ? Need smaller errors to constrain pQCD and determine the effects in Cosmic Ray Showers Pamir, Nuovo Cim 24c (2001) 557; NPB 122(2003) 353c X. Dong USTC
SQM06, Zhangbu Xu (BNL)4 Pamir EM shower depth With charm Without charm XREC upgrade Pamir, Nuovo Cim 24c (2001) 557
SQM06, Zhangbu Xu (BNL)5 Muons on the Side Two techniques, Two Spectra Fluorescence vs Muon/scintillator What is the problem? Incorrect Model of Detector? Incorrect Model of Showers? Heavy Primaries? New Physics? A. Olinto, PANIC05
SQM06, Zhangbu Xu (BNL)6 Can we get rid of data points we don’t like? if the data points shouldn’t be there in the first place? R. Vogt
SQM06, Zhangbu Xu (BNL)7 What’s right and what’s wrong X. Dong (USTC) PH.D. Thesis
SQM06, Zhangbu Xu (BNL)8 CDF/ISR c e Spectra CDF directy D measurement -- high pT hep-ex/ X. Dong, Thesis, nucl-ex/
SQM06, Zhangbu Xu (BNL)9 Discrepancy at RHIC? PHENIX, PRL 94, (2005) dN e /dy[0.8<pT<4.0]/N coll Y.F. Zhang, H.B.Zhang, C. Zhong, SQM06
SQM06, Zhangbu Xu (BNL)10 Which part of the lepton spectrum is sensitive to cc ? 90% 15% σ cc = 1.1 0.1 0.3 mb Change (n, ), Left: 0.16<pT ( ) <0.26, ±10% Right: pT(e)>1.0 GeV/c, x8
SQM06, Zhangbu Xu (BNL)11 Measure cc vs sqrt(s) Propose to measure total cross sections with low-pt muons: CDF, ALICE, Energy Scans at STAR H.D. Liu et al.,nucl-ex/ )Constrains pQCD 2)Baseline for charm Coalescence Model 3)Test PBM thermal model x4 below STAR measurements
SQM06, Zhangbu Xu (BNL)12 Are they talking about the same thing? H.B. Zhang, Y.F. Zhang, C. Zhong SQM06 PHENIX, PRL 94, (2005) consistent with N bin scaling! Produced at initial impact! Large values: pQCD J/psi coalescence No sensitive to FSI Dynamics FSI Dynamics
SQM06, Zhangbu Xu (BNL)13 Are lepton spectra sensitive to flow? Electron spectra cannot disentangle different charm hadron shapes at low p T S. Batsouli, et al, Phys.Lett.B 557 (2003) 26 Electrons: Smearing in p T axis X. Dong QM05
SQM06, Zhangbu Xu (BNL)14 Preserve the Orientation for v2? B. Zhang nu-th/ H. Va Hees hep-ph/ v2 and other calculations shows sensitivity? Is it by accident?
SQM06, Zhangbu Xu (BNL)15 Charm Decay Form Factors PDG Form factor is different between PYTHIA and PDG Electron spectrum depends strongly on charm spectrum shape at pT~1—2 GeV/c H.D. Liu, nucl-ex/ e c s u,d,ud
SQM06, Zhangbu Xu (BNL)16 Charm flows, but not quite as large S. Esumi: (Next session) Overview of non-photonic electron v2 BlastWave model-dependent fit shows sensitivity of electron spectrum to charm spectrum shape Likely, Freeze-out early with less flow H.B. Zhang, Y.F. Zhang AuAu Central , K, p AuAu Central charm hadron
SQM06, Zhangbu Xu (BNL)17 R AA of non-photonic electrons Evidence of large heavy quark energy loss! STAR Highlight talk PHENIX, PRL96
SQM06, Zhangbu Xu (BNL)18 Flavor or Color factor? Radiative dE/dx and Radiation+Elasitic The bigger difference is gluon vs quarks charm vs u/d is quite small The biggest difference between and charm R AA is due to gluon The ten thousand things rise and fall without cease– 道德经 S. Wicks, nucl-th/ dE/dx(g) ~=9/4 dE/dx(uds) pbar, p vs dE/dx(c/b)<dE/dx(uds)
SQM06, Zhangbu Xu (BNL)19 Gluon vs light quarks dE/dx(g) ~=9/4 dE/dx(uds) pbar, p vs dE/dx(c/b)<dE/dx(uds) STAR nucl-ex/ from quarks, pbar (p) from gluons at pT~=10 GeV/c
SQM06, Zhangbu Xu (BNL)20 Pbar(p), same suppression STAR Preliminary L.J. Ruan, WWND06 Same suppression
SQM06, Zhangbu Xu (BNL)21 First thing first! p+p (PHENIX,STAR)/FONLL=(3,5.7) Are we worried? What if charm is off, but bottom is correct Cacciari, PRL95 STAR |y|<1 PHENIX, X.R. Wang, SQM06
SQM06, Zhangbu Xu (BNL)22 Speculations Gluon and light quark have similar dE/dx –color-factor 9/4 doesn’t work for large dE/dx? But, I. Vitev hep-ph/ : dE/E(g)=50%, (q)=25% NLO underpredicts charm but predicts bottom correctly –Mc~ 1.5 GeV/c too small –Other processes? These will explain: pbar(p), pion,electron RAA
SQM06, Zhangbu Xu (BNL)23 Outlook Measure cc by low-pt muons LHC, Tevetron and energy scan at RHIC Measure D, c, and B separately and cleanly Explain why gluons and light quarks have same dE/dx Does pQCD dE/dx work all the way to pT(e)~=1 GeV/c?
SQM06, Zhangbu Xu (BNL)24 A same ending of charm production at RHIC?? Thanks to PBM Whatever the truth, Triumph over mistrust!
SQM06, Zhangbu Xu (BNL)25 Effects related to Open Charm Radiation Energy Loss Collision Energy Loss Dead Cone Effect Ter-Mikayelian Effect Transition Radiation Flow (radial & elliptic) (quark) Coalescence Death of “dead cone” Charm Resonance CGC All these happen at intermediate p T Emphasize on experimental measurements Down Up Down Up Down Up?
SQM06, Zhangbu Xu (BNL)26 Challenges to theory Current energy loss mechanisms can only account for part of strong suppression of R AA for electrons. N. Armesto et. al. private comm.M. Djordjevic, et. al. nucl-th/ any beauty? X. Dong QM05
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