SQM06, Zhangbu Xu (BNL)1 Overview of charm production at RHIC Zhangbu Xu (BNL) Presentions: Xiaorong...
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Transcript of SQM06, Zhangbu Xu (BNL)1 Overview of charm production at RHIC Zhangbu Xu (BNL) Presentions: Xiaorong...
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/0601030X. Dong, thesis, nucl-ex/0509011
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
Mc1.5 GeV>>Tc, QCD, Muds
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,pQCDEnergy 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 SpectraFluorescence 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
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What’s right and what’s wrong
X. Dong (USTC) PH.D. Thesis
SQM06, Zhangbu Xu (BNL) 8
CDF/ISR ce SpectraCDF directy D measurement -- high pT
hep-ex/0307080
X. Dong, Thesis, nucl-ex/0509011
SQM06, Zhangbu Xu (BNL) 9
Discrepancy at RHIC?
PHENIX, PRL 94, 082301(2005)
dNe/dy[0.8<pT<4.0]/Ncoll
Y.F. Zhang, H.B.Zhang, C. Zhong, SQM06
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Which part of the lepton spectrum is sensitive to cc ?
90%
15%
σcc = 1.1 0.1 0.3 mb
Change (n, <pT>), Left: 0.16<pT () <0.26, ±10%Right: pT(e)>1.0 GeV/c, x8
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Measure cc vs sqrt(s)
Propose to measure total cross sections with low-pt muons: CDF, ALICE, Energy Scans at STARH.D. Liu et al.,nucl-ex/0601030
1) Constrains pQCD2) 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, 082301(2005)
•consistent with Nbin scaling!•Produced at initial impact!•Large values:
•pQCD•J/psi coalescenceNo 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 pT
S. Batsouli, et al, Phys.Lett.B 557 (2003) 26 Electrons: Smearing in pT axis
X. Dong QM05
SQM06, Zhangbu Xu (BNL) 14
Preserve the Orientation for v2?
B. Zhang nu-th/0502056
H. Va Hees hep-ph/0601166
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/0601030
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
RAA 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 RAA is due to gluon
The ten thousand things rise and fall without cease– 道德经 http://www.actus.org/laotzu.html
S. Wicks, nucl-th/0512076
• 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/0601033
from quarks, pbar (p) from gluonsat 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/0601010: 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
• Measurecc by low-pt muonsLHC, 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 PBMWhatever 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 pT
Emphasize on experimental measurements
DownDownUpUpDownUpUpDownDownUp?
SQM06, Zhangbu Xu (BNL) 26
Challenges to theory
Current energy loss mechanisms can only account for part of strong suppression of RAA for electrons.
N. Armesto et. al. private comm.M. Djordjevic, et. al. nucl-th/0507019
any beauty?
X. Dong QM05
SQM06, Zhangbu Xu (BNL) 27