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,

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


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


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


Pamir EM shower depth

With charm

Without charm

XREC upgrade

Pamir, Nuovo Cim 24c (2001) 557


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


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


What’s right and what’s wrong

X. Dong (USTC) PH.D. Thesis


CDF/ISR ce SpectraCDF directy D measurement -- high pT

hep-ex/0307080

X. Dong, Thesis, nucl-ex/0509011


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


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


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


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


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


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?


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


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


RAA of non-photonic electrons

Evidence of large heavy quark energy loss!

STAR Highlight talk PHENIX, PRL96


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)


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


Pbar(p), same suppression

STAR Preliminary

L.J. Ruan, WWND06

Same suppression


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


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


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?


A same ending of charm production at RHIC??

Thanks to PBMWhatever the truth,Triumph over mistrust!


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?


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


Documents

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,