Shingo Sakai
Univ. of California, Los Angeles

1 Non-photonic e result in AuAu
 b/c separation in non-photonic electron

by electron-hadron correlations @ pp Bottom production
 Discuss heavy flavor energy loss in thedense matter2

 Heavy quarks (charm & bottom)
are produced by gluon fusion in
the initial collisions.

D mesons, Ψ’, χ Total charm yields in AuAu

collisions @ RHIC is scaledby binary collisions

PRL 94, 082301 (2005)

 heavy quarks are produced
before the medium formed
and through the matter.

 probe of QCD matter

AuAu 200 GeV
3Charm quark study @ RHIC

 Heavy flavor production has beenstudied by measuring electrons
decay from charm and bottom(non-photonic electron)
at RHICBR D0->Kπ (3.85±0.10 %)BR D±->e+X (17.2 %) Measured electron Photonic electron- photon conversion- Dalitz decay Non-photonic electron- primarily semi-leptonic decayof mesons containing c & b

D meson M = 1.869 [GeV]τ~ 10-12 [s] cτ ~ 300 [μm]4 electron ID is carried witho DC + PC ; momentumo RICH ; ring imageo EMC ; energyo TPC ; momentum, dE/dx
o EMC ; energyo SMD ; shower shape Main background in electron measurement is photonic electron
photonic e Invariant mass

 Cocktail method

 Converter method

Reconstruct photonic
electron by calculating
Inv. Mass of ee(STAR)

Calculate photonic
electron by using
measured photonic
sources(PHENIX)

Install additional
converter.
Then compare
yield w. w/oconverter (PHENIX)PRL 98, 172301 (2007)

 binary scaling of total e± yield from heavy flavor decay=> hard process production
 high pT e± suppression increasing with centrality=> heavy flavor energy loss=> very high dense matter is formed in AuAu collisions

7 radiative energy loss with typicalgluon densities is not enough(Djordjevic et al., PLB 632(2006)81)
 models involving a very opaquemedium agree better(Armesto et al., PLB 637(2006)362)
 collisional energy loss / resonant

A. Suaide QM06

elastic scattering(Wicks et al., nucl-th/0512076,
van Hees & Rapp, PRC73(2006)034913)

 radiative energy loss with typicalgluon densities is not enough(Djordjevic et al., PLB 632(2006)81)
 models involving a very opaquemedium agree better(Armesto et al., PLB 637(2006)362)
 collisional energy loss / resonant

A. Suaide QM06

elastic scattering(Wicks et al., nucl-th/0512076,
van Hees & Rapp, PRC
73(2006)034913)

 Uncertainty from bottom quark contribution

not only theory but also experiment @ high pT

trigger0 – 20%: 3 < pTtrig < 6 GeV/c & 0.15 < pTasso < 1 GeV/cSTAR preliminary
QM08Gang Wang

 Away side structure is similar to mach cone shape The other evidence of heavy quark energy lose

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PRL 98 172301 (2007)

 Strong elliptic flow for non-photonic electron(1) Charm quark thermal + flow(2) large cross section ; ~10 mb(3) Elastic scattering in QGP[Phys.Lett. B595 202-208 ][PRC72,024906][PRC73,034913]

 charm quark flow -> partonic level thermalization
 There is also uncertainty from bottom @ high pT Since charm and bottom

are heavy, their production
have been predicted by pQCD

 FONLL predicts bottom quark

contribution significant (c/b = 1)
around 5 GeV/c in non-photonic
electron yield withlarge uncertainty.

 Separate charm/bottom

by using e-h correlations*Uncertainty comes from mass,PDF, etc in the calculation*FONLL=A Fixed-Order plus Nextto-Leading-log

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pp@200 GeV

eD – h (MC)eB – h (MC)fitting Near side width for B decay is wider thanthat of D decay due to decay kinematics
 measuring e-h correlation in pp & fit by MCwith B/(B+D) as parameter
expMCΔφ e−h= RB Δφ eMC+(1−R)Δ
φ, RB = eB /(eD + eB )B
B−he D −h13 Electron-Kaon charge correlation
 D meson decay=> opposite sign eK pair B meson decay=> same sign eK pair

MoppeK−M

QM08
Y. MorinosameeK

disentangle charm andremaining bottom contribution
via (PYTHIA) simulation
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 Request like-sign e-K pairo near-side ; bottom dominanto away-side ; charm dominantcompared with MC simulations toget B/D ratio

QM08
A.Mischke15

 B decay contribution to non-photonic electron Three independent method (STAR & PHENIX) are consistent B decay contribution increase with pT
 > 50% e decay from B above 4-5 GeV/c
 good agreement with pQCD (FONLL) prediction

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Data/pQCD

QM08
Y. Morino

Charm decay

Bottom decay

upper limitof pQCD

 data (c->e & b->e)/pQCD from PHENIX
 ratio is almost flat -> pQCD well represent the pT shape σdata/σFONLL ~2 reasonable value17 Bottom quark contribution

is ~50% above 4-5 GeV/c @ pp=> there would be significant
bottom contribution inAuAu, too RAA for non-photonic electron
consistent with hadrons⇒ Indicate large energy loss

not only charm but alsobottom in the dense matter
C:B ~ 1:1 @ pp
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Relation between RAA for charm and bottom decay

eBAA + eCAA
RAA =N bin (eBpp + eCpp )
eBAA
eBpp
eCAA
eCpp
=
⋅ pp+⋅ pp
pp
pp
pp
N bin eB (eB + eC ) N bin eC (eB + eCpp )B
C= RAAr + RAA(1− r)

r = eBpp /(eBpp + eCpp )€ RAAC and RAAB are connected B decay contribution @ pp
 With the measurements of r @ pp and RAA,
we can derive a relationship between RAAc and RAAb.

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pT>5 GeV/co RAAc & RAAb correlationfrom STARo Dominant uncertainty isnormalization in RAA analysis
o RAAb< 1 ; B meson suppressedo prefer Dissociate andresonance model(large b energy loss)

STAR preliminary

I; Phys. Lett. B 632, 81 (2006) ; dNg/dy = 1000
II; Phys. Lett. B 694, 139 (2007)
III; Phys.Rev.Lett.100(2008)192301 20

Azmuthal correlation

RAAd+Au

Au+Auv2

Heavy quark behavior is same as light quarkin the hot & dense matter @ RHIC=> energy loss & flow
 STAR & PHENIX extract B decay contribution
in non-photonic electron by using electron-hadroncorrelations in pp.
 B decay contribution is more than 50% above
5 GeV/c in pp collisions
 PHENIX study bottom production @ pp
and it is consistent with pQCD prediction.
 STAR study bottom energy loss and the result show
B meson suppression with 90% C.L.