Gines Martinez-Garcia * , Sebastien Gadrat *,# , and Philippe Crochet &

Consequences of a Consequences of a cc/D enhancement /D enhancement effect on the non-photonic electron effect on the non-photonic electron

nuclear modification factor in central nuclear modification factor in central heavy ion collisions at RHIC energiesheavy ion collisions at RHIC energiesGines Martinez-GarciaGines Martinez-Garcia**, Sebastien Gadrat, Sebastien Gadrat*,#*,#, and , and

Philippe CrochetPhilippe Crochet&&

(*) Subatech, Nantes, France(*) Subatech, Nantes, France(&) LPC Clermont Ferrand, France(&) LPC Clermont Ferrand, France(#) Now at LPSC, Grenoble, France(#) Now at LPSC, Grenoble, France

Hot Quarks 2008, Estes Park, Colorado, USA.More details in Physics Letter B663 (2008) 55.

Sébastien Gadrat, Hot Quarks 08Sébastien Gadrat, Hot Quarks 08 22

Outline of the talkOutline of the talkPhysics Motivations:

– Non-photonic electron nuclear modification factor (RAA) at RHIC energies;

– Enhancement of baryon/meson ratio at RHIC energies;

Enhancement of the c/D ratio in HIC:– Model to compute the consequences on the

non-photonic electron RAA;Considering all ingredients:

c/D enhancement;– Quark energy loss;– Beauty contribution.


Non-photonic electron RNon-photonic electron RAAAA @ RHIC @ RHIC

Non-photonic electrons are assumed to arise from the semi-leptonic decay of charm and beauty hadrons;

Suppression increases with the centrality of the collision; Suppression similar to light hadron suppression at high pT; Radiative energy loss is not enough to explain the data.

PHENIX, PRL 172301 (2007) STAR, PRL 192301 (2007)


ee±± R RAAAA @ RHIC @ RHIC understood ? understood ?


Baryon/meson enhancement @ RHICBaryon/meson enhancement @ RHIC

STAR, nucl-ex/0703040STAR, nucl-ex/0701052 STAR, nucl-ex/0703033

already observed for light (u, d) and strange species ; the heavier the baryon, the higher in pT the maximum occurs (Ω/Φ) ;

quark coalescence models qualitatively describe the data (PRC65, PRL90, PRC68, PRC67, JPG30, PRC70).(PRC65, PRL90, PRC68, PRC67, JPG30, PRC70).


What about a What about a cc/D enhancement in HIC ?/D enhancement in HIC ?

D0, D0 D+, D- Ds+, Ds

- c+, c

-

BR (Xe)in %

6.71 0.29 17.2 1.9 8 +6-5 4.5 1.7

BR(c e anything) is smaller than any BR(D e anything)

A relative enhancement of the A relative enhancement of the cc/D would lead to a /D would lead to a « natural » single electrons suppression « natural » single electrons suppression withwith respect to respect to

p+p scaling !p+p scaling ! ee±± R RAAAA not exclusively sensitive to heavy quarks dE/dx ! not exclusively sensitive to heavy quarks dE/dx !


Proof in numbers…Proof in numbers…

ss

cccc

DDDDDDD NNNNNN

NN

NN

C00

,

eDe

eDe

D

DAA NN

NNCNNC

NNR

c

c

cc

cc

/1)/(1

)/(1

/1

,

,

ss

cccc

DDDDDDDDDDD

DeDe BRNNBRNNBRNN

BRNNNN

)/()/()/(

)/(/

0000 ,,

,,

%63.31%63.31

%3.71%3.71

C

CRAA

with C the c/D enhancement

factor

and

pp collisions @ 200 GeV :

1. Perfect binary scaling

2. Same D0,D+,Ds relative yields

RAA=0.90 (0.79) for c/D=0.35(0.84) C=5 (12)Yields (Pythia phenix settings) c/D ~ 0.073


Theoretical predictionsTheoretical predictionsV. Greco, Private communication &

Quenching Day, INFN (2005)

pT [GeV]

c/D

L. Cunqueiro & C. Pajares, Private communication & Eur. Phys J C53 585 (2008), arXiv:0712.0509v1 [hep-ph]

Enhancement of c/D is expected in HIC;

Maximum at 5-6 GeV/c; Existence of diquarks

correlations in the sQGP;

S. Yasui et al., arXiv:0803.1366v1 [nucl-th]S. H. Lee et al., arXiv:0709.3637v2 [nucl-th]

Recombination Percolation of strings

Diquark correlations


First study of this effect First study of this effect dondone by e by P. SorensenP. Sorensen and X. Dong and X. Dong

New RAA including c/D effect

Results:Results: enhancement effect for low pT: 2 ≾≾ pT ≾ 5≾ 5 GeV/c GeV/c; high value for the max c/D ratio required (~ 1.7 taken from the /Ks

0); suppression less than 20%.

Assumptions:Assumptions: use /Ks

0 measured shapes as a reference for c/D ones; the charm RAA is similar to light hadrons RAA.

~20%~20%

PRC74 024902 (2006), SQM06 & HQ06


A more detailed study of the charm A more detailed study of the charm enhanced B/M effect on the non-photonic Renhanced B/M effect on the non-photonic RAAAA

Sorensen and Sorensen and DongDong Our studyOur study

c/D shape in Au+Au as /Ks

0 Gaussian

c/D shape in p+p as /Ks0 from Pythia

Maximum of the c/D ratio

~ 1.7 (from the /Ks

0) for pT ~ 3 GeV/c

~ 1 for pT ~ 6 GeV/c

Energy loss From the scaling of the hadron shape

From S. Wicks et al., NPA 784(07)426

Beauty contribution No Yes


Pythia: p+p at 200 GeVPythia: p+p at 200 GeV

PHENIX data are well reproduced by Pythia (tuned according to PRL88 192303 (2002)) though Pythia spectrum slightly softer;

Decay electrons from c exhibit a softer spectrum: suppression of non-photonic electrons is further

enhanced !


cc/D enhancement hypothesis/D enhancement hypothesis

Evolution of the c/D (pT) assumed in the present work: Gaussian shape centred at 5 GeV, maximum at 0.9 and =2.9 GeV;

ppTT differential cross section is conserved ; differential cross section is conserved ;

dN/dpdN/dpTT with nuclear effects with nuclear effects RRAAAA = =

dN/dpdN/dpTT w/o any nuclear effect w/o any nuclear effect

Shape of the c/D (pT) enhancement


RRAAAA(p(pTT) from ) from cc/D enhancement/D enhancement

Natural suppression of the non-photonic electron till 40% in the pT region 2-4 GeV/c;

Suppression of 20% up to pT~9 GeV/c;

Attention ! Shadowing has not been taken into account but only relevant for pT < 2GeV/c.

Non-photonic electrons from charm


RRAAAA(p(pTT) with ) with cc/D enhancement and /D enhancement and charm energy losscharm energy loss

Collisional energy loss leads to a similar effect as c/D enhancement (light blue vs red);

Suppression 0.2 level, like light quarks seen for pT>3 GeV/c (blue);


Beauty contributionBeauty contribution

Not well known from experimental data;Large uncertainty from theory (mc, mb, Qr,

Qf);

T. Ullrich, Hard Probes 08

Crossing-points:4.5 and 10.5 GeV/c


RRAAAA (p (pTT) with all the effects) with all the effects

Additional suppression of the

non-photonic electrons of 10(25)%

due to c/D enhancement for a charm vs beauty

crossing point of 4.5 (10.5) GeV/c;


ConclusionsConclusionsEnhancement of the c/D ratio in HIC would lead to

a suppression of non-photonic electrons;

Assuming an enhancement similar to light hadrons with a maximum at pT=5 GeV, as expected from recombination models, the suppression of non-photonic electrons is increased by 10-25% in the pt range 4-9 GeV;

Direct measurement of open heavy flavour production are imperative before solid conclusion on the e± RAA can be drawn.


PRELIMINARYRun-4

Run-7

Rapp & van Hees, PRC 71, 034907 (2005)

minimum-bias

R. Averbeck, QM2008

PerspectivesPerspectives Role of the c/D

enhancement on the elliptic flow of non-photonic electron has to be understood …

Simulation in progress…


Back upBack up


Other effects related to the chemical Other effects related to the chemical composition of heavy flavoured composition of heavy flavoured

hadronhadron Enhancement of Ds meson production:

– BR in the semi-leptonic channel is not well known 8+6-5 %.

However, similar BR expected from the spectator model;– Small effect expected with this BR.

Enhancement of beauty B/M ratio:– The mass of the beauty quark being higher, beauty semi-

leptonic decays exhibit similar behaviour in beauty hadrons. Expected from the spectator model;

– Large enhancement is expected form diquarks correlations (factor 10);

S. H. Lee et al., arXiv:0709.3637v2


Qualitative differences: light vs heavy Qualitative differences: light vs heavy quark recombinationquark recombination

1. For the same velocity, the pT of the heavy quark is larger, ~ mQ/mq factor:

– Recombination extend to higher pT;– Estimation pT

c~1 GeV x mc/mq = ~4 GeV (mc=1.25 GeV, mq=300 MeV);

2. Full pT : – Light: pT of the hadron (2 or 3) times the pT of the quarks; – Heavy: pT of the hadron slightly higher than the pT of the

heavy quark;3. The light (heavy) quark fragmentation time is long (short):

– 20, 1.5 & 0.4 fm/c for a 10 GeV/c , D & B meson (hep-ph/0611109)


New parameterisationNew parameterisationGaussian shape centred at ~7 GeV, maximum of 0.9 and =2.9 GeV.

40%


New parameterisationNew parameterisation

10(25)% up to p10(25)% up to pTT ~9 GeV/c for a charm vs beauty crossing point at 4.5(10.5) ~9 GeV/c for a charm vs beauty crossing point at 4.5(10.5) GeV/c!GeV/c!

Gines Martinez-Garcia * , Sebastien Gadrat *,# , and Philippe Crochet &

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