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1 ture Prospects in QCD L, July 17-22, 2006 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL
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Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

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Page 1: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

1Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Jet and Heavy Flavor Probes of Hot QCD MatterPeter Jacobs, LBNL

Page 2: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

2Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Calibrated in p+p and p/d+A

Calculable final state medium effects

Why hard probes? (= perturbative processes)

Calculable interactions of energetic partons with the medium calibrated, penetrating tomographic probes

Page 3: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

3Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Outline• jet quenching and radiative energy loss• inclusive hadron suppression • heavy quark suppression• dihadron correlations: modification of jet structure• outlook to the LHC

(not discussed: quarkonium)

Most up-to-date reference:http://hp2006.lbl.gov/source/program.htm

Page 4: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

4Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

pQCD in p+p at RHIC

Good agreement with NLO pQCD pQCD should be broadly applicable at RHIC (e.g. heavy flavor production…)

Inclusive jets

Page 5: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

5Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Inclusive hadron spectra in 200 GeV Au+Au

pT (GeV)

PHENIX

PHOBOS

Page 6: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

6Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Jet quenching I: hadrons are suppressed, photons are not

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

Binary collision scaling

p+p

Page 7: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

7Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Jet quenching II: recoiling jets are strongly modified

cos()

pTassoc > 0.15 GeV

STAR, Phys Rev Lett 95, 152301

4< pTtrig < 6 GeV

STAR, Phys Rev Lett 91, 072304

pTassoc > 2 GeV

I & II: conclusive evidence for large partonic energy loss (“jet quenching”) in dense QCD matter

trigger

recoil

?

Page 8: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

8Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Radiative energy loss in QCD

CS

coherent

LPM Nq

dzd

dI

ldzd

dI ˆHeitlerBethe

2ˆ~ˆ~ LqLqdzd

dIddzE SCS

LPML

med

C

cformation Lt

BDMPS approximation: multiple soft collisions in a medium of static color charges

E independent of parton energy (finite kinematics E~log(E))E L2 due to interference effects (expanding medium E~L)

Medium-induced gluon radiation spectrum:

Total medium-induced energy loss:

2

2

22ˆ

qd

dqqdq mediumTransport coefficient:

Baier, Schiff and Zakharov, AnnRevNuclPartSci 50, 37 (2000)

Page 9: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

9Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Extracting qhat from hadron suppression data

RAA: qhat~5-15 GeV2/fm

Page 10: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

10Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

What does measure?q̂

LqxxGN

Nq medium

C

CS ˆ,1

2

2

Equilibrated gluon gas:number density ~T3

energy density ~T4

43

ˆ cq

qhat+modelling energy density

• pQCD result: c~2 (S? quark dof? …)• sQGP (multiplicities+hydro): c~10

R. Baier, Nucl Phys A715, 209c

Hadronic matter

QGP

~RHIC data

Model uncertainties

Page 11: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

11Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

EASW BDMPS sCR

4ˆ q L2

ˆ q 2

L2d

0

L

ˆ q ()2 ˆ q 00

L

/log

1

4

92

3

ELdy

dN

R

C

Eg

Rs

GLV

BDMPS(ASW) vs. GLVBaier, Dokshitzer, Mueller, Peigne, Schiff, Armesto, Salgado, Wiedemann, Gyulassy, Levai, Vitev

1800dy

dN g

ˆ q 10GeV 2

fm

Rough correspondence: (Wiedemann, HP2006) 900

dy

dN g

fm

GeVq

2

BDMPS

GLV

Medium-induced radiation spectrum

Salgado and Wiedemann PRD68 (2003) 014008

2ˆLqC

30-50 x cold matter density

Page 12: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

12Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Alternatively: AdS/CFT Liu, Rajagopal and Wiedemannhep-ph/0605178

Raj

agop

al, H

P20

06

Page 13: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

13Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

RAA only provides lower bound on q̂

The limitations of RAA

Page 14: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

14Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Inclusive hadrons and surface bias

?

Inclusive measurementsinsensitive to opacity of bulk

Eskola et al., hep-ph/0406319

RAA~0.2-0.3 for broad range of q̂

Large energy loss opaque core

More differential observables are needed to probe deeper…

Page 15: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

15Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Heavy quark energy loss• In vacuum, gluon radiation suppressed at < mQ/EQ

• “dead cone” effect: heavy quarks fragment hard into heavy mesons

QDokshitzer, Khoze, Troyan, JPG 17 (1991) 1602.Dokshitzer and Kharzeev, PLB 519 (2001) 199.

Dead cone also implies lower heavy quark energy loss in matter: (Dokshitzer-Kharzeev, 2001)

1

1

dd

d

d2

2

2

Q

Q

LIGHT

HEAVY

E

m

II

Page 16: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

16Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Heavy quarks are “grey probes”Wicks, Horowitz, Djordjevic and Gyulassy, nucl-th/0512076

Origin of surviving jets(radial propagation only)

jets go thataway

Heirarchy of “surface bias” correlated with opacity/suppression differential probes of the medium

RAA

Page 17: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

17Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Heavy flavor suppression via b,ce+X

Gluon density/qhat constrained by light quark supression+entropy density (multiplicity) under-predicts electron suppression charm vs beauty? elastic energy loss? …?

RAA(non-photonic electrons) ~ 0.2 ~ RAA() !!

S.Wicks et al., nucl-th/0512076Armesto et al., Phys.Lett.B637:362-366,2006

Page 18: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

18Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

b vs c suppression

pT~5 GeV/c: ce suppression ~0.2 puzzle resolved if c e dominates non-photonic electron spectrum - is that permissible?

S.Wicks et al., nucl-th/0512076RAA

Page 19: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

19Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

N. P. electrons in p+p vs FONLL

~factor 2

CD

F, P

RL

91, 241804 (2003)

D0

FONLL

M. Cacciari, Hard Probes

State of the art: Fixed-Order Next-to-Leading Log

STAR, nucl-ex/0607012

Tevatron charm and beauty vs FONLL: OK

• RHIC n.p. electrons: factor 3-5 excess(!)• Large ambiguity in relative contribution of ce/be need to resolve b and c explicitly

Page 20: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

20Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Elastic (collisional) energy loss revisitedS.Wicks et al., nucl-th/0512076

Elastic E comparable to Radiative E – not negligible

Elastic E important even for light quarks revisit energy density estimates?

Page 21: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

21Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Resolution of non-photonic electron suppression puzzle needs

• experiment: explicit measurement of c vs b suppression

• theory: unified framework incorporating both elastic and radiative energy loss

Page 22: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

22Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Jet structure via hadron correlationsp+p dijet

Full jet reconstruction in the heavy ion environment is difficult probe jet structure via dihadron correlations

trigger

Phys Rev Lett 90, 082302

Page 23: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

23Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

cos()

pTassoc > 0.15 GeV

STAR, Phys Rev Lett 95, 152301

Established results…

4< pTtrig < 6 GeV

STAR, Phys Rev Lett 91, 072304

pTassoc > 2 GeV

Page 24: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

24Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Dihadron correlations at higher pT

Recoil jet clearly seen above background but at suppressed ratedifferential measurement of`E upper bound on qhat?

trigger

recoil

?

pTtrigger>8 GeV/c

Yie

ld p

er tr

igge

r

STAR, nucl-ex/0604018

Page 25: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

25Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Recoiling hadrons: details

No angular broadening

No modificationof fragmentation

Recoil rate is suppressed but jet features unmodified see only non-interacting jets?

D(z

T)

Recoiling hadron distribution

STAR, nucl-ex/0604018

Page 26: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

26Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

STAR preliminary

T. Renk, hep-ph/0602045

High pT dihadrons: detailed dynamical calculation

Trigger direction

Different geometrical biases underly trigger and recoil distributions

~75% of recoils due to non-interacting jets

All bremsstrahlung models: discrete term

Page 27: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

27Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Correlations and dynamics (cont’d)

T. Renk, hep-ph/0602045

Calculation ~reproduces recoil yields with params fit to RAA • additional sensitivity to dynamics of the collision? (in progress…)

Suggestive calculation need larger dynamic range in pT

trig and pTassoc to probe energy loss

(not only discrete term)Ultimately: +jet (experimentally challenging, in progress)

T. Renk, HP2006

Various models of bulk expansion

Page 28: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

28Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Medium response to jet energy loss I

PHENIX, QM05 and nucl-ex/0507004

Leadinghadrons

Medium

away

near

STAR, Phys Rev Lett 95, 152301

Look at low pT recoils…

• experimentally challenging to discriminate signal/bkgd• new development: 3-particle correlations• Mach cone, Cerenkov radiation,…?

Page 29: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

29Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Medium response to jet energy loss II

Au+Au 0-10%preliminary

3<pt,trigger<4 GeV

pt,assoc.>2 GeV

Armesto et al, nucl-ex/0405301

Near-side “ridge” correlated with jet trigger

Induced radiation dragged by longitudinally expanding fluid?

Page 30: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

30Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Jet quenching at the LHC

Pb+Pb at 5.5 TeV:• First ion collisions 2008• qualitatively new probes full (~unbiased) jet reconstruction in HI events

Page 31: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

31Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

SummaryExperiment • jet quenching is well-established: multiple strong effects• key open issue: how does the medium respond to E?• second generation of high precision measurements:

• heavy flavor, correlations, +jet• RHIC upgrades (charm reco), high luminosity (+jet)• LHC brings qualitatively new physics

Theory• qualitative but not yet quantitative understanding of jet quenching• significant uncertainties in

• underlying mechanism (elastic vs radiative)• heavy quark production• modeling of dynamical evolution

Page 32: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

32Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Final comment

Current theoretical uncertainties present the largest barrier to quantitative understanding and full exploitation of RHIC and LHC Heavy Ion measurements

The situation is analogous to the early days of the Solar Neutrino puzzle:

We need a Standard Solar Model for Ultra-relativistic Heavy Ion physics

(The good news: this is in progress)

Page 33: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

33Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Extra slides

Page 34: Future Prospects in QCD BNL, July 17-22, 2006 1 Jets and Heavy Flavors Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL.

34Future Prospects in QCDBNL, July 17-22, 2006 Jets and Heavy Flavors

Further limitation of RAA

Can RAA of light quarks/gluons constrain the energy loss distribution?T. Renk (HP2006): accurate geometry/expansion, toy models for P(E)

Can always tune medium density to reproduce RAA: only weak constraint on e-loss distribution

Prob. distributions for parton to lose E

parton with E<0.5 GeV is absorbed by medium

More differential observables are needed to probe deeper…