Hallman: ICHEP06

T. HallmanICHEP06Moscow

July 31, 2006

New Results and Future Perspectives in Relativistic Heavy Ion Physics

Hallman: ICHEP06

Outline of this talk

– Recent results from RHIC & SPS• Hard Probes (RAA of heavy quarks, di-hadron correlations)

• Quarkonium

• Interplay of high pT partons with the medium

• Flow, global observables, etc.

– Search for QCD Critical point– On the eve of new discoveries at the LHC– Summary

Hallman: ICHEP06

1. Introduction:N. Armesto: ICHEP06

Hard Processes in Heavy Ion Collisions 3

Jet quenching/heating

Quarkonium suppression

Control of the benchmark:prompt photons anddileptons

● Hard processes (probes of the medium created in a HIC): those whosebenchmark (result of the probe in cold nuclear matter) is computable withinperturbative QCD, for which a hard scale is required (p

T, m

Q,...>>1/R

h).

● Strategy: no medium (pp) and cold nuclear matter (pA) understood inpQCD define the benchmark for the probe; results in hot medium (AB) andtheir difference with expectation provide a (pQCD or not) characterization.

Hallman: ICHEP06pQCD in p+p at RHIC

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

Inclusive jets

Hallman: ICHEP06

By comparison, in central Au+Au collisions, jet quenching is observed:

hadrons are suppressed; direct photons (the control) are not as we expect

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

Binary collision scaling

p+pNuclear Modification Factor

sNN = 200

Hallman: ICHEP06

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

Up to QM05, a reasonably strong consensus that the suppression was basically understood: radiative energy loss in a medium 30-50 times normal nuclear matter density

Then these measurements were extended to the heavy quark sector (c, b) by studying suppression of electrons from their semi-leptonic decays

Hallman: ICHEP06Heavy flavor suppression via b,c e+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

Hallman: ICHEP06

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?

Hallman: ICHEP06

One possibility: maybe all the non-photonic electrons are from charm decays?

BDMPS: N. Armesto et al, nucl-ex/0511257

c+b, collisional+radiative

c only, collisional+radiative

DGLV: Wicks et al, nucl-ex/0512076

c+b, radiative only

Submitted to PRL, nucl-ex/0607012

Hallman: ICHEP06Another thing to understand: N. P. electrons in p+p at RHIC 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

?

NB: Consistent data between multiple independent measurements; problem is comparison with theory

Hallman: ICHEP06

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

The short summary:

Hallman: ICHEP06

Di-hadron correlations: recoiling jets are strongly modified due quenching

cos()

pTassoc > 0.15 GeV

STAR, Phys Rev Lett 95, 152301

4< pTtrig < 6 GeV

STAR, Phys Rev Lett 91, 072304

pTassoc > 2 GeV

trigger

recoil

?

Well established experimental observation

Hallman: ICHEP06What is new: di-hadron correlations at higher pT

Recoil jet clearly seen above background but at suppressed rate

trigger

recoil

?

pTtrigger>8 GeV/c

Yie

ld p

er tr

igge

r

STAR, nucl-ex/0604018

Armesto: ICHEP06

Hallman: ICHEP06Recoiling 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

Detailed dynamical calculations (see T. Renk, hep-ph/0602045) suggest 75% of observed recoils are due to non-interacting jets

c.f. Armesto: ICHEP06

Hallman: ICHEP06High PT Summary

Experiment • 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 (topological 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

Hallman: ICHEP06

Conclusions:N. Armesto: ICHEP06

Hard Processes in Heavy Ion Collisions 16

● Hard processes in HIC have a twofold interest:

* Extension of pQCD to new domains: new theoretical tools, relation with other domains (hard QCD, high density QCD),...* Characterization of the produced medium.

● Together with v2 and the (anti)baryon to meson anomaly, they have been

key to establish the production of high density matter in HIC at RHIC.

● Lesson from RHIC: control experiments(pp, dAu) must be an integral part of theHIC program to get clear conclusions.

● LHC: large yields of hard processes willbe available: if problems are solved, thissubject will play a central role in theheavy ion program.

Hallman: ICHEP06

Quarkonia

Hallman: ICHEP06J/ production from p-A to Pb-Pb collisions

In S-U and peripheral Pb-Pb collisions, the data points follow this normal nuclear absorption, which scales with L, the length of nuclear matter crossed by the (pre-resonant) J/.

In central Pb-Pb collisions the L scaling is broken and an “anomalous suppression” sets in.

J/

L

Projectile

Target

The study of J/ production in p-A collisions at 200, 400 and 450 GeV, by NA3, NA38, NA50 and NA51, gives a “J/ absorption cross-section in normal nuclear matter” of 4.18 ± 0.35 mb.

J/ normal nuclear

absorption curve

S(J/) ~ exp(-L abs)NA38/NA50

450 GeV

400 GeV

200 GeV

extrap. to 158 GeV

Woehri: ICHEP06

Hallman: ICHEP06

Set A (lower ACM current)

• Combinatorial background (, K decays) from event mixing method (negligible)

• Mass shape of signal processes from MC (PYTHIA+GRV94LO pdf)

• Multi-step fit: a) DY (M>4.2 GeV), b) IMR (2.2<M<2.5 GeV), c) charmonia (2.9<M<4.2 GeV)

• Results from set A and B statistically compatible → use their average in the following

• Stability of the J/ / DY ratio:• change of input distributions in MC calculation → 0.3% (cos), 1% (rapidity)

• level of muon spectrometer target cut → < 3%

Set B (higher ACM current)

J/ / DY analysis

Woehri: ICHEP06

Hallman: ICHEP06

• Data points have been normalised to the expected J/ normal nuclear absorption, calculated with

as measured with p-A NA50 data

B. Alessandro et al., Eur. Phys. J. C39(2005) 335

J/abs = 4.18 0.35 mb

bin1 Npart = 63

bin2 Npart = 123

bin3 Npart = 175

3 centrality bins

• Qualitative agreement with NA50 results plotted as a function of Npart

Anomalous suppression present in Indium-Indium

J/ / DY vs. centrality

Woehri: ICHEP06

Hallman: ICHEP06

The J/ suppression patterns are in fair agreement when plotted versus Npart

Comparison with other SPS results

Woehri: ICHEP06

Hallman: ICHEP06

Npart

Mea

s/E

xp

1

Step position

A1A2

Step position: Npart = 82 ± 9

A1= 0.98 ± 0.03

A2= 0.85 ± 0.01

2/dof = 2.0

Resolution on Npart estimate (due to the measured EZDC resolution) taken into account

A certain amount of physics smearing can be accommodated by the data

Comparison with the extreme case of a step-like function

Woehri: ICHEP06

Hallman: ICHEP06

Sequential suppression:N. Armesto, ICHEP06

23

● In the last 5 years, lattice results and potential model calculations supporta sequential melting of quarkonium in the QGP.

● Sequential melting provides an alternative mechanism (others: comovers,percolation,...) to explain data (Karsch, Kharzeev, Satz '05): p

T broadening?

Hallman: ICHEP06

PHENIX PRL96 (2006) 012304

Proton-Proton at 200 GeV

(ppJ/) = 2.610.200.26b

RHIC Baseline MeasurementsDeuteron-Gold at 200 GeV

Consistent with 1-3 mb nuclear absorption and modest hint of

shadowing effect

Hallman: ICHEP06

Preliminary RHIC Gold-Gold Results

Sup

pres

sion

Fac

tor

Collision Centrality

Higher energy density at RHIC leads to prediction of greater suppression than at SPS.

Models over predict suppression. In fact, suppression is very similar to that found at the SPS (?): charm recombination, no J/ melting, only c? CuCu, AuAu J/ data as a function of centrality, rapidity and pT will hopefully settle these questions.

Arkhipkin, Armesto: ICHEP06

Hallman: ICHEP06

Interplay of high pT partons with the medium:

one of the most exciting questions

Hallman: ICHEP06

Medium response to jet energy loss ?

Au+Au 0-10%preliminary

3<pt,trigger<4 GeV

pt,assoc.>2 GeV

Armesto et al, nucl-ex/0405301

One example: near-side “ridge” correlated with jet trigger

Induced radiation dragged by longitudinally expanding fluid?

Hallman: ICHEP06

Another intriguing conjecture

Three-particle correlations which would show such effects (mach cone, Cherenkov gluons) are actively being pursued by STAR and PHENIX

Hallman: ICHEP06

Flow, Global Observables, etc.

Hallman: ICHEP06RHIC Initial Conditions: CGC

19.6 GeV 130 GeV 200 GeV

Charged hadron pseudo-rapidity

1) High number of Nch indicates initial high density;2) Mid-y, Nch Npart nuclear collisions are not incoherent;3) Saturation model works (Kharzeev et al)

Initial high parton density at RHICPRL 85, 3100 (00); 91, 052303 (03); 88, 22302(02); 91, 052303

(03)

PHOBOS Collaboration

Xu: ICHEP06

Hallman: ICHEP06

Yield Ratio Results

- The system is thermalized at RHIC.- Short-lived resonances show deviations. There is life after chemical freeze-out. RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184.

Thermalmodel fits

data

Tch = 163 ± 4 MeV

B = 24 ± 4 MeV

Xu: ICHEP06

pT-integrated particle yield ratios in central Au+Au collisions consistent with Grand Canonical Stat. distribution across u, d and s quark sectors (S = 1). Inferred Temp. consistent with Tcrit (LQCD) phase transition

Hallman: ICHEP06

2cos2 vx

y

p

patan

Anisotropic Flow

x

yz

px

py

Elliptic Flow in Heavy Ion Collisions

Peripheral Collisions

Hallman: ICHEP06

Comparison of elliptic flow and predictions of hydro potentially provide evidence for local thermalization and an EOS with a soft point

- Minimum bias data! At low pT, model result fits mass hierarchy well!- Details do not work, need more flow in the model!

P. H

uo

vi ne

n, p

r ivate

com

mu

nica

t i on

s, 20

04

Xu: ICHEP06

Hallman: ICHEP06

-mesons Flow: Partonic Flow

-mesons are very special:- they do not re-interact in hadronic environment

- they show strong collective flow - they are formed via coalescence with thermal s-quarks

STAR Preliminary: QM05, M. Lemont, S. Blyth Hwa and Yang, nucl-th/0602024; Chen et al., PRC73 (2006) 044903

STAR Preliminary

Xu: ICHEP06

Hallman: ICHEP06

Collectivity, Deconfinement at RHIC

- v2 of light hadrons and multi-strange hadrons - scaling by the number of constituent quarks

At RHIC: mT - NQ scaling

Partonic Collectivity

Deconfinement

PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04), 95, 122301(05) nucl-ex/0405022, QM05

S. Voloshin, NPA715, 379(03)Models: Greco et al, PRC68, 034904(03)Chen, Ko, nucl-th/0602025Nonaka et al. PLB583, 73(04)X. Dong, et al., Phys. Lett. B597, 328(04).….

i ii

Xu: ICHEP06

Hallman: ICHEP06

KEKETT/n scaling across collision centralities/n scaling across collision centralities

KET/n scaling observed across centralities

R. Lacey

Lacey: ICHEP06

Hallman: ICHEP06A remarkable scaling of the fine structure of

elliptic flow is observed at RHIC

At midrapidity v2 (pt,M,b,A)/n = F(KET/n)*ε(b,A) R. Lacey

Lacey: ICHEP06

Hallman: ICHEP06

v2{2}, v2{4}, non-flow, and flow fluctuations

* 2 21 2 2

* 1/ 22 1 2

* * 4 2 21 2 3 4 2 2

1/ 4* 2 * *2 1 2 1 2 3 4

;

{2}

2 2 2

{4} 2

iu u v u e

v u u

u u u u v v

v u u u u u u

Several reasons for v to fluctuate in a centrality bin:1) Variation in impact parameter in a centrality bin

(taken out in STAR results)2) Real flow fluctuations (due to fluctuations in the

initial conditions or in the system evolution)

2

* 22 2 2 22 1

2 2vv uu v vv v

22

22 2* * * 2 24 4

2 2 24 2 12

vv

v uu uuu u v vv

Different directions to resolve the problem:- Find methods which suppress / eliminates non-flow

- Add more equations assuming no new unknowns

- Estimate flow fluctuations by other means

2 equations, at least 3 unknowns: v, δ, σ

22 2 2; {2} /v v v

Correlations with large rapidity gaps

Subject of this talk

Non-flow Flow fluctuations

Non-flow (not related to the orientationof the reaction plane) correlations:- resonance decays- inter and intra jet corelations

Use equations for v2{n}, n>4

Voloshin: ICHEP06

Hallman: ICHEP06

Shown in black are resultsobtained by correlatingtwo random particles from Main TPC. Non-flow contribution can be largeand positive.

In blue are results forv2 in the Main TPC regionobtained from correlations (Forward*Main) and(East*West). These resultsare affected insignificantly by non-flow correlations.

Note: significantly largerrelative non-flow contribution in Cu+Cu case compared to Au+Au

v2 from (Forward TPC * Main TPC) correlations

| η | < 0.9 (Main TPC) -3.9 < η < -2.9 (FTPC East)

2.9 < η < 3.9 (FTPC West)

Voloshin: ICHEP06

Hallman: ICHEP06

Some next steps for flow studies

Disentangle fluctuations and correlations to measure <v2> and use the rapidity dependence of the v2 fluctuations to eliminate the uncertainty in the initial conditions (CGC or Glauber)

Understand non-flow at high pt to extract precise particle type dependence of intermediate and high pt v2

Study the systematics (pt, centrality and -/sNN dependence) of ncq scaling and phi or Omega v2. Do indications of a quark and gluon phase disappear anywhere?

Measure direct D meson v2

Hallman: ICHEP06Energy Dependence of Particle Production

PHENIX @ QM01Nucl. Phys. A698, 171 (2002).

dNch/dη ~ ln(√s)

PHENIXPRC 71, 034908 (2005)

dNch/dη = (½Npart·A)ln(√sNN/√s0)A = 0.74±0.01 √s0 = 1.48±0.02 GeV

LHC prediction based on data trend for 350 participants:

dNch/dη @ η=0: 1100Total Nch : 13000

PHOBOS PRL 91,52303 (2003)

Milov: ICHEP06

Hallman: ICHEP06

The QCD critical point search

Ejiri, et.al.Taylor Expansion

Fodor, KatzLattice Re-weighting

Gavai, GuptaB Lower Limit

B √sNN

———————————————————

180 MeV 25 GeV420 MeV 7.5 GeV725 MeV 4.5 GeV

———————————————————Cleymans, et.al. M. Stephanov: hep-ph/0402115

For B=0, lattice QCD predicts a smooth crossover between hadrons and quark-gluon plasma at Tc=190 MeV

For B>0, lattice calculations are less reliable: predictions for location of the critical point are highly uncertain

Hallman: ICHEP06NUCLOTRON JINRProject parameters: maximum energy

5 GeV/nucl. for nuclei with А ~ 200.Upgraded Nuclotron: up to 10 GeV/nucl.

Sissakian, Sorin, Toneev: ICHEP06

Hallman: ICHEP06

1. A study of the phase diagram in the domain populated by heavy-ion collisions with the bombarding energy ~ 5 ÷ 10 GeV/nucleon to search

for the mixed phase seems to be a very attractive task.

2. The use of the isospin asymmetry as an additional conserving parameter to characterize the created hot and dense system attracts new interest in this problem (critical end-boundary hypersurface ? ).

3. The available theoretical predictions are strongly model dependent giving rather dispersive results. There are no lattice QCD predictions for this highly nonpertubative region. Much theoretical work should be done and only future experiments may disentangle these models.

4. A JINR Nuclotron possibility of accelerating heavy ions to the project energy of 5A GeV and increasing it up to 10A GeV can be realized in two-three years. This will enable us to effort a unique opportunity for scanning heavy-ion interactions in energy, centrality and isospin asymmetry. It seems to be optimal to have the gold and uranium beams in order to scan in isospin asymmetry in both central and semi-central collisions at not so high temperatures.

Conclusions

Sissakian, Sorin Toneev: ICHEP06

Hallman: ICHEP06

Large Heavy-ion Collider (LHC)

Hallman: ICHEP06Solenoid magnet 0.5 T Cosmic-ray trigger

PHOS

HMPID

Central tracking system• ITS • TPC• TRD• TOF

Dipole MagnetForward detectors

• FMD, T0, V0, ZDC• PMD

• absorbers• trigger chambers

Tracking Stations

Muon Spectrometer

The ALICE Detector Safarik: ICHEP06

Hallman: ICHEP06

ALICE PID • , K, p identified in large acceptance (2 * 1.8 units ) via a combination of dE/dx in Si and TPC and TOF from ~100 MeV to 2 (p/K) - 3.5 (K/p) GeV/c•Electrons identified from 100 MeV/c to 100 GeV/c (with varying efficiency) combining Si+TPC+TOF with a dedicated TRD •In small acceptance HMPID extends PID to ~5 GeV •Photons measured with high resolution in PHOS, counting in PMD, and in EMC

0 1 2 3 4 5 p (GeV/c)

1 10 100 p (GeV/c)

TRD e / PHOS /

TPC + ITS (dE/dx)

/K

/K

/K

K/p

K/p

K/p

e /

e /

HMPID (RICH)

TOF

Alice uses ~all known techniques!

Safarik: ICHEP06

Hallman: ICHEP06

Hadronic charmCombine ALICE tracking + secondary vertex finding capabilities (d0~60m@1GeV/c pT) + large acceptance PID to detect processes as D0K-+

~1 in acceptance / central event ~0.001/central event accepted after reconstruction and all cuts

S/B+S ~ 37

S/B+S ~ 8for 1<pT<2 GeV/c(~12 if K ID required)

significance vs pTResults for 107 PbPb ev. (~ 1/2 a run)

Safarik: ICHEP06

Hallman: ICHEP06

PDFsm RFc ,,,

00

PDFsm RFc ,,,

00

s = 14 TeV

Charm in pp (D0 → K) Sensitivity to NLO pQCD params

down to pt ~ 0 !

Safarik: ICHEP06

Hallman: ICHEP06

0 1 2 10 100

pt (GeV/c)

Bulk propertiesHard processes

Modified by the medium

ALICE

CMS&ATLAS

LHC Experiments

PID

T=QCD Qs

Single particle spectraCorrelation studies

Jet reconstruction

Safarik: ICHEP06

Hallman: ICHEP06

1.1 CMS detector

Si tracker with pixels | | < 2.4 good efficiency and low fake rates for pt > 1 GeV, excellent momentum resolution, p: pt/pt < 2%

Muon chambers || < 2.4 Fine grained high resolution calorimetry (HCAL, ECAL, HF) with hermetic coverage up to || < 5

TOTEM (5.3 η 6.7) CASTOR (5.2 < || < 6.6) ZDC (z = ±140 m, 8.3 ||)

B = 4 T

Fully functional at highest multiplicities; high rate capability for (pp, pA, AA), DAQ and HLT capable of selecting HI events in real time

CASTOR ZDCTOTEM

5.2 << 6.6 8.3 <5.3 << 6.7

Sarycheva: ICHEP06

Hallman: ICHEP06

2.3 J/ and spectra for multiplicity dNch/d = 2500

For Pb-Pb at integrated luminosity 0.5 nb-1

/K decays into b,c-hadrons into

S/B N

J/ 1.2 180000

0.12 25000

Combinatorial background: Mixed sources, i.e. 1 from /K + 1 from J/ 1 from b/c + 1 from /KSarycheva, Kodolova: ICHEP06

Hallman: ICHEP06

2.4 J/ and spectra

(subtraction of the like sign spectra)

both

muons

|| < 2.4

both

muons

|| < 0.8

both

muons

|| < 2.4

both

muons

|| < 0.8

See talk of Olga Kodolova for details.See talk of Olga Kodolova for details.

Sarycheva, Kodolova: ICHEP06

Hallman: ICHEP06

Channel Time = 1.2 106 s,

AA = A2pp, A = 208 (Pb) (Pythia6.2, CTEQ5M)

jet+jet, ETjet > 100 GeV 4 106

jet tagged by h,0, ET

jet > 100 GeV,

zh,0 > 0.5

2 105

B-jet tagged by ,

ETjet > 100 GeV, z > 0.3

ETjet > 50 GeV, z > 0.3

700

2 104

3.1 Jet cross section & expected event rate

Expected statistics for CMS acceptance(no trigger and reconstruction efficiency)

jet,| < 3, |h,| < 2.4

CERN Yellow Report, hep-ph/0310274

Sarycheva: ICHEP06

Hallman: ICHEP06

6.1 Summary and outlook

• At LHC a new regime of heavy ion physics will be reached where hard particle production can dominate over soft events, while the initial gluon densities are much higher than at RHIC, implying stronger partonic energy loss observable in new channels.

• CMS is an excellent device for the study of quark-gluon plasma by hard probes: - Quarkonia and heavy quarks - Jets, ''jet quenching'' in various physics channels • CMS will also study global event characteristics: - Centrality, Multiplicity - Correlation and Energy Flow reaching very low pT

• CMS is preparing to take advantage of its capabilities - Excellent rapidity and azimuthal coverage, high resolution

- Large acceptance, nearly hermetic fine granularity hadronic and electromagnetic calorimetry - Excellent muon and tracking systems - New High Level Trigger algorithms specific for A+A

- Zero Degree Calorimeter, CASTOR and TOTEM will be important additions extending to forward physics

Sarycheva: ICHEP06

Hallman: ICHEP06

For completeness…

Hallman: ICHEP06

Hallman: ICHEP06

Hallman: ICHEP06

Hallman: ICHEP06

Novel aspects of heavy ions at CERN:

• Probe initial partonic state in a novel Bjorken-x range

(10-3 – 10-5) :– nuclear shadowing,– high-density saturated

gluon distribution (CGC)– effectively moves RHIC

forward region to mid-rapidity at LHC

• Larger saturation scale (QS=0.2A1/6√s= 2.7 GeV) particle production dominated by the saturation region

Qualitatively new regime

J/ψ

ALICE PPR CERN/LHCC 2003-049

10-6 10-4 10-2 100

x

108

106

104

102

100

M2 (

Ge

V2)

10 GeV

Safarik: ICHEP06

Hallman: ICHEP06

Already a glimpse of saturation (TBC) in d+Au at RHIC

Cronin enhancement Cronin enhancement suppression suppression

I. Arsene et al., BRAHMS PRL 93 (2004) 242303.

Staszel: ICHEP06 See also talk by B. Gay Ducati

Hallman: ICHEP06

The heavy ion session covered all the above,

Plus other important experimental topics that could not be covered in the summary due to time:

– Ultra-peripheral heavy ion collisions (Timoshenko, Emel’yanov)

– Femptoscopic Correlations in Heavy Ion Collisions (Lednicky)

– Scale Dependent Analysis Approach for STAR AuAu Collisions (Rogachevsky)

Hallman: ICHEP06

Conclusions• It is unequivocal that a new form of dense matter is produced at

RHIC (jet quenching, v2, (anti) baryon / meson anomaly)– The data have led to new intriguing questions

• Strong suppression of NPE’s for open charm & bottom ( c,b quark abundances or collisional vs radiative energy loss?)

• How much influence does recombination/feed-down have for J/Psi yields at RHIC. Why does the apparent suppression seem so similar to the SPS where the energy density is lower?

• How much elliptic flow is the result of the initial-state conditions (CGC)?• Do we see other effects predicted by the CGC?• What is the full significance of observed NCQ scaling for bulk hadronic properties

– Probing this new matter in detail is going to be extremely exciting (Cherenkov gluons, jet tomography…)

Such questions are the focus of ongoing RHIC upgrades which are beginning to come on line

Other exciting new horizons are now within view (QCD critical point search, start-up of the heavy ion program at the LHC

The comparison of the sQGP at RHIC and the matter produced in heavy ions collisions at the LHC will provide a watershed of new insight

Hallman: ICHEP06

Backup Slides

Hallman: ICHEP06Radiative 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)

Hallman: ICHEP06

Extracting qhat from hadron suppression data

RAA: qhat~5-15 GeV2/fm

Hallman: ICHEP06

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…

Hallman: ICHEP06

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

Hallman: ICHEP06

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

Hallman: ICHEP06

Light hadrons:N. Armesto

Hard Processes in Heavy Ion Collisions: 3. Jet quenching 70

pT

parton>5 GeV

Detailed modeling of geometry.(Quark Matter 05)

Dainese, talk at PANIC05

D'Enterria '05Dainese et al '04

Hallman: ICHEP06

Recombination:N. Armesto ICHEP06

71

● At RHIC/LHC, ~ 10/100 ccbar pairs per collision: regeneration?

● To be tested by rapidity distributions, pT broadening, LHC?

Hallman: ICHEP06

• Event selection: 1-2%

• Input to Glauber model (Indium density distributions)

• Link EZDC – Npart

• Error on scaling J/pp from 450 to 158 GeV: 8% (centrality independent)

• Error on abs: 3–4 % (almost centrality independent)

• Error due to the J// DY normalization: ~ 6% (centrality independent)

>10% for EZDC < 3 TeV,negligible elsewhere

5–10 % for EZDC < 3 TeVnegligible elsewhere

Various sources of systematic errors have been investigated; their effects on the measured suppression pattern are:

• The most central bin is affected by a sizeable systematic error relatively to the others

• There is a ~10% systematic error, independent on centrality

Summary on systematic errors

We can accurately evaluate the shape of the suppression pattern, but its absolute normalisation is more uncertain

Woehri: ICHEP06

Hallman: ICHEP06

1.2 Forward Region Layout

|| > 3

(5.3 << 6.7)

TOTEM

Forward Forward HCalHCal

(3 << 5)

CASTOR (~ 10 λI)

(5.2 << 6.6)

ZDC

HADHADEMEM

(z = 140 m)

(8.3 <)

Hallman: ICHEP06

STAR capabilitiescorrelations

resi

dual

/re

f (G

eV

/c)2

STAR and NA49 K/ fluctuations

With 2 azimuthal coverage: STAR will excel at measurements of:

v1, v2, v4, for many particle-types (is and v2 from a QGP stage? does it go to zero at lower sNN?)correlations & fluctuations (is there a max. in fluctuations? what’s the signal source?)

Particle identification can be achieved over a broad pT range using:

TPC dE/dx, ToF, Topology, etc

Hallman: ICHEP06

εBJ=(Sτ)-1dET/dy √sNN = 200GeV (0%-5%) & τ =1fm/c 5.4 ± 0.6GeV/(fm2c)

What about “τ”? Limiting: τ = 1/(2Rγ) 0.15 fm/c Formation: τ = h/mT ≈ 0.6ET/Nch 0.3 fm/c

Bjorken Energy Density estimate

PHENIX PRC 71, 034908 (2005)

Milov: ICHEP06