High Energy and Nuclear Physics

Town Meeting at BNLJanuary 21-23, 2001

Diverse group of theorists and experimentalists

RHICHadron partonic structure

Exploit physics commonality among this broad community Presentation today:

Heavy Ion Physics - BarbaraSpin, p-A physics - Steve Vigdor

Overarching goal of High Energy Nuclear Physics

Understanding strong interactions at the partonic levelconfinementgeneration of mass of ordinary matterquark-gluon structure of h, nucleibehavior of gluons at high density

QCD: theory underlying the physicsNotoriously hard to solve in strong coupling

regime(most of the interesting cases!)

Synergism: QGP partonic structure initial conditions in RHI quantitative calculation of QGP probes measurement of QGP properties

Significance: mysteries of structure of matter cosmological impact nuclei: laboratory for the many body problem

in QCD

Approach

Create high energy density matterStudy confinement, mass generation by

inducing transition to QGPProperties 10 s after big bang

tool: heavy beams at RHIC p-p, p-A for baseline physics

Universal behavior of gluonic matter?many-parton features of QCD in hadrons and

nuclei (cold & hot)

int vs collision energy & gluon density do gluons saturate? Bose condensate?

tool: A-A, p-A, e-A at high energy highest gluon densities

Resolving power of high energy beamsdistribution of pointlike q,g in matterrole of chirality in phase transition and in the

hadron properties

Achievements: first collisions at RHIC!

Amazing RHIC completion and commisioningThanks to TomRoser & BNL team !

Within 6 months:

record first collisionscommission 4 detectorspublish first PRLs

Extensive scientific results at Quark Matterconference at Stony Brook in January 2001

I’ll show some of the most exciting ones here

Charged particle multiplicity: RHIC enters a new regime!

with quenching

No jet quenchingSTARPHENIXBRAHMS

Highest ever!

Energy density>50% higher thanat CERN

nucl-ex/0012008

PHOBOS PRL85, 3100 (2000)

hard scattering important!produces ~ 40% of charged particles

hard: scales with Ncollsoft: scales with Npart

data begin to distinguishamong predictions!

Collective effects?see via elliptic flow

Origin: spatial anisotropy of the system when created followed by rescattering of evolving system spatial anisotropy momentum anisotropy

v2: 2nd harmonic Fourier coefficient in azimuthal distribution of particles with respect to the reaction plane

y2 x2 y2 x2

2cos2 v

x

y

p

patan

Almond shape overlap region in coordinate space

Large v2 at RHIC (as predicted by hydrodynamics)

STARPRL 86 (2001) 402

Hydro. CalculationsHuovinen, P. Kolb and U. Heinz

v2 = 6%: larger than at CERN or AGS!

Implies early pressure buildup therefore early equilibration !?

Presence of large collective elliptic flow confirmed by PHOBOS and PHENIX!

Central region approaching net baryon-free

BRAHMS preliminary

¯

_

-

--

---

-

STAR preliminary

s

anti

bar

yon/

bary

onantiproton/protonratio much largerat RHIC central regiondominated by produced pairs, notby initial baryons

Long predicted new QGP signaturefirst becoming accessible at RHIC

first hints of jet quenching?

J.C. Dunlop, STARF. Messer, PHENIX

Spectra to pt > 5 GeV/cby PHENIX & STAR

Observe a deficit of high pt

particles in central collisions predicted signal of jet quenching in dense matterby Wang, Gyulassy

0

constrain explanations with systematic data

How yields scale with Ncoll or Npart volume dependence

2

2

2

2

t

ppcoll

t

AA

dp

dN

dpd

plot as function of pt and Ncoll

(AuA

u/c

olli

s ion

)/pp

NN collisions 103

pt = 0.5 GeV/c

soft physicsscales as Npart,not Ncoll

pt = 3, 4 GeV/c

do scale with Ncoll

as expected forhard scattering

deficit sets in atNcoll > 300??

PHENIX preliminary

Deficit in both 0 and charged

Identify particles to separate competing processes

Note excess in charged particle spectrum due to baryons - this is new!

Achievements in theory

Color superconductivity and QCD phase diagram

phases at low T and high densityapplying BCS & QCD asymptotic

freedom find new phases of QCD matter

understanding initial conditions and small-x gluons

increasing gluon density drives system to weak coupling regime

theoretical techniques, numerical methods for gluon distribution at high density

Quantitative predictions for many observables at RHIC!!

reported at QM00,01 and compiled

Computing infrastructure

developed computing infrastructure successfully handle massive data setssupport analysis by many users

in disparate places

pioneering in scopenot just in nuclear physics, but lead the

particle physicists also

Compare central Au-Au to p-p

Deficit at high pt seen by both STAR and PHENIX

different from expectation:increase at low pt approach 1 at high pt

deficit predicted if quarkslose energy in dense medium(jet quenching)

X.N. Wang

Central Au + Au

p-QCD overestimates the cross-sectionfor 0 at least a factor of 5for charged factor of 2 misses p &p contribution

shadowing & pt-broadening insufficient

dE/dx = 0.25 GeV/fm consistent with 0

magnitude & shape differ for charged

Radial Flow analysis: mt - slopes versus mass

Naïve: T = Tfreeze-out + m r 2 where r = averaged flow velocity

Increased radial flow at RHICßr (RHIC) = 0.6c ßr (SPS/AGS) = 0.4 - 0.5c

Tfo (RHIC) = 0.1-0.12 GeV Tfo (SPS/AGS) = 0.12-0.14 GeV

STARSTAR

Challenges

What are the properties of QCD at high temperature and density?Universal behavior of gluonic matter?

Is there evidence for deconfinement?Correlated onset of predicted signals?

e.g. J/ suppression, s,c enhancement, jet quenching, fluctuations

will measure this year!control via p-A, p-p measurementsmap collision volume, energy

What is the initial energy density & T?compare data to lattice QCD predictions

comprehensive theoretical description Evidence for gluon saturation?

do gluon dynamics dominate the physics?

Restoration of chiral symmetry?Evidence of in-medium mass changes?Branching ratio modifications?

Challenges, II

What are the initial conditions for heavy ion collisions?

Hard processes (early) probese.g. jets, heavy quarks

Energy loss: interactions in the mediumBound states: color propertiesHard photons: partonic structurec,b quarks: gluonic interactions

Challenges, III

Does the matter approach thermal equilibrium?Thermalization & gluon multiplication driven by

energy transfer from fast particles?particle yields & correlations will tell

Thermal radiation: & dileptonsMomentum & flavor distributions reflect

chemical, thermal equilibrationMultiparticle collective observables

equilibration early or late (or never?)What is the equation of state?

How does the hadronic phase evolve?Hadrons measure dynamics, temperatureSpace-time evolution vs. initial conditions

vary volume, temperature

Build coherent theoretical picture constrained by observed initial conditions and final state!

International Role

RHIC facilityUnique capability in the world

Flagship facility in the U.S.LHC in >2006: will explore different physics

regimeStrong international participation in

experiments Fraction of collaborators from how many

countries Continue close collaboration pioneered at

CERN Major contributions from Japan

experiment & RHIC hardwaretheory

contributions to experiments Sweden, France, Germany, Russia (in kind),

Denmark, Poland, Israel, China, India

High Energy Density Theory is truly international

Establishment of RIKEN-BNL CenterFunded by JapanLed by T.D. Lee

International sponsorship of theory centers

INT (US), ECT* (Europe), RBRC (Japan)

Many international collaborations and exchanges

Strong collaboration with experimenters

Opportunities for U.S. nuclear physicists at LHC

complementary physics regime to RHIC high density of virtual low-x gluons

should be saturated time evolution by classical dynamics

high production rate for hard strongly interacting QGP probes

use also weakly interacting probes W, Z along with spatial dependence of saturation &

shadowing effectsparton dynamics expected to dominate

collective features of collisions US participation essential

to maintaining our position at frontier of heavy ion research

Initiatives for High Energy Nuclear Physics

Run RHIC fully

Detector upgradesnear term

extend kinematic reachphysics coverageability of experiments to cross check

fully utilize running time!major upgrades

open additional physics– charm, low mass lepton pairs

optimize detectors for x40 luminosity

R&D for luminosity upgrade for RHIC

Endorse development of eIC

RHIC running time driven by

Low production probeshigh pt hadrons (need >10 GeV/c)J/ and charmed mesonsmultistrange baryons-jet and jet-jet coincidences

Need rare processes in energy, beam scansnot just soft physicsp-p and p-A comparisons crucial!

10 weeks of running at design L0 to 20 GeV/c pt

30K J/ , 6K J/ e+e-15K e from charm, e-coincidencemultistrange baryon pt spectra-jet correlation sample

“Strawman” run plan

Year Run Plan Physics

2001 long 200 GeV/A Au+Au

commission, run p+p

2 lower energy Au+Au

J/, high pt, multistrange

1st spin run, comparison

scan Tinit, vt

2002 200 GeV/A Au+Au (7wks)

lighter beams (3x5 wks)

polarized p+p (10wks)

Complete 2001 program

scan system volume, Npart

spin

2003 Au+Au (10 wks)

polarized p+p (10 wks)

p+Au (12 wks)

High pt, observe, multi-strange baryon slopes

comparison & spin

comparison, structure fns.

2004 p+nucleus (22 wks) polarized p+p

comparison, Drell-Yan studies

2005 long Au + Au

lighter ion

open charm

Impact of shorter runs:scan in energy, volume not possible within 2-3 years (need these for reasonable first conclusions)p-A comparison, open charm measurements compromised

Energy scan at RHIC

Elliptic and radial flow excitation functions

map outgenerated pressure

H. AppelshauserCERES/QM01

N. XuSTAR/QM01

volume scan

importance of p-A

Luminosity upgrade for RHIC

Physics goals spectroscopy, Drell-YanW,Z, high pt open charm, B yields and distributionstagged jetsgreater kinematic reach

y, Q2, pt

development of electron ring for cooling overlaps with eIC development

R&D in the coming 5 yearsaccelerator development: electron

cooling of ion beamsdetector R&D

Recommendations I: The RHIC program

Highest priority is full operation of RHICRunning time recommended by NSAC in

1996 is neededStatistics for rare processesScans in energy, ion sizePolarized p-pp-A

Support of theory and experiment group operations

Near term upgrades to detectorsComplete utilization of RHIC runningExtend kinematic and physics reach

Recommendations II: R&D on accelerator & detector upgrades

To elucidate QCD structure of matter via rare QGP probes at RHICincrease luminosity by > order of

magnitudepursue R&D toward this goal

Develop high luminosity e-ion collider

R&D on detector technologiesImprove background rejection for

charm, dilepton QGP probesOptimize tracking with high vertex

resolution and rate capability

Recommendations III: Massively Parallel Computing

Develop multi-teraflop parallel computing facility For lattice gauge Other large-scale theoretical problems,

(e.g. hydrodynamics, cascades, Green’s function MC)

Joint effort between BNL, JLAB, FNAL Aim for 10 teraflop capability~ $1.5M per teraflop

apply to DOE Initiative SciDAC(Scientific Discovery through Advanced

Computing)

Recommendations IV: Physics at the LHC

in 2006, LHC will provide highest energy HI beams

with dedicated HI experiment (ALICE)

new physics domain

focussed program of U.S. participation

moderate resourceseven moderate U.S. effort ~50 physicists significant impact on LHC heavy ion

program

p-p interpolated for s=130 GeV

P. Braun-Munzinger, nucl-ex/0007021

Chemical Freeze-out

Baryonic Potential B [MeV]

Chem

ical Tem

pera

ture

Tch

[M

eV

]

0

200

250

150

100

50

0 200 400 600 800 1000 1200

AGS

SIS

LEP

/ SppS

SPS

RHIC quark-gluon plasma

hadron gas

neutron stars

early universe

thermal freeze-out

deconfinementchiral restauration

Lattice QCD

atomic nuclei