March 27, 2003University of Buffalo Colloquium1 Status of the Search for the Quark-Gluon Plasma at...

March 27, 2003University of Buffalo Colloquium 1

Status of the Search for the Quark-Gluon Plasma at RHIC

Steven ManlyUniv. of Rochester

Colloquium at Univ. of BuffaloMarch 27, 2003

[email protected]://hertz.pas.rochester.edu/smanly/


The starting point

Yo! What’s da matter?


What forces exist in nature?

What is a force?

How do forces change with energy or temperature?

How has the universe evolved?

How do they interact?


Force Source Range StrengthGravitation mass infinite 10-39

Electromagnetism Electriccharge

infinite 10-2

Strong nuclear Colorcharge

10-15 m 1

Weak nuclear Weakcharge

10-18 m 10-5


quarks leptonsGauge bosons

u c t

d s b

e

e

W, Z, , g, Gg

Hadrons

Baryons qqq qq mesons

p = uud

n = udd

K = us or us

= ud or ud

Strong interaction

nuclei

e

atomsElectromagnetic

interaction


Quantum Chromodynamics - QCD

Gauge field carries the charge

q q

distance

energy density, temperature

rela

tive

stre

ngth

asymptotic freedom

qq qq

confinement

q qqq


Why do we believe QCD is a good description of the strong interaction?

Deep inelastic scattering: There are quarks.

From D.H. Perkins, Intro. to High Energy Physics

nucleon

parton

P

Px



No direct observation of quarks: confinement



ee

qqhadronseeR

)(

P. Burrows, SLAC-PUB7434, 1997

R. Marshall, Z. Phys. C43 (1989) 595

Need the “color” degree of freedom



Event shapes

e+e- Zo qq e+e- Zo qqg



Measure the coupling

P. Burrows, SLAC-PUB7434, 1997


Strong interaction is part of our heritage


Chiral symmetry: the “other” source of mass

qq

qq qq

qq

qq

qq

q

QCD vacuum

Quark condensate

A naïve view …


Relativistic heavy ions

•Two concentric superconducting magnet rings, 3.8 km circum.

•A-A (up to Au), p-A, p-p collisions, eventual polarized protons

•Funded by U.S. Dept. of Energy $616 million

•Construction began Jan. 1991, first collisions June 2000

•Annual operating cost $100 million

•Reached 10% of design luminosity in 2000 (1st physics run)!!

•AGS: fixed target, 4.8 GeV/nucleon pair

•SPS: fixed target, 17 GeV/nucleon pair

•RHIC: collider, 200 GeV/nucleon pair

•LHC: collider, 5.4 TeV/nucleon pair


The view from above

March 27, 2003University of Buffalo Colloquium 19STAR


Au-Au collision in the STAR detector


Isometric of PHENIX Detector


Brahms experiment

From F.Videbœk


The PHOBOS Detector (2001)

Ring Counters

Time of Flight

Spectrometer

• 4 Multiplicity Array

- Octagon, Vertex & Ring Counters• Mid-rapidity Spectrometer• TOF wall for high-momentum PID• Triggering

- Scintillator Paddles Counters- Zero Degree Calorimeter (ZDC)

Vertex

Octagon

ZDC

z

yx

Paddle Trigger Counter

Cerenkov

1m

137000 silicon pad readout channels


Central Part of the Detector

(not to scale)

0.5m


Au-Au event in the PHOBOS detector


The goals Establish/characterize the expected QCD deconfinement phase transition

quarks+gluons hadrons

Establish/characterize changes in the QCD vacuum at high energies: chiral symmetry restoration and/or disoriented chiral condensates

Understand the nuclear equation of state at high energy density

Polarized proton physics


Beamline

Terminology: angles


Beamline

Terminology: anglesPseudorapidity = = Lorentz invariant

angle with repect to the beampipe

0

+1

+2

+3

-1

-2

-3


Terminology: angles = azimuthal angle about the beampipe

Beamline


“Spectators”

Zero-degreeCalorimeter

“Spectators”

Paddle Counter

peripheral collisions central collisions

Nch

Npart

6%

Terminology: centrality

Thanks to P. Steinberg for constructing much of this slide

“Participants”


Signatures/observables

Energy density or number of participants

Measured value

•Strange particle enhancement and particle yields

•Temperature

•J/ and ’ production/suppression

•Vector meson masses and widths

•identical particle quantum correlations

•DCC - isospin fluctuations

•Flow of particles/energy (azimuthal asymmetries)

•jet quenching

Each variable has different experimental systematics and model dependences on extraction and interpretation

MUST CORRELATE VARIABLES


RHIC operation

12 June, 2000: 1st Collisions @ s = 56 AGeV

24 June, 2000: 1st Collisions @ s = 130 AGeV

July 2001: 1st Collisions @ s = 200 AGeV

Dec. 23, 2002: 1st d-Au collisions @ s = 200 AGeV

Peak Au-Au luminosity = 5x1026 cm-2s-1

Design Au-Au luminosity = 2x1026 cm-2s-1

Ave luminosity for last week of ‘02 run = 0.4x1026 cm-2s-1

Run 1

Run 2Run 3

Run 2:


From Thomas Roser


Energy flow, Particle multiplicity high energy density

Particle production QCD is QCD is QCD

Large flow, species yields equilibration/thermalization

Spectra, flow, jets Jet quenching

Not talking about Bose-Einstein correlations, strangeness enhancement, J/ suppression, balance function, direct photon production, mass shifts, width shifts, etc.


Energy density of proton and lattice QCD calculations

Expect deconfinement phase transition to occur at an energy

density of 1-2 GeV/fm3

Experimental results at RHIC imply 5 GeV/fm3

3/6.4

2

0/

fmGeVo

yT

BJ R

dydE

4.6 GeV/fm3

Assumes R=size of Au nucleus and To=1fm/c

PHENIX Collaboration, PRL 87 (2001) 052301


PHOBOS Data on dN/din Au+Auvs Centrality and s

dN

/d

19.6 GeV 130 GeV 200 GeVPreliminary

PHOBOS PHOBOS PHOBOS

Typical systematic band (90%C.L.)

Basic systematics of particle production


Energy Dependence of Central dN/dScale by Npart/2 & shift to =- ybeam

The “fragmentation region” extent grows with sNN

19.6 GeV is preliminary19.6 GeV is

preliminary Systematic errors not shown

PHOBOS Au+Au

PHOBOS Au+Au

dN

ch/d

/<

Np

art>

dN

ch/d

6% central

beamy

Once you are smashed by a fast moving wall of bricks, it doesn’t

make much difference if the bricks are going a little faster. That only determines how far your parts are spread along the

path.


(Mueller 1983)

)/exp( sAsch BN

Universality of particle production

From P.Steinberg


pp/pp

A+Ae+e-

From P.Steinberg



Universality

e+e- Au+Au pps s effs

2/sseff

p+pp+X :


From P.Steinberg


Collision region is an extruded football/rugby ball shape

CentralPeripheral

Elliptic flow


Elliptic flow

12

63

9

12 3 6 9 12

Num

ber

of p

arti

cles


12

63

9

Num

ber

of P

arti

cles

12 3 6 9 12


b (reaction plane)

Elliptic flow

dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R) + ... )

Determine to what extent is the initial state spatial/momentum anisotropy is mapped into the final state.


Elliptic Flow at 130 GeV

(PHOBOS : Normalized Paddle Signal)

Hydrodynamic limit

STAR: PRL86 (2001) 402

PHOBOS preliminary

Hydrodynamic limit

STAR: PRL86 (2001) 402

PHOBOS preliminary

Thanks to M. Kaneta


Flow vs Pt and Hydro describes low pt vs.

particle mass, fails at high pt and high-

T. Hirano

(consider velocity and early, self-quenching asymmetry)


Chemical equilibration and freezeout temperature

M. Kaneta, STAR Collaboration

• Thermal models can describe data VERY well.

• Thermal model lets us put data on QCD phase diagram– RHIC energies appear close to Tc

LEP

F. Becattini, hep-ph/9701275


Spectra

0.2<y<1.4

The fun starts when one

compares this to pp spectra

STAR results, shown at QM02


– Production of high pT particles dominated by hard scattering

– High pT yield prop. to Ncoll

(binary collision scaling)

– Compare to pp spectra scaled up by Ncoll

– Violation of Ncoll scaling observed at 130GeV(PHENIX/STAR)

– Jet quenching?

Comparing Au+Au and pp Spectra_

_

Au+Au


Suppression in Hadron Spectra

Shown by T. Peltzmann at QM02


Jet-quenching: hard parton interacts with medium, which softens the momentum spectrum in A-A relative to pp


Peripheral Au+Au data vs. pp+flow

STAR, David Hartke - shown at QM02

Count tracks around very high pT particle


Central Au+Au data vs. pp+flow

STAR, David Hartke - shown at QM02

Away side jet disappears!!


Jet-quenching also gives break in flow vs. pT


Initial state vs. final state effects

Jet-quenching is a final state effect - “Weisaker-Williams” color field of parton interacting with colored medium. Energy loss is medium-size dependent (radiated wavelengths less than source size)

Initial state effect - saturation models color glass condensate (recent review: Iancu, Leonidov, McLerran, hep-ph/0202270)

can also qualitatively explain some features of the data

Current d-Au run will help untangle this mess!


Showed you too much - I apologize

Showed you too little - I apologize

Status of the search for the QGP at RHIC?

RHIC/experiments running very well

Up till now …

characterization and model tuning


Hot, dense, opaque medium is formed

Energy density above lattice predictions for deconfined state

Local thermal equilibrium achieved

Full 3-d structure away from mid-rapidity not yet understood

Interesting signals being pursued … jet-quenching?

Probably standing on the precipice of a claim/discovery

Remains to be seen if systematic study and pursuit of the surprises leads to anything beyond the duck!

Future = statistics (J/+ more), vary species/energies, LHC

Is it a duck?

March 27, 2003University of Buffalo Colloquium1 Status of the Search for the Quark-Gluon Plasma at...

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