Evidence from d+Au measurements for final-state suppression of high p
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Evidence from d+Au measurements for final-state suppression of high p T hadrons in Au+Au collisions at RHIC The STAR Collaboration PowerPoint PPT Presentation

Evidence from d+Au measurements for final-state suppression of high p T hadrons in Au+Au collisions at RHIC The STAR Collaboration. Peter Jacobs Lawrence Berkeley National Laboratory. nucl-ex/0306024. The STAR detector. E-M Calorimeter. Projection           Chamber.

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Evidence from d+Au measurements for final-state suppression of high p T hadrons in Au+Au collisions at RHIC The STAR Collaboration

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Star

Evidence from d+Au measurements for final-state suppression of high pT hadrons in Au+Au collisions at RHICThe STAR Collaboration

Peter Jacobs

Lawrence Berkeley National Laboratory

nucl-ex/0306024

d+Au and final-state suppression in Au+Au


The star detector

The STAR detector

E-M Calorimeter

Projection           Chamber

Time of    Flight

d+Au and final-state suppression in Au+Au


Partonic energy loss in dense matter

Partonic energy loss in dense matter

Bjorken, Baier, Dokshitzer, Mueller, Pegne, Schiff, Gyulassy, Levai, Vitev, Zhakarov, Wang, Wang, Salgado, Wiedemann,…

Multiple soft interactions:

Gluon bremsstrahlung

Opacity expansion:

  • Strong dependence of energy loss on gluon density glue:

    • measure DE color charge density at early hot, dense phase

d+Au and final-state suppression in Au+Au


Jets at rhic

jet

parton

nucleon

nucleon

Jets at RHIC

Find this……….in this

p+p jet+jet ([email protected])

Au+Au ??? ([email protected])

d+Au and final-state suppression in Au+Au


Partonic energy loss via leading hadrons

Binary collision scaling

p+p reference

Partonic energy loss via leading hadrons

Energy loss  softening of fragmentation  suppression of leading hadron yield

d+Au and final-state suppression in Au+Au


Au au and p p inclusive charged hadrons

Au+Au and p+p: inclusive charged hadrons

nucl-ex/0305015

PhysRevLett 89, 202301

p+p reference spectrum measured at RHIC

d+Au and final-state suppression in Au+Au


Suppresion of inclusive hadron yield

Suppresion of inclusive hadron yield

RAA

Au+Au relative to p+p

RCP

Au+Au central/peripheral

nucl-ex/0305015

  • central Au+Au collisions: factor ~4-5 suppression

  • pT>5 GeV/c: suppression ~ independent of pT

d+Au and final-state suppression in Au+Au


Jets and two particle azimuthal distributions

trigger

Jets and two-particle azimuthal distributions

p+p  dijet

  • trigger: highest pT track, pT>4 GeV/c

  • Df distribution: 2 GeV/c<pT<pTtrigger

  • normalize to number of triggers

Phys Rev Lett 90, 082302

N.B. shifted horizontally by p/2 relative to previous STAR plots!

d+Au and final-state suppression in Au+Au


Azimuthal distributions in au au

?

Azimuthal distributions in Au+Au

Au+Au peripheral

Au+Au central

pedestal and flow subtracted

Phys Rev Lett 90, 082302

Near-side: peripheral and central Au+Au similar to p+p

Strong suppression of back-to-back correlations in central Au+Au

d+Au and final-state suppression in Au+Au


Is suppression an initial or final state effect

Is suppression an initial or final state effect?

Initial state?

Final state?

partonic energy loss in dense medium generated in collision

strong modification of Au wavefunction (gluon saturation)

d+Au and final-state suppression in Au+Au


Inclusive suppression theory vs data

RCP

nucl-ex/0305015

Inclusive suppression: theory vs. data

pQCD-I: Wang, nucl-th/0305010

pQCD-II: Vitev and Gyulassy, PRL 89, 252301

Saturation: KLM, Phys Lett B561, 93

Final state

Initial state

pT>5 GeV/c: well described by KLM saturation model (up to 60% central) and pQCD+jet quenching

d+Au and final-state suppression in Au+Au


Is suppression an initial or final state effect1

partonic energy loss

Is suppression an initial or final state effect?

Initial state?

Final state?

gluon saturation

How to discriminate? Turn off final state d+Au collisions

d+Au and final-state suppression in Au+Au


D au vs p p theoretical expectations

Inclusive spectra

RAB

If Au+Au suppression is final state

1.1-1.5

1

If Au+Au suppression is initial state

(KLM saturation: 0.75)

~2-4 GeV/c

pT

High pT hadron pairs

broadening?

pQCD: no suppression, small broadening due to Cronin effect

saturation models: suppression due to mono-jet contribution?

0

suppression?

/2

0

 (radians)

d+Au vs. p+p: Theoretical expectations

All effects strongest in central d+Au collisions

d+Au and final-state suppression in Au+Au


D au event selection

FTPC-Au

ZDC-Au

ZDC-d

Au

d

d+Au event selection

Minimum bias trigger: ZDC-Au (953% of shadronic)

Centrality tags:

1. FTPC-Au: charged particle multiplicity in -3.8<h<-2.8

2. ZDC-d: neutron spectator from deuteron

d+Au and final-state suppression in Au+Au


Centrality tags

Centrality tags

  • ZDC-d neutron spectator tag:

  • measured: 191% of shadronic

  • Glauber: 183% of shadronic

    •  peripheral events

FTPC-Au cut selects more central collisions

Modeling FTPC-Au multiplicity: convolute Au-participant (Glauber) with UA5 mult. distribution (pbar+p @ 200 GeV, 2.5<h<3.5)

min. bias <Nbinary>=7.00.3; central 20% <Nbinary>=12.91.0

d+Au and final-state suppression in Au+Au


Inclusive charged particle spectra

Inclusive charged particle spectra

d+Au and final-state suppression in Au+Au


Inclusive yield relative to binary scaled p p

Inclusive yield relative to binary-scaled p+p

  • d+Au : enhancement

  • Au+Au: strong suppression

  • pT=4 GeV/c:

    • cent/minbias= 1.110.03

    • central collisions enhanced wrt minbias

Suppression of the inclusive yield

in central Au+Au is a final-state effect

d+Au and final-state suppression in Au+Au


Azimuthal distributions

pedestal and flow subtracted

Azimuthal distributions

Near-side: p+p, d+Au, Au+Au similar

Back-to-back: Au+Au strongly suppressed relative to p+p and d+Au

Suppression of the back-to-back correlation in central Au+Au is a final-state effect

d+Au and final-state suppression in Au+Au


Star

The strong suppression of the inclusive yield and back-to-back correlations at high pT previously observed in central Au+Au collisions are due to

final-state interactions with the dense medium generated in such collisions.

d+Au and final-state suppression in Au+Au


Have we found the quark gluon plasma at rhic

Have we found the Quark Gluon Plasma at RHIC?

We now know that Au+Au collisions generate a medium that

  • is dense (pQCD theory: many times cold nuclear matter density)

  • is dissipative

  • exhibits strong collective behavior

This represents significant progress in our understanding of strongly interacting matter

We have yet to show that:

  • dissipation and collective behavior both occur at the partonic stage

  • the system is deconfined and thermalized

  • a transition occurs: can we turn the effects off ?

Not yet, there is still work to do

d+Au and final-state suppression in Au+Au

We have developed the tools necessary to complete this program


The star collaboration

The STAR Collaboration

Brazil:

Universidade de Sao Paulo

China:

IHEP – Beijing

IMP - Lanzou

IPP – Wuhan

USTC

SINR – Shanghai

Tsinghua University

Great Britain:

University of Birmingham

France:

IReS Strasbourg

SUBATECH - Nantes

Germany:

MPI – Munich

University of Frankfurt

India:

IOP - Bhubaneswar

VECC - Calcutta

Panjab University

University of Rajasthan

Jammu University

IIT - Bombay

VECC – Kolcata

Poland:

Warsaw University of Tech.

Russia:

MEPHI - Moscow

LPP/LHE JINR - Dubna

IHEP - Protvino

U.S. Laboratories:

Argonne

Berkeley

Brookhaven

U.S. Universities:

UC Berkeley

UC Davis

UC Los Angeles

Carnegie Mellon Creighton University

Indiana University

Kent State University

Michigan State University

City College of New York

Ohio State University

Penn. State University

Purdue University

Rice University

Texas A&M

UT Austin

U. of Washington

Wayne State University

Yale University

d+Au and final-state suppression in Au+Au


Extra slide

Extra slide

d+Au and final-state suppression in Au+Au


Two particle azimuthal distributions

Two-particle azimuthal distributions

  • near-side and back-to-back peaks seen in minbias and central d+Au

  • p+p  d+Au minbias  d+Au central:

    • growth of off-jet pedestal

    • small, if any, growth of back-to-back width

d+Au and final-state suppression in Au+Au


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