Gunther Roland - Hard Probes ‘04

Gunther Roland/MITfor the PHOBOS collaboration

Summary of High pT Physics

with PHOBOS

Gunther Roland - Hard Probes ‘04

Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail

Bickley,

Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Vasundhara Chetluru,

Patrick Decowski, Edmundo García, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen,

Clive Halliwell, Joshua Hamblen, Ian Harnarine, Conor Henderson, David Hofman, Richard Hollis,

Roman Holynski, Burt Holzman, Aneta Iordanova, Jay Kane, Nazim Khan, Piotr Kulinich,

Chia Ming Kuo, Wei Li, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen,

Rachid Nouicer, Andrzej Olszewski, Robert Pak, Heinz Pernegger, Corey Reed, Christof Roland,

Gunther Roland, Joe Sagerer, Iouri Sedykh, Wojtek Skulski, Chadd Smith, Peter Steinberg,

George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale,

Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger, Frank Wolfs,

Barbara Wosiek, Krzysztof Wozniak, Alan Wuosmaa, Bolek Wyslouch

ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORYINSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY

NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGOUNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

PHOBOS Collaboration

Gunther Roland - Hard Probes ‘04

Spectrometer

Octagon

Paddle Trigger Counter

137000 Silicon Pad Channels

NIM A 499, 603-623 (2003)

SpecTrig TOF

T0 counter

PHOBOS Detector

Gunther Roland - Hard Probes ‘04

pT (GeV/c)0.05 0.5 5.0

Stoppingparticles dE/dx TOF

Eloss (MeV)

dE

/dx

0.4

0.6

0.8

25

1.2

1.4

20151050

0.2

0

1.0

1/v

(ps/

cm)

PHOBOS PID Capabilities

dE

/dx

[MIP

]

PRC in pressnucl-ex/0401006

Gunther Roland - Hard Probes ‘04

PHOBOS Data Sets

200 GeV d+Au 62.4 GeV Au+Au 200 GeV Au+Au

PLB 578297, 2004PLB 578297, 2004 nucl-ex/0405003

Run 3 Run 4 Run 2

Gunther Roland - Hard Probes ‘04

200 GeV d+Au

Results for d+Au

Gunther Roland - Hard Probes ‘04

6% mostcentral Au+Au

PRL 91, 072302 (2003)

peripheral

central

RdAu vs. Centrality

~ 1

Gunther Roland - Hard Probes ‘04

RdAu as a Function of

nucl-ex/0406017, PRC in press nucl-ex/0406017, PRC in press

Gunther Roland - Hard Probes ‘04

Identified pT -spectra in d+Au

Scale uncertainty: 15%

Not feed-down corrected

Gunther Roland - Hard Probes ‘04

Particle Composition in d+Au

Not feed-down corrected

Gunther Roland - Hard Probes ‘04

mT=m +p

T

2 2 2

mT-spectra in d+Au

Scale uncertainty: 15%

Not feed-down corrected

Gunther Roland - Hard Probes ‘04

PRC in pressnucl-ex/0401006

d+Au

Scale uncertainty: 15%

Not feed-down corrected

Au+Au Spectra normalized at 2 GeV/c

mT Scaling in d+Au vs Au+Au

Gunther Roland - Hard Probes ‘04

Results for Au+Au

62.4 GeV Au+Au 200 GeV Au+Au

Gunther Roland - Hard Probes ‘04

62.4 GeV200 GeV

At 62.4 GeV, significantly higher RAA than at 200 GeV

PLB 578297, 2004

Energy Dependence of RAA

nucl-ex/0405003

Gunther Roland - Hard Probes ‘04

Energy Dependence of RAA

nucl-ex/0405003

Gunther Roland - Hard Probes ‘04

RAA at 62.4 GeV from TheoryVitev: nucl-th/0404052 XN Wang: nucl-th/0405029

Adil, Gyulassy: nucl-th/0405036

Gallmeister, Cassing: hep-ph/0408223

Eskola, Honkanen, Salgado,

Wiedemann: hep-ph/0406319

Gunther Roland - Hard Probes ‘04

RAA at 62.4 GeV vs Theory

nucl-ex/0405003

Gunther Roland - Hard Probes ‘04

62.4 GeV200 GeV

Features of centrality dependence?

PLB 578297, 2004

Centrality Dependence of RAA

nucl-ex/0405003

Gunther Roland - Hard Probes ‘04

Participant Scaling

200 GeV

130 GeV

19.6 GeV

<Nch>e+e-*<0.5Npart>

PHOBOS nucl-ex/0301017

<Nch>pp *<0.5Npart>

PHOBOS nucl-ex/0309021

d+Au Au+Au

Gunther Roland - Hard Probes ‘04

Centrality Evolution in Au+Au

• Use central A+A as denominator

• Scale with 1/<Npart>

Gunther Roland - Hard Probes ‘04

RAA at 200 and 62.4 GeV (Au+Au) Npart

62.4 GeV200 GeV

Yields normalized by Npart less centrality-dependent

nucl-ex/0405003

Gunther Roland - Hard Probes ‘04

Factorization of Energy/Centrality Dependence

• Yield/participant changes by less than 25% for all pT

• Factorization of energy and centrality dependence

62.4 GeV200 GeV

nucl-ex/0405003

Gunther Roland - Hard Probes ‘04

Factorization of Energy/Centrality Dependence

PHOBOS nucl-ex/0405027, PRC in press

Gunther Roland - Hard Probes ‘04

Factorization of Energy/Centrality Dependence

1- errors

• dN/d / <Npart/2> changes with sqrt(s), <Npart>

• Energy and Centrality Dependence Factorize

PHOBOS nucl-ex/0405027, PRC in press PHOBOS nucl-ex/0405027, PRC in press

Gunther Roland - Hard Probes ‘04

Factorization of Energy/Centrality Dependence

1- errorsArmesto, Salgado, Wiedemann hep-ph/0407018

PHOBOS nucl-ex/0405027, PRC in press

Gunther Roland - Hard Probes ‘04

Factorization of Longitudinal Dynamics

PHOBOS

PHOBOS

PRL 91, 052303 (2003).  

Gunther Roland - Hard Probes ‘04

Factorization of Longitudinal Dynamics

PHOBOS

PHOBOS

PRL 91, 052303 (2003).  

RP

C

Np

art

Again: Factorization of

energy/centrality dependence

PRL 91, 052303 (2003).  

Gunther Roland - Hard Probes ‘04

• Study of energy and system-size dependence

• Opaque medium created in A+A– Magnitude and energy dependence of suppression calculable

• Soft scaling at intermediate pT?– mT-Scaling in d+Au– Factorization of energy and centrality dependence

• More information from– PID spectra– high statistics 200 GeV Au+Au data– Cu+Cu run

Summary

Gunther Roland - Hard Probes ‘04

RPC vs. pT, PHOBOS and STAR, 200 GeV

PLB 578297, 2004

PRL 91, 172302, 2003

Npart

Gunther Roland - Hard Probes ‘04

Collision Scaling vs Centrality

Gunther Roland - Hard Probes ‘04

Factorization of Energy/Centrality Dependence

62.4 GeV200 GeV

Gunther Roland - Hard Probes ‘04

Npart scaling relative to p+p

• Keep p+p as denominator

• Scale with <Npart> instead of <Ncoll>