global observables from au+au, cu+cu, d+au and p+p collisions at rhic energies

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Rachid Nouicer - BNLPHOBOS PANIC2005

Global Observables from Au+Au, Cu+Cu, d+Au and p+p Collisions

at RHIC Energies

Rachid NOUICER Rachid NOUICER Brookhaven National Laboratory (BNL)Brookhaven National Laboratory (BNL)

(for PHOBOS Collaboration)(for PHOBOS Collaboration)

PANIC05 Particles and Nuclei International Conference

Santa Fe, NM - October 24-28, 2005

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

Wit Busza (Spokesperson), Zhengwei Chai, Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Kristjan Gulbrandsen, Clive Halliwell, Joshua Hamblen, Ian Harnarine, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Jay Kane,Piotr

Kulinich, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Eric Richardson, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Chadd Smith, Maciej Stankiewicz, Peter Steinberg,

George Stephans, Andrei Sukhanov, Artur Szostak, Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger, Donald

Willhelm, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Shaun Wyngaardt, Bolek Wysłouch

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

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Outline What can we learn from Au+Au and Cu+Cu What can we learn from Au+Au and Cu+Cu Collisions Collisions at RHIC Energies?at RHIC Energies? • What can we learn from charged hadron production in Cu+Cu compared to Au+Au? • What is the interplay between collision centrality (geometry) and collision energy?

• How does elliptic flow scale with geometry and density? (See Alice Mignerey’s Talk: session 4, Section I.7).

• Summary

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19.6 GeV 62.4 GeV 130 GeV 200 GeV

Cu+Cu

d+Au

Au+Au

centrality

Pseudorapidity Distributions of Charged Particles

There is no evidence for two separate regions “mid-rapidity and fragmentation regions”

in any of the RHIC energies “Continuous distributions”

New Results from PHOBOS Cu+Cu at 62.4 and 200 GeV

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19.6 GeV 62.4 GeV 130 GeV 200 GeV

Cu+Cu

d+Au

Au+Au

centrality

Pseudorapidity Distributions of Charged Particles We define the mid-rapidity region: |

| < 1

PHOBOS references for the data:• Au+Au : PRL 91, 052303 (2003) PRC: nucl-ex/0509034 • d+Au : PRL 93, 082301 (2004)• Cu+Cu : QM2005: e-Print nucl-ex/0510042

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Au+Au : PRL 91, 052303 (2003) PRC: nucl-ex/0509034

Au+Au, Pb+Pb and p(p)+ p Collisions Interplay Between Collision Energy and System Size Particle Density at Mid-rapidity || < 1

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Au+Au : PRL 91, 052303 (2003) PRC: nucl-ex/0509034Cu+Cu: QM2005: e-Print nucl-ex/0510042

Au+Au, Pb+Pb, Cu+Cu and p(p)+ p Collisions

Interplay Between Collision Energy and System Size Particle Density at Mid-rapidity || < 1

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Au+Au, Pb+Pb, Cu+Cu and p(p)+ p Collisions

Interplay Between Collision Energy and System Size

In symmetric collisions Nucleus-Nucleus:

it seems the density per nucleon doesn’t depend on the size of the

two colliding nuclei but it depends on the colliding energy Au+Au : PRL 91, 052303 (2003)

PRC: nucl-ex/0509034Cu+Cu: QM2005: e-Print nucl-ex/0510042

Particle Density at Mid-rapidity || < 1

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Unscaled dN/dvery similar for Au+Au and Cu+Cu at same Npart

Cu+CuPreliminary

3-6%, Npart = 100

62.4 GeV 200 GeV

Cu+CuPreliminary

3-6%, Npart = 96Au+Au35-40%, Npart = 99

Au+Au35-40%,Npart = 98

Similarity Between Cu+Cu vs Au+Au CollisionsdN/d in Cu+Cu vs Au+Au Collisions at Similar Npart

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Cu+CuPreliminary

15-25%, Npart = 61

Au+Au45-50%,Npart = 62

Cu+CuPreliminary

15-25%, Npart = 60

Au+Au45-55%, Npart = 56

For same system size (Npart ),Cu+Cu and Au+Au are very similar.

62.4 GeV 200 GeVThis is not coincidence

dN/d in Cu+Cu vs Au+Au Collisions at Similar Npart

Similarity Between Cu+Cu vs Au+Au Collisions

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Charged Particle Production in Forward RegionsExtended Longitudinal Scaling “Limiting Fragmentation” Scenario

Au+Au/Cu+Cu Collisions

Extended longitudinal scaling appears

to be independent of energy and size of the colliding nuclei for

more central collisionover a very

large range of ||-ybeam

In the rest frame of one of the colliding nuclei:

Centrality: 0-6%

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preliminary preliminary

62.4 GeV 200 GeV

Cu+Cu

d+Au

Au+Au

PHOBOS references for the data:• Au+Au: PRL 94, 082304 (2005),

PLB 578, 297 (2004) • d+Au: Phys. Rev. Lett 91, 072302 (2003)• Cu+Cu : QM2005: e-Print nucl-ex/0510042

Charged Hadron pT Spectra (Rapidity Range: 0.2 < y <1.4)

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Au+Au

Similarity Between Cu+Cu vs Au+Au Collisions

Au+Au: PRL 94, 082304 (2005), PLB 578, 297 (2004)

Nuclear Modification Factor vs Npart 200 GeV

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Cu+Cupreliminary

Au+Au

Au+Au: PRL 94, 082304 (2005), PLB 578, 297 (2004) Cu+Cu: G. Roland Talk QM2005, e-Print nucl-ex/0510042

Similarity Between Cu+Cu vs Au+Au CollisionsNuclear Modification Factor vs Npart 200 GeV

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Cu+Cupreliminary

Au+Au

Similarity Between Cu+Cu vs Au+Au CollisionsNuclear Modification Factor vs Npart 62.4 GeV

Au+Au: PRL 94, 082304 (2005) Cu+Cu: G. Roland Talk QM2005, e-Print nucl-ex/0510042

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p/p ratio very similar in Cu+Cu and Au+Au

Similarity Between Cu+Cu vs Au+Au CollisionsAnti-proton/proton Ratio

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FactorizationWhat is the interplay between collision centrality

(geometry) and collision energy?

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Au+Au

PHOBOS

Cu+Cupreliminary

200/19.6

200/62.4

200/130Cu+Cupreliminary

Au+Au

PHOBOSHIJING

Saturation

We observe Energy/Centrality Factorization.Is this factorization an initial state effect?

Factorization of Particle Density at Mid-rapidity (||<1) Interplay Between Collision Centrality (Geometry) and Collision Energy

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Energy/Centrality factorization up to pT ≈ 4 GeV/cfor Npart > 40

Factorization in pT at Mid-rapidity Interplay Between Collision Centrality (Geometry) and Collision Energy

Ratio of charged hadron yields in 200 GeV to 62 GeV

Au+Au: PRL 94, 082304 (2005)

<pT> = 0.25 GeV/c <pT> = 1.25 GeV/c <pT> = 2.5 GeV/c <pT> = 3.38 GeV/c <pT> = 3.88 GeV/c

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Factorization of dN/d Shapes

Does this factorization work and can we predict the dN/d distributions of Cu+Cu based on Au+Au?

dNFact.(Cu+Cu: x%) = dNMeas.(Cu+Cu: x%)d d

?

Systematic errors are not shown

Cu+Cu at 200 GeV

Au+Au at 200 GeV

dNFact.(CuCu: x %) = RAu (0-6%) dNMeas.(AuAu: x %)d d

Cu

dN/d (Cu+Cu: 0-6%) =dN/d(Au+Au: 0-6%)

R Au (0-6%)Cu

Au+Au : PRL 93, 082302 (2004) for AuAuCu+Cu: QM2005, e-Print nucl-ex/0510042

System Size Independence of Pseudorapidity Shapes

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Factorization of dN/d Shapes System Size Independence of Pseudorapidity Shapes

It thus appears that dN/d shapes are independent of the overall size of the colliding

nuclei, at least between the Cu+Cu and Au+Au systems studied here.

200 GeV

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What we can learn from charged hadron production

in Cu+Cu compared to Au+Au?For the same system size (Npart, Ncoll) and at the same energy,

Cu+Cu and Au+Au are very similar:– Particle Density– Extended Longitudinal Scaling– Total Multiplicity– Particle Ratio p/p– Nuclear Modification dN/dpT (RAA)

Scaling of Hadron ProductionSummary I

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What is the interplay between collision centrality (geometry) and collision energy?

Factorization of geometry and energy dependence is observed: – Particle Density at Mid-rapidity (||<1) – pT spectra – dN/d Shapes

Geometry and EnergySummary II

Do these “Scaling and Factorization” observations in charged particle production persist to HIC at LHC?

global observables from au+au, cu+cu, d+au and p+p collisions at rhic energies

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