# Presentation: 703844

## Global Observables from 

***Global Observables from ***
***Au+Au, Cu+Cu, d+Au and p+p Collisions ***
***at RHIC Energies***

- Rachid NOUICER
- Brookhaven National Laboratory (BNL)

*(for PHOBOS Collaboration)*

***PANIC05 ***
***Particles and Nuclei International Conference ***
***Santa Fe, NM - October 24-28, 2005***

**Notes:**
Formation au développement de contenus applicatifs pour ESUP-Portail (uPortal)

## PHOBOS Collaboration

-  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 LABORATORY
- 	INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW	MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- 	NATIONAL CENTRAL UNIVERSITY, TAIWAN	UNIVERSITY OF ILLINOIS AT CHICAGO
- 	UNIVERSITY OF MARYLAND	UNIVERSITY OF ROCHESTER

*PHOBOS Collaboration*

## Outline

-           **What can we learn from Au+Au and Cu+Cu Collisions **
**                                  ****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
* *

## Pseudorapidity Distributions of Charged Particles 

- 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

## Pseudorapidity Distributions of Charged Particles 

- 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**

##  Particle Density at Mid-rapidity  || < 1 

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

- Interplay Between Collision Energy and System Size

-  Particle Density at Mid-rapidity ** ****|****| < 1**** **

##  Particle Density at Mid-rapidity  || < 1 

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

##  Particle Density at Mid-rapidity  || < 1 

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

-  Particle Density at Mid-rapidity ** ****|****| < 1**** **

## Similarity Between Cu+Cu vs Au+Au Collisions

**Cu+Cu**
**Preliminary**
**3-6%, N****part**** = 100**

**62.4 GeV**

**200 GeV**

**Cu+Cu**
**Preliminary**
**3-6%, N****part**** = 96**

**Au+Au**
**35-40%, N****part ****= 99**

**Au+Au**
**35-40%,N****part ****= 98**

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

## Similarity Between Cu+Cu vs Au+Au Collisions

**Cu+Cu**
**Preliminary**
**15-25%, N****part**** = 61**

**Au+Au**
**45-50%,N****part ****= 62**

**Cu+Cu**
**Preliminary**
**15-25%, N****part**** = 60**

**Au+Au**
**45-55%, N****part ****= 56**

-  *For same system size (N**part **),*
*Cu+Cu and Au+Au are very similar.*

**62.4 GeV**

**200 GeV**

- This is not coincidence

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

## Charged Particle Production in Forward Regions

- Extended 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 collision*_
*over a very *
*large range of |****|-y**beam*

*In the rest frame of one of the colliding nuclei:*

- Centrality: 0-6%

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

- 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)

## 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

## Similarity Between Cu+Cu vs Au+Au Collisions

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

**Cu+Cu: G. Roland Talk QM2005, e-Print nucl-ex/0510042 **

- Nuclear Modification Factor vs Npart

- 200 GeV

## Similarity Between Cu+Cu vs Au+Au Collisions

- Nuclear Modification Factor vs Npart

- 62.4 GeV

**Au+Au: PRL**** ****94, 082304 (2005)**

**Cu+Cu: G. Roland Talk QM2005, e-Print nucl-ex/0510042 **

## Similarity Between Cu+Cu vs Au+Au Collisions

- Anti-proton/proton Ratio

## Factorization

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

## We observe Energy/Centrality Factorization.

**Au+Au**

- PHOBOS

**Cu+Cu**
**preliminary**

*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

## Energy/Centrality factorization up to pT ≈ 4 GeV/c

- Energy/Centrality factorization up to pT ≈ 4 GeV/c
- for 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)**

**<p****T****> = 0.25 GeV/c**

**<p****T****> = 1.25 GeV/c**

**<p****T****> = 2.5 GeV/c**

**<p****T****> = 3.38 GeV/c**

**<p****T****> = 3.88 GeV/c**

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

- Factorization of dN/d**** Shapes

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

**dN****Fact.****(Cu+Cu: x%) =  dN****Meas.****(Cu+Cu: x%)**

- Systematic errors are not shown

**Cu+Cu at 200 GeV**

**Au+Au at 200 GeV**

- 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. 

- 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

## Scaling of Hadron Production

- 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)

- Summary I

## Geometry and Energy

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

- Summary II

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