# Presentation: 146442

## RHIC: Physics Results

**Gunther Roland **

**IV International Symposium on LHC Physics and Detectors**
**Fermilab 5/1-5/3 2003**

## Exploring QCD with Heavy Ions

**Matter Density ********B**** (GeV)**

**I**

**II**

**III**

**IV**

**Temperature (MeV)**

**Quark-Gluon Plasma**

**Hadron Gas**

**Phase Boundary**

**Early Universe**

**0**

**200**

**0**

**Atomic Nuclei**

**1**

**Critical Point**

**I**

**II**

**III**

**IV**

**Structure of Relativistic Nuclei **
**Mechanism of Entropy Production**
**QCD phase diagram**
**Properties of QGP**

## Interlude: Collision Geometry

**b**

**2R ~ 15fm**

**Spectators**

**Spectators**

**Participant Region**

**Smaller Impact Parameter ****b**

**Bigger Collision System**

**More Participants (****N****part****)**

**More Produced Particles!**

## Relativistic Heavy Ion Collider

**Relativistic Heavy Ion Collider**

**First Physics in ‘00**
**Versatile machine **
**Au+Au (‘00-’02)**
**19.6 GeV**
**56 GeV**
**130 GeV**
**200 GeV**
**p+p (‘02,’03)**
**200 GeV polarized**
**d+Au (‘03)**
**200 GeV**

**4 Experiments**
**2 big**
**2 small**
**Complementary capabilities**

## STAR

**STAR**

- Large acceptance tracking detector
- Mass, charge and momentum for >1000 hadrons per event

## PHENIX

- High Rate, Particle ID, Triggering
- Rare particles: Leptons, High pT

## PHOBOS

- Full Acceptance Multiplicity Detector
- High precision spectrometer near y=0 (low pT)

## BRAHMS

**Particle Production at small angles**
**High resolution spectrometer & good particle ID**

## Bulk Particle Production @ RHIC

**Initial Conditions/Energy Density**
**Thermalization**
**Hadro-Chemistry**
**Expansion Dynamics**

## 4- Multiplicity at RHIC

**4-******** Multiplicity at RHIC**

**dN/d******

**Pseudo-rapidity**

**19.6 GeV**

**130 GeV**

**200 GeV**

**PHOBOS**

**PHOBOS**

**PHOBOS**

**BRAHMS**

**130 GeV**

**BRAHMS**

**200 GeV**

**dN/d******

**Nice agreement!**

- PHOBOS  nucl-ex/0210015

- BRAHMS  PLB 523 (2001) 227, PRL 88 (2002) 202301

## Energy Density

**Initially released energy density **
**~ 5GeV/fm****3**
- Note: energy density inside proton ≈ 0. 5GeV/fm3

- Total energy released ~2000GeV

- Max. initial overlap volume

**Density  of Particles Produced at y=0**

- Energy of Collision

**Energy Density**

- W. Busza, Moriond ‘03

## Azimuthal Anisotropy

- “Head on” view of colliding nuclei

**Peripheral**

**Central**

**Initial State Anisotropy**
**Coordinate Space**

## Anisotropy v2 vs Centrality

- STAR

**|********| < 1.3**
**0.1 < p****t**** < 2.0**

- PHENIX

- from R. Snellings

**Consistent results**
**Hydro-limit reached for **
**mid-central collisions**

## Bulk Particle Production @ RHIC

**Initial Conditions/Energy Density: ****> 5 GeV/fm****3**
**Thermalization: **
**Hadro-Chemistry**
**Expansion Dynamics**

## Charged Particle Spectra

**Results (largely) consistent**
**Clear Mass Hierarchy of Slopes**

- Th. Ullrich QM’02

## Multi-Strange Particles

- J. Castillo SQM’03

## Statistical Model Fit 

**Relative Abundance: Two Parameters !**

## Bulk Particle Production @ RHIC

**Initial Conditions/Energy Density: ****> 5 GeV/fm****3**
**Thermalization: **
**Hadro-Chemistry: ****T****ch**** ~ 180 MeV, ********B****~25MeV**
**Expansion Dynamics**

## ‘Hydro’ Fits to Spectra

**Simultaneous Fit to ********,k,p gives**
**Kinetic Freeze-Out Temperature,**
**Transverse Expansion velocity**

## ‘Hydro’ Fit to Correlation Data

- Fabrice Retiere SQM ‘03, Mike Lisa

**Consistent Data from**** **
**STAR, PHENIX, PHOBOS**
**Also **
**	****HBT vs reaction plane**
**	****Unlike particles**
**	****Balance Functions**
**	****Short-lived Resonances**
**Consistent Results**
**	****Lifetime ~ ****10 fm/c**
**	****Particle emission over**
**	****few fm/c**

## Bulk Particle Production @ RHIC

**Initial Conditions/Energy Density: ****> 5 GeV/fm****3**
**Thermalization: **
**Hadrochemistry: ****T****ch**** ~ 180 MeV, ********B****~25MeV**
**Expansion Dynamics: ****T****th**** ~ 110 MeV, <********T****> ~ 0.6c**
**	****	****	****	**** ****<********fo****>~ 10 fm/c, ********fo****~ 0-3 fm/c **

## Bulk Particle Production @ RHIC

**Initial Conditions/Energy Density: ****> 5 GeV/fm****3**
**Thermalization: **
**Hadrochemistry: ****T****ch**** ~ 180 MeV, ********B****~25MeV**
**Expansion Dynamics: ****T****th**** ~ 110 MeV, <********T****> ~ 0.6c**
**	****	****	****	**** ****<********fo****>~ 10 fm/c, ********fo****~ 0-3 fm/c**** **

**Consistent *****Description***** of Final State**
**But we’re missing a picture of *****Dynamical Evolution***

## II. Dense Matter Diagnostics @ RHIC

**Jets**
**Virtual and Real Photons**
**Quarkonia**

## Dense Matter Diagnostics

**Leading Particle**

**Jet cross-section calculable in QCD**

**Study fate of jets in dense matter in Au+Au**

**Leading Particle**

## STAR Au+Au

**STAR Au+Au**

**Opal e****+****e****-**

## Dense Matter Diagnostics

**Leading Particle**

**Jet cross-section calculable in QCD**

**Study fate of jets in dense matter in Au+Au**

**Poor man’s jet:  Leading Particles**

**Leading Particle**

## “Jet Quenching” at High pT

**Yield at high p****T**** in AA  is 6 times smaller than expected**

**expected**

**observed**

**proton+proton**

**Au+Au**

## Jets in Dense Matter

**Are we really looking at jets?**
**Look for  jet structure by measuring**
**small angle correlations**
**back-to-back correlations**
**    ****relative to  high p****T**** leading particle**

**Leading Particle**

## Peripheral Au+Au data

**Jets seen in peripheral Au+Au and p+p**
**Azimuthal correlations**
**Small angle (******** ~ 0)**
**Back-to-Back (******** ~ p)**

**D. Hardtke**
**QM ‘02**

## Central Au+Au data

**Disappearance**** of back-to-back correlations in central Au+Au**
**Away-side particles absorbed or scattered in medium**

**D. Hardtke**
**QM ‘02**

## “Instant” Thermalization

- E. Shuryak,
- nucl-th/0112042

**Central**

**Peripheral**

**High p****T**** particles**
**produced early:**
**Biggest anisotropy**

**Limit (********mfp**** = 0)**

## Thermalization timescale

**To fully preserve anisotropy:**
**Instant formation of dense system (********mfp**** small)**
**Why “****instant****”? Once washed out, anisotropy can’t be recovered! **

**time**

**t=0**

## Anisotropy in Parton Cascade

- HIJING x 80
- HIJING x 35
- HIJING x 13
- HIJING x 1
- hydro , sBC

**0.06**

**0.1**

**0.02**

**Anisotropy**

**Parton cascade can describe data...**
**...****if cross-sections are multiplied by 13!**

**Molnar, Gyulassy**

## “Proton puzzle”

**?**

## Understanding low vs high pT

**Fries, Mueller, Nonaka,Bass nucl-th/0301087**

## III.  RHIC in Context

## Total Multiplicity vs. Beam Energy

**Total Multiplicity vs. Beam Energy**

- PHOBOS QM’02, Steinberg

## Chemistry vs sqrt(s)

## Asymptotic region at RHIC?

**Universality?**
**Energy**
**Hadrons**

**e****+****e****-**

***What about strangeness?***

##  Mid-Rapidity K/

**Non-monotonic Evolution! **
- Oeschler et al:** Thresholds vs Baryo-chemical potential**

**NA49** (V. Friese SQM’03)

## Kaon Slope Parameters

**NA49** (V. Friese SQM’03)

**NA49**

**NA49**

**AGS**

**AGS**

**PHENIX**

**PHENIX**

##  Summary

- Extensive and Consistent Data Sets
- BRAHMS, PHENIX, PHOBOS, STAR
- AGS, SPS, RHIC
- Consistent and Concise description of Final State
- Bulk particle production
- Intermediate pT spectra + correlations
- Challenge: ***Consistent Dynamical Scenario***
- What makes all this happen in 10fm/c?