# Presentation: 658830

##  Measurements with BRAHMS

- I.G. Bearden,
- Niels Bohr Institute
- For
- The BRAHMS collaboration

- Riken BNL Workshop

- 15. Maj 2004

## The BRAHMS Collaboration

**I.Arsene****10****,I.G. Bearden****7****, D. Beavis****1****, C. Besliu****10****, Y. Blyakhman****6****, J.Brzychczyk****4****,**
** ****B. Budick****6****,H. Bøggild****7 ****,C. Chasman****1****, C. H. Christensen****7****, P. Christiansen****7****,**
**J.Cibor****4****,R.Debbe****1****,J. J. Gaardhøje****7****,****M. Germinario****7****, K. Hagel****8****,**
** ****O. Hansen****7****, H. Ito****11****, E. Jacobsen****7****, A. Jipa****10****, J. I. Jordre****10****, F. Jundt****2,**** **
**C.E.Jørgensen****7****, E. J. Kim****5****, T. Kozik****3****, T.M.Larsen****12****, J. H. Lee****1****, Y. K.Lee****5****, **
**G. Løvhøjden****2****, Z. Majka****3****, A. Makeev****8****, B. McBreen****1****, M. Murray****8****, J. Natowitz****8****, **
**B. Neuman****11****,B.S.Nielsen****7****, K. Olchanski****1****, D. Ouerdane****7****, R.Planeta****4****, F. Rami****2****, **
**D. Roehrich****9****,  B. H. Samset****12****, S. J. Sanders****11****, I. S. Sgura****10****, R.A.Sheetz****1,**** Z.Sosin****3****, **
**P. Staszel****7****, T.S. Tveter****12****, F.Videbæk****1****, R. Wada****8**** ,A.Wieloch****3****,Z. Yin****9**
**1****Brookhaven National Laboratory, USA, ****2****IReS and  Université Louis Pasteur, Strasbourg, France**
**3****Jagiellonian University, Cracow, Poland, ****4****Institute of Nuclear Physics, Cracow, Poland**
**5****Johns Hopkins University, Baltimore, USA,**** 6****New York University, USA**
**7****Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark**
**8****Texas A&M University, College Station. USA, ****9****University of Bergen, Norway **
**10****University of Bucharest, Ro****mania,**** ****11****University of Kansas, Lawrence,USA   **
**12**** University of Oslo Norway**** **

- - 12 institutions-

- Riken BNL Workshop

- 15. Maj 2004

## The BRAHMS Experiment

- Riken BNL Workshop

- 15. Maj 2004

## Charged Particle MultiplicitydN/d

- According to
- Bjorken,
- >5GeV/fm3

- Riken BNL Workshop

- 15. Maj 2004

## 0

**AMPT**
**High density QCD**
**gluon saturation**
**Kharzeev and Levin,**
**PLB523(2001)79**

- 0

- 1

- 4

- Riken BNL Workshop

- 15. Maj 2004

## Particle Spectra 

- final invariant yields over a broad range of rapidity and pT

*Particle Spectra** *

- 

- K

- p

- Riken BNL Workshop

- 15. Maj 2004

## Particle Spectra 

- Top 5% central collisions

- Riken BNL Workshop

- 15. Maj 2004

## Rapidity Densities

- N()    ~ 1780   N(+)  ~1760
- N(K+)    ~   290   N(K) ~  240
- N(pbar) ~     85

*Rapidity Densities*

- At y ~ 0, dN/dy is
-        ~ 300 (300) for + (-)
-        ~   47   (44) for K+ (K)
-        ~   27   (20) for p (pbar)

- N() >> N(K) > N(p)
- N(+) = N()

- N(K+) > N(K)  and
- N(p) > N(pbar)  systematically

- Riken BNL Workshop

- 15. Maj 2004

## Nuclear Stopping

- BRAHMS, submitted
- to PRL,
- nucl-ex/0312023
- P. Christiansen
- Ph.D. Thesis

- Net-proton rapidity densities (top 5% central collisions)

- Riken BNL Workshop

- 15. Maj 2004

## Nuclear Stopping

*Nuclear Stopping*

- Net-baryon after
- feed-down & neutron corrections

- Riken BNL Workshop

- 15. Maj 2004

## Energy Balance

-  Fit , K and p distributions (dN/dy and mT vs y)
-      total energy of , K and p
-  Assume reasonable distribution
-    for particles we don’t detect (0,n,...)
-  Calculate the total energy...

- Riken BNL Workshop

- 15. Maj 2004

## Strangeness with Kaons 

*Strangeness with Kaons** *

*RAPIDITY DEPENDENCE*

- Riken BNL Workshop

- 15. Maj 2004

## ENERGY DEPENDENCE

- At y = 0, ratios converge
- to ~ 15 %

- Riken BNL Workshop

- 15. Maj 2004

## Transverse Flow...

**Points: BRAHMS Data**
**Curves: 3D Hydro (Hirano)**
**Histos: AMPT**

- p

- 

- Riken BNL Workshop

- 15. Maj 2004

## Spectra with BW Fits at y~0,1,2,3 (T,s, in the fit Rmax=13fm) 

- y~0

- y~3

- y~2

- y~1

- pT (GeV/c)

**Spectra with BW Fits at y~0,1,2,3**** ****(****T****,********s****,******** ****in the fit R****max****=13fm****)**

- BRAHMS Preliminary

- Fix ,T

- Fix ,

- Riken BNL Workshop

- 15. Maj 2004

## Jets at RHIC

- p+p jet+jet (STAR@RHIC)

- Au+Au ??? (STAR@RHIC)

- Find this..........in this

- And, in BRAHMS, we only
- “see” this much...

- Riken BNL Workshop

- 15. Maj 2004

## Characterize “high” pT by single particle spectra 

****

****

- Characterize “high” pT by single particle spectra

- Riken BNL Workshop

- 15. Maj 2004

## Arsene et al.PRL2003

- Arsene et al.PRL2003

- To look at ‘only’ data, form ratioR=Rcp(=2.2)/Rcp(=0)

- Riken BNL Workshop

- 15. Maj 2004

## d+Au Nuclear Modification  =0

- High pT enhancement
- observed in d+Au collisions
- at sNN=200 GeV.

- Comparing Au+Au to d+Au
-  strong effect of
-     dense medium

- Riken BNL Workshop

- 15. Maj 2004

## Predictions from theory

- I. Vitev nucl-th/0302002 v2

- D. Kharzeev et al. **Phys.Rev.D68:094013,2003**

**CGC at y=0**

**Y=0**

**Y=3**

**Y=-3**

- Very high energy

**As y grows**

- Riken BNL Workshop

- 15. Maj 2004

## RdAu 

**R****dAu**** **

- Cronin like enhancement at =0.
- Clear suppression as  changes up to 3.2
- Same ratio made with dn/d follows the low pT RdAu

- RdA 

-  d2Nd+Au/dpTd

- <Ncoll> d2Nppinel/dpTd

- where * <* Ncoll*> = 7.2*±0.3

- Riken BNL Workshop

- 15. Maj 2004

## pbar/- ratio  probes extent of new medium in y

**pbar/********-**** ratio  probes extent of new medium in y**

- Au+Au

- d+Au

- p+p

- Riken BNL Workshop

- 15. Maj 2004

## Preliminary results from 63GeV

- Riken BNL Workshop

- 15. Maj 2004

## Preliminary results from 63GeV

- Riken BNL Workshop

- 15. Maj 2004

## Conclusions

- High energy density
- Gluon saturation describes data, though not uniquely
- 70% of energy available for particle production
- Source (nearly) same over >1 unit rapidity

- High pT suppression persists to high y in Au+Au
- Grows vs y in d+Au
- Lots left to do...

- Riken BNL Workshop

- 15. Maj 2004

## Reference Spectrum

- Global Parameterization
- Of ISR DATA

- Fit to
- ISR (R203) DATA

- ISR DATA
- =1

- Riken BNL Workshop

- 15. Maj 2004