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### Measurements with BRAHMS

I.G. Bearden,

Niels Bohr Institute

For

The BRAHMS collaboration

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

The BRAHMS Collaboration

- 12 institutions-

I.Arsene10,I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J.Brzychczyk4,

B. Budick6,H. Bøggild7 ,C. Chasman1, C. H. Christensen7, P. Christiansen7,

J.Cibor4,R.Debbe1,J. J. Gaardhøje7,M. Germinario7, K. Hagel8,

O. Hansen7, H. Ito11, E. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2,

C.E.Jørgensen7, E. J. Kim5, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5,

G. Løvhøjden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Murray8, J. Natowitz8,

B. Neuman11,B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2,

D. Roehrich9, B. H. Samset12, S. J. Sanders11, I. S. Sgura10, R.A.Sheetz1, Z.Sosin3,

P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8 ,A.Wieloch3,Z. Yin9

1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France

3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland

5Johns Hopkins University, Baltimore, USA, 6New York University, USA

7Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark

8Texas A&M University, College Station. USA, 9University of Bergen, Norway

10University of Bucharest, Romania,11University of Kansas, Lawrence,USA

12 University of Oslo Norway

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

8%

10%

0-5%

5-10%

10-20

Charged Particle MultiplicitydN/dhAccording to

Bjorken,

e>5GeV/fm3

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

High density QCD

gluon saturation

Kharzeev and Levin,

PLB523(2001)79

h=0

h=1

h=4

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Particle Spectra

After appropriate corrections, we combinine all data sets to obtain

final invariant yields over a broad range of rapidity and pT

p

K

p

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Kaons: exponential

Protons: Gaussian

Particle SpectraTop 5% central collisions

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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

Integrated multiplicities (Gaussian fit)

N() ~ 1780 N(+) ~1760

N(K+) ~ 290 N(K) ~ 240

N(pbar) ~ 85

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

up to y = 3

AGS : high stopping

RHIC: more

transparent

Nuclear StoppingNet-proton rapidity densities (top 5% central collisions)

BRAHMS, submitted

to PRL,

nucl-ex/0312023

P. Christiansen

Ph.D. Thesis

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Gaussians in pz:

Gaussians in pz:

2.03 0.16

empirical scaling

2.00 0.10

6 order polynomial

scaling broken

Total E=25.72.1TeV

Nuclear StoppingNet-baryon after

feed-down & neutron corrections

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

p : 3108

p : 428

K+ : 1628

K- : 1093

+ : 5888

- : 6117

- 0 : 6004
- n : 3729
- n : 513
- K0 : 1628
- K0 : 1093
- : 1879
- : 342

sum: 33.4 TeV

produced: 24.8TeV

- 35 TeV (EbeamNpart)
- of which 25 TeV are
- carried by produced
- particles.

NB: the method is very

sensitive to the tails of

the dN/dy dist. (10-15%)

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

I.G.Bearden, Niels Bohr Institute

Y < 1 : consistent with

Hadron Gas Stat. Model

K+/+ : 15.6 0.1 % (stat)

K/ : 14.7 0.1 % (stat)

[Phys. Lett. B 518 (2001) 41]

Divergence at higher y :

Associated K+ production

No single source with

unique T and B

BRAHMS, PRL90 (2003) 102301

T~constant, Bvaries with y

63 GeV

Strangeness with KaonsRAPIDITY DEPENDENCE

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Over the full phase space:

K+/+ = 16.6 1.5 % (syst)

K/ = 13.7 2.0 % (syst)

Why this behavior ?

Net-Kaon distribution

evolves like net-proton

ENERGY DEPENDENCE

At y = 0, ratios converge

to ~ 15 %

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Transverse Flow…

p

p

Points: BRAHMS Data

Curves: 3D Hydro (Hirano)

Histos: AMPT

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Spectra with BW Fits at y~0,1,2,3(T,bs,ain the fit Rmax=13fm)

BRAHMS Preliminary

Fix a,T

y~0

y~1

Fix a,b

y~2

y~3

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

pT (GeV/c)

parton

nucleon

nucleon

Jets at RHICFind this……….in this

And, in BRAHMS, we only

“see” this much…

p+p jet+jet ([email protected])

Au+Au ??? ([email protected])

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Characterize “high” pT by single particle spectra

h=0

h=2.2

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Arsene et al.PRL2003

To look at ‘only’ data, form ratioRh=Rcp(h=2.2)/Rcp(h=0)

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

d+Au Nuclear Modification h =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

I.G.Bearden, Niels Bohr Institute

Predictions from theory

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

I. Vitev nucl-th/0302002 v2

CGC at y=0

Y=0

As y grows

Y=3

Y=-3

Very high energy

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Croninlike enhancement at =0.

Clear suppression as changes up to 3.2

Same ratio made with dn/d follows the low pT RdAu

1 d2Nd+Au/dpTdh

RdA=

<Ncoll> d2Nppinel/dpTdh

where < Ncoll> = 7.2±0.3

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

central

h~3

Periph.

pbar/- ratio probes extent of new medium in y

p+p

d+Au

Au+Au

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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…

ConclusionsRiken BNL Workshop

I.G.Bearden, Niels Bohr Institute

ISR DATA

h=1

Fit to

ISR (R203) DATA

Global Parameterization

Of ISR DATA

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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