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Measurements with BRAHMS

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Measurements with BRAHMS

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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

- 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

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Sys. Error :

8%

10%

0-5%

5-10%

10-20

According to

Bjorken,

e>5GeV/fm3

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

AMPT

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

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

Pions: power law

Kaons: exponential

Protons: Gaussian

Top 5% central collisions

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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

Net-proton measured

up to y = 3

AGS : high stopping

RHIC: more

transparent

Net-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

Rapidity loss:

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

Net-baryon after

feed-down & neutron corrections

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Energy (in GeV)

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%)

- 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

Increasing y

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

RAPIDITY DEPENDENCE

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

no change for +

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

p

p

Points: BRAHMS Data

Curves: 3D Hydro (Hirano)

Histos: AMPT

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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)

jet

parton

nucleon

nucleon

Find this……….in this

And, in BRAHMS, we only

“see” this much…

p+p jet+jet (STAR@RHIC)

Au+Au ??? (STAR@RHIC)

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

h=0

h=2.2

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

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

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

RdAu

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

Preliminary

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

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Preliminary results from 63GeV

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…

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute

Reference Spectrum

ISR DATA

h=1

Fit to

ISR (R203) DATA

Global Parameterization

Of ISR DATA

Riken BNL Workshop

I.G.Bearden, Niels Bohr Institute