BRAHMS Y2000 + Y2001 @ RHIC: s nn =130 GeV, and s nn =200 GeV

Dec 6, 2001 BH-symposium, Jens Jørgen Gaardhøje, Niels Bohr Institute

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First physics at RHIC with 65 AGeV + 65 AGeV and 100 AGeV + 100 AGeV Au+Au collisions

Ecm= s 40 TeV

4000-5000 charged particles produced per collision

Transparency or Stopping ?

Towards nuclear ’stuff’ with matter-antimatter balance

BRAHMS Y2000 + Y2001 @ RHIC: snn=130 GeV, and snn=200 GeV


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I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J. Bondorf7, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, J.Cibor4, R.Debbe1, J. J. Gaardhøje7, M. Germinario7, K. Grotowski4, K. Hagel8, O.

Hansen7, H. Heiselberg7, A. Holm7, A.K. Holme12, H. Ito11, E. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2, C. E. Jørgensen7, T. Keutgen9, 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.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2, D.

Roehrich9, B. H. Samset12, S. J. Sanders11, D. Sandberg7,I. S. Sgura10, R.A.Sheetz1, Z.Sosin3, P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8 and A.Wieloch3.

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

BRAHMS Intl. collaboration


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RHIC physicsAugust 2000 & August 2001

2:00 o’clock

4:00 o’clock6:00 o’clock

8:00 o’clock

10:00 o’clock

STARPHENIX

RHIC

AGS

LINACBOOSTER

TANDEMS

9 GeV/uQ = +79

1 MeV/uQ = +32

HEP/NP

g-2

U-lineBAF (NASA)

BRAHMS: Lpeak = 3.3 1025 cm-2 s-1

Lave = 1.7 1025 cm-2 s-1

Rcoll= 350 HzPHOBOS

6 b-1

2 wks

August 2000 and 2001


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Quark Gluon PlasmaHot and dense matter

QGP

HG

Freeze out

Hadron gas

Mixed phase

QGP

Pre-equil. quark

2.1012K


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URQMD simulation of Au+Au at snn=200 GeV

Rapidity y = ½ ln (E+pz / E- pz) = ½ ln(1+cos / 1-cos) y(lab) = y + y(cm)

Pseudorapidity = ln (cot [/2])

Transverse momentum pt= p sin


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Central Au+AU collision event in STAR


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BRAHMS in the 2’ hall

… in 1998


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Forward & Midrapidity spectrometers in 2001

FS: 2 TPC, 2 TOF, C1-threshold, 3 Drift Ch. Mod., RICH, 4 Dipoles

2.5 - 30 deg. = 1.5 - 4

MRS: 2 TPC, 1 Dipole, 1TOF

30 - 90 deg. = 0 - 1.5


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First BRAHMS collision at 100 AGeV+100AGeV

T1

MTPC1

T2

MTPC2

MRS: 90 deg

6.5 msr

FS: 6 deg

0.8 msr


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BRAHMS acceptance Y2000 & Y2001


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Centrality determinationVertex distribution

1m


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TPC tracks, Vertex reconstruction, Charged particle track density

MTPC1

z

y


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dNch/d @ snn= 130 GeVSiMA, TMA, BB, TPC

N=dE /<dE> P(0)/P(n1) Background corr.due

to secondaries (37-50%)

Consistency between 4 independent detector systems

65 AGeV+ 65 AGeV: N(ch)d= 3860±300 Central 0-5% dN(ch)/d (=0) =550 FWHM of distribution

= 7.6 0.7

0-5%

10-20%

20-30%

30-40%

40-50%

5-10%

600

BRAHMS Phys. Lett. B 523 (2001) 227; nucl-ex 0108015


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RHIC: 200 AGeVWill this happen?


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Pseudorapidity densities@ 200 AGeV

5630 charged particles produced for 0-5% central

14% increase over 130GeV 50% increase over p +p (UA5) => significant medium effects

Bjorken energy density

BJ = (1/R20) dEt/d 5 GeV/fm3

dEt=dN • <pt>

cf: QGPcritical 1 GeV/fm3

Brahms 200

pp


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Hard and Soft vs.High Density QCD @ 200 AGeV

Kharzeev and Levin (nucl-th/0108006)

HIGH DENSITY QCD MODEL

Soft-Hard: dN/d=(1-X) npp <Npart>/2

+ X npp <Ncoll>

<Ncoll>=1049, <Npart>=339, npp=2.43 =>dN/d=668 (with X=0.9)

High Density QCD-saturation:

dN/dy = f( Npart, Qs

2, ,QCD,s,y)

with =0.3 from HERA data => dN/d=620 (using dN/d=549 at

s=130GeV)

BRAHMS

Submitted to PRL dec. 2001

Nucl-ex. 00112001

=4.5

=3.0

=0

Gluon saturation ?


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Saturation of excitations in fragmentation region

Shift data to beam frame of reference

BRAHMS subm. to PRL- n-ex. 00112001


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Hadron identification MRS (90 - 40 deg). TOF

m2=p2( t2 / L2 -1)


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Hadron IdentificationFS (4-20deg @200AGeV)

C1,H1,T2

+

p

K+

4 deg


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C1 Threshold CherenkovPID

Cos=1/n

=>

th=1/n


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Ring Imaging Cherenkovfor high momentum PID

R


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Bjorken limit reached for Au+Au snn= 130GeV?

ISR R803

s=23

s=63

BRAHMS

PRL87(2001)112305


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Antiparticle/particle ratios @ 200AgeV

’+’ ’-’

p-/p = p-(pair) / [p+p(pair)]

K-/K+ = K-(pair) / [K+(pair)+K+(ap)]

(p+p p++K+)

+- pair prod (& ch. exch).

Midrapidity: near matter-antimatter balance

+ +

BRAHMS Preliminary


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How consistent are the models @ snn= 130GeV?


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Summary: First Au+Au snn=130 & 200 GeV

Highest particle multiplicity in nuclear collisions ( 4600 ch. part) ever seen

Large energy density > 5 crit

High reaction transparency Decoupling of central and

’fragmentation’ regions Partonic (color) description

appears necessary Central region dominated by

matter-antimatter balance: Qualitatively new physics regime

To come: Strangeness

net baryon density

jet quenching, ….

2006: ALICE @ LHC -CERN

snn=6000 GeV, Pb+Pb


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A few Extra’s


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Pbar/p ratio systematics


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Documents

BRAHMS Y2000 + Y2001 @ RHIC: s nn =130 GeV, and s nn =200 GeV