brahms y2000 run @ rhic: s nn =130 gev

April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute

1

Reaction features in 65 AGeV Au + 65AGeV Au

Electromagnetic dissociation dN(ch)/d distribution -

4<<4 vs. Collision Centrality

Production of charged particles, N(ch)/pr.participant

Bjorken limit attained ? Transparency or Stopping

p-bar/p vs y, b, pt

Strangeness vs y Future…

BRAHMS Y2000 run @ RHIC: snn=130 GEV


2

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, 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, 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


3

RHIC physicsAugust 2000

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


4

BRAHMS in the 2’ hall

… in 1998


5

Forward & Midrapidity spectrometers

FS: 2 TPC, 2 TOF, C, 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


6

BRAHMS acceptanceAugust 2000


7

Global detectorsSiMA, TMA, BB

SiMA (2.0< | |<2.0) PTMA (2.2< || <2.2) Beam-Beam (3 < | | < 4)

97% (geom)


8

Centrality determinationVertex distribution

1m


9

Electromagnetic nuclear dissociation

LO+NLO Mutual EM

•Mutual Electromagnetic dissociation

•(Spectrum of virtual photons) * (absorption cross section) = WW

•Multiphonon GDR excitation, abs

•EM vs Nuclear coll.

•=> neutron (L*R) coincidences

•RELDIS. Pshenichnov et al.

EM dissociation selected by ZDC coincidences

and TMA Veto in BRAHMS

n

n n

2n

1n

LO

NLO


10

Neutral Energy correlations (ZDC)

C2(EL,ER)=P(EL,ER)/(P(EL)*P(ER))


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dNch/dSiMA, TMA, BB, TPC

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

to secondaries (20-50%)

Consistency between several independent. detector systems

N(ch)d= 4000±200 Central 0-5% dN(ch)/d (=0) =550 FWHM of distribution

= 7.6 0.7

BRAHMS preliminary

MTPC1 (CEJ)

Yuri Blyakhman. BRAHMS Thesis


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TPC tracks, Vertex reconstruction, Charged particle track density

MTPC1

z

y


13

Multiplicity of Charged Particle tracks in TPC’s

B = 0


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Total production of Charged particles

4000 charged part. observed Nch 23.5 pr. part. Pair cf. Nch 17 in p+p at s=130GeV 35-40% increase over p+p

Syst

?


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Centrality and Number of Participants

Cent %

b (fm) HIJING Fritiof

Glauber

0-10 0-5 329.2 321.7 316

10-20 5-7 233.8 230.0 223

20-30 7-8.5 163.3 162.9 154

30-40 8.5-10 108.6 111.8 102

40-50 10-11 70.0 72.9 63


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NCharged vs. number of participant nucleon pairs

dN/d 3 (=0) pr.part pair. Cf. HIJING, FRITIOF No saturation effects

observed

Claus Ekman Jørgensen.

BRAHMSThesis

FRITIOF

HIJING

MTPC1 CEJ

EKRT

22

2


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Hadron identification MRS (90, 40 deg)

m2=p2( t2 / L2 -1)

p-bar

K p

=0

=3

p

K

0

p, pbar

K±


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Hadron IdentificationFS (4 deg)

p-bar

=3

C1,H1,T2

+

p

m2=p2( t2 / L2 -1)

+

p

K+


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N(pbar)/N(p)Centrality and Pt dependence

Antiproton absorbtion correction to pbar/p ratio:

5 % for FS at 4 deg 2 % for MRS at 90, 40 deg 10% corr. (low pt) p from Be-

tube Applied to data

Most pbar and p from Hyperon decays fall into spectrometer acceptance.

Correction factor depends on H/B, H-bar/B-bar and TB/TH

For H/B < 0.5 systematic correction is < 5% on ratio

Model dependent not applied to data


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Bjorken limit reached for Au+Au s= 130AGeV?

ISR R803

s=23

s=63

BRAHMS-RHIC

Subm. to PRL


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P-bar/p ratioCentrality dependence

BRAHMS


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N(p-bar)/N(p) systematics vs CM energy

0,00

2,00

4,00

6,00

8,00

10,00

12,00

0,0 0,5 1,0 1,5 2,0 2,5

rapidity y

RH

IC/S

PS

STAR

PHENIX

BRAHMS


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N(pbar)/N(p)Au+Au s= 130AGeV

BRAHMS

Subm. to PRL


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StrangenessK-/K+ vs rapidity

Preliminary

CERN-SPS


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How consistent are the models?


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Summary First Au+Au s=130 AGeV

FUTURE RHIC startup June 2001 Au+Au s=200 AGeV Higher Luminosity Narrower vertex distribution p + p running

BRAHMS full forward spectrometer ready

Start full scan =0 to =4 High pt coverage (PID in FS to

p=25 GeV/c)

RESULTS Nch (0-5%) 4000 dN/d (y=0) 550. FWHM 7.6 N(ch) 23 pr. participant-pair dN/d (y=0) 3 pr. part. Pair

AntiMeson/Meson close to unity

p-bar/ p vs y shows increased but still incomplete transparency

Midrapidity Plateau? y =0,0.7,2 : pbar/p 0.64, 0.66,

0.41 (±0.05 ± 0.06) Weak pt and centrality

dependence Bjorken limit not reached Models inconsistent with data

brahms y2000 run @ rhic: s nn =130 gev

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