brahms y2000 + y2001 @ rhic: s nn =130 gev, and s nn =200 gev

Sept 4, 2001 Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute 1

Reaction features in 65 AGeV + 65 AGeV and 100 AGeV + 100 AGeV Au-AU collisions

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


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


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


BRAHMS in the 2’ hall

… in 1998


Forward & Midrapidity spectrometers

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


First BRAHMS collision at 100 AGeV+100AGeV

T1

MTPC1

T2

MTPC2

MRS: 90 deg

6.5 msr

FS: 6 deg

0.8 msr


BRAHMS acceptanceAugust 2000 & 2001


Global detectorsSiMA, TMA, BB

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

97% (geom)


Centrality determinationVertex distribution

1m


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, JPB, IM, et al.

EM dissociation selected by ZDC coincidences

and TMA Veto in BRAHMS

n

n n

2n

1n

LO

NLO


Neutral Energy correlations (ZDC)

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


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= 4050±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 Subm. Phys. Lett. B 7/2001.


TPC tracks, Vertex reconstruction, Charged particle track density

MTPC1

z

y


Charged Particle Mult.snn=130 GeV

BRAHMS. Subm. to Phys Lett. B. 2001

SPS


NCharged vs. number of participant nucleon pairs. snn=130AGeV

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

observed

Claus Ekman Jørgensen.

Thesis NBI 2001

FRITIOF

HIJING

MTPC1 CEJ

EKRT


RHIC: 200 AGeVWill this happen?


dNch/d for100 AGeV + 100 AGeV

100 AGeV + 100 AGeV Au+Au

N(ch)d= 5100±300 Central 0-6% dN(ch)/d (=0) =61050 FWHM of distribution

= 7.9 1.0

BRAHMS 200AGEV


Hard and Soft vs.High Density QCD @ 200 AGeV

Kharzeev and Levin (nucl-th/0108006)

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)


Total production of Charged particles

130 AGeV 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

?BRAHMS

200 AGeV 130AGeV

200 AGeV 5100 charged part. observed Nch 30 pr. part. pair cf. Nch 20 in p+p at

s=200GeV 50% increase over p+p


Hadron identification MRS (90, 40 deg)

m2=p2( t2 / L2 -1)

p-bar

K p

=0

=3

p

K

0

p, pbar

K±


Hadron IdentificationFS (4 deg & 130AGeV)

p-bar

=3

C1,H1,T2

+

p

m2=p2( t2 / L2 -1)

+

p

K+


N(pbar)/N(p) @ 130 AGeV 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


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

ISR R803

s=23

s=63

BRAHMS

PRL sept. 2001


FS Hadron identificationfor snn = 200 GeV Au+Au

TOF and Cherenkov veto in FFS


Particle ratios snn = 200 GeV (y=2)

Y=2 : p-bar/p = 0.48 0.08 -/+= 0.98 0.04

BRAHMS: Preliminary Integrated over centrality and

pt rangeK- p-

K+ p


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


StrangenessK-/K+ vs y @ snn= 130GeV

BRAHMS Preliminary

CERN-SPS


How consistent are the models @ snn= 130GeV?


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

RESULTS: 100+100 Nch (0-5%) 5100 dN/d (y=0) 625. FWHM 7.8 N(ch) 30 pr. participant-pair dN/d (y=0) 3.6 pr. part. Pair

p-bar/p = 0.48 (y=2) Moderate growth in baryon

poor ’plateau’. Total mult. Increases by 25%, Central mult increases by 14% Pbar/p increases by 17% (y=2)

Large y and pt coverage to come

RESULTS: 65+65 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 + y2001 @ rhic: s nn =130 gev, and s nn =200 gev

Documents

jens jrgen gaardhje

niels bohr institutednchd

jagiellonian university

university of bucharest

university of kansas

university of copenhagen

university of bergen

agev 100agevt1mtpc1t2mtpc2mrs