March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute1 nReaction features in 65 AGeV Au + 65AGeV Au ndN(ch)/d distribution -4

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute

1

Reaction features in 65 AGeV Au + 65AGeV Au

dN(ch)/d distribution -4<<4 vs. Collision Centrality

Total production of charged particles

Production of particles pr. participant

Bjorken limit attained ? Tranparency or Stopping

P-bar/p vs y, b, pt

Future…

Results from Y2000 run @ RHIC: snn=130AGEV


2

I.G. Bearden7, D. Beavis1, Y. Blyakhman6, J. Bondorf7, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, P. Christiansen7, J.Cibor4, R.Debbe1, J. J. Gaardhøje7, K.Grotowski4, J. I. Jordre10, F. Jundt3, K. Hagel8, O. Hansen7, H.Heiselberg7, A. Holm7, C. H. Christensen7, A.K. Holme2, H. Ito9, E. Jacobsen7, A. Jipa11, C. E. Jørgensen7, E. J. Kim5, T.Kreutgel4, T. Kozik4, T.M.Larsen2, J. H. Lee1, Y. K.Lee5, G. Løvhøjden2, Z. Majka4, A. Makeev8, B. McBreen1, M. Murray8, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami3, D. Roehrich9, B. Samset2, S. Sanders9, I. S. Sgura11, R.A.Sheetz1, Z.Sosin4, P. Staszel7, T.S. Tveter2, F.Videbæk1, R. Wada8 and A.Wieloch4.

1Brookhaven National Laboratory, USA 2Fysisk Institutt, University of Oslo Norway

3IReS, Université Louis Pasteur, Strasbourg, France 4Jagiellonian University, 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 Kansas, USA.

10University of Bergen, Norway 11University of Bucharest, Romania

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

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


5

BRAHMS acceptanceAugust 2000


6

Global detectorsSiMA, TMA, BB

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

97% (geom)


7

Centrality determinationVertex distribution

1m


8

TPC tracks, Vertex reconstruction, Charged particle track density

MTPC1

z

y


9

dN/d (charged) SiMA, TMA, BB, TPC

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

to secondaries (30-50%)

Consistency betwqen several independent. detector systems

N(ch)d= 4020±150 Central 0-5% dN(ch)/d (=0) =550 FWHM of distribution

= 7.6 0.7

BRAHMS preliminary

MTPC1 (CEJ)


10

Charged Particle production vs. Npart

Nch 23.5 pr. part. Pair cf. Nch 17 in p+p at s=130GeV (35-40% increase) dN/d 3 (=0) pr.part pair. Cf. HIJING, FRITIOF

BRAHMS preliminary


11

Hadron identification MRS (90, 40 deg)

m2=p2( t2 / L2 -1)

p-bar

K p

=0

=3

p

K

0

p, pbar

K±


12

Hadron IdentificationFS (4 deg)

p-bar

=3

C1,H1,T2

+

p

m2=p2( t2 / L2 -1)

+

p

K+


13

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

Antiproton absorbtion correction to pbar/p ratio:

9.5 % for FS at 4 deg 3 % for MRS at 90, 40 deg 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 < 0.5% on ratio

Model dependent not applied to data


14

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

ISR R803

BRAHMS-RHIC

To be Subm. to PRL


15

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

BRAHMS

To be Subm. to PRL


16

How consistent are the models?


17

Model predictions:FRITIOF 7.02 and HIJING


18

Summary First Au+Au s=130 AGeV

FUTURE RHIC startup May 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 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

y =0,2 : N(pbar)/N(p) 62%,44%

Weak pt and centrality dependence

Bjorken limit not reached Models inconsistent with data


19

dN/d (=0) vs NpartMTPC1 track counting

BRAHMS (CEJ)


20

Particle Identification in FS at 4 deg.

-, K-, pbar +, K+, p


21

BRAHMS Acceptance

Acceptance for charged in MRS at =0 (both signs accepted)

Acceptance in FS (august 2000)

h+

h-


22

Total charged particle

Multiplicity

BRAHMS


23

PionsFritiof 7.02, Hijing


24

Charged Particle production vs. Npart

Nch 23.5 pr. part. Pair

cf. Nch 17 in p+p at s=130GeV

(35-40% increase)

dN/d 3 (=0) pr.part pair.

Cf. HIJING, FRITIOF, UrQMD


25


26

Documents

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute1 nReaction features in 65 AGeV Au + 65AGeV Au ndN(ch)/d distribution -4