Charged-particle pseudorapidity densities in d-Au collisions at

s=200GeV/A

Hironori Ito

Brookhaven National Laboratory

BRAHMS Collaboration

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.

1 Brookhaven National Laboratory, USA2 IreS and Université Louis Pasteur, Strasbourg, France3 Jagiellonian Univeristy, Cracow, Poland4 Institute of Nuclear Physics, Cracow, Poland5 Johns Hopkins University, Baltimore, USA6 New York University, USA7 Niels Bohr Institude, University of Copenhagen, Denmark8 Texas A&M University, College Station, USA9 University of Bergen, Norway10 University of Bucharest, Romania11 University of Kansas, Lawrence, USA12 University of Oslo, Norway

Member of the BRAHMS Collaboration

Beam-Beam Counter Arrays

Right Array

Left Array

Two Arrays located at 219 cm from the nominal collision vertex along the beam axis on either size of the vertex

Two sizes of Cherenkov radiator--- Diameter of ¾ in and 2 in

Pseudorapidity coverage at nominal vertex location:

--- 3 < < 4.2

Multiplicity ArraysTwo Layers of Multiplicity Arrays1. Silicon Strip Multiplicity Array (SiMA)

--- 175 detector channels--- Si strip dimension .86 cm x 4 cm x .3 mm

2. Scintillation Tile Multiplicity Array (TMA)--- 38 tiles--- Tile dimension 12 cm x 12 cm x .5 cm

TMA

SiMA

At nominal vertex location,two arrays cover <2.2

Centrality determination

0-30% central

30-60% central

•Average charged-particle multiplicities from silicon and scintilator tile detectors determine event centralities. •Forward energy in Zero-degree calorimeter is used to exclude peripheral collisions.

Preliminary

Preliminary

Pseudorapidity density

Square box --- Beam-beam counterCircle --- Multiplicity detectorBlue marker --- Systematic errors

0-30% Central Events 30-60% Central Events

Preliminary

Preliminary

Model comparison

0-30% Central Events 30-60% Central Events

Red line: Saturation model(hep-ph/0212316), Green line: Hijing model (centrality selection by impact parameter)Pink line: Hijing model (centrality selection by numbers of charged particles)

Preliminary

Preliminary

Pseudorapididty dependence (deuteron fragmentation region)

Circle --- η = 0Square --- η = 1Up triangle --- η = 2Down triangle --- η = 3

Saturation model Hijing model

0-30% Central

30-60% Central

0-30% Central

30-60% Central

Preliminary Preliminary

Pseudorapididty dependence (Au fragmentation region)

Circle --- η = 0Square --- η = 1Up triangle --- η = 2Down triangle --- η = 3

Saturation model Hijing model

30-60% Central 0-30% Central0-30% Central30-60% Central

Preliminary Preliminary

Summary

• Charged-particle pseudorapidty densities in d-Au collisions have been measured at s=200 GeV/A.

• Centrality-dependent charged-particle productions are compared with two different models.

• Experimental results are largely in line with Hijing model prediction.