1 Mar. 26 SQM2006

J.H. Lee (BNL)

Recent Results from BRAHMSRecent Results from BRAHMS

J.H. LeePhysics Department

Brookhaven National Laboratory

For the Collaboration

March 27 2006

Mostly

Stran

geness

2 Mar. 26 SQM2006

J.H. Lee (BNL)

Short Introduction

BRAHMS in “1 page”

What have we learned so far?

Selected Published + Preliminary Results

Outlook/Summary

3 Mar. 26 SQM2006

J.H. Lee (BNL)

Forward Physics in R.H.I. Collisions: Mapping Forward Physics in R.H.I. Collisions: Mapping Space-time EvolutionSpace-time Evolution

Formation of Hot Matter, QGP?

-Identifying and Characterizing the Hot Matter

- How does the system extend/develop? Transverse and longitudinal dynamics

- Strong constraints for theoretical modeling/interpretation

• Initial Conditions/Partonic Dynamics: High-pT vs y

• Collective Hydro-dynamics: Flow (radial and elliptic) vs y: “Viscometer”

• Thermodynamic and freeze-out properties: Temperatures, Ratios, HBT vs y

• Baryon Transport: Net-baryon vs y

• Bulk Properties: multiplicity, dN/dy

4 Mar. 26 SQM2006

J.H. Lee (BNL)

Braod RAnge Hadron Magnetic Spectrometers• Designed to study nuclear reactions in broad kinematic range (y-pT)• 2 movable spectrometers with small solid angle measuring charged

identified hardrons precisely• Centrality detectors (Si+Scintillator Tiles) to characterize events• 53 people from 12 institutions from 5 countries

FS PID using RICH

Multiple settings

5 Mar. 26 SQM2006

J.H. Lee (BNL)

Au+Au 200 GeV 0-5% Central

Baryon Transport: How much energy available from the Baryon Transport: How much energy available from the collision?collision?

• AGS->RHIC : Stopping -> Transparency

• Rapidity Loss <y>: 2±0.4: not linearly increase with ybeam

• Energy loss <E> per nucleon: 73±6 GeV • Available energy for excitation: ~3/4 of total energy

PR

L 93 1

02301

(2004)

Net-proton in p+p

H. Yang, Symposium

6 Mar. 26 SQM2006

J.H. Lee (BNL)

Rapidity Dependent Kaon Balence: “Net”-kaon (KRapidity Dependent Kaon Balence: “Net”-kaon (K++--KK--))

• longitudinal net-kaon evolution similar as net-proton

in |y|< 3 at RHIC (AuAu @ 200 GeV)• strong “association”: net-kaon / net-lambda

/net-proton?

7 Mar. 26 SQM2006

J.H. Lee (BNL)

Baryon/meson (p/Baryon/meson (p/++,pbar/,pbar/--) at √s = 200 GeV) at √s = 200 GeV

• Scale with <Npart>, independent of system at =0 and 3.2

• Decrease with rapidity and increase with <Npart> and pT

• (flow , medium effect) • Ratio independent of centrality

• proton dominates at y~3: R(p/y~3 ~ 2*

R(p/y~0 for central AuAu, CuCu and pp: baryon

transport

• pbar at y~3: R(pbar/y~3 ~ 0.5* R(p/y~0

8 Mar. 26 SQM2006

J.H. Lee (BNL)

d+Au sNN=200GeV sNN=19.4GeV Au+Au sNN=200GeV

Limiting Fragmentation: Longitudinal ScalingLimiting Fragmentation: Longitudinal Scaling

PR

L 9

4 (

20

05

)

PR

L 8

8 (

2002)

• Particle production independent of beam energy near beam rapidity: Limiting fragmentation behavior • “Crucial Observation” (L.M.) for universal QCD

9 Mar. 26 SQM2006

J.H. Lee (BNL)

Limiting Fragmentation of pion and KaonLimiting Fragmentation of pion and Kaon

BRAHMS/RHIC + SPS + AGS

-

10 Mar. 26 SQM2006

J.H. Lee (BNL)

““Extended” Longitudinal Scaling for <mExtended” Longitudinal Scaling for <mTT> for K> for K--

PHOBOS PRL 94 (2005)

BRAHMS PreliminaryBRAHMS Preliminary

• K- <mT> decreases with rapidity

• Longitudinal Scaling in all available rapidity ranges• <pt> driving Hydro

11 Mar. 26 SQM2006

J.H. Lee (BNL)

200GeV

63 GeV

Energy dependent K/Energy dependent K/for central AuAufor central AuAu

• K/: No surprises at 63 GeV• 200 and 63 GeV: Similar rapidity dependence

12 Mar. 26 SQM2006

J.H. Lee (BNL)

K/K/ vs p vs pTT at at ~3.2 at √s = 200 GeV~3.2 at √s = 200 GeV

• K/ increase with system size • K/ increase with pT (~ < 2GeV/c) at forward

13 Mar. 26 SQM2006

J.H. Lee (BNL)

Flowing at ForwardFlowing at Forward

v2 for pion

• Understanding missing low-pt fraction is important for integrated v2 from FS

• Kaon and proton v2 will come: Statistically Challenging

• v2(y~0) ~ v2(y~3) for 0.5<pT<2 GeV/c

14 Mar. 26 SQM2006

J.H. Lee (BNL)

At the RHIC energies, hard scattering processes at high-pT become important

Partons are expected to loose energy in the dense matter

Different rapidities provide different densities of the medium: Sensitive to the dynamics

“Dialing” initial condition channel

Largest medium effect at mid-rapidity (“Scale” to multiplicity)?

Rapidity dependent high-pT suppression factors: provide information on dynamical medium effect

at fixed time

y~0

high-y

Rapidity Dependent High-pRapidity Dependent High-pTT Measurement Measurement

BRAHMS

NA49

AGS

15 Mar. 26 SQM2006

J.H. Lee (BNL)

pp at forward : more then reference spectra pp at forward : more then reference spectra

• NLO pQCD describes data at forward rapidity at 200 GeV• K- are described best by KKP (Kniehl-Kramer-Potter) than Kretzer (NLO pQCD Calculations done by W. Vogelsang)

pT (GeV/c)

BRAHMS

Preliminary

16 Mar. 26 SQM2006

J.H. Lee (BNL)

Energy and System Dependent Energy and System Dependent Nuclear Modification Factors at Nuclear Modification Factors at ~0 and 1~0 and 1

• R AuAu (200 GeV) < RAuAu(63 GeV) < RCuCu(63 GeV) for charged hadrons

• Pp at 63 GeV is ISR Data (NPB100), RHIC-Run6 will provide better reference

17 Mar. 26 SQM2006

J.H. Lee (BNL)

Nuclear Modification Factors (Rcp, RNuclear Modification Factors (Rcp, RAuAuAuAu) for ) for ,K,p ,K,p at y~3.1at y~3.1

• Suppression for pions and Kaons: RAuAu: <K<p

• RAuAu ≠ Rcp (<Ncoll>,<Npart> for 40-60% ~ 70,56)

18 Mar. 26 SQM2006

J.H. Lee (BNL)

RRAuAuAuAu(Y=0) ~ R(Y=0) ~ RAuAuAuAu(y~3) for 0-10% Central at √s = 200 (y~3) for 0-10% Central at √s = 200 GeV GeV

• R AuAu (Y=0) ~ RAuAu(y~3) for pions and protons: Accidental?

• Rapidity dependent interplay of Medium effect + Hydro + baryon transport

19 Mar. 26 SQM2006

J.H. Lee (BNL)

RdAu Update: Identified Particle RdAu at y~3RdAu Update: Identified Particle RdAu at y~3

• RdAu of identified particle consistent with published h- results

• dAu(-)/dAu(+): Valance quark isospin dominates in pp?

BRAHMS

Preliminary

+ blue- red

20 Mar. 26 SQM2006

J.H. Lee (BNL)

• System, Energy dependent - Strangeness production - Freeze-out chemistry• Turning off the medium effect in Rapidity, Energy,

Species? - Rcp, RAA at higher-rapidity ~3.5 for Kaon • Universal (QCD) property at forward? Saturation – Fragmentation - “Complete” rapidity and pT-dependent kaon measurement

for pp, dA, AA • Longitudinal (partonic) dynamics of strangeness: - rapidity, pt, centrality, reaction-plane dependent

kaon yield,ratios - v2 vs y for kaons• pQCD vs forward kaons in pp • Strangeness spin physics also: - Transverse single spin Asymmetries for K at “high”-xF

Strangeness Physics from 5 years of BRAHMS Strangeness Physics from 5 years of BRAHMS runningrunning

21 Mar. 26 SQM2006

J.H. Lee (BNL)

Non-hadronic energy loss through the medium in |y|<3:

High energy density >> nuclear density

- y 2 - 25 TeV left for particle production

Strong transverse/elliptic flow in y<3

(local) Chemical equilibration

Onset of gluon saturation?

SummarySummary

Limitingfragmentation

22 Mar. 26 SQM2006

J.H. Lee (BNL)

BRAHMS White PaperBRAHMS White Paper

23 Mar. 26 SQM2006

J.H. Lee (BNL)

I.Arsene7, I.G. Bearden6, D. Beavis1, S. Bekele6 , C. Besliu9, B. Budick5, H. Bøggild6 , C. Chasman1, C. H. Christensen6, P. Christiansen6, R.

Clarke9, R.Debbe1, J. J. Gaardhøje6, K. Hagel7, H. Ito10, A. Jipa9, J. I. Jordre9, F. Jundt2,

E.B. Johnson10, C.E.Jørgensen6, R. Karabowicz3, E. J. Kim4, T.M.Larsen11, J. H. Lee1, Y.

K. Lee4, S.Lindal11, G. Løvhøjden2, Z. Majka3, M. Murray10, J. Natowitz7,

B.S.Nielsen6, D. Ouerdane6, R.Planeta3, F. Rami2, C. Ristea6, O. Ristea9, D. Röhrich8, B. H. Samset11, D. Sandberg6, S. J. Sanders10, R.A.Sheetz1, P. Staszel3, T.S. Tveter11, F.Videbæk1, R. Wada7, H. Yang6, Z. Yin8, and I. S. Zgura9

1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France3Jagiellonian University, Cracow, Poland,

4Johns Hopkins University, Baltimore, USA, 5New York University, USA6Niels Bohr Institute, University of Copenhagen, Denmark

7Texas A&M University, College Station. USA, 8University of Bergen, Norway 9University of Bucharest, Romania, 10University of Kansas, Lawrence,USA

11 University of Oslo Norway

The BRAHMS The BRAHMS CollaborationCollaboration