Phases of matter in the BRAHMS experiment Paweł Staszel, Marian Smoluchowski Institute of Physics Jagiellonian University for the BRAHMS Collaboration

Phases of matter inthe BRAHMS experiment

Paweł Staszel, Marian Smoluchowski Institute of Physics

Jagiellonian Universityfor the BRAHMS Collaboration

XXXIII International Conference On High Energy Physics

Moscow, 26.07 – 2.08.2006

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2P. Staszel - Jagiellonian University, KrakówICHEP, Moscow 2006

BRAHMS

Outline

1. Detector setup.

2. General (bulk) characteristics of nucleus-nucleus reactions.

3. Nuclear modification at mid-rapidity

4. Nuclear modification at forward rapidity

5. Elliptic Flow

6. Summary.

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BRAHMS

Relativistic Heavy Ion Collider

Au+Au d+Au

p+p

energies:sNN=200GeV,

sNN=62GeV

Cu+Cu

PHOBOS

STAR

PHENIX BRAHMS

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BRAHMS

BBroad RaRange HHadron MMagnetic SSpectrometers

Tile Ring 1

Flow Ring 2

Si Ring 1

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BRAHMS

Particle production and energy loss

Energy density: Bjorken 1983

eBJ = 3/2 (<Et>/ R20) dNch/d

assuming formation time t0=1fm/c:

>5.0 GeV/fm3 for AuAu @ 200 GeV

>4.4 GeV/fm3 for AuAu @ 130 GeV

>3.7 GeV/fm3 for AuAu @ 62.4 GeV

p

p

y

y

BB

yT dyydy

dNm cosh)(

Total E=25.72.1TeV72GeV per participant

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BRAHMS

Primary versus produced matter

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

proton?

BRAHMS

NA49

AGS

primary matter is concentrated around y3 (y2.2)

At 200GeVcreated matter is at picked at y=0

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BRAHMS

q

q

hadronsleadingparticle

leading particle

Schematic view of jet production Particles with high pt’s (above ~2GeV/c) are primarily produced in hard scattering processes early in the collision

Experimentally depletion of the high pt region in hadron spectra

In A-A, partons traverse the medium Probe of the dense and hot stage

p+p experiments hard scattered partons fragment into jets of hadrons

If QGP partons will lose a large part of their energy (induced gluon radiation) suppression of jet production Jet Quenching

High pt suppression jet quenching

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BRAHMS

Charged hadron invariant spectra

AuAu @200GeV

Scaled N+N reference

RAA =Yield(AA)

NCOLL(AA) Yield(NN)

Nuclear Modification Factor

RAA<1 Suppression relative to scaled NN reference

SPS: data do not show suppression enhancement (RAA>1) due to initial state

multiple scattering (“Cronin Effect”)

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BRAHMS

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

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

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

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BRAHMS

Control measurement: d+Au @ sNN=200

Suppression in AuAu dueto Jet Quenching or due toInitial State PartonSaturation (CGC)?

What about d+Au? - Jet Quenching – No - CGC - Yes/No?

Excludes alternative interpretation in terms of Initial State Effects Supports the Jet Quenching for central Au+Au collisions

+ back-to-back azimuthal correlation by STAR

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BRAHMS

Nuclear modification factors (RCP, RAuAu) for p,K,p at y~3.1

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

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

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BRAHMS

RAuAu(Y=0) ~ RAuAu(y~3)

for central Au+Au at √s = 200 GeV

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

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

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BRAHMS

... more on RAA rapidity dependence

•Similar level of suppresion for central collisions•At forward rapidity RAA shows stronger rise towards peripheral coll. (surface -> volume emmission)Looking for scaling: dN/d ?

BE: eBJ = 3/2 (<Et>/ S0) dNch/d S is transwers area of overlaping region <Et> dirived from and K spectra

Is the energy density the only parameter that controls RAA?

New pp data @62GeV will allow for various comparisions at the same rapidities

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BRAHMS

Flowing 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

dN 1ddpt 2(1 + 2v1cos +

2v2(,pt)cos2)

dN ddptd

=

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BRAHMS

Examine d+Au at all rapidities

Cronin enhancement Cronin enhancement suppression suppression

I. Arsene et al., BRAHMS PRL 93 (2004) 242303.

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BRAHMS

RdAu and RAA for anti-protons and pions @200

BRAHMS PRELIMINARY

• suppression for - but stronger for AuAu• both RdA and RAA show enhancement for p-bar

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BRAHMS

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?

Summary

Limitingfragmentation

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BRAHMS

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, N. Katrynska3, 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

48 physicists from 11 institutions

The BRAHMS Collaboration

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BRAHMS

BACKUP SLIDES

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BRAHMS

•At 200 GeV: -/+ = 1.0, K-/K+ = 0.95, pbar/p = 0.75 •At 62 GeV: -/+ = 1.0, K-/K+ = 0.84, pbar/p = 0.45,• At |y|<1 matterantimatter

Anti-particle to particle ratios

• pbar/p verus K-/K+ : good statistical model description with B= B(y) with T~170MeV•But this describes also energy depencency at y=0 only B controls the state of matter•STAR and NA47 measures pbar/p versus -/+

Chemical freeze-out

BRAHMS PRELIMINARY

It is not true for p+p

BRAHMS PRELIMINARY

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BRAHMS

K-/K+ and antihyperon/hyperon

K-/K+ = exp((2s - 2u,d)/T)pbar/p = exp(-6u,d/T)s=0 K-/K+ = (pbar/p)1/3

Fit shows that K-/K+ = (pbar/p)1/4

s= ¼ u,d

How s= ¼ u,d will work for

hyperons?Hbar/H = (pbar/p)3/4 for Lambdas = (pbar/p)1/2 for Xis = (pbar/p)1/4 for Omegas

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BRAHMS

RAuAu 200 GeV

BRAHMS, PRL 91, 072305 (2003)

Cronin enhancement Cronin enhancement

suppression at high pT

significant medium effects

suppression at high pT

significant medium effects

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BRAHMS

Strong rapiditydependence

CuCu data consistent with AuAu for the same Npart

pp

pp

pbar/- scaling with Npart

sNN=200GeV

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BRAHMS

K/ ratios at =3.1, Au+Au @200GeV

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BRAHMS

Strong energy absorption model from a static 2D matter source. (Insprired by A.Dainese (Eur.Phys.J C33,495) and A.Dainese , C.Loizides and G.Paic (hep-ph/0406201) )

• Parton spectrum using pp reference spectrum• Parton energy loss E ~ q.L**2• q adjusted to give observed RAA at ~1.

The change in dN/d will result in slowly rising RAA .

The modification of reference pp spectrum causes the RAA to be approximately constant as function of .

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BRAHMS

Summary Large hadron multiplicities Almost a factor of 2 higher than at SPS energy( higher ) Much higher than pp scaled results( medium effects)

p/ show strong dependency for given energy depend only on Npar

High-pT

suppression increases with energy for given centrality bin weak dependency on rapidity of RAA which is consistent with surface jet emission RCP can hide or enhance nuclear effects At y=3.2 RAA shows larger suppression than RdA

Identified hadron spectra Good description by statistical model Large transverse flow consistent with high initial density

v2(pt) is seem to not depend on rapidity

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BRAHMS

FS PID using RICH

Multiple settings

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BRAHMS

RdAu Update: Identified Particle RdAu at y~3

• RdAu of identified particle consistent with published h- results• dAu(-)/dAu(+): Valance quark isospin dominates in pp?

BR

AH

MS

P

relim

inary

+ blue- red

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BRAHMS

Limiting FragmentationShift the dNch/d distribution by the beam rapidity, and scale by Npart. Lines up with lower energy limiting fragmentation

Au+Au sNN=200GeV (0-5% and 30-40%)Au+Au sNN=130GeV (0-5%)Pb+Pb sNN=17GeV (9.4%)

Documents

Phases of matter in the BRAHMS experiment Paweł Staszel, Marian Smoluchowski Institute of Physics Jagiellonian University for the BRAHMS Collaboration