Phases of matter in

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Phases of matter in the BRAHMS experiment
Pawel Staszel, Marian Smoluchowski Institute of
Physics Jagiellonian University for the BRAHMS
Collaboration
XXXIII International Conference On High Energy
Physics Moscow, 26.07 2.08.2006
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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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Relativistic Heavy Ion Collider
PHOBOS
PHENIX
STAR
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Broad Range Hadron Magnetic Spectrometers
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Particle production and energy loss
Energy density Bjorken 1983 eBJ 3/2 ?(ltEtgt/
pR2t0) dNch/d? assuming formation time
t01fm/c gt5.0 GeV/fm3 for AuAu _at_ 200 GeV gt4.4
GeV/fm3 for AuAu _at_ 130 GeV gt3.7 GeV/fm3 for AuAu
_at_ 62.4 GeV
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Primary versus produced matter
At 200GeV created matter is at
picked at y0
primary matter is concentrated around y?3
(?y?2.2)

• longitudinal net-kaon evolution similar as
  net-proton
• in ylt 3 at RHIC (AuAu _at_ 200 GeV)
• strong association net-kaon / net-lambda
  /net-proton?

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High pt suppression ? jet quenching

• Particles with high pts (above 2GeV/c)
• are primarily produced in hard scattering
• processes early in the collision

• pp experiments ? hard scattered
• partons fragment into jets of hadrons

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

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

Experimentally ? depletion of the high pt region
in hadron spectra
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Charged hadron invariant spectra
RAAlt1 ? Suppression relative to
scaled NN reference

• SPS
• data do not show suppression
• enhancement (RAAgt1) due to initial state
• multiple scattering (Cronin Effect)

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Energy and System Dependent Nuclear Modification
Factors at h0 and 1

• R AuAu (200 GeV) lt RAuAu(63 GeV) lt RCuCu(63 GeV)
  for charged hadrons
• pp at 63 GeV is ISR Data (NPB100), RHIC-Run6
  will provide better reference

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Control measurement dAu _at_ ?sNN200
Suppression in AuAu due to Jet Quenching or due
to Initial State Parton Saturation (CGC)?
What about dAu? - Jet Quenching No - CGC
- Yes/No?
Excludes alternative interpretation in terms of
Initial State Effects ? Supports the Jet
Quenching for central AuAu collisions
back-to-back azimuthal correlation by STAR
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Nuclear modification factors (RCP, RAuAu) for
p,K,p at y3.1

• Suppression for pions and kaons RAuAu ? lt K lt p
• RAuAu ? Rcp (ltNcollgt,ltNpartgt for 40-60 70,56)

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RAuAu(Y0) RAuAu(y3) for central AuAu at vs
200 GeV

• R AuAu (Y0) RAuAu(y3) for pions and protons
  accidental?
• Rapidity dependent interplay of Medium effect
  Hydro baryon transport

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... more on RAA rapidity dependence

• Similar level of suppresion for central
  collisions
• At forward rapidity RAA shows stronger rise
  towards peripheral coll.
• (surface -gt volume emmission)

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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(y0) v2(y3) for 0.5ltpTlt2 GeV/c

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Examine dAu at all rapidities
I. Arsene et al., BRAHMS PRL 93 (2004) 242303.
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RdAu and RAA for anti-protons and pions _at_200
BRAHMS PRELIMINARY

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

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Summary
Strong transverse/elliptic flow in ylt3
High energy density gtgt nuclear density
Limiting fragmentation
- ??y? ? 2 - 25 TeV left for particle
production
(local) Chemical equilibration
Non-hadronic energy loss through the medium in
ylt3
Onset of gluon saturation?
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The BRAHMS Collaboration
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, France 3Jagiellonian
University, Cracow, Poland, 4Johns Hopkins
University, Baltimore, USA, 5New York University,
USA 6Niels Bohr Institute, University of
Copenhagen, Denmark 7Texas AM 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
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BACKUP SLIDES
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Anti-particle to particle ratios
BRAHMS PRELIMINARY

• pbar/p verus K-/K good statistical model
  description with ?B ?B(y) with T170MeV
• But this describes also energy depencency at y0
  ? only ?B controls the state of matter
• STAR and NA47 measures pbar/p versus
• ?-/?

• 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 ylt1 matter?antimatter

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K-/K and antihyperon/hyperon
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
K-/K exp((2?s - 2?u,d)/T) pbar/p
exp(-6?u,d/T) ?s0 ? K-/K
(pbar/p)1/3 Fit shows that K-/K (pbar/p)1/4
? ?s ¼ ?u,d
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RAuAu 200 GeV
Cronin enhancement
suppression at high pT significant medium
effects
BRAHMS, PRL 91, 072305 (2003)
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pbar/?- scaling with Npart
?sNN200GeV
pp
pp
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K/? ratios at ?3.1, AuAu _at_200GeV
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• 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 DE q.L2
• q adjusted to give observed RAA at h1.

The change in dN/dh will result in slowly rising
RAA .
The modification of reference pp spectrum causes
the RAA to be approximately constant as function
of h .
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Summary

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

• 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

• 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 y3.2 RAA shows larger suppression than RdA

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FS PID using RICH
Multiple settings
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RdAu Update Identified Particle RdAu at y3
blue - red
BRAHMS Preliminary

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

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Limiting Fragmentation
Shift the dNch/d? distribution by the beam
rapidity, and scale by ?Npart?. Lines up with
lower energy ? limiting fragmentation
AuAu ?sNN200GeV (0-5 and 30-40) AuAu
?sNN130GeV (0-5) PbPb ?sNN17GeV (9.4)