Azimuthallysensitive HBT in STAR

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Azimuthally-sensitive HBT in STAR
Mike Lisa Ohio State University

• Motivation
• Noncentral collision dynamics
• Azimuthally-sensitive interferometry previous
  results
• STAR results
• Hydrodynamic predictions for RHIC and LHC
• Summary

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Central collision dynamics _at_ RHIC

• Hydrodynamics reproduces p-space aspects of
  particle emission up to pT2GeV/c (99 of
  particles)? hopes of exploring the early, dense
  stage

Heinz Kolb, hep-th/0204061
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Central collision dynamics _at_ RHIC

• Hydrodynamics reproduces p-space aspects of
  particle emission up to pT2GeV/c (99 of
  particles)? hopes of exploring the early, dense
  stage

• x-space is poorly reproduced
• model source lives too long and disintegrates too
  slowly?
• Correct dynamics signatures with wrong space-time
  dynamics?

• Turn to richer dynamics of non-central collisions
  for more detailed information

Heinz Kolb, hep-th/0204061
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Noncentral collision dynamics
hydro evolution

• Dynamical models
• x-anisotropy in entrance channel ? p-space
  anisotropy at freezeout
• magnitude depends on system response to pressure

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Effect of dilute stage
hydro evolution

• hydro reproduces v2(pT,m) (details!) _at_ RHIC for
  pT lt 1.0 GeV/c
• system response ? EoS
• early thermalization indicated

• dilute hadronic stage (RQMD)
• little effect on v2 _at_ RHIC

Teaney, Lauret, Shuryak, nucl-th/0110037
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Effect of dilute stage
hydro evolution

• hydro reproduces v2(pT,m) (details!) _at_ RHIC for
  pT lt 1.5 GeV/c
• system response ? EoS
• early thermalization indicated

• dilute hadronic stage (RQMD)
• little effect on v2 _at_ RHIC

• significant (bad) effect on HBT radii

calculation Soff, Bass, Dumitru, PRL 2001
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Effect of dilute stage
hydro evolution

• hydro reproduces v2(pT,m) (details!) _at_ RHIC for
  pT lt 1.5 GeV/c
• system response ? EoS
• early thermalization indicated

• dilute hadronic stage (RQMD)
• little effect on v2 _at_ RHIC

• significant (bad) effect on HBT radii
• related to timescale? - need more info

Teaney, Lauret, Shuryak, nucl-th/0110037
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Effect of dilute stage
hydro evolution

• hydro reproduces v2(pT,m) (details!) _at_ RHIC for
  pT lt 1.5 GeV/c
• system response ? EoS
• early thermalization indicated

• dilute hadronic stage (RQMD)
• little effect on v2 _at_ RHIC

• significant (bad) effect on HBT radii
• related to timescale? - need more info

• qualitative change of freezeout shape!!
• important piece of the puzzle!

Teaney, Lauret, Shuryak, nucl-th/0110037
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Possible to see via HBT relative to reaction
plane?

• for out-of-plane-extended source, expect
• large Rside at 0?
• small Rside at 90?

2nd-order oscillation
Rs2 no flow expectation
fp
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Traditional HBT - cylindrical sources
Decompose q into components qLong in beam
direction qOut in direction of transverse
momentum qSide ? qLong qOut
(beam is into board)
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Anisotropic sources? Six HBT radii vs f

• explicit and implicit (xmxn(f)) dependence on f

Wiedemann, PRC57 266 (1998).
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Symmetries of the emission function
Heinz, Hummel, MAL, Wiedemann, nucl-th/0207003
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Fourier expansion of HBT radii _at_ Y0
Insert symmetry constraints of spatial
correlation tensor into Wiedemann relations
and combine with explicit F-dependence
Note These most general forms of the Fourier
expansions for the HBT radii are preserved when
averaging the correlation function over a finite,
symmetric window around Y0. Relations between
the Fourier coefficients reveal interplay between
flow and geometry, and can help disentangle space
and time
Heinz, Hummel, MAL, Wiedemann, nucl-th/0207003
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Anisotropic HBT results _at_ AGS (?s2 AGeV)
AuAu 2 AGeV E895, PLB 496 1 (2000)
xside
xout
K
fp 0

• strong oscillations observed
• lines predictions for static (tilted)
  out-of-plane extended source ? consistent with
  initial overlap geometry

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Meaning of Ro2(f) and Rs2(f) are clearWhat about
Ros2(f) ?
AuAu 2 AGeV E895, PLB 496 1 (2000)
fp 0
fp 45

• Ros2(f) quantifies correlation between xout and
  xside
• No correlation (tilt) b/t between xout and xside
  at fp0 (or 90)

• Strong (positive) correlation when fp45
• Phase of Ros2(f) oscillation reveals orientation
  of extended source

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Indirect indications of x-space anisotropy _at_ RHIC

• v2(pT,m) globally well-fit by hydro-inspired
  blast-wave

temperature, radial flow consistent with fits to
spectra
?
anisotropy of flow boost
spatial anisotropy (out-of-plane extended)
STAR, PRL 87 182301 (2001)
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STAR data AuAu 130 GeV minbias

• significant oscillations observed
• blastwave with same parameters as used to
  describe spectra v2(pT,m)
• additional parameters
• R 11 fm
• ? 2 fm/c !!

preliminary
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STAR data AuAu 130 GeV minbias
no spatial anisotropy

• significant oscillations observed
• blastwave with same parameters as used to
  describe spectra v2(pT,m)
• additional parameters
• R 11 fm
• ? 2 fm/c !!

preliminary

• both flow anisotropy and source shape contribute
  to oscillations, but
• geometry dominates dynamics

• freezeout source out-of-plane extended? fast
  freeze-out timescale !

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Azimuthal HBT hydro predictions

• RHIC (T0340 MeV _at_ t00.6 fm)
• Out-of-plane-extended source (but flips with
  hadronic afterburner)
• flow geometry work together to produce HBT
  oscillations
• oscillations stable with KT

(note RO/RS puzzle persists)
Heinz Kolb, hep-th/0204061
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Azimuthal HBT hydro predictions

• RHIC (T0340 MeV _at_ t00.6 fm)
• Out-of-plane-extended source (but flips with
  hadronic afterburner)
• flow geometry work together to produce HBT
  oscillations
• oscillations stable with KT

• LHC (T02.0 GeV _at_ t00.1 fm)
• In-plane-extended source (!)
• HBT oscillations reflect competition between
  geometry, flow
• low KT geometry
• high KT flow

sign flip
Heinz Kolb, hep-th/0204061
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HBT(f) Results 200 GeV

• Oscillations similar to those measured _at_ 130GeV
• 20x more statistics ?explore systematics in
  centrality, kT
• much more to come

STAR PRELIMINARY
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Summary

• Quantitative understanding of bulk dynamics
  crucial to extracting real physics at RHIC
• p-space - measurements well-reproduced by models
• anisotropy ? system response to compression (EoS)
• probe via v2(pT,m)
• x-space - generally not well-reproduced
• anisotropy ? evolution, timescale information,
  geometry / flow interplay
• Azimuthally-sensitive HBT correlating quantum
  correlation with bulk correlation
• reconstruction of full 3D source geometry
• Freezeout geometry out-of-plane extended
• early (and fast) particle emission !
• consistent with blast-wave parameterization of
  v2(pT,m), spectra, R(pT), K-p
• With more detailed information, RHIC HBT puzzle
  deepens
• what about hadronic rescattering stage? - must
  occur, or?
• does hydro reproduce ?t? or not??
• right source shape via oscillations, but misses
  RL(mT)
• Models of bulk dynamics severely
  (over?)constrained