Femtoscopic and long-range correlations in p p and Au Au collisions

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Femtoscopic and long-range correlations in pp
and AuAu collisions
Midwest Critical MassToledo, Ohio, 21-22
October, 2005

• Zbigniew Chajecki
• The Ohio State Universityfor the STAR
  Collaboration

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Outline

• Dynamics of the collisions
• mT dependence of HBT radii in pp, d(p)Au,
  AuAu
• pp ? AuAu New (changing) physics?
• Non-femtoscopic correlations
• problem with baseline of CF in low multiplicity
  collisions
• shape analysis of correlation function
• phase-space distortion

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Transverse mass dependence in AuAu
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Transverse mass dependence in AuAu
AuAu 62GeV STAR preliminary
bx0.907
bx0.974
p
K
p
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Transverse mass dependence pp, d(p)Au

• pp HBT radii decrease with increase of mT

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pp like a little AuAu ?
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Surprising scaling

• All pT(mT) dependences of HBT radii observed by
  STAR scale with pp although its expected that
  different origins drive these dependences

HBT radii scale with pp Scary coincidence or
something deeper?
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Let's look in more detail at where these radii
come from
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Decomposition of CF onto Spherical Harmonics
AuAu central collisions
C(Qout)
C(Qside)
C(Qlong)
Z.Ch., Gutierrez, Lisa, Lopez-Noriega,
nucl-ex/0505009 Pratt, Danielewicz
nucl-th/0501003
STAR preliminary
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Including Al2,m in a fit
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Scaling (fit w/ baseline param.)
Ratio of (AuAu, CuCu, dAu) HBT radii by pp
STAR preliminary
NEW fit w/ baseline parameterization
Fit w/o baseline parameterization
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NA22 parametrization of CF
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NA22 1D projections of 3D CF
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NA22 fit to STAR data
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p-lambda correlations at CLAS, A. Stavinsky, WPCF
2005
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Phase-Space Distortion with GenBod

• Generator needs the following information
• Multiplicity
• Mass of each particle
• Energy of the collision
• Cross-section (constant or Fermi
  energy-dependent)
• Generator returns
• Momentum of each particle, mass and energy
• Weight for each event that is proportional to
  the phase space integral
• Energy and momentum is conserved !

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SHD of CF generated with GenBod
arbitrary
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Summary

• mT dependence of HBT radii for AuAu, CuCu, dAu
  and pp seems to be the same although its
  expected to have different origins
• Decomposition of CF in terms of spherical
  harmonics
• Spherical harmonics allow efficent diagnostic of
  the correlation function
• Use symmetry of the Q-space
• Pratt and Danielewicz nucl-th/0501003
  connection of one-to-one CF and spatial
  anisotropies
• Hope to parametrize non-femtoscopic correlations
  (phase-space distortion)

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.
SUPPORT SLIDES
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Transverse mass dependence pp, d(p)Au

• pp HBT radii decrease with increase of mT

• dAu collisions
• centrality dependence observed
• Rside sensitive to the size of a smaller nucleus
  (dAu vs pAu)

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Universal scaling ?
STAR DATA (pp,dAu,CuCu,AuAu_at_62GeV - prelim.)
Radii scale with multiplicity Forget A,B,vs,
Npart...dN/d? determines HBT radii,at all mT
(!!!!)
Lisa, Pratt, Soltz, Wiedemann, nucl-ex/0505014
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System expansion Initial vs Final Size
Collisions at 200GeV only
Smooth (but not trivial) expansion of the system
from pp to AuAu
AuAu system expands pp (dAu) no or less
expansion
Proton initial size 0.89 fm from e-scattering
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Decomposition of CF onto spherical harmonics
Z.Ch., Gutierrez, Lisa, Lopez-Noriega,
nucl-ex/0505009

• Cartesian-space (out-side-long) naturally encodes
  physics, but is poor/inefficient representation
• Recognize symmetries of Q-space -- decompose by
  spherical harmonics!
• Direct connection to source shapes
  Danielewicz,Pratt nucl-th/0501003
  decomposition of CF on cartesian harmonics
• immune to acceptance
• full information content at a glancethanks to
  symmetries

? 0,2p ? 0,p
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Some properties of Alm coefficients

• Alm 0 for l or m odd identical particle
  correlations
• (for non-id particles, odd l encodes shift
  information)
• A00(Q) one-dimensional CF(Qinv) (bump
  1/R)
• Alm(Q) ?l,0 where correlations vanish
• Al?0,m(Q) ? 0 ? anisotropy in Q space
• ImAlm 0

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Baseline in pp, dAu and AuAu

• Some coefficients dont vanish for large Q
• Bias from zero is larger for more peripheral
  collisions
• This problem is getting more significant for
  small systems (pp dAu)
• It can be due to
• an experimental artifact
• long range correlations (e.g. Jets)
• problem with momentum conservation ?
• or ?