status of STAR femtoscopy program

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status of STAR femtoscopy program

• Mike Lisa
• Ohio State University

http//www.star.bnl.gov/STAR/html/hbt_l/
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Outline

• Published
• ?-? PRL 87 (2001) 082301PRL 93 (2004) 012301
  PRC 71 (2005) 044906
• ?-?-? PRL 87 (2003) 262301
• K-? PRL 87 (2003) 262302
• Submitted / collaboration review
• p-? final review at PRC - Gael Renault
• K0- K0 2B submitted RSN... - Selemon Bekele
• Under way
• ?-? Petr Chaloupka
• p-p, p-?p Hania Gos
• ? -p, K- ? Adam Kisiel
• ?- ? pp, dAu Zbigniew Chajecki
• ?- ? CuCu, Au62Au Debasish Das
• Future plans

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Motivation
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Femtoscopic information
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R(vSNN) simple signal ?
R(vSNN, b, Npart, A, B, mT, y, ?, PID)
No glaring signal in simple measures The real
(experimentalists) puzzle
Rout/Rside
e
Rischke, Gyulassy, NP A 608 (1996) 479
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R(vSNN, b, Npart, A, B, mT, y, ?, PID)

• Vary colliding system
• does physics change?
• requires dedicated program
• Vary kinematic variables
• space-time dynamics
• requires large acceptance
• Vary particle type
• consistent picture?
• unique probe of dynamical structure
• requires good particle identification
  acceptance

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PublishedResults
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STAR-HBT published
R(vSNN, b, Npart, A, B, mT, y, ?, PID)
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STAR-HBT published
R(vSNN, b, Npart, A, B, mT, y, ?, PID)
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STAR-HBT published
R(vSNN, b, Npart, A, B, mT, y, ?, PID)
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STAR-HBT published
R(vSNN, b, Npart, A, B, mT, y, ?, PID)
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STAR-HBT published
R(vSNN, b, Npart, A, B, mT, y, ?, PID)
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submitted
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Species systematics

• STAR femtoscopy
• published
• submitted
• shown and in-progress

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p-? correlations - final referee stage at
PRCGael Renault
STAR-HBT submitted

• First-ever ????p-?, p-?????, ????p-?????
  correlations
• Consistency from baryon sector for flow-generated
  x-p correlations
• Extraction of real/imaginary ????p-?, p-?????
  scattering lengths from CF !!
• important new physics direction
• possible effect of residual correlations - could
  not reliably calculate (for now...)
• significant technical effort (and more
  information) required

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K0S-K0S correlations - well along in starpapers
reviewSelemon Bekele
STAR-HBT submitted

• First quality K0 correlations
• novel
• entirely different exptl. details
• little resonance feed
• high pT coverage
• sufficient detail such that strong FSI
  (subthreshold a0, f0) were needed (and explored)
• more consistency for flow-generated x-p
  correlations

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Present Studies
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HBT radii AuAu vs CuCu / ?s62, 200Debasish
Das
STAR-HBT underway

• central collisions of heaviest system
• no obvious jumps in energy
• consistent with PHOBOS
• no onset behaviour manifest in space-time probe
• centrality dependence driven by multiplicity, not
  Npart, for all systems
• consistent with lower energies
• universal scaling confirmed - entropy dominance
  of bulk?
• mT dependence similar for all centralities for
  all systems
• consistent with AuAu _at_ 200
• spatial evidence of similar flow

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HBT effects in particle collisions Zbigniew
Chajecki
STAR-HBT underway

• Suggestive - expansion/flow turn-on?
• But...
• significant x-p correlations similar to AA
  collisions
• (seen before, but no direct comparison)
• Now... the first comparison
• what the...?
• Under study
• resonances
• formation times
• jets
• non-Gaussian shape
• No matter what... quite a coincidence!

...its solution may provide a new insight into
the hadronization process of QCD - A. Bialas,
ISMD 2005
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Significant technical improvement - SHD
STAR-HBT underway

• Traditional representation of multidimensional
  CF
• limited representation of shape
• 3D Cartesian projections in id
• set of zero measure of 3D CF
• Fit-violating trends may be hidden
• Salient geometrical effects non-trivially
  convoluted
• double ratios in non-id

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Significant technical improvement - SHD
STAR-HBT underway

• Traditional representation of multidimensional
  CF
• limited representation of shape
• 3D Cartesian projections in id
• double ratios in non-id
• Spherical Harmonic representation
• use all the data to probe/view all shape
  information
• see all 3D CF in just a few relevant 1D plots
• efficient use full symmetry of CF

This new method of analysis represents a real
breakthrough. ...(should) become a standard
tool in all experiments. - A. Bialas, ISMD 2005
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STAR Central AuAu collisions -- Spherical HD
1D o-s-l projections
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Mental calibration - a Gaussian CF

• Full 3D structure
• (high-L (fine structure) coefficients drop off)
• Different geometrical aspects separate use
  all relevant information in the CF
• AL?0 vanishes in non-femtoscopic region

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SHD in pp Zbigniew Chajecki
STAR-HBT underway

• SHD - prompted by problems in low-multiplicity
  (esp pp) collisions

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SHD in pp Zbigniew Chajecki
STAR-HBT underway

• SHD - prompted by problems in low-multiplicity
  (esp pp) collisions
• Non-femtoscopic large-q correlations
• worsening _at_ low mult
• worsening (?) _at_ high kT
• driving cause
• NOT experimental artifact
• resonances? (no)
• jets (no)
• flow (no)
• p conservation - probably
• but quantification nontrivial...

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?-? correlations Petr Chaloupka
STAR-HBT underway

• unique system
• meson (ss) Baryon
• 10x mass difference
• Coulomb strong (?) FSI - driven

• --
• consistent
• Coulomb-dominated
• - -
• consistent
• Coulomb strong

Wonderful...but theres more!...

• Expected centralitydependence
• ? sensitive

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SHD of non-identical particle correlations

• A00 - monopole ? size
• A11 - dipole ? shift
• A2m - quadrupole ? shape
• .....

!!
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?-? correlations Petr Chaloupka
STAR-HBT underway

• A11 ? 0 in correlation regions
• Asymmetry in the average emission point between
  p-X
• Quant. consistent w/ BW (and RQMD) using
  standard (not fitted) parameters
• ? region unclear in unlike sign correlations
• resonance / FSI duality called into
  question(under study)

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?-? correlations - side focus on ?1530 Petr
Chaloupka
STAR-HBT underway

• study of mixing details and cuts affect BG
  subtracted (not divided) resonance peak

circa QM05
AuAu 200 GeV 10-40
Minv?? (GeV/c2)
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??-K?, ??-p - getting to fine detailsAdam Kisiel
and Marcin Zawisza
STAR-HBT underway

• Extracting shifts from common species
• beyond first observation to more fine-grained
  structure
• Approx. consistency with BW (as in first report),
  but better statistics makes clear problem at
  large k
• one consequence 5 fm syst. err
• another worry about screw-up
• standard/simplest mix 1-2
• MultAnalysis 0.5
• Mult and pT mix lt ppm
• ...
• development of new method (Adamss way) of
  combining events? strong suppression of EbyE
  effects
• syst. err. 1 fm now

(?-K mirror representation)
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p-p, ?p- ?p, ?p-p femtoscopyHanna Gos
STAR-HBT underway

• nice signals
• conflicting results
• poor fits

Data corrected for non-primary (feed-down)
protons assuming they constitute uncorrelated
combinatorics -- done in all analyses --
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p-p, ?p- ?p, ?p-p femtoscopyHanna Gos
STAR-HBT underway
dominant correlated feed-down from p-? (but many
significant sources)
convolution of kinematics yields with
Therminator model Broniowski,...Kisiel, et al
nucl-th/0504047
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p-p, ?p- ?p, ?p-p femtoscopyHanna Gos

• building the correlation net
• convolve measured parent correlations to account
  for correlated feeddown
• other contributions estimated (FSI not fully
  known)
• unique effort, necessary at present energies
• non-trivial feed-down effect. greater effect on
  p-?p, due to wider (if not stronger) structure in
  p??

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p-p, ?p- ?p, ?p-p femtoscopyHanna Gos
AuAu 200 GeV, centrality cut
p-p

• Fully corrected baryon CFs
• regain consistency of homogeneity lengths
• consistent w/ BW
• SHD underway (shape of proton H.R.)

?p-p
?p-?p
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• Studies well along
• Baryon femtoscopy (Gos Kisiel)
• systematic error evaluation
• pion femtoscopy in hadronic collisions (Chajecki)
• model studies, e-by-e
• energy, system dep. of pion HBT (Das Panitkin)
• drafting stage
• ?-K, K-p, ?-p (Kisiel Zawisza)
• technical issues approaching asymtopia
• ?-? (Chaloupka)
• (over?-)detailed purity estimate

• Brief Summary
• Continuing precision studies in a systematic
  femtoscopy program
• extending species to form/disprove consistent
  picture
• considerable technical development spurred
• potentially fundamental issues (FSI/resonance
  duality, pp vs AA)

• Some future directions
• HBTv1 - tilt/twisted CGC (Aihongs talk)
• pi-p with TOF patch
• build correlation network
• excitation function / scan
• imaging (3D) focus

• QM abstracts
• meson (?) HBT
• scaling, size/energy evolution
• baryon and non-id femtoscopy
• p(?p)-p(?p), p(?p)-?(??), ??-??