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Why x-t correlation may be important for HBT

Why x-t correlation may be important for HBT Origin of a large&positive x-t correlation: partonic? resonance decays? hadronic rescatterings? Can a (hydro-type) negative x-t correlation survive decays/rescatterings in a transport model? Rout/Rside:

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Why x-t correlation may be important for HBT

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  1. Why x-t correlation may be important for HBT Origin of a large&positive x-t correlation: partonic? resonance decays? hadronic rescatterings? Can a (hydro-type) negative x-t correlation survive decays/rescatterings in a transport model? Rout/Rside: from Gaussian fit vs from emission function Strong and positive x-t correlation and its effect on Rout/Rside Zi-Wei Lin The Ohio State University

  2. HBT Radii fromEmission function S(x,p)or correlation function C(q) . 2 Pratt,PRL84 2) Often use 4-parameter fit for C(q) w/o Coulomb effects: 1) Curvature at q=0: Dx,y=<x*y>-<x><y> If source is Gaussian in space-time, then: Pratt,PRL84 Wiedemann,PRC57 Rsource,ij=Rfit,ij

  3. Study HBT with a transport model Advantage: freezeout in transport is natural as the mean free path grows too big compared with system size How to relate to hydro calculations (Cooper-Frye formula at a sharp hypersurface is usually imposed)

  4. Structure of AMPT model with String Melting HIJING energy in strings and minijet partons A+A Fragment excited strings into partons ZPC (Zhang's Parton Cascade) Till Parton freezeout Coalescence into hadrons ART (A Relativistic Transport model for hadrons) Decay all resonances; Final particle spectra

  5. From Gaussian fits to 3-d correlation function C(q) Au+Au at 130AGeV (b=0 fm) ZWL,Ko&Pal,PRL89

  6. Why x-t correlation may be important? x-t correlation duration-time Spatial-size Magnitude and sign of x-t correlation are important for Rout, Rout/Rside, & extraction of duration-time

  7. Correlations in pion emission source: out-side out-t ZWL,Ko&Pal,PRL89 <Xout (t)> x-t correlation Duration time Spatial-size Source Values: (17fm)**2 = 185 -2*168 + 431 Positive and large, tends to reduce Rout Note:includes  decays

  8. K emission source (excludes  decays): out-side out-t ZWL&Ko,JPG29 <Xout (t)> K source Values: (3.4fm)**2 = 35 -2*22 + 20 also positive and large for K

  9. Turn off  decays to study HBT radii from the emission function • Test hydro-like negative x-t correlation upon hadron formation in AMPT

  10. Pions at freezeout mostly partons ~volume emission ~surface emission y x xside xout <xout> >0 parton transverse flow

  11. x-t correlation for pions Au+Au at 200AGeV (b=0 fm)

  12. Already present for quarks x-t correlation for pions Au+Au at 200AGeV (b=0 fm)

  13. Effect of decays on source radii Hadronic decays produce mt-dependence in Rout & Rside

  14. Rout/Rside from emission function

  15. Can an initial negative x-t correlation survive later? Test negative x-t correlation from hydro models at RHIC energies

  16. Initial hadrons: large initial Rout/Rside ratio (source)

  17. Final hadrons: large final Rout/Rside ratio (source) Negative x-t term becomes positive after hadronic scatterings

  18. Radii are different from source or from Gaussian fit to C(Q) Hardtke&Voloshin, PRC61

  19. AMPT: Au+Au at 200AGeV at b=0 fm, 3mb from source from C(Q) fit Rout/Rside=1 big decrease for fitted Rout, Rout/Rside

  20. With an initial negative x-t correlation at hadron formation from source from C(Q) fit Rout/Rside=1 huge decrease for fitted Rout & Rout/Rside Rout/Rside >>1 ~=1

  21. HBT summary • Strong and positive xout-t correlation term • tends to reduce Rout and Rout/Rside. • already present at parton freezeout/hadron formation • An initial negative x-t correlation can lead to large Rout/Rside (when evaluated from emission function) • Rout/Rside:>1 from emission function ~=1 from Gaussian fits to C(Q). • Even with an large initial negative x-t (with Rout/Rside >>1 from the emission function) • Further investigation is needed to find the reason.

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