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Medium induced jet absorption at RHIC

Summary of high p T observables Collision geometry and jet absorption model Comparison with data summary. Medium induced jet absorption at RHIC. Jiangyong Jia 1,2 , Axel Drees 1 1) SUNY at Stony Brook 2) Columbia University. nucl-th/0310044.

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Medium induced jet absorption at RHIC

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  1. Summary of high pT observables Collision geometry and jet absorption model Comparison with data summary Medium induced jet absorption at RHIC Jiangyong Jia1,2, Axel Drees1 1) SUNY at Stony Brook 2) Columbia University nucl-th/0310044

  2. High pT observables in heavy-ion collisions hadron yield, RAA Suppression in central collisions Azimuthal anisotropy, v2 Large v2 at high pT di-jet correlation, DAA Suppression of away side yield Jiangyong Jia

  3. Centrality dependence of high pT observables • hadron yield, RAA di-jet correlation, DAA Azimuthal anisotropy, v2 • All observables depend strongly on centrality. • “quenching” of jets in the collision zone is controlled by impact parameter Jiangyong Jia

  4. surface volume Collision rate f Jet Tomography(I) • Large suppression of RAA and DAA indicates a very opaque medium. • Detected jets comes mainly from hard–scattering at the surface. • Surface emission gives approximate Npart scaling. • Surface emission naturally leads to the suppression of away side suppression. Jiangyong Jia

  5. In plane Out plane Jet Tomography(II) • Energy loss depends on the azimuthal direction • RAA depends on the azimuthal angle M. Gyulassy, I. Vitev and X.N. Wang, PRL86,2537 (2001) E. Wang, and X.N. Wang, PRL 89, 162301, (2002) C.A. Salgado and U.A. Wiedemann, PRL 89,092303 (2002) Jet absorption + nuclear geometry suggested by Bjorken 1982 Jiangyong Jia

  6. Jet absorption model E. Shuryak PRC 66 027902(2002) • Generate and propagate jet through dense medium • Look the geometrical aspect of the energy loss • Focus on the centrality dependence • Describe all three related effects in the same framework • We need to model both jets (hard-scattering) and medium Jiangyong Jia

  7. Hard scattering probability rNcoll (x,y) Energy density rNpart (x,y) Determined from the collision geometry Hard scattering and Energy density • Glauber Modelling of Au+Au Collisions (Woods-Saxon) • Centrality selected by impact parameter Jiangyong Jia

  8. Jet Absorption Picture • Generate di-jet isotropically according to rNcoll (x,y) • Jets are absorbed in dense reaction volume according to • I is the line integral, take into account the quadratic dependence and longitudinal expansion. (l0=0.2fm) • expanding source absorption  l2 • static source absorption  l • static source absorption  l2 • expanding source absorption  l • k is the absorption parameter (only free parameter) fix k to give f = 0.22 for central collisions Jiangyong Jia

  9. Centrality Dependence of High pT Yields • Compare with at high pT from PHENIX and STAR • I3 (expanding and  l) tend to localize the absorption. • I2 (static and  l2) have stronger dependence on jet path. • Describes centrality dependence of yield • Small sensitivity on absorption pattern around 100 participants. centrality dependence of yield reflects mostly collision geometry Jiangyong Jia

  10. Dijet correlations • Compare STAR data to absorption picture • by construction, same side jet (Df~0) will always give unity • Away side jet (Df~p) suppression by factor ~ 7, described by jet absorption and collision geometry • Central DAA is more sensitive to absorption patterns. However, distinguish power is limited by experimental statistics. Near side centrality dependence of yield reflects mostly collision geometry Away side Jiangyong Jia

  11. Azimuthal Anisotropy • Centrality dependence of v2 at pT > 4 GeV/c from data • Measured v2 for different methods are quite different • The difference comes from contributions that do not correlate with RP • 4 particle cumulant method is less affected by non-flow contribution • Comparing to jet absorption calculation • largest v2 from jet absorption picture 5-10% • Sensitive to the energy loss assumption and dynamic evolution of the medium • Below data! Jiangyong Jia

  12. Dependence on nuclear profile • Woods-Saxon matter density has defuse surface • The dense medium has a different diffuseness? • v2 increase by using hard sphere or cylindrical nuclear geometry • However, it misses the centrality dependence of the suppression 10% 15% Jiangyong Jia

  13. STAR V4 • Model V4<0!. Jiangyong Jia

  14. Dependence on system size • Calculate RAA and DAA for lighter systems in central collisions (for I1) • The Npart dependences are similar to centrality selected Au+Au collisions. • To first order, the overlap volume and average energy density are similar Jiangyong Jia

  15. Summary • Jet absorption picture and Wood-Saxon collision geometry • Describe general features of centrality dependence of jet quenching • Consistent with suppression of hadron yields • Consistent with back-to-back jet correlation • Azimuthal anisotropy is below the data. • Absorption pattern and matter profiles dependence • RAA is insensitive. • DAA is more sensitive in central collisions, but experimental error is too big. • v2 is very sensitive • Surface diffuseness is smaller? • Real suppression is stronger and soft contamination still important? • System size dependence of RAA and DAA is similar to AuAu centrality dependence. Jiangyong Jia

  16. Line integral distribution • Line integral (I1) distributions are similar • DE  I, so DE distributions should also be similar. Jiangyong Jia

  17. Other absorption patterns • System size dependence for other absorption patterns(also the integral distribution) • expanding source absorption  l2 • expanding source absorption  l • static source absorption  l2 • Solid lines for AuAu, dashed lines for light systems Jiangyong Jia

  18. Jiangyong Jia

  19. Reaction plane dependence of RAA • Jet absorption produces a f dependent suppression: a • A 15% v2 would imply almost a factor of 2 difference in plane and out of plane. Jiangyong Jia

  20. Jiangyong Jia

  21. At Pt>4-6 GeV/c, particle production are consistent with jet fragmentation outside the medium • Spectra shape, flavor composition, xT scaling behavior. Nucl-ex/0308006 • Strength, width and charge composition of jet correlation. Jiangyong Jia

  22. Energy loss (B.Mueller, nucl-th/0208038) Energy loss (X.N.Wang,nucl-th/0307036) jet absorption with Woods-Saxon geometry (next) Jiangyong Jia

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