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Flow and Femtoscopy from QGP Hydro + Hadronic Cascade Tetsufumi Hirano Dept. of Physics The Univ. of Tokyo WPCF, Aug. 1-3, 2007
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Outline Part 1 Mass ordering of v 2 (p T ) revisited Violation of mass ordering for mesons Part 2 Source functions from hydro + cascade 1D 3D (r side, r out, r long )-directions Summary TH, U.Heinz, D.Kharzeev, R.Lacey, and Y.Nara (in preparation)
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Is Mass Ordering of v 2 (p T ) a Direct Signal of Perfect Fluidity? STAR white paper (’05) PHENIX white paper (’05) Lines: Results from Ideal hydro
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Motivation To understand the QGP in H.I.C., need to understand the hadronic stage since Indispensable to disentangle these effects for understanding of unknowns.
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A Hybrid Approach: QGP hydro + hadronic cascade 0 collision axis time Au QGP fluid Initial condition: Transverse Glauber Longitudinal “BGK triangle” QGP fluid: 3D ideal hydrodynamics (Hirano) massless free u,d,s+g gas + bag const. T c = 170 MeV Hadron gas: Hadronic cascade, JAM1.09 (Nara) T sw = 169 MeV hadron gas TH et al.(’06) (1D) Bass, Dumitru (2D) Teaney, Lauret, Shuryak, (3D) Nonaka, Bass, Hirano et al.
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Pseudorapidity Distribution Tune initial parameters with T th = 100MeV to reproduce dN/deta. Then, switch to hadronic cascade below T=T sw. Caveat: Rejecting in- coming particles at T sw
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p T spectra for pi, K, and p Reasonable reproduction of yields and spectra in low p T region (p T <~1.5 GeV/c) TH et al. (in preparation).
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v 2 (p T ) for pi, K, and p OK! Fail to reproduce data due to (absence of) fluctuation of geometry Miller&Snelling (’03), Bhalerao&Ollitrault(’06) Andrade et al (’06),Drescher&Nara (’07) Browniowski et al(’07) TH et al. (in preparation).
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Hydro + Cascade at Work in Forward Rapidity Regions Adapted from S.J.Sanders (BRAHMS) @ QM2006
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Origin of Mass Ordering Mass ordering behavior results from hadronic rescatterings. Not a direct signal of “perfect fluid QGP” TH et al. (in preparation). b=7.2fm
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What happens to strangeness sector?
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Additive Quark Model in Transport Codes (JAM/RQMD/UrQMD) For cross sections without exp. data, Expected to be very small for phi, Omega, etc.
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Distribution of Freeze-Out Time b=2.0fm (no decay) TH et al. (in preparation). Early kinetic freezeout for multistrange hadrons: van Hecke, Sorge, Xu(’98)
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-meson case in p T < 1 GeV/c Just after hadronization Final results T = T sw = 169 MeV b=7.2fm TH et al. (in preparation). Caveat: Published PHENIX data obtained in p T >~1GeV/c for mesons This is NOT obtained within ideal hydrodynamics.
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Summary of flow part A QGP fluid with hadronic rescattering Reproduction of v 2 (p T,m) A hybrid model works well. Origin of mass ordering of v 2 (p T ) Radial flow effect, not “ mass effect ”. Violation of mass ordering for phi mesons Mass ordering itself is not a direct signal of perfect fluidity!
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Femtoscopy from Hydro + Cascade From momentum space to configuration space
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Source Imaging Primed in PCMS (P = 0) Source Imaging: Inverse problem from C to D with a kernel K No more Gaussian parametrization! Source Imaging: Inverse problem from C to D with a kernel K No more Gaussian parametrization! Koonin-Pratt eq.: Source function and normalized emission rate (Brown&Danielewicz (’97-))
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Distribution of the Last Interaction Point from Hydro + Cascade Blink: Ideal Hydro, Kolb and Heinz (2003) x-t x-y p x ~ 0.5 GeV/c for pions Long tail ( decay? elastic scattering?) Positive x-t correlation
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1D Source Function from Hydro + Cascade 0.48 < K T <0.6 GeV/c0.2 < K T <0.36 GeV/c Angle averaged source function Broader than PHENIX data Almost no K T dependence PHENIX data Significant effects of hadronic rescatterings K T =P T /2
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1D Source Function from Hydro + Cascade (contd.) K T dependence Centrality dependence Almost no K T dependence Sensitive to impact parameter lambda=1.0 0.2< K T <0.36 GeV/c b=5.8fm lambda = 1.0
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3D Source Function from Hydro + Cascade (preliminary!) side outlong Source function in PCMS 1fm-slice in each direction 0.2<K T <0.4 GeV/c, | | < 0.35, + - +, - - - pairs Red: Without rescattering, Black: With rescattering No longer Gaussian shape (Lines: Gaussian) Broaden by hadronic rescatterings
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Summary of Femtoscopy 1D- and 3D-source functions from a dynamical model (QGP hydro + hadronic cascade) Significant rescattering effects are seen. Source function is no longer Gaussian. Long tail in 1D source function is described within hadronic rescatterings. K T dependence?
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Outlook Pair-angle dependence of source function in non-central collisions Other pairs (K, p, …) Just get started. Many other things to do…
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