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大西 陽一 (阪 大) QCDの有効模型に基づく光円錐波動関数を用い た 一般化パートン分布関数の研究 若松 正志 (阪大)
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In QCD, the candidates for the missing spin In this thesis, we study the GPDs using the light-cone wave function based on the chiral quark soliton model (CQSM) Generalized parton distributions (GPDs) contain information ofthe orbital angular momentum and “Spin structure of the nucleon” reflects non-perturbative physics in QCD Natural questions are what carries the rest of the nucleon spin?
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Why light-cone wave function ? Non-local quark operator High energy observable (GPDs, parton distribution) In the light-cone frame Quark (anti-quark) number operator Light-cone wave function Partonic interpretation very clear
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QCD definitions of the GPDs Deeply virtual Compton scattering Soft part including non-perturbative information GPD
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Spin unpolarized case Spin polarized case Squared momentum transferFeynman variable longitudinal momentum transfer Light-cone coordinate
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Properties of the GPDs Forward limit : x moments of GPDs momentum space distribution coordinate space distribution GPDs provide totally new information on baryon structure
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Ji’s sum rule Knowing and, one can extract the quark orbital angular momentum Total quark contribution can be decomposed gauge invariantly into the quark spin and orbital contribution
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Partonic interpretation of GPD Dirac field Three kinematical regions : quark (anti-quark) creation and annihilation operators Quark distribution Antiquark distribution Meson distribution amplitude
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Overlap representation Fock state decomposition Non-diagonal matrix element Need for the theory which can deal with the higher Fock component (Meson distribution amplitude)
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Light-cone wave function in the CQSM Effective action Dynamical quark mass M=375MeV Spontaneous chiral symmetry breaking of the QCD vacuum Strong coupling between pion and quark Basic lagrangian
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3 valence quarks Deep Dirac sea Indefinite number of quark and anti-quark pairs Distorted Dirac sea continuum : Fourier transform of equal time quark Green function quarkanti-quark
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Baryon w.f. is given by the product of valence part and coherent exponential of quark anti-quark pair valence quark w.f.Dirac sea continuum w.f. Lorentz boost Light-cone w.f. w.f. in the Infinite Momentum Frame (IMF)
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Light-cone wave function representation of the GPDs in the CQSM Normalization we take up to 5Q components in the w.f.
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Physical observable Matrix elements of some operators sandwiched between the initial and the final wave functions unpolarized case : polarized case : 3q contribution to GPDs unpolarized case : polarized case :
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5Q contributions to GPDs valence part initialfinal Quark antiquark pair 3 valence quark
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Dirac sea quark part 5Q contributions to GPDs quark contribution antiquark contribution
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Non-diagonal Fock components contribution Final representation
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Numerical results for GPDs
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zero momentum transverse case : spin unpolarized u quark distribution spin polarized u quark distribution
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Impact parameter space parton distribution represents a spatial density in the transverse directions and momentum density in the longitudinal direction
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Impact parameter space parton distribution
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Large spatial distribution in the low x region the pion cloud surrounding the three valence quark core
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Summary and conclusions Light-cone wave function based on the CQSM 3 valence quarks + coherent exponential of quark anti-quark pair GPDs region Non-diagonal matrix elements in Fock space Discontinuity at We have derived the light-cone w.f. representations for the GPDs based on the CQSM
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With phase conventions of the Brodsky-Lepage light-cone spinors Light-cone helicity non-flip part Light-cone helicity flip part
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Valence quark wave function h(p) : upper component j(p) :lower component Wave function of the Dirac continuum mean chiral fields quarkanti-quark
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Forward limit
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asymmetry NMC measurement pion cloud effects Dirac sea polarization Gottfried sum
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NuTeV anomaly NuTeV group reported the value of the weak mixing angle :prediction from standard model ? :CQSM but Strange sea asymmetry explains nearly 70% of the NuTeV anomaly
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3 valence quarks Deep Dirac sea Hedgehog ansatz Soliton is not spin isospin eigenstateHedgehog Projection method
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