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Accessing Orbital Angular Momentum Thru Pion Cloud. Itaru Nakagawa RIKEN/RBRC. Proton Spin +1/2. Proton Spin +1/2. Proton Spin +1/2. P-wave. Proton Spin +1/2. Proton Spin +1/2. Proton Spin +1/2. Proton Spin +1/2. P-wave. P-wave. Nucleon EM Form Factors. Nucleon EM Form Factors low Q.
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Accessing Orbital Angular Momentum Thru Pion Cloud Itaru Nakagawa RIKEN/RBRC
Proton Spin +1/2 P-wave
Proton Spin +1/2 P-wave P-wave
Nucleon EM Form Factors J.Friedrich & Th. Walcher, EPJA A17, 607 (2003) phenomenological fit : “smooth” part (sum of 2 dipoles) + “bump” (gaussian) 6 parameter fit for each FF pion cloud pronounced structure in all FF around Q 0.5 GeV/c
Profounding Example of Pion Cloud Towell et al., Phys.Rev. D64 (2001) 052002 Sea Asymmetry from Drell-Yan Processes
excess Extra dbar in proton g.s. Sea Quarks Carry Major Orbital Angular Momentum Component?
Pion Model Prediction of Orbital Angular Momentum A.W. Thomas JLab
Proton Spin +1/2 70% 20~25% 5~10%
+ Probing Pion Cloud Calculation by T. Horn Virtual pion pickup Need : Q2 ~ 0.2 GeV/c2 Compass Atomic Electron Scattering
Summary • pion cloud is one of the way to access Orbital Angular Momentum • There are (will be) many experiments which explore pion cloud • Not good idea yet to be done at J-PARC
Concerns • So far, q-interchange model is only quantitative level Qualitatively, regge pole) • Elastic Soft Mechanism • Elastic No Fragmentation? • Sensitivity to sea? p
Relativistic Valence Quark rXiv:0709.4067ハ[hep-ph]