Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
QCD Factorization for Semi-inclusive DIS Feng Yuan RBRC , Brookhaven National Laboratory Sep. 22, 2005 APS/JPS Hawaii 1 Outline Introduction: physics of TMD QCD factorization for semi-inclusive DIS Some phenomenological results Summary Sep. 22, 2005 APS/JPS Hawaii 2 Inclusive and Semi-inclusive DIS Inclusive DIS: Partonic Distribution depending on the longitudinal momentum fraction Semi-inclusive DIS: Probe additional information for parto transverse distribution in nucleon Sep. 22, 2005 APS/JPS Hawaii 3 Different P? Region Integrate out P? -- similar to inclusive DIS, probe int. PDF Large P? (ÀQCD) -- hard gluon radiation, can be calculated from perturbative QCD, Polarized ->q-g-q correlations Low P? (»QCD) -- nonperturbative information (TMD): new factorization formula Sep. 22, 2005 APS/JPS Hawaii 4 TMD Physics A way to measure Transversity Distribution, the last unkown leading twist distribution Collins 1993 The Novel Single Spin Asymmetries Connections with GPDs, and Quantum Phase Space Wigner distributions Quark Orbital Angular Momentum and Many others … Sep. 22, 2005 APS/JPS Hawaii 5 TMD Distribution: the definition Gauge Invariance requires the Gauge Link Sep. 22, 2005 APS/JPS Hawaii Brodsky,Hwang,Schmidt 02’ Collins 02’ Belitsky,Ji,Yuan 02’ 6 This definition is also consistent with the QCD factorization Sep. 22, 2005 APS/JPS Hawaii 7 One-loop Factorization: virtual •Vertex corrections (single quark target) p′ p k Four possible regions for the gluon momentum k: 1) k is collinear to p (parton distribution) 2) k is collinear to p′ (fragmentation) 3) k is soft (Soft factor) 4) k is hard (pQCD correction) Sep. 22, 2005 APS/JPS Hawaii 8 One-Loop Factorization: real Gluon Radiation (single quark target) p′ k p Three reagions for the gluon momentum k: 1) k is collinear to p (parton distribution) 2) k is collinear to p′ (fragmentation) 3) k is soft (Soft factor) Sep. 22, 2005 APS/JPS Hawaii 9 All Orders in Perturbation Theory Consider an arbitrary Feynman diagram Find the singular contributions from different regions of the momentum integrations Power counting to determine the leading regions Factorize the soft (Grammer-Yennie) and collinear gluons (Ward Identity) Factorization theorem. (Collins, Soper, Sterman, Perturbative QCD, Mueller ed.) Sep. 22, 2005 APS/JPS Hawaii 10 Factorization Soft Factor Sep. 22, 2005 APS/JPS Hawaii Ma, Ji, Yuan, 2004 11 SIDIS Cross Section: QCD Factorization At leading power of 1/Q Sivers Asym. Collins Asym. Sep. 22, 2005 APS/JPS Hawaii 12 The Factorization Applies to Semi-inclusive DIS (polarized and unpolarized) Drell-Yan at Low transverse momentum Di-hadron production in e+e- annihilation (extract the Collins function) Di-jet and/or di-hadron correlation at hadron collider (work in progress) Many others, … Sep. 22, 2005 APS/JPS Hawaii 13 Phenomenology Semi-inclusive DIS (Vogelsang, Yuan, 05) See also Efremov, et al., 04, 05; Anselmino, et al., 05 Sep. 22, 2005 APS/JPS Hawaii 14 COMPASS Sep. 22, 2005 APS/JPS Hawaii 15 At RHIC Sep. 22, 2005 APS/JPS Hawaii 16 Summary The QCD factorization theorem has been proved for semi-inclusive DIS Some phenomenological studies showed very promising results as compared with the old data and on the predictions for the future experiments as well Sep. 22, 2005 APS/JPS Hawaii 17