1 / 20

Collinear expansion and SIDIS at twist-3

Collinear expansion and SIDIS at twist-3. Yu-kun Song (USTC) 2013.10.28 Jinan YKS , Jian-hua Gao , Zuo -tang Liang, Xin-Nian Wang, arXiv:1308.1159. Outline. Introduction Collinear expansion extended to SIDIS Azimuthal asymmetries & nuclear effects Discussions and outlook.

nerita
Télécharger la présentation

Collinear expansion and SIDIS at twist-3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Collinear expansion and SIDIS at twist-3 Yu-kun Song (USTC) 2013.10.28 Jinan YKS, Jian-huaGao, Zuo-tang Liang, Xin-Nian Wang, arXiv:1308.1159

  2. Outline • Introduction • Collinear expansion extended to SIDIS • Azimuthal asymmetries & nuclear effects • Discussions and outlook

  3. Semi-inclusive DIS • A large scale (Q) and a small scale (k) • Large scale →factorization • Small scale →structure information (intrinsic k ) An ideal probe of nucleon/nuclear structure ! • TMD factorization works at leading twist • Higher twist • Gauge invariant parton correlation functions • Factorization proof/arguments • NLO calculations • Experiments : Compass, Jlab, EIC,…

  4. Leading twist: collinear approximation • Gauge invariant parton distribution functions • Finite, perturbatively calculable partonic cross section Sterman-Libby power counting X Leading twist

  5. Higher twist: collinear expansion • Gauge invariant parton correlation functions • Finite, perturbatively calculable partonic cross section X Higher twist (1/Q power corrections)

  6. Systematic applications to SIDIS • Collinear expansion in DIS Ellis, Furmanski, Petronzio, 1982, 1983 Qiu, 1990 • Collinear expansion applied to SIDIS e+N →e+q+X Liang, Wang, 2006 • Nuclear medium effects of azimuthal asymmetries • Gauge link →nuclear modification of PDFs Liang, Wang, Zhou, 2008 • SIDIS e+N →e+q+Xat twist-4 YKS, Gao, Liang, Wang, 2011 • Doublelypolarized SIDIS e+N →e+q+Xat twist-3 YKS, Gao, Liang, Wang, Arxiv: 1308.1159

  7. Collinear expansion in DIS • [Ellis, Furmanski, Petronzio, 1982,1983 ;Qiu,1990] • Collinear Expansion: • Taylor expand at , and decompose • Apply Ward Identities • Sum up and rearrange all terms,

  8. Collinear expansion in SIDIS e+N→e+q+X • In the low region, we consider the case when final state is a quark(jet) Compared to DIS, the only difference is the kinematical factor Collinear expansion is naturally extended to SIDIS Parton distribution/correlation functions are -dependent [Liang, Wang, 2006]

  9. Hadronic tensor for SIDIS • : color gauge invariant

  10. Structure of correlation matrices • Time reversal invariance relate and • Lorentz covariance + Parity invariance, SIDIS DY

  11. Structure of correlation matrices • QCD equation of motion, , induce relations

  12. Relations from QCD EOM • Sum up and , one has (up to twist-3) • Explicit color gauge invariance for and . • Explicit EM gauge invariance

  13. Unpolarized SIDIS at twist-4 level • Cross section for • Twist-4 parton correlation functions [YKS, Gao, Liang, Wang,2011] 13

  14. Doubly polarized e+N →e+q+Xat twist-3 [YKS, Gao, Liang, Wang, 2013] Leading twist Twist-3

  15. kT- broadening of PDF in a nucleus • Two facts about the gauge link • Generated by QCD multiple gluon scattering between struck quark and medium • It induce physical effects, cannot be removed by a wise choice of gauge →Different interaction induce different PDFs: fNq & fAq More FSI !

  16. kT- broadening of PDF in a nucleus • Relations between nucleon and nuclear PDFs simplify under “maximal two-gluon exchange ” approximation. • It is just Gaussian broadening. More FSI diffuse the scattered parton!

  17. Nuclear modification of ˂cosφ>˂cos2φ> • Nuclear twist-3/4 parton correlation function • Gaussian ansatz for distribution • Take identical Gaussian parameter for parton distribution/correlation functions ˂cosφ>˂cos2φ> are Suppressed!

  18. Nuclear modification of ˂sinφ>LU • Nuclear modification for • depend on • dependence

  19. Nuclear modification of ˂sinφ>LU • kT- dependence Sensitive to the ratio of γ/α!

  20. Discussions and outlook • Collinear expansion is the systematic and essential method to calculate higher twist effects to SIDIS. • Gauge invariance ofcorrelation functions are automatically fulfilled as a result of collinear expansion. • Azimuthal asymmetries for doubly polarized e+N →e+q+Xare obtained up to twist-3, and for unpolarized case up to twist-4. Much more abundant azimuthal asymmetries at high twist, and their gauge invariant expressions are obtained. • Extension to hadronic production process are interesting and are underway. Thanks for your attention!

More Related