RHIC spin talk

Slide1: 

March 9. 2004@RHIC-SPIN Discussion Y. Koike (BNL&Niigata Univ.) Single Transverse Spin Asymmetry : Theoretical Overview

Slide2: 

Content: Introduction: Basics for single spin asymmetry (SSA) Data, Ingredients of SSA, “T-odd” observable, SSA and chiral symmetry breaking. T-odd distribution and fragmentation functions. Twist-3 effects Summary

Slide4: 

Single　Spin　Asymmetry (SSA) 　 E704(’91) and STAR(’02) found big asymmetry in the forward direction !

Slide5: 

FNAL-E704:

Slide6: 

RHIC-STAR, hep-ex/0310068

Slide7: 

Fundamentals of SSA: Ingredients for SSA BUT, in conventional twist-2: Other mechanisms necessary for a big SSA!

Slide8: 

Origin of “T-Odd” observable By T-inv. (De Rujula et al. NP,B35(’71)365)

Slide9: 

Usual twist-2:

Slide10: 

“T-odd” Twist-3 Sivers Collins Qiu&Sterman

Slide12: 

“T-odd” mechanism: Introduction of nonperturbative intrinsic k_T of partons. Intuitively understandable. Smooth start of SSA at low P_T: (Collins’93) Factorization theorem ?

Slide15: 

Applications of “T-odd” functions

Slide16: 

Applications of “T-odd” functions (continued)

Slide17: 

(Sivers) (Collins)

Slide18: 

FNAL-E704:

Slide21: 

Twist-3 mechanism for SSA Systematic approach based on collinear factorization P_T is produced solely from the partonic hard cross section Suited for large-P_T production SSA is a probe of quark-gluon correlation. SSA is 1/Q suppressed: At what P_T, does the data fall on twist-3 mechanism? Twist-3 functions are all “T-even”.

Slide23: 

Factorization for twist-3: three twist-3 cross sections (Qiu&Sterman’99) (Kanazawa&Koike’00) (Koike’02) Unpolarized: twist-2 :Hard part

Slide26: 

Characteristics of the twist-3 analysis (cf. Qiu & Sterman ’91 for p+p↑→γ+X)

Slide27: 

Characteristics of the twist-3 analysis (continued)

Slide29: 

RHIC-STAR, hep-ex/0310068

Slide31: 

FNAL-E704: P.L. B264 (’91) 462 P.L. B261 (’91) 201 A. Bravar, Proc. of Spin’96

Slide33: 

: Chiral-odd Summary table of “T-odd” and Soft-gluon-pole (SGP) functions

Slide34: 

Summary and outlook