1. Yuji Koike (Niigata Univ.)
Single Transverse Spin Asymmetry in QCD
Yuji Koike (Niigata Univ.)
9th Circum-Pan-Pacific Symposium on High Energy Spin Physics
Oct. 28~31 , 2013, Ji’nan, China

4. FNAL-E704
P.L. B264 (’91) 462
P.L. B261 (’91) 201

20. ★ RHIC-STAR (‘04) ★ RHIC-BRAHMS (‘07)
First, we have to confirm the validity of the perturbative calculation .

21. Qiu, Sterman (‘99), Kouvaris et.al.(‘06),Kanazawa,Koike(‘10)
Kang, Yuan, Zhou (‘10),
Metz, Pitonyak,(‘12)
Kanazawa, Koike (‘00)
⇒ The 3rd term can be ignored.
- Graphical representation of the 1st and 2nd terms :
In this process, there are three nonperturbative functions.
So, the twist-3 contributions to the spin dependent cross-section are obtaind by replacing a twist-2 distribution or fragmentation function by corresponding twist-3 distribution of fragmentation functions.
So, two resaonable contribution to the SSA.
The calculation is implete.

22. - Reasonable description of SSA for pions and kaons with this formula:
Koike-Tomita (2009)
Kouvaris-Qiu-Vogelsang-Yuan (2006)
- Reasonable description of SSA for pions and kaons with this formula:
KK-Koike (2010)

23. ★ STAR (2008)

34. ★ Decomposition of the asymmetries into each fragmentation channel
- The difference comes from the strange components.