| 日時: |
2007-03-09 15:00 - 15:45 |
| 場所: |
研究本館３階３２１室 |
| 会議名: |
Twist-3 Approach to Single Transverse Spin Asymmetry |
| 連絡先: |
津田 |
| 講演者: |
小池裕司 (新潟大学) |
| 講演言語: |
英語 |
| アブストラクト: |
Single transverse spin asymmetry (SSA) is a "naively T-odd" observable which occurs from an interference between the amplitudes which have different phases, one of which providing single helicity flip in the scattering process. In the framework of the collinear factorization in QCD, it is described as a twist-3 observable. In this talk, we present a consistent framework for the twist-3 calculation for SSA. We prove that the consistent use of the Ward identity for color gauge invariance is crucial to obtain the factorization property and the gauge invariance of the twist-3 single-spin-dependent cross section. This proof had been missed in the previous literature. As an application, we present a complete twist-3 cross section formula for SSA for semi-inclusive deep inelastic scattering in terms of the complete set of the twist-3 quark-gluon distributions which include all kinds of pole (soft-gluon-pole (SGP), soft-fermion-pole and hard-pole) contributions. We will also prove that the SGP partonic hard cross section has a simple connection with a certain twist-2 cross section. This property leads to a very simple compact form for the total SGP cross section for p^\uparrow p \to \gamma X, p^\uparrow p\to \pi X and pp\to\Lambda^\uparrow X etc, where the scattering occurs among massless partons. |
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