Spin dependence of diffractive DIS
نویسنده
چکیده
The motto of high energy QCD is the quark helicity conservation which is often believed to entail the s-channel helicity conservation (SCHC) at small x. Here I review the recent work ([ 1, 2, 3, 4, 5], which shows this belief is groundless and there is an extremely rich helicity-flip physics at small x. The backbone of DIS is the Compton scattering (CS) γ μp → γ ∗ ′ ν p , which at small-x can be viewed as a (i) dissociation γ → qq̄ followed by (ii) elastic scattering qq̄p → qq̄p with exact conservation of quark helicity and (iii) fusion qq̄ → gamma ′ . The CS amplitude Aνμ can be written as Aνμ = Ψ ∗ ν,λλ̄ ⊗Aqq̄ ⊗Ψμ,λλ̄ (1)
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