Twist–3 Effects in Deeply Virtual Compton Scattering Made Simple
نویسنده
چکیده
We show that electromagnetic gauge invariance requires a “spin rotation” of the quarks in the usual twist–2 contribution to the amplitude for Deeply Virtual Compton Scattering. This rotation is equivalent to the inclusion of certain kinematical twist–3 (“Wandzura–Wilczek type”) terms, which have been derived previously using other methods. The new representation of the twist–3 terms is very compact and allows for a simple physical interpretation.
منابع مشابه
Transverse Spin / Transverse Momentum Analogy and Gauge Invariance of Deeply Virtual Compton Scattering
Using the similarity between twist 3 contributions to transverse spin for usual parton distributions and transverse momentum for non-diagonal parton distributions, we determine for the simple case of a scalar (pion, He) target the linear in transverse momentum twist-3 contribution to Deeply Virtual Compton amplitude. This allows to write a gauge invariant amplitude for this non-forward process.
متن کاملv 2 3 1 M ay 2 00 1 Leading twist asymmetries in deeply virtual Compton scattering
We calculate spin, charge, and azimuthal asymmetries in deeply virtual Compton scattering at leading twist-two level. The measurement of these asymmetries gives access to the imaginary and real part of all deeply virtual Compton scattering amplitudes. We note that a consistent description of this process requires taking into account twist-three contributions and we give then a model dependent e...
متن کاملTwist-three Observables in Deeply Virtual Compton Scattering on the Nucleon
We study twist-three effects in deeply virtual Compton scattering on an unpolarized spin-1/2 target. A careful definition of observables as Fourier moments w.r.t. the azimuthal angle allows for a clear separation of twist-two and-three effects. Although the latter are power suppressed, they give leading contributions to the twist-three asymmetries and do not affect the twist-two observables.
متن کاملM ar 2 00 1 Twist - three observables in deeply virtual Compton scattering on the nucleon
We study twist-three effects in deeply virtual Compton scattering on an unpolarized spin-1/2 target. A careful definition of observables as Fourier moments w.r.t. the azimuthal angle allows for a clear separation of twist-two and-three effects. Although the latter are power suppressed, they give leading contributions to the twist-three asymmetries and do not affect the twist-two observables.
متن کامل0 Leading twist asymmetries in deeply virtual Compton scattering
We calculate spin, charge, and azimuthal asymmetries in deeply virtual Compton scattering at leading twist-two level. The measurement of these asymmetries gives access to the imaginary and real part of all deeply virtual Compton scattering amplitudes. We note that a consistent description of this process requires taking into account twist-three contributions and we give then a model dependent e...
متن کامل