Azimuthal asymmetry as a new handle on σL/σT in diffractive DIS

Abstract

We propose a new method of the determination of R D = σ

Anatomy of the differential gluon structure function of the proton from the experimental data onF2p(x,Q2)

“…Such a nonperturbative component of DGSF would have certain high-κ 2 tail which should not extend too far. The desired suppression of soft DGSF at large-κ 2 and of hard DGSF (41) at moderate and small κ 2 can be achieved by the extrapolation of the form suggested in [5,6] …”

“…For instance, it is precisely DGSF of the target proton which emerges in the familiar color dipole picture of inclusive DIS at small x [3] and diffractive DIS into dijets [4]. Another familiar example is the QCD calculation of helicity amplitudes of diffractive DIS into continuum [5,6] and production of vector mesons [7,8]. DGSF's are custom-tailored for QCD treatment of hard processes, when one needs to keep track of the transverse momentum of gluons neglected in the standard collinear approximation [9].…”

“…We analyze x and Q 2 dependence of the proton structure function F 2p (x, Q 2 ) in the framework of the κ-factorization approach, which is closely related to the color dipole factorization. In the formulation of our Ansatz for F (x, κ 2 ) we take advantage of large body of the early work on color dipole factorization [3,16,17] and follow a very pragmatic strategy first applied in [5,6]: (i) for hard gluons with large κ we make as much use as possible of the existing DGLAP parameterizations of G(x, κ 2 ), (ii) for the extrapolation of hard gluon densities to small κ 2 we use an Ansatz [4] which correctly describes the color gauge invariance constraints on radiation of soft perturbative gluons by colour singlet targets, (iii) as suggested by color dipole phenomenology, we supplement the density of gluons with small κ 2 by nonperturbative soft component, (iv) as suggested by the soft-hard diffusion inherent to the BFKL evolution, we allow for propagation of the predominantly hard-interaction driven small-x rise of DGSF into the soft region invoking plausible soft-to-hard interpolations. The last two components of DGSF are parameterized following the modern wisdom on the infrared freezing of the QCD coupling and short propagation radius of perturbative gluons.…”

Inclusive diffraction at HERA with a measured leading proton

“…Theoretical predictions for the behavior of A LT [5,6] mostly concern the high β region, which was not accessible in this analysis. No strong dependence of A LT on x IP , β, t and Q 2 is observed in the data.…”

Spin dependence of diffractive DIS

“…The most exciting point about helicity flip in γ * p → V p ′ is that it uniquely probes spin-orbital angular momentum coupling and Fermi motion in vector mesons.Experimentally the SCHNC LT-interference in diffractive DIS can be observed via azimuthal correlation between the (e, e ′ ) and (p, p ′ ) scattering planes. Our work on this asymmetry and its use for the determination of R = σ L /σ T for diffractive DIS has been reported at DIS'97 & DIS'98 and published elsewhere [ 1]. Here I only recall that azimuthal asymmetry is the twist-3 effect,where g D LT is the scaling structure function.…”