The New F_L Measurement from HERA and the Dipole Model

Abstract

From the new measurement of F_L at HERA we derive fixed-Q^2 averages <F_L/F_2>. We compare these with bounds which are rigorous in the framework of the standard dipole picture. The bounds are sharpened by including information on the charm structure function F_2^(c). Within the experimental errors the bounds are respected by the data. But for 3.5 GeV^2 <= Q^2 <= 20 GeV^2 the central values of the data are close to and in some cases even above the bounds. Data on F_L/F_2 significantly exceeding the bounds would rule out the standard dipole picture at these kinematic points. We discuss, furthermore, how data respecting the bounds but coming close to them can give information on questions like colour transparency, saturation and the dependencies of the dipole-proton cross section on the energy and the dipole size.

12 pages

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Cited by in corpus (13)

• The High-Energy Behavior of Photon, Neutrino and Proton Cross Sections
• The Tensor Pomeron and Low-x Deep Inelastic Scattering
• Measurements of the Separated Longitudinal Structure Function F_L from Hydrogen and Deuterium Targets at Low Q^2
• On the longitudinal structure function in the dipole model
• The Color Dipole Picture and extracting the ratio of structure functions at small $x$
• Longitudinal structure function from the parton parameterization
• Ratio of the structure functions and the color dipole model bound
• Nonlinear corrections on the parameterization methods
• The exponent of the longitudinal structure function $F_L$ at low $x$
• Heavy quark structure functions from unifying the color dipole picture and double asymptotic scaling approaches
• Reduced cross section and gluon distribution in a momentum-space approach
• The Proton Gluon Distribution from the Color Dipole Picture
• Investigation of the ratio $\frac{{\sigma }_r}{F_2}(Q^2/s,Q^2)$ in the momentum-space approach