Measurement of the Photon Structure Function F_2^gamma at Low x

TL;DR

This paper reports the measurement of the photon structure function F_2^gamma at low x and low Q^2 using electron-positron collision data, extending the exploration into previously unmeasured kinematic regions.

Contribution

It provides new measurements of F_2^gamma at lower x and Q^2 values than previously available, using OPAL data from electron-positron collisions.

Findings

Measured F_2^gamma at <Q^2> = 1.86 GeV^2 and 3.76 GeV^2

Extended the x range down to 0.0025

Provided data for Q^2 dependence of F_2^gamma

Abstract

Deep inelastic electron-photon scattering is studied using e+e- data collected by the OPAL detector at centre-of-mass energies sqrt{s_ee} ~ M_{Z^0}. The photon structure function F_2^gamma(x,Q^2) is explored in a Q^2 range of 1.1 to 6.6 GeV/c^2 at lower x values than ever before. To probe this kinematic region events are selected with a beam electron scattered into one of the OPAL luminosity calorimeters at scattering angles between 27 and 55 mrad. A measurement is presented of the photon structure function F_2^gamma(x,Q^2) at <Q^2> = 1.86 GeV^2 and 3.76 GeV^2 in five logarithmic x bins from 0.0025 to 0.2.