Determination of the Longitudinal Proton Structure Function F_L(x,Q^2) at Low x

C. Adloff

doi:10.1016/S0370-2693(96)01684-X

paper

Determination of the Longitudinal Proton Structure Function F_L(x,Q^2) at Low x

arXiv:hep-ex/9611017 · doi:10.1016/S0370-2693(96)01684-X

Abstract

A measurement of the inclusive cross section for the deep-inelastic scattering of positrons off protons at HERA is presented at momentum transfers $8.5 \leq Q^{2} \leq 35 G e V^{2}$ and large inelasticity $y = 0.7$ , i.e. for the Bjorken-x range $0.00013 \leq x \leq 0.00055$ . Using a next-to-leading order QCD fit to the structure function F_2 at lower y values, the contribution of F_2 to the measured cross section at high y is calculated and, by subtraction, the longitudinal structure function F_{L} is determined for the first time with an average value of $F_{L} = 0.52 \pm 0.03 (s t a t)$ ^ {+0.25}_{-0.22} $(sy s t) a t$ Q^2=15.4 GeV^2 $an d$ x=0.000243$.

17 pages, latex, 4 Figures