Measurement of the Q^2 evolution of the photon structure function F_2^gamma

TL;DR

This paper presents new measurements of the photon structure function F_2^gamma at various Q^2 values, demonstrating its increase with Q^2 and providing insights into photon structure evolution.

Contribution

It provides the first detailed measurement of the Q^2 evolution of F_2^gamma across a broad range, using data from the OPAL detector at LEP.

Findings

F_2^gamma increases with Q^2 in the measured range.

Measured slope of F_2^gamma evolution is 0.10 with uncertainties.

Results agree with theoretical predictions of photon structure functions.

Abstract

New measurements are presented of the photon structure function F_2^gamma(Q) at four values of Q^2 between 9 and 59 GeV/c^2 based on data collected with the OPAL detector at centre-of-mass energies of 161-172 GeV, with a total integrated luminosity of 18.1 pb^-1. The evolution of F_2^gamma with Q^2 in bins of x is determined in the Q^2 range from 1.86 to 135 GeV/c^2 using data taken at centre-of-mass energies of 91 GeV and 161-172 GeV. F_2^gamma is observed to increase with Q^2 with a slope of 1/alpha_em dF_2^gamma/dln(Q^2) = 0.10 +0.05 -0.03 measured in the range 0.1 < x < 0.6.