Study of double-tagged gamma gamma events at LEPII

TL;DR

This paper analyzes double-tagged gamma gamma events at LEPII, comparing experimental data with QED and BFKL theoretical predictions to enhance understanding of photon interactions at high virtualities.

Contribution

It provides the first detailed measurement of gamma* gamma* -> hadrons cross-section at high virtualities and compares results with leading and next-to-leading order BFKL calculations.

Findings

Muon pair production agrees with QED predictions.

Measured hadronic cross-section compared with BFKL calculations.

Data supports or constrains theoretical models of photon interactions.

Abstract

Double-tagged interactions of photons with virtualities Q^2 between 10 GeV^2 and 200 GeV^2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated luminosity of 550 pb^{-1}. The gam* gam* -> mu+mu- data agree with QED predictions. The cross-section of the reaction gam* gam* -> hadrons is measured and compared to the LO and NLO BFKL calculations.