Observation of Highly Virtual Photon-Photon Collisions to Hadrons at TRISTAN

TL;DR

This paper reports the observation of highly virtual photon-photon collisions producing hadrons at TRISTAN, measuring cross sections that are compared with theoretical predictions, thus providing insights into photon structure at high virtuality.

Contribution

First experimental observation of highly virtual photon-photon collisions to hadrons at TRISTAN with detailed cross section measurements.

Findings

Measured cross section of 4.11±0.66 pb for high virtuality photon collisions.

Observed 115 hadronic events with low background, confirming theoretical predictions.

Cross section exceeds the lowest order quark-parton model prediction of 3.00 pb.

Abstract

We have observed highly virtual ($Q^2>1.05 GeV^2$) photon-photon collisions to hadronic final states at $\sqrt{s_{e^+e^-}}=58 GeV$. The integrated luminosity of the data sample was 241pb$^{-1}$. Both scattered beam-electrons and scattered beam-positrons were detected using low-angle calorimeters (i.e., both photons were highly virtual, "double-tag"); we obtained 115 hadronic events with an estimated background of $10.2\pm1.1$. The cross section obtained was $4.11\pm0.66$pb in the $2<W_{\gamma \gamma}<25$ GeV and $Q^2_{\gamma, min}>2$ GeV region, while the lowest order quark-parton model predicted 3.00pb.