Search for long-lived particles decaying into electron or photon pairs with the D0 detector

TL;DR

This paper reports a search for long-lived particles decaying into electron or photon pairs using the D0 detector, setting new limits on their production cross section and lifetime, but finds no evidence of such particles.

Contribution

It introduces a novel method to probe longer particle lifetimes by precise electromagnetic shower direction reconstruction, extending previous experimental sensitivity.

Findings

No evidence of long-lived particles was observed.

Set new upper limits on production cross sections.

Constrained models with long-lived particles and fourth generation quarks.

Abstract

In this Letter we report on a search for long-lived particles that decay into final states with two electrons or photons. Such long-lived particles arise in a variety of theoretical models, like hidden valleys and supersymmetry with gauge-mediated breaking. By precisely reconstructing the direction of the electromagnetic shower we are able to probe much longer lifetimes than previously explored. We see no evidence of the existence of such long-lived particles and interpret this search as a quasi model-independent limit on their production cross section, as well as a limit on a long-lived fourth generation quark.