Search for pair-produced long-lived neutral particles decaying in the ATLAS hadronic calorimeter in $pp$ collisions at $\sqrt{s}$ = 8 TeV

TL;DR

This paper reports a search for long-lived neutral particles decaying within the ATLAS calorimeters in 8 TeV proton-proton collisions, setting limits on their production and decay properties.

Contribution

It introduces a novel search strategy for long-lived particles decaying in the calorimeter, extending sensitivity to new physics scenarios.

Findings

No significant excess observed.

Limits set on production cross section times branching ratio.

Constraints provided for a range of masses and lifetimes.

Abstract

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb$^{-1}$ of data collected in proton--proton collisions at $\sqrt{s}$ = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.