Searches for massive, long-lived particles in events with displaced vertices with ATLAS

TL;DR

This paper reports on ATLAS searches for long-lived particles via displaced vertices in Run 2 and Run 3, introducing new algorithms and triggers to improve detection of exotic decay signatures.

Contribution

It presents novel displaced vertex reconstruction algorithms and muon triggers, enabling new limits on Higgs Portal, SUSY, and axino models.

Findings

First use of fuzzy DV reconstruction algorithm for heavy quark decays.

First application of displaced muon trigger in Run 3 search.

Set limits on RPV SUSY, Higgs Portal, and axino models.

Abstract

Many recent efforts at the LHC have been made to search for new particles that do not decay promptly but are instead long-lived. This has been done via many different exotic signatures, including searches performed at ATLAS for displaced vertices (DV), where the new long-lived particle decays into multiple visible tracks after having traveled a certain distance into the detector. This talk covers two such searches: a Run 2 search for DVs in events triggered by missing transverse energy, and a Run 3 search for DVs in events triggered by muons. The former search is the first to use a new "fuzzy" displaced vertex reconstruction algorithm, alongside the standard one, to effectively reconstruct cases where the long-lived particle decays into heavy quarks that are themselves slightly long-lived, hence causing the final visible decay products to not point back exactly to the same vertex, setting limits on Higgs Portal, SUSY, and DFSZ axino models. The latter search is the first to use a new displaced muon trigger, setting limits on RPV SUSY models.