Karlsruhe 2024 – scientific programme

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T: Fachverband Teilchenphysik

T 28: Search for new particles 3 (ALPS)

T 28.2: Talk

Tuesday, March 5, 2024, 16:15–16:30, Geb. 20.30: 1.067

Search for top quark decays to long-lived axion-like particles with ATLAS — •Frederic Fischer, Alexander Basan, Lucia Masetti, Jessica Höfner, Eftychia Tzovara, and Doğa Elitez — Universität Mainz

The Standard Model (SM), although confirmed with great precision experimentally, is still insufficient to answer many fundamental questions. Hence, axion-like particles (ALPs) appear in many beyond Standard Model (BSM) theories trying to address these questions.

One way to approach ALPs is to parameterise ALP couplings to Standard Model particles like top quarks. ALPs appear in flavour-changing exotic top decays where the top quark decays into an ALP and an up- or charm-quark. Within this decay mode, parts of the allowed parameter space suggests ALPs to have lifetimes long enough to travel macroscopic distances before decaying. This search is dedicated to top-antitop events with one SM semi-leptonically decaying top quark and one exotically decaying top quark.

In this topology the focus is on ALPs decaying in the hadronic calorimeter at ATLAS with a centre-of-mass energy of 13 TeV. They are assumed to be electrically neutral and thus leave no signal in the ATLAS tracking system. Moreover, the ratio of energy deposits in the electromagnetic calorimeter and hadronic calorimeter are used to suppress SM backgrounds.

This talk presents the search for long-lived ALPs from exotic top decays at ATLAS.

Keywords: ALPs, Top Quarks, BSM Physics