Erlangen 2026 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 58: Searches/BSM III

T 58.5: Vortrag

Mittwoch, 18. März 2026, 17:15–17:30, KH 02.018

Improved strategy for searches for Heavy Neutral Leptons decaying into ℓ+π with ATLAS — •Andrej Prescher — Humboldt Universität zu Berlin

Heavy Neutral Leptons (HNLs) appear in beyond Standard Model scenarios and can address open problems such as neutrino masses and the matter-antimatter asymmetry. At the LHC, long-lived HNLs might be produced in leptonic W decays, W→ℓ N (ℓ=e,µ), and lead to displaced decay signatures inside the detector.

The most stringent limits set in ATLAS searches so far have been achieved in the purely leptonic decay channels N→ℓℓ^′ν. For small HNL masses, in the mass range of 2-3 GeV the two body decay N→ℓ+π might help to increase the search sensitivity.

In a recently published ATLAS analysis this decay channel however could not significantly improve the sensitivity beyond the one from N→ℓℓ^′ν, due to higher background level in the N→ℓ+π search.

In this presentation we show studies how this background can be significantly reduced while keeping or even increasing the signal efficiency.

Keywords: Heavy Neutral Leptons; ATLAS; Displaced Vertices; Semileptonic