First observation of the rare decay \(K^+ → μ^+ ν_μ μ^+ μ^−\) at the NA62 experiment

Tomczak, Adam M. ORCID: 0000-0001-5635-3567 (2025). First observation of the rare decay \(K^+ → μ^+ ν_μ μ^+ μ^−\) at the NA62 experiment. University of Birmingham. Ph.D.

This is the latest version of this item.

Tomczak2025PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (9MB)

Abstract

The first observation of the rare decay \(K^+ → μ^+ν_μμ^+μ^−\) using data collected by the NA62 Experiment in 2017 and 2018 is presented in this thesis. The \(K^+ → μ^+ν_μμ^+μ^−\) branching ratio is measured using the \(K^+ → π^+μ^+μ^−\) process as a normalisation channel. The number of observed data candidates is 1832, with a background contamination of 168 ± 9. The analysis yields \(\mathfrak{B}(K^+ → μ^+ν_μμ^+μ^−) = (1.307±0.034_{Stat}±0.025_{Syst}±0.012_{Ext})×10^{−8}\), including a complete treatment of relevant systematic effects.

The complete software package for the ANTI-0 detector, added to the NA62 setup in 2021, was developed by the author within the NA62 software framework and is described in detail. The software tools allowing for short and long-term verification of ANTI-0 data quality are presented, with their output used to summarise the commissioning and performance of the detector in the 2021, 2022 and 2023 NA62 datataking campaigns.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):