# Kaon tagging system and measurement of the $$K^+\rightarrow\pi^+ \gamma \gamma$$ decay at the NA62 experiment at CERN

Brunetti, Maria Brigida ORCID: 0000-0003-1639-3577 (2020). Kaon tagging system and measurement of the $$K^+\rightarrow\pi^+ \gamma \gamma$$ decay at the NA62 experiment at CERN. University of Birmingham. Ph.D.

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## Abstract

A model-dependent measurement of the branching ratio of the $$K^+\rightarrow\pi^+ \gamma \gamma$$ decay and a model-independent measurement in bins of the z kinematic variable, performed on the world’s largest data sample, collected by NA62, are presented. In particular, the event selection, the main backgrounds and the addition of an option to bias MC generators to increase the precision of estimates, and the study of systematics are discussed. The combined model-independent branching ratio was found to be $$BR_{MI}$$ = (0.73 ± 0.04) x 10$$^{-6}$$. The implementation in the NA62 high-level trigger framework of decoding tools for the STRAW sub-detector, necessary for running trigger algorithms, and of output structures to transfer data to storage is discussed. The performance of the KTAG sub-detector, which has the task of identifying the kaon component in the NA62 secondary beam, is presented. The sub-detector is shown to meet the efficiency requirements during all the 2016-2018 data-taking.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Lazzeroni, CristinaUNSPECIFIEDUNSPECIFIED
Goudzovski, EvgueniUNSPECIFIEDUNSPECIFIED