First observation of a tau neutrino charged current interaction with charm production in the Opera experiment

TL;DR

This paper reports the first observation of a tau neutrino charged current interaction with charm production in the Opera experiment, using advanced analysis techniques to distinguish it from background processes.

Contribution

The study presents the first detection of tau neutrino CC interactions with charm production, employing a dedicated Monte Carlo simulation and multivariate analysis for process identification.

Findings

Most likely a $ u_{ au}$ CC interaction with charm production

Event topology consistent with tau and charm decays

Significance of the observation evaluated

Abstract

An event topology with two secondary vertices compatible with the decay of short-lived particles was found in the analysis of neutrino interactions in the Opera target. The observed topology is compatible with tau neutrino charged current (CC) interactions with charm production and neutrino neutral current (NC) interactions with $c\overline{c}$ pair production. However, other processes can mimic this topology. A dedicated analysis was implemented to identify the underlying process. A Monte Carlo simulation was developed and complementary procedures were introduced in the kinematic reconstruction. A multivariate analysis technique was used to achieve an optimal separation of signal from background. Most likely, this event is a $\nu_{\tau}$ CC interaction with charm production, the tau and charm particle decaying into 1 prong and 2 prongs, respectively. The significance of this observation is evaluated.