In Spring 2020 the NA62 simulation software was extended to accommodate dark neutrino signatures, and large samples of simulated events were produced. A procedure to isolate potential dark neutrino events from the NA62 2017-18 data was developed, requiring several novel techniques to be designed. The efficiency of the selection was evaluated using the simulated events prepared earlier in the project. A detailed understanding of the low-level trigger of the NA62 calorimeters (used to measure particle energies) was established as it proved vital for the analysis. The sensitivity of the analysis (how many dark neutrino events can be isolated in the data, over the background of other processes) was evaluated, proving that the discovery of the dark neutrino is feasible in the 2017-2018 NA62 data. Strategies to improve the selection were investigated in order to optimise the analysis and further improve the sensitivity.
In spring 2021, the simulation of the calorimeter trigger was extended to facilitate the design of a new trigger algorithm, which included a software routine to decode new data expected from 2021. In addition, simulated data was examined to identify a potential trigger to exploit data from the new ANTI0 detector.
In summer 2021 the secondment at CERN began. The initial secondment lasted for 6 months, however the stay was extended for another 3 weeks to cover the full duration of the 2021 data-taking. During that time, the new ANTI0 detector was set-up, and all other aspects of the NA62 experiment were successfully commissioned. Running NA62 for around 6 months included work as an NA62 operator, an on-call expert for several NA62 systems, and taking charge of NA62 operations for 4 weeks as ‘run coordinator’, a position of major responsibility within NA62. As the 2021 data was collected, the data was examined in detail to ensure it was of high quality.
The trigger algorithms for the calorimeter and ANTI0 could not be used during 2021 due to issues outside of the project. These issues were highlighted as risks in the original proposal. As a result, alternative developments of the trigger were designed and implemented, leading to an improved trigger for dark neutrinos during 2021. After returning from CERN, developments were made to the NA62 “data preparation” software, which converts the raw data to a form suitable for analysis.
The project was instrumental in fostering discussions between NA62 experimentalists and theorists that are experts in heavy/dark neutrinos. Interactions between the two groups took place in private communications, at weekly meetings of the host group, as invited speakers at NA62 meetings, and at seminars at the host institute.
Social media accounts for NA62 were created in Spring 2021, in time to announce a major result from NA62. The accounts were maintained throughout the project, with some posts reaching more than 1000 people. An article for a CERN newsletter was prepared, plus outreach at a school in the UK.
The key results of the project (so far) include a new data set containing kaon decays collected by NA62 in 2021. Moreover, the researcher produced 7 journal papers in the context of the NA62 collaboration, with a particular contribution to one of the papers. Recent NA62 results were presented at two international conferences (QCD20 and EPS-HEP 2021), each with proceedings contributions.
