The Korean Physical Society 06130 22, Teheran-ro 7-gil, Gangnam-gu, Seoul, Republic of Korea 610 Representation : Tae Won NOH TEL: 02-556-4737 FAX: 02-554-1643 E-mail : webmaster@kps.or.kr Copyright(C) KPS, All rights reserved.

# The XXX International Conference on Neutrino Physics and Astrophysics (Neutrino 2022)

30 May 2022 to 4 June 2022
Virtual Seoul
Asia/Seoul timezone

## GUNDAM: A next-generation fitting tool for future T2K analyses

Not scheduled
5m
Virtual Seoul

#### Virtual Seoul

Poster Accelerator neutrinos

### Description

The phase II of T2K will permit a measurement of the CP violating phase in the leptonic sector ($\delta_{CP}$) with unprecedented level of accuracy. This will be achieved by the increase of statistics made possible by the upgrades of the neutrino beam production at the JPARC facility. In order to get the best precision on $\delta_{CP}$, a better understanding on the involved systematic uncertainties is essential. The T2K experiment takes advantage of a detector placed near the production site (called ND280) which measure the flux and interaction properties of neutrinos before they oscillate.

In practice, the ND280 data is analysed prior to the oscillation analysis to provide correction on the predictions (i.e. best fit values) as well as additional constraints on each error. This task requires a substantial effort, since it involves a fit of several neutrino samples with hundreds of fit parameters, and will soon become substantially more complicated as upgrades allow the collection of more data that can be analysed in increasingly multi-faceted ways. To meet the challenges of analyses using this upgraded hardware it is necessary to create similarly upgraded analysis tools. In this poster such a tool is presented: GUNDAM (Generic fitter for Upgraded Near Detector Analysis Methods) is a next-generation fitting tool capable of analysing large amounts of of near-detector data in the context of both oscillation and cross-section measurements.

In this poster we will showcase the main features of GUNDAM, demonstrating its flexible and fast set of libraries which can be setup with a set of user-friendly yaml configuration files, before showing various examples of its applications to T2K analyses. These include the potential to perform complete near detector fits in a fraction of the time they have previously taken, and to provide diagnostic tools to identify pathologies in parameter configurations that can impact MINUIT-based fitters.