# ICHEP2018 SEOUL

Jul 4 – 11, 2018
COEX, SEOUL
Asia/Seoul timezone

## Search for heavy neutrinos with the near detector ND280 of the T2K experiment

Jul 5, 2018, 6:00 PM
15m
103 (COEX, Seoul)

### 103

#### COEX, Seoul

Parallel Neutrino Physics

### Speaker

Mathieu Lamoureux (Université Paris-Saclay (FR))

### Description

Heavy Neutral Leptons (HNLs, heavy neutrinos) with masses below the electroweak
scale are introduced in some extensions of the Standard Model to address
consistently such effects as neutrino oscillations, light neutrino masses,
dark matter and baryon asymmetry. In the mass range below 500 MeV/$c^2$ these
heavy neutrinos can be produced in pion or kaon decays, and further decay
themselves into charged particles, hence giving a possibility for their
detection.
The T2K long-baseline neutrino oscillation experiment utilises an
intense neutrino beam, originating mainly from $\pi$ and K parents. Usage of the
K flux allows the study of a wider mass range of heavy neutrinos. The near
detector complex ND280, located 280 m from the target and composed of various
sub-modules operated inside a magnetic field, provides the tracking
capabilities to identify the products of HNLs` decays.
A selection aimed to search for heavy neutrino events in the
gas-filled ND280 TPCs was developed and optimised to significantly reduce the
background from active neutrino interactions down to few events for the
current dataset. After applying the selection to the T2K ND280 data $(12.34 \nu + 6.29 \bar{\nu}) \times 10^{20}$ protons-on-target, 2010-2017 statistics), no
events in the signal region were observed. The results were used to extract
limits on the mixing parameters between heavy neutrino and electron-, muon-
and tau- flavoured currents in the mass range of 140 < $M_{HNL}$ < 493
MeV/$c^2$. The T2K data allow an improvement of the limits provided by the
previous experiments such as the CERN PS191 which, together with the BNL E949
data, put the most stringent constraints in the mass region studied by T2K.

### Primary authors

Dr Marat Khabibullin (Russian Academy of Sciences (RU)) Mathieu Lamoureux (Université Paris-Saclay (FR))