# Search for heavy neutrinos with the T2K near detector ND280

Abe, K. and Akutsu, R. and Andreopoulos, C. and Antonova, M. and Aoki, S. and Ariga, A. and Ashida, Y. and Awataguchi, Y. and Azuma, Y. and Ban, S. and Barbi, M. and Barker, G. J. and Barr, G. and Barry, C. and Batkiewicz-Kwasniak, M. and Bench, F. and Berardi, V. and Berkman, S. and Berner, R. M. and Berns, L. and Bhadra, S. and Bienstock, S. and Blondel, A. and Bolognesi, S. and Bourguille, B. and Brailsford, D. and Bravar, A. and Bronner, C. and Avanzini, M. Buizza and Calcutt, J. and Campbell, T. and Cao, S. and Catanesi, M. G. and Cervera, A. and Chappell, A. and Checchia, C. and Cherdack, D. and Chikuma, N. and Christodoulou, G. and Coleman, J. and Collazuol, G. and Dealtry, T. and Finch, A. J. and Knox, A. and Kormos, L. L. and Lawe, M. and Nowak, J. and O'Keeffe, H. M. and Ratoff, P. N. and Shaw, D. (2019) Search for heavy neutrinos with the T2K near detector ND280. Physical Review D, 100. ISSN 1550-7998

Text (1902.07598v1)
1902.07598v1.pdf - Accepted Version

## Abstract

This paper reports on the search for heavy neutrinos with masses in the range $140 <M_N <493$ MeV/c$^2$ using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are $N \to \ell^{\pm}_{\alpha} \pi^{\mp}$ and $N \to \ell^+_{\alpha} \ell^-_{\beta} \nu (\bar\nu)$ ($\alpha,\beta=e,\mu$). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavoured currents ($U_e^2$, $U_{\mu}^2$, $U_{\tau}^2$) as a function of the heavy neutrino mass, e.g. $U_e^2 <10^{-9}$ at $90\%$ C.L. for a mass of $390$ MeV/c$^2$. These constraints are competitive with previous experiments.

Item Type:
Journal Article
Journal or Publication Title:
Physical Review D
Subjects:
Departments:
ID Code:
135507
Deposited By:
Deposited On:
22 Jul 2019 09:00
Refereed?:
Yes
Published?:
Published