Search for heavy neutral leptons decaying into muon-pion pairs in the MicroBooNE detector

Abratenko, P.; Alrashed, M.; An, R.; Anthony, J.; Asaadi, J.; Ashkenazi, A.; Balasubramanian, S.; Baller, B.; Barnes, C.; Barr, G.; Basque, V.; Berkman, S.; Bhanderi, A.; Bhat, A.; Bishai, M.; Blake, A.; Bolton, T.; Camilleri, L.; Caratelli, D.; Caro Terrazas, I.; Castillo Fernandez, R.; Cavanna, F.; Cerati, G.; Chen, Y.; Church, E.; Cianci, D.; Cohen, E. O.; Conrad, J. M.; Convery, M.; Cooper-Troendle, L.; Crespo-Anadon, J. I.; Del Tutto, M.; Devitt, D.; Domine, L.; Duffy, K.; Dytman, S.; Eberly, B.; Ereditato, A.; Escudero Sanchez, L.; Evans, J. J.; Fitzpatrick, R. S.; Fleming, B. T.; Foppiani, N.; Franco, D.; Furmanski, A. P.; Garcia-Gamez, D.; Gardiner, S.; Genty, V.; Goeldi, D.; Gollapinni, S.; Goodwin, O.; Gramellini, E.; Green, P.; Greenlee, H.; Gu, L.; Gu, W.; Guenette, R.; Guzowski, P.; Hamilton, P.; Hen, O.; Hill, C.; Horton-Smith, G. A.; Hourlier, A.; Huang, E. -C.; Itay, R.; James, C.; Jan De Vries, J.; Ji, X.; Jiang, L.; J. H., Jo; Johnson, R. A.; Joshi, J.; Jwa, Y. -J.; Karagiorgi, G.; Ketchum, W.; Kirby, B.; Kirby, M.; Kobilarcik, T.; Kreslo, I.; Lazur, R.; Lepetic, I.; Li, Y.; Lister, A.; Littlejohn, B. R.; Lockwitz, S.; Lorca, D.; Louis, W. C.; Luethi, M.; Lundberg, B.; Luo, X.; Marchionni, A.; Marcocci, S.; Mariani, C.; Marshall, J.; Martin-Albo, J.; Martinez Caicedo, D. A.; Mason, K.; Mastbaum, A.; Mcconkey, N.; Meddage, V.; Mettler, T.; Miller, K.; Mills, J.; Mistry, K.; Mogan, A.; Mohayai, T.; Moon, J.; Mooney, M.; Moore, C. D.; Mousseau, J.; Murrells, R.; Naples, D.; Neely, R. K.; Nienaber, P.; Nowak, J.; Palamara, O.; Pandey, V.; Paolone, V.; Papadopoulou, A.; Papavassiliou, V.; Pate, S. F.; Paudel, A.; Pavlovic, Z.; Piasetzky, E.; Porzio, D.; Prince, S.; Pulliam, G.; Qian, X.; Raaf, J. L.; Radeka, V.; Rafique, A.; Ren, L.; Rochester, L.; Rogers, H. E.; Ross-Lonergan, M.; Rudolf Von Rohr, C.; Russell, B.; Scanavini, G.; Schmitz, D. W.; Schukraft, A.; Seligman, W.; Shaevitz, M. H.; Sharankova, R.; Sinclair, J.; Smith, A.; Snider, E. L.; Soderberg, M.; Soldner-Rembold, S.; Soleti, S. R.; Spentzouris, P.; Spitz, J.; Stancari, M.; John, J. S.; Strauss, T.; Sutton, K.; Sword-Fehlberg, S.; Szelc, A. M.; Tagg, N.; Tang, W.; Terao, K.; Thornton, R. T.; Toups, M.; Tsai, Y. -T.; Tufanli, S.; Uchida, M. A.; Usher, T.; Van De Pontseele, W.; Van De Water, R. G.; Viren, B.; Weber, M.; Wei, H.; Wickremasinghe, D. A.; Williams, Z.; Wolbers, S.; Wongjirad, T.; Woodruff, K.; Wospakrik, M.; Wu, W.; Yang, T.; Yarbrough, G.; Yates, L. E.; Zeller, G. P.; Zennamo, J.; Zhang, C.

doi:10.1103/PhysRevD.101.052001

We present upper limits on the production of heavy neutral leptons (HNLs) decaying to μπ pairs using data collected with the MicroBooNE liquid-argon time projection chamber (TPC) operating at Fermilab. This search is the first of its kind performed in a liquid-argon TPC. We use data collected in 2017 and 2018 corresponding to an exposure of 2.0×1020 protons on target from the Fermilab Booster Neutrino Beam, which produces mainly muon neutrinos with an average energy of ≈800 MeV. HNLs with higher mass are expected to have a longer time of flight to the liquid-argon TPC than Standard Model neutrinos. The data are therefore recorded with a dedicated trigger configured to detect HNL decays that occur after the neutrino spill reaches the detector. We set upper limits at the 90% confidence level on the element |Uμ4|2 of the extended PMNS mixing matrix in the range |Uμ4|2<(6.6-0.9)×10-7 for Dirac HNLs and |Uμ4|2<(4.7-0.7)×10-7 for Majorana HNLs, assuming HNL masses between 260 and 385 MeV and |Ue4|2=|Uτ4|2=0.