Search for long-lived heavy neutral leptons and Higgs portal scalars decaying in the MicroBooNE detector
P. Abratenko, J. Anthony, L. Arellano, J. Asaadi, A. Ashkenazi, S. Balasubramanian, B. Baller, C. Barnes, G. Barr, J. Barrow, V. Basque, L. Bathe-Peters, O. Benevides Rodrigues, S. Berkman, A. Bhanderi, Meghna Bhattacharya, M. Bishai, A. Blake, B. Bogart, T. Bolton, J. Y. Book, L. Camilleri, D. Caratelli, I. Caro Terrazas, F. Cavanna, G. B. Cerati, Y. Chen, J. M. Conrad, M. Convery, L. Cooper-Troendle, J. I. Crespo-Anadón, M. Del Tutto, S. R. Dennis, P. Detje, A. Devitt, Z. Djurcic, R. Dorrill, K. Duffy, S. Dytman, B. Eberly, A. Ereditato, J. J. Evans, R. Fine, O. G. Finnerud, W. Foreman, B. T. Fleming, N. Foppiani, D. Franco, A. P. Furmanski, D. Garcia-Gamez, S. Gardiner, G. Ge, S. Gollapinni, O. Goodwin, E. Gramellini, P. Green, P. Green, W. Gu, R. Guenette, P. Guzowski, L. Hagaman, O. Hen, R. Hicks, C. Hilgenberg, G. A. Horton-Smith, R. Itay, C. James, X. Ji, L. L. Jiang, J. H. Jo, Rob Johnson, Y. -J. Jwa, D. Kalra, N. Kamp, N. Kaneshige, G. Karagiorgi, W. Ketchum, M. Kirby, T. Kobilarcik, I. Kreslo, M. B. Leibovitch, I. Lepetic, J. -Y. Li, K. Li, Y. Li, K. Lin, B. R. Littlejohn, W. C. Louis, X. Luo, K. Manivannan, C. Mariani, D. Marsden, J. Marshall, D. A. Martínez Caicedo, K. Mason, A. Mastbaum, N. McConkey, V. Meddage, K. Miller, J. Mills
Abstract
We present a search for long-lived Higgs portal scalars (HPS) and heavy neutral leptons (HNL) decaying in the MicroBooNE liquid-argon time projection chamber. The measurement is performed using data collected synchronously with the neutrino beam from Fermilab's Main Injector with a total exposure corresponding to 7.01 10 20 protons on target. We set upper limits at the 90% confidence level on the mixing parameter jU 4 j 2 ranging from jU 4 j 2 < 12.9 10 -8 for Majorana HNLs with a mass of m HNL 246 MeV to jU 4 j 2 < 0.92 10 -8 for m HNL 385 MeV, assuming jU e4 j 2 jU 4 j 2 0 and HNL decays into AE pairs. These limits on jU 4 j 2 represent an order of magnitude improvement in sensitivity compared to the previous MicroBooNE result. We also constrain the scalar-Higgs mixing angle by searching for HPS decays into -final states, excluding a contour in the parameter space with lower bounds of 2 < 31.3 10 -9 for m HPS 212 GeV and 2 < 1.09 10 -9 for m HPS 275 GeV. These are the first constraints on the scalar-Higgs mixing angle from a dedicated experimental search in this mass range.