| Literature DB >> 29932721 |
D Banerjee1, V E Burtsev2, A G Chumakov2, D Cooke3, P Crivelli3, E Depero3, A V Dermenev4, S V Donskov5, R R Dusaev2, T Enik6, N Charitonidis7, A Feshchenko6, V N Frolov6, A Gardikiotis8, S G Gerassimov9,10, S N Gninenko4, M Hösgen11, M Jeckel7, A E Karneyeu4, G Kekelidze6, B Ketzer11, D V Kirpichnikov4, M M Kirsanov4, I V Konorov9,10, S G Kovalenko12, V A Kramarenko6,13, L V Kravchuk4, N V Krasnikov4, S V Kuleshov12, V E Lyubovitskij2,12, V Lysan6, V A Matveev6, Yu V Mikhailov5, D V Peshekhonov6, V A Polyakov5, B Radics3, R Rojas12, A Rubbia3, V D Samoylenko5, V O Tikhomirov9, D A Tlisov4, A N Toropin4, A Yu Trifonov2, B I Vasilishin2, G Vasquez Arenas12, P V Volkov6,13, V Volkov13, P Ulloa12.
Abstract
We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e^{+}e^{-} pairs observed in the excited ^{8}Be^{*} nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e^{-}Z→e^{-}ZX by a 100 GeV e^{-} beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e^{+}e^{-} pair. With 5.4×10^{10} electrons on target, no evidence for such decays was found, allowing us to set first limits on the X-e^{-} coupling in the range 1.3×10^{-4}≲ε_{e}≲4.2×10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A^{'}) from nonobservation of the decay A^{'}→e^{+}e^{-} of the bremsstrahlung A^{'} with a mass ≲23 MeV.Year: 2018 PMID： 29932721 DOI： 10.1103/PhysRevLett.120.231802
Source DB: PubMed Journal: Phys Rev Lett ISSN： 0031-9007 Impact factor: 9.161