Search for a new X(16.7) boson and dark photons in the NA64 experiment at CERN

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 8Be* nucleus decays. Due to its coupling to electrons, the X could be produced in the bremsstrahlung reaction e-Z -> e-ZX by a 100 GeV e- beam...

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Detalles Bibliográficos
Autores principales: Banerjee, D., Burtsev, V.E., Chumakov, A.G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A.V., Donskov, S.V., Dusaev, R.R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V.N., Gardikiotis, A., Gerassimov, S.G., Gninenko, SN, Hösgen, M., Jeckel, M., Karneyeu, A.E., Kekelidze, G., Ketzer, B., Kirpichnikov, D.V., Kirsanov, M.M., Konorov, I.V., Kovalenko, S.G., Kramarenko, V.A., Kravchuk, L.V., Krasnikov, N.V., Kuleshov, S.V., Lyubovitskij, V.E., Lysan, V., Matveev, V.A., Mikhailov, Yu.V., Peshekhonov, D.V., Polyakov, V.A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V.D., Tikhomirov, V.O., Tlisov, D.A., Toropin, A.N., Trifonov, A.Yu., Vasilishin, B.I., Vasquez Arenas, G., Volkov, P.V., Volkov, V., Ulloa, P.
Lenguaje:eng
Publicado: 2018
Materias:
Particle Physics - Experiment
Acceso en línea:https://dx.doi.org/10.1103/PhysRevLett.120.231802
http://cds.cern.ch/record/2308201
Descripción
Sumario: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 8Be* nucleus decays. Due to 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 SPS and observed through the subsequent decay into a e+e- pair. With 5.4x10^10 electrons on target no evidence for such decays was found, allowing to set first limits on the X-e- coupling in the range 1.3x10^-4 <epsilon_e < 4.2x10^-4 excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay A' -> e+e- of the bremsstrahlung A' with a mass < 23 MeV.

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