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Depero, E.; Andreev, Yu. M.; Banerjee, D.; Bernhard, J.; Burtsev, V. E.; Charitonidis, N.; Chumakov, A. G.; Cooke, D.; Crivelli, P.; Dermenev, A. V.; Donskov, S. V.; Dusaev, R. R.; Enik, T.; Feshchenko, A.; Frolov, V. N.; Gardikiotis, A.; Gerassimov, S. G.; Girod, S.; Gninenko, S. N.; Hösgen, M.; Kachanov, V. A.; Karneyeu, A. E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D. V.; Kirsanov, M. M.; Kolosov, V. N.; 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.; Bueno, L. Molina; Peshekhonov, D. V.; Polyakov, V. A.; Radics, B.; Rojas, R.; Rubbia, A.; Samoylenko, V. D.; Shchukin, D.; Sieber, H.; Tikhomirov, V. O.; Tlisova, vI; Tlisov, D. A.; Toropin, A. N.; Trifonov, A. Yu; Vasilishin, B. I.; Arenas, G. Vasquez; Volkov, P. V.; Volkov, V. Yu; Ulloa, P.
The European physical journal. C, Particles and fields, 12/2020, Letnik: 80, Številka: 12Journal Article
Recently, the ATOMKI experiment has reported new evidence for the excess of e + e - events with a mass ∼ 17 MeV in the nuclear transitions of 4 He, that they previously observed in measurements with 8 Be. These observations could be explained by the existence of a new vector X 17 boson. So far, the search for the decay X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X 17 decay with the proposed method. To reach this goal an optimization of the X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results 1 , validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible.
