https://doi.org/10.1140/epjc/s10052-020-08725-x
Regular Article - Experimental Physics
Hunting down the X17 boson at the CERN SPS
1
ETH Zürich Institute for Particle Physics and Astrophysics, 8093, Zurich, Switzerland
2
Institute for Nuclear Research, 117312, Moscow, Russia
3
CERN, EN-EA, 1211, Geneva 23, Switzerland
4
University of Illinois at Urbana Champaign, 61801-3080, Urbana, IL, USA
5
Joint Institute for Nuclear Research, 141980, Dubna, Russia
6
Tomsk State Pedagogical University, 634061, Tomsk, Russia
7
UCL Department of Physics and Astronomy, University College London, Gower St., WC1E 6BT, London, UK
8
State Scientific Center of the Russian Federation Institute for High Energy Physics of National Research Center ‘Kurchatov Institute’ (IHEP), 142281, Protvino, Russia
9
Tomsk Polytechnic University, 634050, Tomsk, Russia
10
Physics Department, University of Patras, 265 04, Patras, Greece
11
Physik Department, Technische Universität München, 85748, Garching, Germany
12
P.N. Lebedev Physical Institute, 119 991, Moscow, Russia
13
Universität Bonn, Helmholtz-Institut für Strahlen-und Kernphysik, 53115, Bonn, Germany
14
Departamento de Ciencias Físicas, Universidad Andres Bello, Sazié 2212, Piso 7, Santiago, Chile
15
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991, Moscow, Russia
16
Universidad Técnica Federico Santa María, 2390123, Valparaiso, Chile
Received:
21
September
2020
Accepted:
1
December
2020
Published online:
15
December
2020
Recently, the ATOMKI experiment has reported new evidence for the excess of 
events with a mass 
17 MeV in the nuclear transitions of 
He, that they previously observed in measurements with 
Be. These observations could be explained by the existence of a new vector 
boson. So far, the search for the decay 
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 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the decay with the proposed method. To reach this goal an optimization of the 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.
D. A. Tlisov: Deceased.
© The Author(s) 2020
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