https://doi.org/10.1140/epjc/s10052-021-09705-5
Letter
Probing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel
1
ETH Zürich Institute for Particle Physics and Astrophysics, 8093, Zurich, Switzerland
2
Institute of Physics, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
3
Instituto de Fisica Corpuscular (CSIC/UV), Carrer del Catedrátic José Beltrán Martinez, 2, 46980, Paterna, Valencia, Spain
4
Institute for Nuclear Research, 117312, Moscow, Russia
5
CERN, EN-EA, 1211, Geneva 23, Switzerland
6
University of Illinois at Urbana Champaign, 61801-3080, Urbana, IL, USA
7
Joint Institute for Nuclear Research, 141980, Dubna, Russia
8
Tomsk State Pedagogical University, 634061, Tomsk, Russia
9
UCL Departement of Physics and Astronomy, University College London, Gower St., WC1E 6BT, London, UK
10
State Scientific Center of the Russian Federation Institute for High Energy Physics of National Research Center ‘Kurchatov Institute’ (IHEP), 142281, Protvino, Russia
11
Tomsk Polytechnic University, 634050, Tomsk, Russia
12
Physics Department, University of Patras, 265 04, Patras, Greece
13
Physik Department, Technische Universität München, 85748, Garching, Germany
14
P.N. Lebedev Physical Institute, 119 991, Moscow, Russia
15
Helmholtz-Institut für Strahlen-und Kernphysik, Universität Bonn, 53115, Bonn, Germany
16
Departamento de Ciencias Físicas, Universidad Andres Bello, Sazié 2212, Piso 7, Santiago, Chile
17
Millennium Institute for Subatomic Physics at the High-Energy Frontier (SAPHIR), ICN2019_044, ANID, Santiago, Chile
18
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991, Moscow, Russia
19
Universidad Técnica Federico Santa María, 2390123, Valparaiso, Chile
Received:
18
July
2021
Accepted:
30
September
2021
Published online:
30
October
2021
We report the results of a search for a new vector boson (
) decaying into two dark matter particles 
of different mass. The heavier 
particle subsequently decays to 
and an off-shell Dark Photon 
. For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay 
and axion-like or pseudo-scalar particles 
. With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for 
masses from 2
up to 390 MeV and mixing parameter 
between 
and 
.
D. A. Tlisov and A. Yu. Trifonov: Deceased.
C. Cazzaniga, P. Odagiu, E. Depero and L. Molina Bueno contributed equally to this article.
© The Author(s) 2021
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