https://doi.org/10.1140/epjc/s10052-024-13421-1
Regular Article
Probing hidden leptonic scalar portals using the NA64 experiment at CERN
1
Department of Physics and Astronomy, High Energy Physics, Uppsala University, Ångströmlaboratoriet, Lägerhyddsvägen 1, 752 37, Uppsala, Sweden
2
Institute for Particle Physics and Astrophysics, ETH Zürich, 8093, Zurich, Switzerland
3
Institute for Nuclear Research of the Russian Academy of Sciences, 117312, Moscow, Russia
4
Millennium Institute for Subatomic Physics at High-Energy Frontier (SAPHIR), Universidad Andres Bello, Fernandez Concha, 700, Santiago, Chile
5
Helmholtz-Institut für Strahlen-und Kernphysik, Universität Bonn, 53115, Bonn, Germany
6
Instituto de Fisica Corpuscular (CSIC/UV), Carrer del Catedratic Jose Beltran Martinez, 2, 46980, Paterna, Valencia, Spain
7
Bogoliubov Laboratory of Theoretical Physics, JINR, 141980, Dubna, Russia
8
Matrosov Institute for System Dynamics and Control Theory SB RAS, Lermontov Str., 134, 664033, Irkutsk, Russia
Received:
13
June
2024
Accepted:
26
September
2024
Published online:
9
October
2024
In this study, we demonstrate the potential of the NA64 experiment at CERN SPS to search for New Physics processes involving 
transitions after the collision of 100 GeV electrons with target nuclei. A new Dark Sector leptonic portal in which a scalar boson 
could be produced in the lepton-flavor-changing bremsstrahlung-like reaction, 
, is used as benchmark process. In this work, we develop a realistic Monte Carlo simulation of the NA64 experimental setup implementing the differential and total production cross-section computed at exact tree-level and applying the Weiszäcker–Williams phase space approximation. Using this framework, we investigate the main background sources and calculate the expected sensitivity of the experiment. The results indicate that with minor setup optimization, NA64 can probe a large fraction of the available parameter space compatible with the muon 
anomaly and the Dark Matter relic predictions in the context of a new Dark Sector leptonic portal with 
EOT. This result paves the way to the exploration of lepton-flavour-changing transitions in NA64.
© The Author(s) 2024
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Funded by SCOAP3.
