The Lμ − Lτ extension of the standard model predicts the existence of a lepton-flavor-universality-violating Z0 boson that couples only to the heavier lepton families. We search for such a Z0 through its invisible decay in the process e+ e− → μ+ μ− Z0 . We use a sample of electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019–2020, corresponding to an integrated luminosity of 79.7 fb−1 . We find no excess over the expected standard-model background. We set 90%-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from 3 × 10−3 at low Z0 masses to 1 at Z0 masses of 8 GeV=c2 .
Adachi, I., Adamczyk, K., Aggarwal, L., Ahmed, H., Aihara, H., Akopov, N., et al. (2023). Search for an Invisible Z′ in a Final State with Two Muons and Missing Energy at Belle II. PHYSICAL REVIEW LETTERS, 130(23), 231801-1-231801-8 [10.1103/PhysRevLett.130.231801].
Search for an Invisible Z′ in a Final State with Two Muons and Missing Energy at Belle II
Bernieri, E.Membro del Collaboration Group
;Branchini, P.Membro del Collaboration Group
;Budano, A.Membro del Collaboration Group
;Bussino, S.Membro del Collaboration Group
;De Pietro, G.Writing – Original Draft Preparation
;Laurenza, M.Membro del Collaboration Group
;
2023-01-01
Abstract
The Lμ − Lτ extension of the standard model predicts the existence of a lepton-flavor-universality-violating Z0 boson that couples only to the heavier lepton families. We search for such a Z0 through its invisible decay in the process e+ e− → μ+ μ− Z0 . We use a sample of electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019–2020, corresponding to an integrated luminosity of 79.7 fb−1 . We find no excess over the expected standard-model background. We set 90%-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from 3 × 10−3 at low Z0 masses to 1 at Z0 masses of 8 GeV=c2 .I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
