Charged lepton flavor violating Higgs decays at future colliders

Qin Qin; Qiang Li; Cai-Dian Lü; Fu-Sheng Yu; Si-Hong Zhou

doi:10.1140/epjc/s10052-018-6298-7

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2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2018) 78: 835
https://doi.org/10.1140/epjc/s10052-018-6298-7

Regular Article - Theoretical Physics

Charged lepton flavor violating Higgs decays at future colliders

Qin Qin¹^*, Qiang Li²^,3, Cai-Dian Lü³^,4, Fu-Sheng Yu⁵^,6 and Si-Hong Zhou⁴^,7

¹ Theoretische Physik 1, Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Strasse 3, 57068, Siegen, Germany
² Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 100871, China
³ CAS Center for Excellence in Particle Physics, Beijing, 100049, China
⁴ Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918(4), Beijing, 100049, People’s Republic of China
⁵ School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, People’s Republic of China
⁶ Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, Lanzhou, 730000, People’s Republic of China
⁷ School of Physical Science and Technology, Inner Mongolia University, Hohhot, 010021, China

^* e-mail: qin@physik.uni-siegen.de

Received: 24 November 2017
Accepted: 28 September 2018
Published online: 17 October 2018

Abstract

After the discovery of the Higgs boson, several future experiments have been proposed to study the Higgs boson properties, including two circular lepton colliders, the CEPC and the FCC-ee, and one linear lepton collider, the ILC. We evaluate the precision reach of these colliders in measuring the branching ratios of the charged lepton flavor violating Higgs decays $H\rightarrow e^\pm \mu ^\mp$ , $e^\pm \tau ^\mp$ and $\mu ^\pm \tau ^\mp$ . The expected upper bounds on the branching ratios given by the circular (linear) colliders are found to be ${\mathcal {B}}(H\rightarrow e^\pm \mu ^\mp ) < 1.2~(2.1) \times 10^{-5}$ , ${\mathcal {B}}(H\rightarrow e^\pm \tau ^\mp ) < 1.6~(2.4) \times 10^{-4}$ and ${\mathcal {B}}(H\rightarrow \mu ^\pm \tau ^\mp ) < 1.4~(2.3) \times 10^{-4}$ at 95% CL, which are improved by one to two orders compared to the current experimental bounds. We also discuss the constraints that these upper bounds set on certain theory parameters, including the charged lepton flavor violating Higgs couplings, the corresponding parameters in the type-III 2HDM, and the new physics cut-off scales in the SMEFT, in RS models and in models with heavy neutrinos.