Exact one-loop results for li→ljγ in 3-3-1 models
L.T. Hue (Aff2, 0000 0001 2105 6888, Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Ba Dinh, 100000, Hanoi, Vietnam, Aff1, Institute for Research and Development, Duy Tan University, 550000, Da Nang, Vietnam); L.D. Ninh (Aff4, 0000 0001 2248 7639, Institut für Physik, Humboldt-Universität zu Berlin, Newtonstrasse 15, 12489, Berlin, Germany, Aff3, Institute For Interdisciplinary Research in Science and Education, ICISE, Ghenh Rang, 590000, Quy Nhon, Vietnam); T.T. Thuc (Aff5, Department of Education and Training of Ca Mau, 70 Phan Dinh Phung, 970000, Ca Mau, Vietnam); N.T.T. Dat (Aff7, 0000 0001 2184 9917, International Center for Theoretical Physics, Strada Costiera 11, 34151, Trieste, Italy, Aff6, 0000 0001 1941 4308, Dipartimento di Fisica, Theoretical section, Università di Trieste, Strada Costiera 11, 34151, Trieste, Italy)
We investigate the decays li→ljγ , with li=e,μ,τ in a general class of 3-3-1 models with heavy exotic leptons with arbitrary electric charges. We present full and exact analytical results keeping external lepton masses. As a by product, we perform numerical comparisons between exact results and approximate ones where the external lepton masses are neglected. As expected, we found that branching fractions can reach the current experimental limits if mixings and mass differences of the exotic leptons are large enough. We also found unexpectedly that, depending on the parameter values, there can be huge destructive interference between the gauge and Higgs contributions when the gauge bosons connecting the Standard Model leptons to the exotic leptons are light enough. This mechanism should be taken into account when using experimental constraints on the branching fractions to exclude the parameter space of the model.
