https://doi.org/10.1140/epjc/s10052-021-09896-x
Regular Article - Theoretical Physics
Flipped SU(5) GUT phenomenology: proton decay and 
1
Theoretical Particle Physics and Cosmology Group, Department of Physics, King’s College London, WC2R 2LS, London, UK
2
Theoretical Physics Department, CERN, 1211, Geneva 23, Switzerland
3
National Institute of Chemical Physics and Biophysics, Rävala 10, 10143, Tallinn, Estonia
4
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, 200240, Shanghai, China
5
Department of Physics, University of Tokyo, Bunkyo-ku, 113-0033, Tokyo, Japan
6
George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 77843, College Station, TX, USA
7
Astroparticle Physics Group, Houston Advanced Research Center (HARC), Mitchell Campus, 77381, Woodlands, TX, USA
8
Division of Natural Sciences, Academy of Athens, 10679, Athens, Greece
9
William I. Fine Theoretical Physics Institute, School of Physics and Astronomy, University of Minnesota, 55455, Minneapolis, MN, USA
Received:
19
October
2021
Accepted:
29
November
2021
Published online:
15
December
2021
We consider proton decay and 
in flipped SU(5) GUT models. We first study scenarios in which the soft supersymmetry-breaking parameters are constrained to be universal at some high scale 
above the standard GUT scale where the QCD and electroweak SU(2) couplings unify. In this case the proton lifetime is typically 
years, too long to be detected in the foreseeable future, and the supersymmetric contribution to is too small to contribute significantly to resolving the discrepancy between the experimental measurement and data-driven calculations within the Standard Model. However, we identify a region of the constrained flipped SU(5) parameter space with large couplings between the 10- and 5-dimensional GUT Higgs representations where 
decay may be detectable in the Hyper-Kamiokande experiment now under construction, though the contribution to 
is still small. A substantial contribution to is possible, however, if the universality constraints on the soft supersymmetry-breaking masses are relaxed. We find a ‘quadrifecta’ region where observable proton decay co-exists with a (partial) supersymmetric resolution of the discrepancy and acceptable values of 
and the relic LSP density.
© The Author(s) 2021
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