Abstract
We consider a generic dark photon that arises from a hidden U(1) gauge symmetry imposed on right-handed neutrinos (νR). Such a νR-philic dark photon is naturally dark due to the absence of tree-level couplings to normal matter. However, loop-induced couplings to charged leptons and quarks are inevitable, provided that νR mix with left-handed neutrinos via Dirac mass terms. We investigate the loop-induced couplings and find that the νR-philic dark photon is not inaccessibly dark, which could be of potential importance to future dark photon searches at SHiP, FASER, Belle-II, LHC 14 TeV, etc.
Highlights
Presence of mass terms connecting νR and left-handed neutrinos νL, via one-loop diagrams containing W ±/Z and neutrinos [19]
We consider a generic dark photon that arises from a hidden U(1) gauge symmetry imposed on right-handed neutrinos
Here we draw a less model-dependent conclusion that without finetuning, the νR-philic dark photon mass is expected to be above the lower bound in eq (4.2) or eq (4.3), depending on whether MR breaks the U(1)R symmetry or not, respectively
Summary
We consider a hidden U(1) gauge symmetry, denoted by U(1)R, imposed on n right-handed neutrinos. Note that for most general forms of MR and mD, both the Majorana and Dirac mass terms in eq (2.1) break the U(1)R symmetry. In order to facilitate loop calculations, we need to transform neutrino interaction terms from the chiral basis to the mass basis. We have the following neutrino interaction terms: L⊃. Where the first three terms are the SM charged and neutral current interactions, and L denotes left-handed charged leptons. The above results, which will be used in our loop calculations to cancel UV divergences, have been previously derived in ref. [19]
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