Abstract
That massless dark photons could exist and have flavor-changing magnetic-dipole interactions with down-type light quarks is an attractive possibility which may be realized in various new-physics scenarios. It is potentially testable not only in kaon processes but also via two-body hyperon decays involving missing energy carried away by the massless dark photon. We explore the latter within a simplified model approach and take into account constraints from the kaon sector. We find that the branching fractions of some of these hyperon modes are allowed to be as high as a few times $10^{-4}$. Such numbers are likely to be within the sensitivity reaches of ongoing experiments like BESIII and future ones at super charm-tau factories.
Highlights
Models of new physics (NP) beyond the standard model (SM) may have a dark sector containing an extra Abelian gauge group, Uð1ÞD, under which all SM fields are singlets
That massless dark photons could exist and have flavor-changing magnetic-dipole interactions with down-type light quarks is an attractive possibility which may be realized in various new-physics scenarios
These possibilities are appealing for a number of reasons and have been much studied in the past [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. They have motivated many dedicated hunts for dark photons in recent years [13,14,15,16,17,18,19,20], with negative outcomes so far. The majority of these efforts have been based on the assumption that Uð1ÞD is broken and the accompanying massive dark photon, A0, can interact directly with SM fermions through a renormalizable operator εeA0μJμEM, with eJEM being the electromagnetic current and the small parameter ε originating from kinetic mixing between the dark and SM Abelian gauge fields [12,13,14]
Summary
That massless dark photons could exist and have flavor-changing magnetic-dipole interactions with down-type light quarks is an attractive possibility which may be realized in various new-physics scenarios It is potentially testable in kaon processes and via two-body hyperon decays involving missing energy carried away by the massless dark photon. The quark transition s → d=E gives rise to the FCNC decays of hyperons into a lighter baryon plus missing energy (=E) which is carried away by one or more invisible particles If these are a pair of spin-1=2 fermions or spinless bosons, it is presently possible for NP to enhance the branching fractions of the hyperon modes considerably above the SM expectations to levels discoverable by ongoing or future searches [21,22]. New results on these decays may be forthcoming from the
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