Abstract
Dark photons are massive abelian gauge bosons that interact with ordinary photons via a kinetic mixing with the hypercharge field strength tensor. This theory is probed by a variety of different experiments and limits are set on a combination of the dark photon mass and kinetic mixing parameter. These limits can however be strongly modified by the presence of additional heavy degrees of freedom. Using the framework of dark effective field theory, we study how robust are the current experimental bounds when these new states are present. We focus in particular on the possible existence of a dark dipole interaction between the Standard Model leptons and the dark photon. We show that, under certain assumptions, the presence of a dark dipole modifies existing supernovæ bounds for cut-off scales up to mathcal{O} (10–100 TeV). On the other hand, terrestrial experiments, such as LSND and E137, can probe cut-off scales up to mathcal{O} (3 TeV). For the latter experiment we highlight that the bound may extend down to vanishing kinetic mixing.
Highlights
Given the vast number of possibilities for the presence of additional NP states and the limits from LHC direct searches for particles charged under the SM symmetries, we will assume for definiteness that such states have masses above the EW scale and we will use the Effective Field Theory (EFT) paradigm to frame our discussion
In the previous expression Aμ, Zμ and Aμ describe the physical photon, Z boson and dark photon respectively, cW and sW are the usual cosine and sine of the weak angle, g and g the coupling constants of the SM SU(2)L and U(1)Y gauge groups, is the kinetic mixing once the effect of higher dimensional operators is taken into account, see eq (A.3), and the dark electron dipole moment de is a linear combination of the dipole operators Wilson coefficients
We show in the left panel of figure 3 the dark photon lifetime, computed according to eq (3.2), in the plane for different values of the dark dipole scale Λ
Summary
Where the set of operators considered is presented in table 1 These operators can be classified in i) dipole operators, ii) operators that modify the kinetic terms or that contribute to the vector bosons kinetic mixing and iii) the operator OT that contributes to the Z boson mass.. In the previous expression Aμ, Zμ and Aμ describe the physical photon, Z boson and dark photon respectively, cW and sW are the usual cosine and sine of the weak angle, g and g the coupling constants of the SM SU(2)L and U(1)Y gauge groups, is the kinetic mixing once the effect of higher dimensional operators is taken into account, see eq (A.3), and the dark electron dipole moment de is a linear combination of the dipole operators Wilson coefficients. The higher dimensional operators modify in the usual way the coupling of the Z boson, while the
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