Portal Effective Theories: A framework for the model independent description of light hidden sector interactions

Understand

We present a framework for the construction of portal effective theories (PETs) that couple effective field theories of the Standard Model (SM) to light hidden messenger fields.

• Using this framework we construct electroweak and strong scale PETs that couple the SM to messengers carrying spin zero, one half, or one.
• The electroweak scale PETs encompass all portal operators up to dimension five, while the strong scale PETs additionally contain all portal operators of dimension six and seven that contribute at leading order to quark-flavour violating transitions.
• Using the strong scale PETs, we define a set of portal currents that couple hidden sectors to QCD, and construct portal chiral perturbation theories ($\chi$PTs) that relate these currents to the light pseudoscalar mesons.