Dark sector effective field theory
Jinhan Liang, Yi Liao, Xiaodong Ma, Haolin Wang
Abstract
A bstract We introduce the effective field theory of two different light dark particles interacting with the standard model (SM) light states in a single vertex, termed dark sector effective field theory (DSEFT). We focus on the new light particles with spin up to 1 and being real in essence, namely, new real scalars ϕ and S , Majorana fermions χ and ψ , and real vectors X μ and V μ . In the framework of low energy effective field theory with QED and QCD symmetry, the DSEFT can be classified into six categories, including the scalar-scalar-SM ( ϕS -SM), fermion-fermion-SM ( χψ -SM), vector-vector-SM ( XV -SM), scalar-fermion-SM ( ϕχ -SM), scalar-vector-SM ( ϕX -SM), and fermion-vector-SM ( χX -SM) cases. For each case, we construct the effective operator basis up to canonical dimension 7, which will cover most interesting phenomenology at low energy. As a phenomenological example, we investigate the longstanding neutron lifetime anomaly through the neutron dark decay modes n → χϕ or χX from the effective interactions in the fermion-scalar-SM or fermion-vector-SM case. When treating the light fermion as a dark matter candidate, we also explore the constraints from DM-neutron annihilation signal at Super-Kamiokande. We find the neutron dark decay in each scenario can accommodate the anomaly, at the same time, without contradicting with the Super-Kamiokande limit.