Thin-walled Higgs assisted Q-balls from pseudo-Nambu-Goldstone bosons

Abstract

Abstract We consider the question of whether Q-balls can exist in a chiral Lagrangian truncated at leading order when, in addition, the Standard Model Higgs boson couples to the pseudo-Nambu-Golstone bosons (pNGBs). In particular, we consider the so-called thin-wall limit where volume energy dominates over surface energy. It is known that the leading order chiral Lagrangian alone does not support such multi-field solutions. Augmented by the Higgs, however, we do indeed find that such solutions exist. We then study their properties numerically and, in various limits, analytically. Furthermore, since we consider a mirror-world-like model where the pNGBs are composite states of fundamental fermions, the question of Fermi repulsion in the high density bulk of the Q-ball plays a central role in determining its properties. The main effect is that when the parameter controlling the Fermi repulsion increases beyond a critical value, the radius of the Q-ball increases and continues to increase while the Q-ball becomes more weakly bound. As a result, there are Q-ball solutions with radii well exceeding a femtometer which would interact with nuclei in direct detection experiments via momentum-dependent form factors making their signatures striking. We leave the question of the production and direct detection of these Q-balls to a future study.