Regular Article - Theoretical Physics
The light boson as the mediator of a new force, coupled to a combination of and dark matter
Laboratoire de Physique Théorique de l’École Normale Supérieure (CNRS UMR 8549, ENS, PSL Research University and UPMC, Sorbonne Universités), 24 rue Lhomond, 75231, Paris Cedex 05, France
2 Centre de Physique Théorique, École polytechnique (CNRS UMR 7644, Université Paris-Saclay), 91128, Palaiseau Cedex, France
* e-mail: firstname.lastname@example.org
Accepted: 7 December 2016
Published online: 28 January 2017
A new light gauge boson U may have both vector and axial couplings. In a large class of theories, however, the new U(1) current naturally combines with the weak neutral current , both parity-violating, into a vectorial current , combination of the and electromagnetic currents with a possible dark-matter current.
may be expressed equivalently as (“mixing with the Z”) or (“mixing with the photon”), with coupled to and dark matter. The U boson may be viewed as a generalized dark photon, coupled to SM particles through , with strength . “Kinetic-mixing” terms, gauge invariant or not, simply correspond to a description in a non-orthogonal field basis (rather than to a new physical effect), with the dark photon in general also coupled to B and L.
In a grand-unified theory at the GUT scale for SM particles, invariant under the SU(4) electrostrong symmetry group, with a non-vanishing already present at the GUT scale, leading to at low energy. This also applies, for a very light or massless U boson, to a new long-range force, which could show up through apparent violations of the equivalence principle.
© The Author(s), 2017