Gravitational waves from a dark $U(1)_D$ phase transition in the light of NANOGrav 12.5 yr data. (arXiv:2105.01007v3 [hep-ph] UPDATED)

<a href="http://arxiv.org/find/hep-ph/1/au:+Borah_D/0/1/0/all/0/1">Debasish Borah</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Dasgupta_A/0/1/0/all/0/1">Arnab Dasgupta</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Kang_S/0/1/0/all/0/1">Sin Kyu Kang</a>

We study a possibility of a strong first-order phase transition (FOPT) taking

place below the electroweak scale in the context of $U(1)_D$ gauge extension of

the standard model. As pointed out recently by the NANOGrav collaboration,

gravitational waves from such a phase transition with appropriate strength and

nucleation temperature can explain their 12.5 yr data. We first find the

parameter space of this minimal model consistent with NANOGrav findings

considering only a complex singlet scalar and $U(1)_D$ vector boson. Existence

of a singlet fermion charged under $U(1)_D$ can give rise to dark matter in

this model, preferably of non-thermal type, while incorporating additional

fields can also generate light neutrino masses through typical low scale seesaw

mechanisms like radiative or inverse seesaw.

We study a possibility of a strong first-order phase transition (FOPT) taking

place below the electroweak scale in the context of $U(1)_D$ gauge extension of

the standard model. As pointed out recently by the NANOGrav collaboration,

gravitational waves from such a phase transition with appropriate strength and

nucleation temperature can explain their 12.5 yr data. We first find the

parameter space of this minimal model consistent with NANOGrav findings

considering only a complex singlet scalar and $U(1)_D$ vector boson. Existence

of a singlet fermion charged under $U(1)_D$ can give rise to dark matter in

this model, preferably of non-thermal type, while incorporating additional

fields can also generate light neutrino masses through typical low scale seesaw

mechanisms like radiative or inverse seesaw.

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