Explaining Xenon-1T signal with FIMP dark matter and neutrino mass in a $U(1)_{X}$ extension

TL;DR

This paper extends the standard model with a $U(1)_X$ gauge symmetry, introducing new particles to generate neutrino masses, explain the Xenon-1T signal via an ALP dark matter candidate, and address fermion mass generation.

Contribution

It presents a novel $U(1)_X$ extension that simultaneously explains neutrino masses, keV-scale FIMP dark matter, and the Xenon-1T signal with new particles and mechanisms.

Findings

Successfully generated neutrino masses via type-I seesaw.

ALP can explain Xenon-1T electron recoil signal.

Dark matter relic density consistent with reheat temperature.

Abstract

In the present work, we have extended the standard model by an abelian $U(1)_{X}$ gauge group and additional particles. In particular, we have extended the particle content by three right handed neutrinos, two singlet scalars and two vector like leptons. Charged assignments under different gauge groups are such that the model is gauge anomaly free and the anomaly contributions cancel among generations. Once the symmetry gets broken then three physical Higgses are produced, one axion like particle (ALP), which also acts as the keV scale FIMP dark matter, is produced and the remaining component is absorbed by the extra gauge boson. Firstly, we have successfully generated neutrino mass by the type-I seesaw mechanism for normal hierarchy with the $3\sigma$ bound on the oscillation parameters. The ALP in the present model can explain the Xenon-1T electron recoil signal at keV scale through its coupling with the electron. We also have vector like leptons which help in producing the dark matter from their decay by the freeze in mechanism. Electron and tauon get mass from dimensional-5 operators at Planck scale and if we consider the vevs $v_{1,2} \simeq 10^{12}$ GeV then we can obtain the correct value of the electron mass but not the tauon mass. Vector like leptons help in getting the correct value of the tauon mass through another higher dimensional operator which also has a role in DM production by the $2 \rightarrow 2$ process, giving the correct ballpark value of relic density for suitable reheat temperature of the Universe. We have shown that the ALP production by the higher dimensional operator can explain the electron, tauon mass and Xenon-1T signal simultaneously whereas the decay production can not explain all of them together.