Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Cosmological signature and light Dark Matter in Dirac $L_μ-L_τ$ model

Pritam Das

Abstract

We revisit an anomaly-free extension of the Standard Model (SM) $viz.$ gauged ${L_μ-L_τ}$ model in the Dirac framework, where the local $U(1)_{L_μ-L_τ}$ symmetry breaks and gives rise to a new gauge boson $Z'$ and corresponding gauge coupling $g_{μτ}$. Three additional heavy vector-like fermions, three light right-handed neutrinos and two heavy singlet scalars are added to complete the model framework for Dirac neutrinos. Another singlet vector-like fermion is added with a new gauge charge, which serves as a viable DM candidate, and the correct relic abundance is obtained via the resonance effect. The parameter space is considered after satisfying the current bounds on $M_{Z'}$ and the gauge coupling $g_{μτ}$. The influence of dark radiations coming from the additional light degrees of freedoms are studied in connection with the dark matter. After imposing all relevant theoretical and experimental constraints, the allowed parameter space is found to be highly restricted yet still accessible to ongoing and near-future experiments, rendering the scenario strongly predictive. Moreover, clear correlations among the relevant observables emerge throughout this study, making the model testable in current and future experimental searches.

Cosmological signature and light Dark Matter in Dirac $L_μ-L_τ$ model

Abstract

We revisit an anomaly-free extension of the Standard Model (SM) gauged model in the Dirac framework, where the local symmetry breaks and gives rise to a new gauge boson and corresponding gauge coupling . Three additional heavy vector-like fermions, three light right-handed neutrinos and two heavy singlet scalars are added to complete the model framework for Dirac neutrinos. Another singlet vector-like fermion is added with a new gauge charge, which serves as a viable DM candidate, and the correct relic abundance is obtained via the resonance effect. The parameter space is considered after satisfying the current bounds on and the gauge coupling . The influence of dark radiations coming from the additional light degrees of freedoms are studied in connection with the dark matter. After imposing all relevant theoretical and experimental constraints, the allowed parameter space is found to be highly restricted yet still accessible to ongoing and near-future experiments, rendering the scenario strongly predictive. Moreover, clear correlations among the relevant observables emerge throughout this study, making the model testable in current and future experimental searches.
Paper Structure (12 sections, 20 equations, 6 figures, 1 table)

This paper contains 12 sections, 20 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. Model Framework
  3. Dirac $L_{\mu}-L_{\tau}$ Model
  4. Neutrino mass
  5. Anomalous Muon Magnetic Moment
  6. Cosmological consequences
  7. Fate of $\nu_R$
  8. Dark Matter and Relic Abundance
  9. Direct Detection of DM:
  10. Contribution to $\Delta N_{\rm eff}$ from the decay of light species:
  11. Conclusion
  12. Acknowledgements

Figures (6)

  • Figure 1: Contribution to muon anomalous magnetic moment via the new gauge boson $Z'$
  • Figure 2: Summary plot containing related bounds as indicated in the figure key. The red star is the benchmark value that we have used for further analysis.
  • Figure 3: Interaction rate $vs.$ temperature for the light $\nu_{eR}$. The horizontal line indicates $\Gamma/H=1$.
  • Figure 4: Interaction rate $vs.$ temperature for the new gauge boson mass $M_{Z'}$ and gauge charge, $n_X$ with fixed $g_{\mu\tau}$. The black horizontal line represents $\ Gamma/H=1$. Hence, the region below this line indicates processes that never reach the thermal bath.
  • Figure 8: ($Left$)DM-electron elastic scattering via one looped kinetic mixing between $Z'$ and the photon via $f=\mu,\tau$. ($Right$) Variation of spin-independent elastic scattering cross-section for $\psi e\rightarrow\psi e$ process with DM mass. The vertical grey shaded region is the BBN+PLANCK bound on the Dirac DM candidate, restricting $M_{DM}<10.9$ MeV Sabti:2019mhn. We show existing experimental constraint on spin-independent $DM-e$ scattering cross-sections from DAMIC DAMIC:2019dcn, SENSEI SENSEI:2020dpa, PANDAX-II PandaX-II:2021nsg and XENON1T XENON:2019gfn
  • ...and 1 more figures