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Register a new userDark matter and muon $(g-2)$ in local $U(1)_{L_mu-L_tau}$-extended Ma Model
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Seungwon Baek
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We consider right-handed neutrino dark matter $N_1$ in local $U(1)_{L_mu-L_tau}$-extended Ma model. With the light $U(1)_{mu-tau}$ gauge boson ($m_{Z} sim {cal O}(100)$ MeV) and small $U(1)_{mu-tau}$ gauge coupling ($g_{Z}sim 10^{-4}-10^{-3}$) which can accommodate the muon $(g-2)$ anomaly and is still allowed by other experimental constraints, we show that we can get correct relic density of dark matter for wide range of dark matter mass ($M_1 sim 10-100$ GeV), although the gauge coupling constant $g_{Z}$ is small. This is due to the fact that the annihilation cross section of dark matter pair is enhanced by $M_1^4/m_{Z}^4$ in the processes $N_1 N_1 to Z Z$ or $N_1 N_1 to Z H_2$. We also consider the constraints from direct detection, collider searches.
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Gauged $U(1)_{L_mu - L_tau}$ model has been advocated for a long time in light of muon $g-2$ anomaly, which is a more than $3sigma$ discrepancy between the experimental measurement and the standard model prediction. We augment this model with three right-handed neutrinos $(N_e, N_mu, N_tau)$ and a vector-like singlet fermion $(chi)$ to explain simultaneously the non-zero neutrino mass and dark matter content of the Universe, while satisfying anomalous muon $g-2$ constraints. It is shown that in a large parameter space of this model we can explain positron excess, observed at PAMELA, Fermi-LAT and AMS-02, through dark matter annihilation, while satisfying the relic density and direct detection constraints.
We propose a local $U(1)_{L_mu-L_tau}$ model to explain $b to s mu^+ mu^-$ anomaly observed at the LHCb and Belle experiments. The model also has a natural dark matter candidate $N$. We introduce $SU(2)_L$-doublet colored scalar $widetilde{q}$ to mediate $b to s$ transition at one-loop level. The $U(1)_{L_mu-L_tau}$ gauge symmetry is broken spontaneously by the scalar $S$. All the new particles are charged under $U(1)_{L_mu-L_tau}$. We can obtain $C_9^{mu,{rm NP}} sim -1$ to solve the $b to smu^+mu^-$ anomaly and can explain the correct dark matter relic density of the universe, $Omega_{rm DM} h^2 approx 0.12$, simultaneously, while evading constraints from electroweak precision tests, neutrino trident experiments and other quark flavor-changing loop processes such as $b to s gamma$ and $B_s-overline{B}_s$ mixing. Our model can be tested by searching for $Z$ and new colored scalar at the LHC and $B to K^* u overline{ u}$ process at Belle-II.
We consider a gauged $U(1)_{L_mu-L_tau}$ extension of the left-right symmetric theory in order to simultaneously explain neutrino mass, mixing and the muon anomalous magnetic moment. We get sizeable contribution from the interaction of the new light gauge boson $Z_{mutau}$ of the $U(1)_{L_mu-L_tau}$ symmetry with muons which can individually satisfy the current bounds on muon $(g-2)$ anomaly ($Delta a_mu$). The other positive contributions to $Delta a_mu$ come from the interactions of singly charged gauge bosons $W_L$, $W_R$ with heavy neutral fermions and that of neutral CP-even scalars with muons. The interaction of $W_L$ with heavy neutrino is facilitated by inverse seesaw mechanism which allows large light-heavy neutrino mixing and explains neutrino mass in our model. CP-even scalars with mass around few hundreds GeV can also satisfy the entire current muon anomaly bound. The results show that the model gives a small but non-negligible contribution to $Delta a_mu$ thereby eliminating the entire deviation in theoretical prediction and experimental result of muon $(g-2)$ anomaly. We have briefly presented a comparative study for symmetric and asymmetric left-right symmetric model in context of various contribution to $Delta a_mu$. We also discuss how the generation of neutrino mass is affected when left-right symmetry breaks down to Standard Model symmetry via various choices of scalars.
As experimental null results increase the pressure on heavy weakly interacting massive particles (WIMPs) as an explanation of thermal dark matter (DM), it seems timely to explore previously overlooked regions of the WIMP parameter space. In this work we extend the minimal gauged $U(1)_{L_mu-L_tau}$ model studied in cite{Bauer:2018onh} by a light (MeV-scale) vector-like fermion $chi$. Taking into account constraints from cosmology, direct and indirect detection we find that the standard benchmark of $M_V=3 m_chi$ for DM coupled to a vector mediator is firmly ruled out for unit DM charges. However, exploring the near-resonance region $M_Vgtrsim 2 m_chi$ we find that this model can simultaneously explain the DM relic abundance $Omega h^2 =0.12$ and the $(g-2)_mu$ anomaly. Allowing for small charge hierarchies of $lesssimmathcal{O}(10)$, we identify a second window of parameter space in the few-GeV region, where $chi$ can account for the full DM relic density.
In this paper we introduce a light Dirac particle $psi$ as thermal dark matter candidate in a $U(1)_{L_{mu}-L_{tau}}$ model. Together with the new gauge boson $X$, we find a possible parameter space with $m_X simeq 20$ MeV, $U(1)_{L_{mu}-L_{tau}}$ coupling $g_X simeq 5 cdot 10^{-4}$ and $m_psi gtrsim m_X/2$ where the $(g-2)_mu$ anomaly, dark matter, the Hubble tension, and (part of) the excess of $511$ keV photons from the region near the galactic center can be explained simultaneously. This model is safe from current experimental and astrophysical constraints, but can be probed by the next generation of neutrino experiments as well as low-energy $e^+e^-$ colliders.
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