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Register a new userDark matter contribution to $bto s mu^+ mu^-$ anomaly in local $U(1)_{L_mu-L_tau}$ model
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Seungwon Baek
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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.
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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.
We construct a scalar dark matter model with $U(1)_{L_mu-L_tau}$ symmetry in which the dark matter interacts with the quark flavours, allowing lepton non-universal $b to s ell bar{ell}$ decays. The model can solve $b to s mu mu$ ($R_{K^{(*)}}$) anomaly and accommodate the relic abundance of dark matter simultaneously while satisfying the constraints from other low energy flavour experiments and direct detection experiments of dark matter. The new fields include vector-like heavy quarks $U$ and $D$, $U(1)_{L_mu-L_tau}$ breaking scalar $S$, as well as the dark matter candidate $X_I$ and its heavy partner $X_R$. To explain both $b to s mu mu$ anomaly and the dark matter, {it i)} large mass difference between $X_R$ and $X_I$ is required, {it ii)} electroweak scale dark matter and heavy quarks are favoured, {it iii)} not only electroweak scale but ${cal O}(10)$ TeV dark gauge boson $Z$ and $X_R$ are allowed.
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.
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 study the phenomenology of a Dirac dark matter in the $L_mu-L_tau$ model and investigate the neutrino oscillation in the dark halo. Since dark matter couples to the muon neutrino and the tau neutrino with opposite sign couplings, it contributes effective potentials, $pm A_chi$, to the evolution equation of the neutrino flavor transition amplitude, which can be significant for high energy neutrino oscillations in a dense dark matter environment. We discuss neutrino masses, lepton mixing angles, Dirac CP phase, and neutrino oscillation probabilities in the dark halo using full numerical calculations. Results show that neutrinos can endure very different matter effects. When the potential $A_chi$ becomes ultra-large, three neutrino flavors decouple from each other.
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