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Register a new userExploring Dark Matter, Neutrino mass and flavour anomalies in L_{mu}-L_{tau} model
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We investigate Majorana dark matter in a new variant of $U(1)_{L_{mu}-L_{tau}}$ gauge extension of Standard Model, containing three additional neutral fermions $N_{e}, N_{mu}, N_{tau}$, along with a $(bar{3},1,1/3)$ scalar Leptoquark (SLQ) and an inert doublet, to study the phenomenology of dark matter, neutrino mass generation and flavour anomalies on a single platform. The lightest mass eigenstate of the $N_{mu}, N_{tau}$ neutral fermions plays the role of dark matter. We compute the WIMP-nucleon cross section in leptoquark portal and the relic density mediated by inert doublet components, leptoquark and the new $Z^{prime}$ boson. We constrain the parameter space consistent with Planck limit on relic density, PICO-60 and LUX bounds on spin-dependent direct detection cross section. We also discuss about the neutrino mass generation at one-loop level and the viable parameter region to explain current neutrino oscillation data. The $Z^prime$ gauge boson of extended $U(1)$ symmetry and the SLQ play an important role in settling the known issues of flavor sector.
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We propose an anomaly free unified scenario by invocation of an extra local ${rm U(1)}_{L_{mu}-L_{tau}}$ gauge symmetry. This scenario simultaneously resolves the $R_{K^{(*)}}$ anomalies, the dark matter puzzle and the long-standing discrepancy in muons anomalous magnetic moment. A complex scalar ($eta$) having nonzero ${L_{mu}-L_{tau}}$ charge has been introduced to break this new U(1) symmetry spontaneously. Moreover, for the purpose of studying dark matter phenomenology and $R_{K^{(*)}}$ anomalies in a correlated manner, we introduce an inert ${rm SU(2)}_L$ scalar doublet ($Phi$), a $mathbb{Z}_2$-odd real singlet scalar ($S$) and a $mathbb{Z}_2$-odd coloured fermion ($chi$) which transforms vectorially under the ${rm U(1)}_{L_{mu}-L_{tau}}$ symmetry. This extra gauge symmetry provides a new gauge boson $Z_{mutau}$ which not only gives additional contribution to both $bto s ellell$ transition and $(g-2)_{mu}$ but also provides a crucial annihilation channel for dark matter candidate $rho_1$ of the present scenario. This $rho_1$ is an admixture of CP-even neutral component of $Phi$ and $S$. Our analysis shows that the low mass dark matter regime ($M_{rho_1}lesssim 60$ GeV) is still allowed by the experiments like XENON1T, LHC (via Higgs invisible branching) and Fermi-LAT, making the dark matter phenomenology drastically different from the standard Inert Doublet and the Scalar Singlet models. Furthermore, the present model is also fairly consistent with the observed branching ratio of $Bto X_sgamma$ in $3sigma$ range and is quite capable of explaining neutrino masses and mixings via Type-I seesaw mechanism if we add three right handed neutrinos in the particle spectrum. Finally, we use the latest ATLAS data of non-observation of a resonant $ell^+ell^-$ signal at the 13 TeV LHC to constrain the mass-coupling plane of $Z_{mutau}$.
The observation of neutrino masses, mixing and the existence of dark matter are amongst the most important signatures of physics beyond the Standard Model (SM). In this paper, we propose to extend the SM by a local $L_mu - L_tau$ gauge symmetry, two additional complex scalars and three right-handed neutrinos. The $L_mu - L_tau$ gauge symmetry is broken spontaneously when one of the scalars acquires a vacuum expectation value. The $L_mu - L_tau$ gauge symmetry is known to be anomaly free and can explain the beyond SM measurement of the anomalous muon $({rm g-2})$ through additional contribution arising from the extra $Z_{mutau}$ mediated diagram. Small neutrino masses are explained naturally through the Type-I seesaw mechanism, while the mixing angles are predicted to be in their observed ranges due to the broken $L_mu-L_tau$ symmetry. The second complex scalar is shown to be stable and becomes the dark matter candidate in our model. We show that while the $Z_{mutau}$ portal is ineffective for the parameters needed to explain the anomalous muon $({rm g-2})$ data, the correct dark matter relic abundance can easily be obtained from annihilation through the Higgs portal. Annihilation of the scalar dark matter in our model can also explain the Galactic Centre gamma ray excess observed by Fermi-LAT. We show the predictions of our model for future direct detection experiments and neutrino oscillation experiments.
Positron excess upto energies $sim$350 GeV has been observed by AMS-02 result and it is consistent with the positron excess observed by PAMELA upto 100 GeV. There is no observed excess of anti-protons over the expected CR background. We propose a leptophilic dark matter with an $U(1)_{L_{mu}-L_{tau}}$ gauge extension of MSSM. The dark matter is an admixture of the $L_{mu}-L_{tau}$ gaugino and fermionic partners of the extra $SU(2)$ singlet Higgs boson, which break the $L_{mu}-L_{tau}$ symmetry. We construct the SM$otimes U(1)_{ L_{mu}-L_{tau}}$ SUSY model which provides the correct relic density of dark matter and is consistent with constrain on $Z$ from LHC. The large dark matter annihilation cross-section into $mu^{+}mu^{-}$ and $tau^{+}tau^{-}$, needed to explain PAMELA and AMS-02 is achieved by Breit-Wigner resonance.
Motivated by the growing evidence for lepton flavour universality violation after the first results from Fermilabs muon $(g-2)$ measurement, we revisit one of the most widely studied anomaly free extensions of the standard model namely, gauged $L_{mu}-L_{tau}$ model, known to be providing a natural explanation for muon $(g-2)$. We also incorporate the presence of dark matter (DM) in this model in order to explain the recently reported electron recoil excess by the XENON1T collaboration. We show that the same neutral gauge boson responsible for generating the required muon $(g-2)$ can also mediate interactions between electron and dark fermions boosted by dark matter annihilation. The required DM annihilation rate into dark fermion require a hybrid setup of thermal and non-thermal mechanisms to generate DM relic density. The tightly constrained parameter space from all requirements remain sensitive to ongoing and near future experiments, keeping the scenario very predictive.
We study an extension of the minimal gauged $L_{mu}-L_{tau}$ model in order to explain the anomalous magnetic moments of muon and electron simultaneously. Presence of an additional scalar doublet $eta$ and an in-built $Z_2$ symmetry under which the right handed singlet fermions and $eta$ are odd, leads to light neutrino mass in scotogenic fashion along with a stable dark matter candidate. In spite of the possibility of having positive and negative contributions to $(g-2)$ from vector boson and charged scalar loops respectively, the minimal scotogenic $L_{mu}-L_{tau}$ model can not explain muon and electron $(g-2)$ simultaneously while being consistent with other experimental bounds. We then extend the model with a vector like lepton doublet which not only leads to a chirally enhanced negative contribution to electron $(g-2)$ but also leads to the popular singlet-doublet fermion dark matter scenario. With this extension, the model can explain both electron and muon $(g-2)$ while being consistent with neutrino mass, dark matter and other direct search bounds. The model remains predictive at high energy experiments like collider as well as low energy experiments looking for charged lepton flavour violation, dark photon searches, in addition to future $(g-2)$ measurements.
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