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Bonilla, C., Modak, T., Srivastava, R., & Valle, J. W. F. (2018). U(1)(B3-3L2) gauge symmetry as a simple description of b -> s anomalies. Phys. Rev. D, 98(9), 095002–11pp.
Abstract: We present a simple U(1)(B3-3L2) gauge standard model extension that can easily account for the anomalies in R(K) and R(K*) reported by LHCb. The model is economical in its setup and particle content. Among the standard model fermions, only the third generation quark family and the second generation leptons transform nontrivially under the new U(1)(B3-3L2) symmetry. This leads to lepton nonuniversality and flavor changing neutral currents involving the second and third quark families. We discuss the relevant experimental constraints and some implications.
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Bonilla, C., Ma, E., Peinado, E., & Valle, J. W. F. (2016). Two-loop Dirac neutrino mass and WIMP dark matter. Phys. Lett. B, 762, 214–218.
Abstract: We propose a “scotogenic” mechanism relating small neutrino mass and cosmological dark matter. Neutrinos are Dirac fermions with masses arising only in two-loop order through the sector responsible for dark matter. Two triality symmetries ensure both dark matter stability and strict lepton number conservation at higher orders. A global spontaneously broken U(1) symmetry leads to a physical Diraconthat induces invisible Higgs decays which add up to the Higgs to dark matter mode. This enhances sensitivities to spin-independent WIMP dark matter search below m(h)/2.
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Bonilla, C., & Valle, J. W. F. (2016). Naturally light neutrinos in Diracon model. Phys. Lett. B, 762, 162–165.
Abstract: We propose a simple model for Dirac neutrinos where the smallness of neutrino mass follows from a parameter kappa whose absence enhances the symmetry of the theory. Symmetry breaking is performed in a two-doublet Higgs sector supplemented by a gauge singlet scalar, realizing an accidental global U(1) symmetry. Its spontaneous breaking at the few TeV scale leads to a physical Nambu -Goldstone – boson the Diracon, denoted D – which is restricted by astrophysics and induces invisible Higgs decays such as h -> DD. The scheme provides a rich, yet very simple scenario for symmetry breaking studies at colliders such as the LHC.
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Bonilla, C., Lamprea, J. M., Peinado, E., & Valle, J. W. F. (2018). Flavour-symmetric type-II Dirac neutrino seesaw mechanism. Phys. Lett. B, 779, 257–261.
Abstract: We propose a Standard Model extension with underlying A(4) flavour symmetry where small Dirac neutrino masses arise from a Type-II seesaw mechanism. The model predicts the “golden” flavour-dependent bottom-tau mass relation, requires an inverted neutrino mass ordering and non-maximal atmospheric mixing angle. Using the latest neutrino oscillation global fit[ 1] we derive restrictions on the oscillation parameters, such as a correlation between delta(CP) and m(nu lightest).
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Bonilla, C., Centelles Chulia, S., Cepedello, R., Peinado, E., & Srivastava, R. (2020). Dark matter stability and Dirac neutrinos using only standard model symmetries. Phys. Rev. D, 101(3), 033011–5pp.
Abstract: We provide a generic framework to obtain stable dark matter along with naturally small Dirac neutrino masses generated at the loop level. This is achieved through the spontaneous breaking of the global U(1)(B-L) symmetry already present in the standard model. The U(1)(B-L) symmetry is broken down to a residual even Z(n) (n >= 4) subgroup. The residual Z(n) symmetry simultaneously guarantees dark matter stability and protects the Dirac nature of neutrinos. The U(1)(B-L) symmetry in our setup is anomaly free and can also be gauged in a straightforward way. Finally, we present an explicit example using our framework to show the idea in action.
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Bonilla, C., Sokolowska, D., Darvishi, N., Diaz-Cruz, J. L., & Krawczyk, M. (2016). IDMS: inert dark matter model with a complex singlet. J. Phys. G, 43(6), 065001–39pp.
Abstract: We study an extension of the inert doublet model (IDM) that includes an extra complex singlet of the scalars fields, which we call the IDMS. In this model there are three Higgs particles, among them a SM-like Higgs particle, and the lightest neutral scalar, from the inert sector, remains a viable dark matter (DM) candidate. We assume a non-zero complex vacuum expectation value for the singlet, so that the visible sector can introduce extra sources of CP violation. We construct the scalar potential of IDMS, assuming an exact Z(2) symmetry, with the new singlet being Z(2)-even, as well as a softly broken U(1) symmetry, which allows a reduced number of free parameters in the potential. In this paper we explore the foundations of the model, in particular the masses and interactions of scalar particles for a few benchmark scenarios. Constraints from collider physics, in particular from the Higgs signal observed at the Large Hadron Collider with M-h approximate to 125 GeV, as well as constraints from the DM experiments, such as relic density measurements and direct detection limits, are included in the analysis. We observe significant differences with respect to the IDM in relic density values from additional annihilation channels, interference and resonance effects due to the extended Higgs sector.
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