Batra, A., Câmara, H. B., Joaquim, F. R., Nath, N., Srivastava, R., & Valle, J. W. F. (2025). Axion framework with color-mediated Dirac neutrino masses. Phys. Lett. B, 868, 139629–11pp.
Abstract: We propose a KSVZ-type axion framework in which vector-like quarks (VLQ) and colored scalars generate Dirac neutrino masses radiatively. The global Peccei-Quinn symmetry (under which the exotic fermions are charged) addresses the strong CP problem and ensures the Dirac nature of neutrinos. The axion also accounts for the observed cosmological dark matter. We systematically explore all viable VLQ representations. Depending on the specific scenario, the framework predicts distinct axion-to-photon couplings, testable through haloscope and helioscope experiments, as well as potentially significant flavor-violating quark-axion interactions.
|
de Anda, F. J., Nath, N., Valle, J. W. F., & Vaquera-Araujo, C. A. (2020). Probing the predictions of an orbifold theory of flavor. Phys. Rev. D, 101(11), 116012–8pp.
Abstract: We examine the implications of a recently proposed theory of fermion masses and mixings in which an A(4) family symmetry emerges from orbifold compactification. We analyze two variant schemes concerning their predictions for neutrino oscillations, neutrinoless double-beta decay, and the golden quark-lepton unification mass relation. We find that upcoming experiments DUNE as well as LEGEND and nEXO offer good chances of exploring a substantial region of neutrino parameters.
|
Ding, G. J., Nath, N., Srivastava, R., & Valle, J. W. F. (2019). Status and prospects of 'bi-large' leptonic mixing. Phys. Lett. B, 796, 162–167.
Abstract: Bi-large patterns for the leptonic mixing matrix are confronted with current neutrino oscillation data. We analyse the status of these patterns and determine, through realistic simulations, the potential of the upcoming long-baseline experiment DUNE in testing bi-large ansatze and discriminating amongst them.
|
Hati, C., Leite, J., Nath, N., & Valle, J. W. F. (2025). QCD axion, color-mediated neutrino masses, and B+ → K+ + Emiss anomaly. Phys. Rev. D, 111(1), 015038–16pp.
Abstract: Motivated by the recent Belle II result indicating a 2.76 excess of B+-* K+ + Emiss events compared to the Standard Model (SM) prediction for B+-* K+vv<overline>, we explore an explanation to this anomaly based on a Kim-Shifman-Vainshtein-Zakharov-type QCD axion model featuring a Peccei-Quinn (PQ) symmetry breaking at high scale, which can provide a solution to the strong CP problem with dark matter relic abundance. The model contains a PQ-charged scalar leptoquark which can interact with the SM quarks only via mass mixing of the latter with vectorlike quarks. The mixing between SM and vectorlike quarks is determined by the PQ mass scales and can explain the excess B+-* K+ + Emiss events while respecting other flavor constraints. The same PQ-charged scalar leptoquarks and vectorlike quarks also mediate the two-loop radiative neutrino masses.
|
Kumar, R., Nath, N., & Srivastava, R. (2024). Cutting the scotogenic loop: adding flavor to dark matter. J. High Energy Phys., 12(12), 036–37pp.
Abstract: We introduce a framework for hybrid neutrino mass generation, wherein scotogenic dark sector particles, including dark matter, are charged non-trivially under the A4 flavor symmetry. The spontaneous breaking of the A4 group to residual Z2 subgroup results in the “cutting” of the radiative loop. As a consequence the neutrinos acquire mass through the hybrid “scoto-seesaw” mass mechanism, combining aspects of both the tree-level seesaw and one-loop scotogenic mechanisms, with the residual Z2 subgroup ensuring the stability of the dark matter. The flavor symmetry also leads to several predictions including the normal ordering of neutrino masses and “generalized μ- tau reflection symmetry” in leptonic mixing. Additionally, it gives testable predictions for neutrinoless double beta decay and a lower limit on the lightest neutrino mass. Finally, A4 -> Z2 breaking also leaves its imprint on the dark sector and ties it with the neutrino masses and mixing. The model allows only scalar dark matter, whose mass has a theoretical upper limit of less than or similar to 600 GeV, with viable parameter space satisfying all dark matter constraints, available only up to about 80 GeV. Conversely, fermionic dark matter is excluded due to constraints from the neutrino sector. Various aspects of this highly predictive framework can be tested in both current and upcoming neutrino and dark matter experiments.
|
Nath, N., Srivastava, R., & Valle, J. W. F. (2019). Testing generalized CP symmetries with precision studies at DUNE. Phys. Rev. D, 99(7), 075005–13pp.
Abstract: We examine the capabilities of the DUNE experiment in probing leptonic CP violation within the framework of theories with generalized CP symmetries characterized by the texture zeros of the corresponding CP transformation matrices. We investigate DUNE's potential to probe the two least known oscillation parameters, the atmospheric mixing angle theta(23) and the Dirac CP phase delta(CP). We fix theory-motivated benchmarks for (sin(2)theta(23), delta(CP)) and take them as true values in our simulations. Assuming 3.5 years of neutrino running plus 3.5 years in the antineutrino mode, we show that in all cases DUNE can significantly constrain and in certain cases rule out the generalized CP texture zero patterns.
|
