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Marzocca, D., Petcov, S. T., Romanino, A., & Sevilla, M. C. (2013). Nonzero |U_e3| from charged lepton corrections and the atmospheric neutrino mixing angle. J. High Energy Phys., 05(5), 073–27pp.
Abstract: After the successful determination of the reactor neutrino mixing angle theta(13) not equal 0.16 not equal 0, a new feature suggested by the current neutrino oscillation data is a sizeable deviation of the atmospheric neutrino mixing angle theta(23) from pi/4. Using the fact that the neutrino mixing matrix U = (UeU nu)-U-dagger, where U-e and U-nu result from the diagonalisation of the charged lepton and neutrino mass matrices, and assuming that U-nu has a i) bimaximal (BM), H) tri-bimaximal (TBM) form, or else Hi) corresponds to the conservation of the lepton charge L' = L-e – L μ- L-tau (LC), we investigate quantitatively what are the minimal forms of U-e, in terms of angles and phases it contains, that can provide the requisite corrections to U-nu so that theta(13), theta(23) and the solar neutrino mixing angle theta(12) have values compatible with the current data. Two possible orderings of the 12 and the 23 rotations in U-e, “standard” and “inverse”, are considered. The results we obtain depend strongly on the type of ordering. In the case of “standard” ordering, in particular, the Dirac CP violation phase delta, present in U, is predicted to have a value in a narrow interval around i) delta similar or equal to pi in the BM (or LC) case, H) delta congruent to 3 pi/2 or pi/2 in the TBM case, the CP conserving values delta = 0, pi, 2 pi being excluded in the TBM case at more than 4 sigma.
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Martinez-Mirave, P., Tamborra, I., & Tortola, M. (2024). The Sun and core-collapse supernovae are leading probes of the neutrino lifetime. J. Cosmol. Astropart. Phys., 05(5), 002–39pp.
Abstract: The large distances travelled by neutrinos emitted from the Sun and core -collapse supernovae together with the characteristic energy of such neutrinos provide ideal conditions to probe their lifetime, when the decay products evade detection. We investigate the prospects of probing invisible neutrino decay capitalising on the detection of solar and supernova neutrinos as well as the diffuse supernova neutrino background (DSNB) in the next -generation neutrino observatories Hyper-Kamiokande, DUNE, JUNO, DARWIN, and RES-NOVA. We find that future solar neutrino data will be sensitive to values of the lifetime -to -mass ratio tau 1 /m 1 and tau 2 /m 2 of O(10 – 1 -10 – 2 ) s/eV. From a core -collapse supernova explosion at 10 kpc, lifetime -to -mass ratios of the three mass eigenstates of O(10 5 ) s/eV could be tested. After 20 years of data taking, the DSNB would extend the sensitivity reach of tau 1 /m 1 to 10 8 s/eV. These results promise an improvement of about 6-15 orders of magnitude on the values of the decay parameters with respect to existing limits.
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Mangano, G., Miele, G., Pastor, S., Pisanti, O., & Sarikas, S. (2011). Constraining the cosmic radiation density due to lepton number with Big Bang Nucleosynthesis. J. Cosmol. Astropart. Phys., 03(3), 035–18pp.
Abstract: The cosmic energy density in the form of radiation before and during Big Bang Nucleosynthesis (BBN) is typically parameterized in terms of the effective number of neutrinos N-eff. This quantity, in case of no extra degrees of freedom, depends upon the chemical potential and the temperature characterizing the three active neutrino distributions, as well as by their possible non-thermal features. In the present analysis we determine the upper bounds that BBN places on N-eff from primordial neutrino-antineutrino asymmetries, with a careful treatment of the dynamics of neutrino oscillations. We consider quite a wide range for the total lepton number in the neutrino sector, eta(nu) = eta(nu e) + eta(nu mu) + eta(nu tau) and the initial electron neutrino asymmetry eta(in)(nu e), solving the corresponding kinetic equations which rule the dynamics of neutrino (antineutrino) distributions in phase space due to collisions, pair processes and flavor oscillations. New bounds on both the total lepton number in the neutrino sector and the nu(e)-(nu) over bar (e) asymmetry at the onset of BBN are obtained fully exploiting the time evolution of neutrino distributions, as well as the most recent determinations of primordial H-2/H density ratio and He-4 mass fraction. Note that taking the baryon fraction as measured by WMAP, the H-2/H abundance plays a relevant role in constraining the allowed regions in the eta(nu)-eta(in)(nu e) plane. These bounds fix the maximum contribution of neutrinos with primordial asymmetries to N-eff as a function of the mixing parameter theta(13), and point out the upper bound N-eff less than or similar to 3.4. Comparing these results with the forthcoming measurement of N-eff by the Planck satellite will likely provide insight on the nature of the radiation content of the universe.
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Mangano, G., Miele, G., Pastor, S., Pisanti, O., & Sarikas, S. (2012). Updated BBN bounds on the cosmological lepton asymmetry for non-zero theta(13). Phys. Lett. B, 708(1-2), 1–5.
Abstract: We discuss the bounds on the cosmological lepton number from Big Bang Nucleosynthesis (BBN), in light of recent evidences for a large value of the neutrino mixing angle theta(13), sin(2) theta(13) greater than or similar to 0.01 at 2 sigma. The largest asymmetries for electron and mu, tau neutrinos compatible with He-4 and H-2 primordial yields are computed versus the neutrino mass hierarchy and mixing angles. The flavour oscillation dynamics is traced till the beginning of BBN and neutrino distributions after decoupling are numerically computed. The latter contains in general, non-thermal distortion due to the onset of flavour oscillations driven by solar squared mass difference in the temperature range where neutrino scatterings become inefficient to enforce thermodynamical equilibrium. Depending on the value of theta(13), this translates into a larger value for the effective number of neutrinos, N-eff. Upper bounds on this parameter are discussed for both neutrino mass hierarchies. Values for N-eff which are large enough to be detectable by the Planck experiment are found only for the (presently disfavoured) range sin(2) theta(13) <= 0.01.
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Mandal, S., Srivastava, R., & Valle, J. W. F. (2021). Electroweak symmetry breaking in the inverse seesaw mechanism. J. High Energy Phys., 03(3), 212–28pp.
Abstract: We investigate the stability of Higgs potential in inverse seesaw models. We derive the full two-loop RGEs of the relevant parameters, such as the quartic Higgs self-coupling, taking thresholds into account. We find that for relatively large Yukawa couplings the Higgs quartic self-coupling goes negative well below the Standard Model instability scale similar to 10(10) GeV. We show, however, that the “dynamical” inverse seesaw with spontaneous lepton number violation can lead to a completely consistent and stable Higgs vacuum up to the Planck scale.
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