arXiv subjects
Publications and source records attributed to O. G. Miranda.
Several models of neutrino masses predict the existence of neutral heavy leptons. Here, we review current constraints on heavy neutrinos and apply a new formalism separating new physics from Standard Model. We discuss also the indirect effect of extra heavy neutrinos in oscillation experiments.
Interest in light dark matter candidates has recently increased in the literature; some of these works consider the role of additional neutrinos, either active or sterile. Furthermore, extragalactic neutrinos have been detected with energies higher than have ever been reported before. This opens a new window of opportunities to the study of neutrino properties that were unreachable up to now. We investigate how an interaction potential between neutrinos and dark matter might induce a resonant enhancement in the oscillation probability, an effect that may be tested with future neutrino data.
Gamma-ray bursts (GRBs) are expected to provide a source of ultra high energy cosmic rays, accompanied with potentially detectable neutrinos at neutrino telescopes. Recently, IceCube has set an upper bound on this neutrino flux well below theoretical expectation. We investigate whether this mismatch between expectation and observation can be due to neutrino decay. We demosntrate the phenomenological consistency and theoretical plausibility of the neutrino decay hypothesis. A potential implication is the observability of majoron-emitting neutrinoless double beta decay.
Many extensions to the Standard Model imply the existence of new charged scalar Higgs bosons. We study the contribution of a general scalar or pseudoscalar coupling for the neutrino-electron scattering. We take a phenomenological approach in order to obtain model independent limits to the couplings that arise in this picture. We illustrate the reach of the constraints by studying the particular case of the type III two Higgs doublet model, where we have found new constraints to some elements of the Yukawa couplings mixing matrix ($|Y_{ee}| \leq 1 \times 10^{-1}$ and $|Y_{eμ}| \leq 7\times10^{-2}$ at 90% CL).
Motivated by the stringent flux limits for UHE neutrinos coming from gamma ray burst or active galactic nuclei, we explore the possibility that the active neutrinos generated in such astrophysical objects could oscillate to sterile right handed states due to a neutrino magnetic moment mu_nu. We find that a value as small as mu_nu ~1E-15 mu_B could produce such a transition thanks to the intense magnetic fields that are expected in these objects.
We have analyzed the electron anti-neutrino scattering off electrons and the electron anti-neutrino-nuclei coherent scattering in order to obtain constraints on tensorial couplings. We have studied the formalism of non-standard interactions (NSI), as well as the case of Unparticle physics. For our analysis we have focused on the recent TEXONO collaboration results and we have obtained current constraints to possible electron anti-neutrino-electron tensorial couplings in both new physics formalisms. The possibility of measuring for the first time electron anti-neutrino-nucleus coherent scattering and its potential to further constrain electron anti-neutrino-quark tensorial couplings is also discussed.
Several proposals for studying neutrinos with large detectors are currently under discussion. We suggest that they could provide a precise measurement of the electroweak mixing angle as well as a probe for new physics, such as non-standard neutrino interactions (NSI), and the electroweak gauge structure. We illustrate this explicitly for the case of the LENA proposal, either with an artificial radioactive source or by using the solar neutrino flux.
We study the possible suppression of the extragalactic neutrino flux due to a nonstandard interaction during its propagation. In particular, we study neutrino interaction with an ultra-light scalar field dark matter. It is shown that the extragalactic neutrino flux may be suppressed by such an interaction, leading to a new mechanism to reduce the ultra-high energy neutrino flux. We study both the cases of non-self-conjugate as well as self-conjugate dark matter. In the first case, the suppression is independent of the neutrino and dark matter masses. We conclude that care must be taken when explaining limits on the neutrino flux through source acceleration mechanisms only, since there could be other mechanisms for the reduction of the neutrino flux.
The search for new interactions of neutrinos beyond those of the Standard Model may help to elucidate the mechanism responsible for neutrino masses. Here we combine existing accelerator neutrino data with restrictions coming from a recent atmospheric neutrino data analysis in order to lift parameter degeneracies and improve limits on new interactions of muon neutrinos with quarks. In particular we re-consider the results of the NuTeV experiment in view of a new evaluation of its systematic uncertainties. We find that, although constraints for muon neutrinos are better than those applicable to tau or electron neutrinos, they lie at the few $\times 10^{-2}$ level, not as strong as previously believed. We briefly discuss prospects for further improvement.
We present a reanalysis of nonstandard neutrino-down-quark interactions of electron and tau neutrinos using solar, reactor and accelerator data. In addition updating the analysis by including new solar data from SNO phase III and Borexino, as well as new KamLAND data and solar fluxes, a key role is played in our analysis by the combination of these results with the CHARM data. The latter allows us to better constrain the axial and axial-vector electron and tau-neutrino nonstandard interaction parameters characterizing the deviations from the Standard Model predictions.
We show how neutrino data can be used in order to constrain the free parameters of possible extensions to the standard model of elementary particles (SM). For definiteness, we focus in the recently proposed unparticle scenario. We show that neutrino data, in particular the MUNU experiment, can set stronger bounds than previous reported limits in the scale dimension parameter for certain region (d > 1.5). We compute the sensitivity of future neutrino experiments to unparticle physics such as future neutrino-electron scattering detectors, coherent neutrino-nuclei scattering as well as the ILC . In particular, we show that the measurement of coherent reactor neutrino scattering off nuclei provide a good sensitivity to the couplings of unparticle interaction with neutrinos and quarks.Finally our results are compared with the current astrophysical limits.
Motivated by the interest in searches for violation of CPT invariance, we study its possible effects in the flavour ratios of high-energy neutrinos coming from cosmic accelerators. In particular, we focus on the effect of an energy independent new physics contribution to the neutrino flavour oscillation phase and explore whether it is observable in future detectors. Such a contribution could be related not only to CPT violation but also to a nonuniversal coupling of neutrinos to a torsion field. We conclude that this extra phase contribution only becomes observable, in the best case, at energies greater than 10^{16.5} GeV, which is about five orders of magnitude higher than the most energetic cosmological neutrinos to be detected in the near future. Therefore, if these effects are present only in the oscillation phase, they are going to be unobservable, unless a new mechanism or source capable to produce neutrinos of such energy were detected.
Most neutrino mass extensions of the standard electroweak model entail non-standard interactions which, in the low energy limit, can be parametrized in term of effective four-fermion operators $ν_αν_β\bar f f $. Typically of sub-weak strength, $ε_{αβ} G_F$, these are characterized by dimensionless coupling parameters, $ε_{αβ}$, which may be relatively sizeable in a wide class of schemes. Here we focus on non-universal (NU) flavor conserving couplings ($α= β$) with electrons ($f = e$) and analyse their impact on the phenomenology of solar neutrinos. We consistently take into account their effect both at the level of propagation where they modify the standard MSW behavior, and at the level of detection, where they affect the cross section of neutrino elastic scattering on electrons. We find limits which are comparable to other existing model-independent constraints.
We have constrained unparticle interactions with neutrinos and electrons using available data on neutrino-electron elastic scattering and the four CERN LEP experiments data on mono photon production. We have found that, for neutrino-electron elastic scattering, the MUNU experiment gives better constraints than previous reported limits in the region d>1.5. The results are compared with the current astrophysical limits, pointing out the cases where these limits may or may not apply. We also discuss the sensitivity of future experiments to unparticle physics. In particular, we show that the measurement of coherent reactor neutrino scattering off nuclei could provide a good sensitivity to the couplings of unparticle interaction with neutrinos and quarks. We also discuss the case of future neutrino-electron experiments as well as the International Linear Collider.
New limits on the weak mixing angle and on the electron neutrino effective charge radius in the low energy regime, below 100 MeV, are obtained from a combined fit of all electron-(anti)neutrino electron elastic scattering measurements. We have included the recent TEXONO measurement with a CsI (Tl) detector. Only statistical error of this measurement has been taken into account. Weak mixing angle is found to be sin^2 theta_W = 0.255 +0.022 -0.023. The electron neutrino effective charge radius squared is bounded to be r^2 = (0.9 +0.9 -1.0) x 10^{-32} cm^2. The sensitivity of future low energy neutrino experiments to nonstandard interactions of neutrinos with quarks is also discussed.
We present a detailed analysis on nonstandard neutrino interactions (NSI) with electrons including all muon and electron (anti)-neutrino data from existing accelerators and reactors, in conjunction with the ``neutrino counting'' data (e- e+ -> nu nu gamma) from the four LEP collaborations. First we perform a one-parameter-at-a-time analysis, showing how most constraints improve with respect to previous results reported in the literature. We also present more robust results where the NSI parameters are allowed to vary freely in the analysis. We show the importance of combining LEP data with the other experiments in removing degeneracies in the global analysis constraining flavor-conserving NSI parameters which, at 90 % and 95 % C.L., must lie within unique allowed regions. Despite such improved constraints, there is still substantial room for improvement, posing a big challenge for upcoming experiments.
We have obtained a new limit on the electron neutrino effective charge radius from a new evaluation of the weak mixing angle by a combined fit of all electron-(anti)neutrino electron elastic scattering measurements. Weak mixing angle is found to be sin^2 theta_W=0.259 \pm 0.025 in the low energy regime below 100 MeV. The electron neutrino charge radius squared is bounded to be in the range -0.13 10^-32 cm^2 < r^2 < 3.32 10^-32 cm^2 at 90 % C.L. Both results improve previously published analyses. We also discuss perspectives of future experiments to improve these constraints.
We study the sensitivity of future low energy neutrino experiments to extra neutral gauge bosons, leptoquarks and R-parity breaking interactions. We focus on future proposals to measure coherent neutrino-nuclei scattering and neutrino-electron elastic scattering. We introduce a new comparative analysis between these experiments and show that in different types of new physics it is possible to obtain competitive bounds to those of present and future collider experiments. For the cases of leptoquarks and R-parity breaking interactions we found that the expected sensitivity for most of the future low energy experimental setups is better than the current constraints.