Center for Neutrino Physics
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Browsing Center for Neutrino Physics by Subject "Beyond Standard Model"
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- Analytical approximation of the neutrino oscillation matter effects at large theta (13)Agarwalla, S. K.; Kao, Y.; Takeuchi, Tatsu (Springer, 2014-04-07)
- B-decay anomalies and scalar leptoquarks in unified Pati-Salam models from noncommutative geometryAydemir, Ufuk; Minic, Djordje; Sun, Chen; Takeuchi, Tatsu (Springer, 2018-09-19)Motivated by possible scalar-leptoquark explanations of the recently reported B-decay anomalies, we investigate whether the required leptoquarks can be accommodated within models based on noncommutative geometry (NCG). The models considered have the gauge structure of Pati-Salam models, SU(4) x SU(2)(L) x SU(2)(R), with gauge coupling unification at a single scale. In one of the models, we find a unique scalar leptoquark with quantum numbers (3, 1, -1/3)(321), originating from a complex multiplet (6, 1, 1)(422), which can potentially explain the B-decay anomalies if its mass is on the order of a few TeV. The unification of couplings can be realized with the inclusion of a single step of intermediate symmetry breaking. The scalar leptoquark under consideration does not contribute to proton decay due to the absence of diquark couplings, as dictated by the underlying noncommutative geometry.
- Combining dark matter detectors and electron-capture sources to hunt for new physics in the neutrino sectorColoma, Pilar; Huber, Patrick; Link, Jonathan M. (Springer, 2014-11-10)In this letter we point out the possibility to study new physics in the neutrino sector using dark matter detectors based on liquid xenon. These are characterized by very good spatial resolution and extremely low thresholds for electron recoil energies. When combined with a radioactive nu e source, both features in combination allow for a very competitive sensitivity to neutrino magnetic moments and sterile neutrino oscillations. We find that, for realistic values of detector size and source strength, the bound on the neutrino magnetic moment can be improved by an order of magnitude with respect to the present value. Regarding sterile neutrino searches, we find that most of the gallium anomaly could be explored at the 95% confidence level just using shape information.
- Constraining non-standard interactions of the neutrino with BorexinoAgarwalla, S. K.; Lombardi, Francesco; Takeuchi, Tatsu (Springer, 2012-12-01)We use the Borexino 153.6 ton·year data to place constraints on non-standard neutrino-electron interactions, taking into account the uncertainties in the 7Be solar neutrino flux and the mixing angle θ 23, and backgrounds due to 85Kr and 210Bi β-decay. We find that the bounds are comparable to existing bounds from all other experiments. Further improvement can be expected in Phase II of Borexino due to the reduction in the 85Kr background.
- DUNE sensitivities to the mixing between sterile and tau neutrinosColoma, Pilar; Forero, David V.; Parke, Stephen J. (Springer, 2018-07-11)Light sterile neutrinos can be probed in a number of ways, including electroweak decays, cosmology and neutrino oscillation experiments. At long-baseline experiments, the neutral-current data is directly sensitive to the presence of light sterile neutrinos: once the active neutrinos have oscillated into a sterile state, a depletion in the neutral-current data sample is expected since they do not interact with the Z boson. This channel offers a direct avenue to probe the mixing between a sterile neutrino and the tau neutrino, which is currently only weakly constrained by current data from SuperK, IceCube and NOvA, however, these constrains will continue to improve as more data is collected by these experiments. In this work, we study the potential of the DUNE experiment to constrain the mixing angle which parametrizes this mixing, theta(34), through the observation of neutral-current events at the far detector. We find that DUNE will be able to improve significantly over current constraints thanks to its large statistics and excellent discrimination between neutral- and charged-current events.
- Higgs inflation, vacuum stability, and leptogenesisBarrie, Neil D.; Sugamoto, Akio; Takeuchi, Tatsu; Yamashita, Kimiko (2020-08-17)We consider the introduction of a complex scalar field carrying a global lepton number charge to the Standard Model and the Higgs inflation framework. The conditions are investigated under which this model can simultaneously ensure Higgs vacuum stability up to the Planck scale, successful inflation, non-thermal Leptogenesis via the pendulum mechanism, and light neutrino masses. These can be simultaneously achieved when the scalar lepton is minimally coupled to gravity, that is, when standard Higgs inflation and reheating proceed without the interference of the additional scalar degrees of freedom. If the scalar lepton also has a non-minimal coupling to gravity, a multi-field inflation scenario is induced, with interesting interplay between the successful inflation constraints and those from vacuum stability and Leptogenesis. The parameter region that can simultaneously achieve the above goals is explored.
- Probing non-standard interactions at Daya BayAgarwalla, Sanjib Kumar; Bagchi, Partha; Forero, David V.; Tortola, Mariam (Springer, 2015-07-13)In this article we consider the presence of neutrino non-standard interactions (NSI) in the production and detection processes of reactor antineutrinos at the Daya Bay experiment. We report for the first time, the new constraints on the flavor non-universal and flavor universal charged-current NSI parameters, estimated using the currently released 621 days of Daya Bay data. New limits are placed assuming that the new physics effects are just inverse of each other in the production and detection processes. With this special choice of the NSI parameters, we observe a shift in the oscillation amplitude without distorting the L/E pattern of the oscillation probability. This shift in the depth of the oscillation dip can be caused by the NSI parameters as well as by theta(13), making it quite difficult to disentangle the NSI effects from the standard oscillations. We explore the correlations between the NSI parameters and theta(13) that may lead to significant deviations in the reported value of the reactor mixing angle with the help of iso-probability surface plots. Finally, we present the limits on electron, muon/tau, and flavor universal (FU) NSI couplings with and without considering the uncertainty in the normalization of the total event rates. Assuming a perfect knowledge of the event rates normalization, we find strong upper bounds similar to 0.1% for the electron and FU cases improving the present limits by one order of magnitude. However, for a conservative error of 5% in the total normalization, these constraints are relaxed by almost one order of magnitude.
- Running of oscillation parameters in matter with flavor-diagonal non-standard interactions of the neutrinoAgarwalla, S. K.; Kao, Y.; Saha, D.; Takeuchi, Tatsu (Springer, 2015-11-05)
- Searches for decays of new particles in the DUNE Multi-Purpose near DetectorBerryman, Jeffrey M.; de Gouvea, Andre; Fox, Patrick J.; Kayser, Boris J.; Kelly, Kevin J.; Raaf, Jennifer L. (2020-02-27)One proposed component of the upcoming Deep Underground Neutrino Experiment (DUNE) near detector complex is a multi-purpose, magnetized, gaseous argon time projection chamber: the Multi-Purpose Detector (MPD). We explore the new-physics potential of the MPD, focusing on scenarios in which the MPD is significantly more sensitive to new physics than a liquid argon detector, specifically searches for semi-long-lived particles that are produced in/near the beam target and decay in the MPD. The specific physics possibilities studied are searches for dark vector bosons mixing kinetically with the Standard Model hypercharge group, leptophilic vector bosons, dark scalars mixing with the Standard Model Higgs boson, and heavy neutral leptons that mix with the Standard Model neutrinos. We demonstrate that the MPD can extend existing bounds in most of these scenarios. We illustrate how the ability of the MPD to measure the momentum and charge of the final state particles leads to these bounds.
- Searching for sterile neutrinos at the ESSνSBBlennow, Mattias; Coloma, Pilar; Fernandez-Martinez, Enrique (Springer, 2014-12-17)The ESS nu SB project is a proposed neutrino oscillation experiment based on the European Spallation Source with the search for leptonic CP violation as its main aim. In this letter we show that a near detector at around 1 km distance from the beamline is not only very desirable for keeping the systematic errors affecting the CP search under control, but would also provide a significant sensitivity probe for sterile neutrino oscillations in the region of the parameter space favored by the long-standing LSND anomaly. We find that the effective mixing angle theta(mu e) can be probed down to sin(2)(2 theta(mu e)) similar or equal to 2(8) . 10(-3) at 5 sigma assuming 15% bin-to-bin (un) correlated systematics.
- Sizable NSI from the SU(2)(L) scalar doublet-singlet mixing and the implications in DUNEForero, David V.; Huang, Wei-Chih (Springer, 2017-03-03)We propose a novel and simple mechanism where sizable effects of non-standard interactions (NSI) in neutrino propagation are induced from the mixing between an electrophilic second Higgs doublet and a charged singlet. The mixing arises from a dimensionful coupling of the scalar doublet and singlet to the standard model Higgs boson. In light of the small mass, the light mass eigenstate from the doublet-singlet mixing can generate much larger NSI than those induced by the heavy eigenstate. We show that a sizable NSI epsilon(e tau) (similar to 0.3) can be attained without being excluded by a variety of experimental constraints. Furthermore, we demonstrate that NSI can mimic effects of the Dirac CP phase in the neutrino mixing matrix but they can potentially be disentangled by future long-baseline neutrino experiments, such as the Deep Underground Neutrino Experiment (DUNE).
- Statistical significance of the sterile-neutrino hypothesis in the context of reactor and gallium dataBerryman, Jeffrey M.; Coloma, Pilar; Huber, Patrick; Schwetz, Thomas; Zhou, Albert (Springer, 2022-02-08)We evaluate the statistical significance of the 3+1 sterile-neutrino hypothesis using nu(e) and (nu) over bar (e) disappearance data from reactor, solar and gallium radioactive source experiments. Concerning the latter, we investigate the implications of the recent BEST results. For reactor data we focus on relative measurements independent of flux predictions. For the problem at hand, the usual chi(2)-approximation to hypothesis testing based on Wilks' theorem has been shown in the literature to be inaccurate. We therefore present results based on Monte Carlo simulations, and find that this typically reduces the significance by roughly 1 sigma with respect to the naive expectation. We find no significant indication in favor of sterile-neutrino oscillations from reactor data. On the other hand, gallium data (dominated by the BEST result) show more than 5 sigma of evidence supporting the sterile-neutrino hypothesis, favoring oscillation parameters in agreement with constraints from reactor data. This explanation is, however, in significant tension (similar to 3 sigma) with solar neutrino experiments. In order to assess the robustness of the signal for gallium experiments we present a discussion of the impact of cross-section uncertainties on the results.
- Sterile neutrinos and the global reactor antineutrino datasetBerryman, Jeffrey M.; Huber, Patrick (2021-01-26)We present results from global fits to the available reactor antineutrino dataset, as of Fall 2019, to determine the global preference for a fourth, sterile neutrino. We have separately considered experiments that measure the integrated inverse-beta decay (IBD) rate from those that measure the energy spectrum of IBD events at one or more locations. The evidence that we infer from rate measurements varies between less than or similar to 3 sigma and negligible depending on the reactor antineutrino flux model employed. Moreover, we find that spectral ratios ostensibly imply greater than or similar to 3 sigma evidence, consistent with previous work, though these measurements are known to be plagued by issues related to statistical interpretation; these results should therefore be viewed cautiously. The software used is the newly developed GLoBESfit tool set which is based on the publicly available GLoBES framework and will be released as open-source software.