Confusing nonzero θ13 with nonstandard interactions in the solar neutrino sector (original) (raw)
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Confusing nonzero theta13 with nonstandard interactions in the solar neutrino sector
Phys Rev D, 2009
Solar and KamLAND data are in slight tension when interpreted in the standard two-flavor oscillations framework and this may be alleviated allowing for a nonzero value of the mixing angle θ13. Here we show that, likewise, nonstandard flavor-changing interactions (FCI), possibly intervening in the propagation of solar neutrinos, are equally able to alleviate this tension and therefore constitute a potential source of confusion in the determination of θ13. By performing a full three-flavor analysis of solar and KamLAND data in presence of FCI we provide a quantitative description of the degeneracy existing between θ13 and the vectorial coupling γeτdV characterizing the nonstandard transitions between νe and ντ in the forward scattering process with d-type quarks. We find that couplings with magnitude γeτdV˜10%, compatible with the existing bounds, can mimic the nonzero values of θ13 indicated by the latest analyses.
Constraining nonstandard neutrino-quark interactions with solar, reactor, and accelerator data
Physical Review D, 2009
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.
ON RECONCILING ATMOSPHERIC, LSND, AND SOLAR NEUTRINO-OSCILLATION DATA
Modern Physics Letters A, 1998
The L/E-flatness of the e-like events observed in the recent atmospheric-neutrino data from Super-Kamiokande (SuperK) is interpreted to reflect a new symmetry of the neutrino-oscillation mixing matrix. From that we obtain an analytical set of constraints yielding a class of mixing matrices of the property to simultaneously fit both the Su-perK and the LSND data. The resulting mass squared difference relevant for the LSND experiment is found as 0.3 eV 2 . The discussed symmetry, e.g., carries the nature that expectation values of masses for νµ and ντ are identical. These considerations are purely data dictated. A different framework is then applied to the solar neutrino problem. It is argued that a single sterile neutrino is an unlikely candidate to accommodate the data from the four solar neutrino experiments. A scenario is discussed which violates CPT symmetry, and favors the νe-νe system to belong to the 'self'-'anti-self' charge conjugate construct in the (1/2, 0) ⊕ (0, 1/2) representation space, where the needed helicity flipping amplitudes are preferred, rather than the usual Dirac, or Majorana, constructs. In the presented framework the emerging SuperK data on solar neutrino flux is reconciled with the Homestake, GALLEX, and SAGE experiments. This happens because the former detects not only the solar νe but also, at a lower cross section, the oscillated solar νe; while the latter are sensitive only to the oscillation-diminished solar νe flux. A direct observation of solar νe by SNO will confirm our scenario. Finally, we consider the possibility for flavor-dependent gravitational couplings of neutrinos as emerging out of the noncommutativity of the quantum operators associated with the measurements of energy and flavor.
Status of the solution to the solar neutrino problem based on nonstandard neutrino interactions
2000
We analyze the current status of the solution to the solar neutrino problem based both on: a) non-standard flavor changing neutrino interactions (FCNI) and b) non-universal flavor diagonal neutrino interactions (FDNI). We find that FCNI and FDNI with matter in the sun as well as in the earth provide a good fit not only to the total rate measured by all solar neutrino experiments but also to the day-night and seasonal variations of the event rate, as well as the recoil electron energy spectrum measured by the SuperKamiokande collaboration. This solution does not require massive neutrinos and neutrino mixing in vacuum. Stringent experimental constraints on FCNI from bounds on lepton flavor violating decays and on FDNI from limits on lepton universality violation rule out ν e → ν µ transitions induced by New Physics as a solution to the solar neutrino problem. However, a solution involving ν e → ν τ transitions is viable and could be tested independently by the upcoming Bfactories if flavor violating tau decays would be observed at a rate close to the present upper bounds.
Physics Letters B, 1995
We derive the constraints imposed on neutrino masses and mixing angles by performing a combined analysis of the data from the Los Alamos and the Bugey neutrino oscillation experiments with the assumption of the avormixing solutions to the solar neutrino problem. In a general three-avor mixing scheme we obtain severe constraints on the pattern of masses and avor mixing of neutrinos. For example, we show that in the standard Kobayashi-Maskawa t ype mixing matrix s 2 13 10 2 independent of the choice of the solar neutrino solutions. The constraint from the double decay is also discussed.
Solar and atmospheric neutrino oscillations with three flavors
Physical Review D, 1996
We analyze the solar and the atmospheric neutrino problems in the context of three flavour neutrino oscillations. We assume a mass hierarchy in the vacuum mass eigenvalues µ 2 3 ≫ µ 2 2 ≥ µ 2 1 , but make no approximation regarding the magnitudes of the mixing angles. We find that there are small but continuous bands in the parameter space where the constraints imposed by the current measurements of 71 Ga, 37 Cl and Kamiokande experiments are satisfied at 1σ level. The allowed parameter space increases dramatically if the error bars are enlarged to 1.6σ. The electron neutrino survival probability has different energy dependence in different regions of the parameter space. Measurement of the recoil electron energy spectrum in detectors that use ν−e scattering may distinguish between some of the allowed regions of parameter space. Finally we use the results for the parameter space admitted by the solar neutrinos as an input for the atmospheric neutrino problem and show that there exists a substantial region of parameter space in which both problems can be solved. PACS numbers: 14.60.Gh, 96.60.Kx, 95.30.Cq, 96.40.Tv
Solar neutrinos with three-flavor mixings
Physical Review D, 1993
The recent71Ga solarneutrinoobservationiscombined with the 37CI and Kamiokande-II observations in an analysis forneutrinomasses and mixings. The allowed parameter regionis found formatter enhanced mixings among allthree neutrinoflavors.Distortions of the solarneutrinospectrum unique to threeflavors are possibleand may be observed in continuingand next generationexperiments.
Revising neutrino oscillation parameter space with direct flavor-changing interactions
Physical Review D, 2000
We formulate direct, neutrino flavor-changing interactions in a framework that fits smoothly with the parameterization of two-and three-state mixing of massive neutrino states. We show that even small direct interaction strengths could have important consequences for the interpretation of currently running and proposed oscillation experiments. The oscillation amplitude and the borders of the allowed regions in two-and three-flavor mixing parameter space can be sensitive to the presence of direct interactions when the transition probability is small. We use extensively the high sensitivity of the NOMAD experiment to illustrate potentially large effects from small, direct flavor violation. In the purely leptonic sector, we find that the clean νµ and νe beams from a µ + − µ − collider could provide the sharpest tests of direct flavor violation.
1996
We discuss constraints on three flavor neutrino mixings from the accelerator and reactor experiments, the Kamiokande multi-GeV data, and the solar neutrino observations. The LSND result is excluded at 90\%CL by the constraints imposed by all the data of reactor and accelerator experiments and the Kamiokande multi-GeV data if the mass scale required for the solution to the solar neutrino problem is hierarchically small. The region of a set of the effective two-flavor mixing parameters ($\Delta m^2$, sin22theta\sin^22\thetasin22theta) is given for the channel numurightarrownue\nu_\mu\rightarrow\nu_enumurightarrownue which is allowed at 90\%CL by the multi-GeV Kamiokande data alone.
Journal of High Energy Physics
We explore the implications of the Borexino experiment's real time measurements of the lowest energy part of the neutrino spectrum from the primary pp fusion process up to 0.420 MeV through the 7 Be decay at 0.862 MeV to the pep reaction at 1.44 MeV. We exploit the fact that at such low energies, the large mixing angle solution to the Mikheyev-Smirnov-Wolfenstein matter effects in the sun are small for 7 Be and pep and negligible for pp. Consequently, the neutrinos produced in the sun change their flavor almost entirely through vacuum oscillations during propagation from the sun's surface and through possible nonstandard interactions acting at the solar source and Borexino detector. We combine the different NSI effects at source and detector in a single framework and use the current Borexino data to bound NSI non-universal and flavor-changing parameters at energies below the reach of reactor neutrino experiments. We also study the implication of the current data for the weak-mixing angle at this "low-energy frontier" data from the Borexino experiment, where it is expected to be slightly larger than its value at the Z mass. We find sin 2 θ W = 0.224 ± 0.016, the lowest energy-scale estimate to date. Looking to the future, we use projected sensitivities to solar neutrinos in next generation dedicated solar experiments and direct dark matter detection experiments and find a potential factor five improvement in determination of the weak-mixing angle and up to an order of magnitude improvement in probing the NSI parameters space.