We present the results of a systematic study of the constraints on neutrino neutral-current nonstandard interactions (NSIs) that can be obtained from the analysis of the COHERENT spectral and ...temporal data. First, we consider the general case in which all ten relevant neutral-current NSI parameters are considered as free. We show that they are very weakly constrained by the COHERENT data because of possible cancellations between the up and down quark contributions. However, the up-down average parameters are relatively well constrained, and the strongest constraints are obtained for an appropriate linear combination of up and down NSI parameters. We also consider the case in which there are only NSIs with either up or down quarks, and we show that the LMA-Dark fit of solar neutrino data is excluded at 5.6σ and 7.2σ, respectively, for NSIs with up and down quarks. We finally present the tight constraints that can be obtained on each NSI parameter if it is the dominant one, assuming that the effects of the others are negligible.
We consider a scenario with unitary mixing of the three light standard neutrinos and a non-unitary mixing contribution of a heavier massive neutrino that can generate short-baseline neutrino ...oscillations. We show that this scenario predicts constant flavor-changing probabilities at short-baseline distances. Therefore, it cannot explain the spectral distortions observed in the LSND and MiniBooNE appearance experiments. On the other hand, the survival probabilities oscillate as functions of L/E and could explain oscillations in short-baseline disappearance experiments. We also derive the bounds on the mixing parameters from the existing short-baseline neutrino oscillation data.
A
bstract
We present the results of an updated fit of short-baseline neutrino oscillation data in the framework of 3+1 active-sterile neutrino mixing. We first consider
ν
e
and
ν
¯
e
disappearance in ...the light of the Gallium and reactor anomalies. We discuss the implications of the recent measurement of the reactor
ν
¯
e
spectrum in the NEOS experiment, which shifts the allowed regions of the parameter space towards smaller values of |
U
e
4
|
2
. The
β
-decay constraints of the Mainz and Troitsk experiments allow us to limit the oscillation length between about 2 cm and 7 m at 3
σ
for neutrinos with an energy of 1 MeV. The corresponding oscillations can be discovered in a model-independent way in ongoing reactor and source experiments by measuring ν
e
and
ν
¯
e
disappearance as a function of distance. We then consider the global fit of the data on short-baseline
ν
μ
−
→
ν
e
−
transitions in the light of the LSND anomaly, taking into account the constraints from
ν
e
−
and
ν
μ
−
disappearance experiments, including the recent data of the MINOS and IceCube experiments. The combination of the NEOS constraints on |
U
e
4
|
2
and the MINOS and IceCube constraints on |
U
μ
4
|
2
lead to an unacceptable appearance-disappearance tension which becomes tolerable only in a pragmatic fit which neglects the MiniBooNE low-energy anomaly. The minimization of the global
χ
2
in the space of the four mixing parameters Δ
m
41
2
, |
U
e
4
|
2
, |
U
μ
4
|
2
, and |
U
τ
4
|
2
leads to three allowed regions with narrow Δ
m
41
2
widths at Δ
m
41
2
≈ 1.7 (best-fit), 1.3 (at 2
σ
), 2.4 (at 3
σ
) eV
2
. The effective amplitude of short-baseline
ν
μ
−
→
ν
e
−
oscillations is limited by 0.00048 ≲ sin
2
2
ϑ
eμ
≲ 0.0020 at 3
σ
. The restrictions of the allowed regions of the mixing parameters with respect to our previous global fits are mainly due to the NEOS constraints. We present a comparison of the allowed regions of the mixing parameters with the sensitivities of ongoing experiments, which show that it is likely that these experiments will determine in a definitive way if the reactor, Gallium and LSND anomalies are due to active-sterile neutrino oscillations or not.
We investigate which among the reactor antineutrino fluxes from the decays of the fission products of U235, U238, Pu239, and Pu241 may be responsible for the reactor antineutrino anomaly if the ...anomaly is due to a miscalculation of the antineutrino fluxes. We find that it is very likely that at least the calculation of the U235 flux must be revised. From the fit of the data we obtain the precise determination σ235=(6.33±0.08)×10−43cm2/fission of the U235 cross section per fission, which is more precise than the calculated value and differs from it by 2.2σ. The cross sections per fission of the other fluxes have large uncertainties and in practice their values are undetermined by the fit.
We consider the ratio of the spectra measured in the DANSS neutrino experiment at 12.7 and 10.7 m from a nuclear reactor. These data give a new model-independent indication in favor of short-baseline ...ν¯e oscillations which reinforce the model-independent indication found in the late 2016 in the NEOS experiment. The combined analysis of the NEOS and DANSS spectral ratios in the framework of 3+1 active–sterile neutrino mixing favor short-baseline ν¯e oscillations with a statistical significance of 3.7σ. The two mixing parameters sin22ϑee and Δm412 are constrained at 2σ in a narrow-Δm412 island at Δm412≃1.3eV2, with sin22ϑee=0.049±0.023 (2σ). We discuss the implications of the model-independent NEOS+DANSS analysis for the reactor and Gallium anomalies. The NEOS+DANSS model-independent determination of short-baseline ν¯e oscillations allows us to analyze the reactor rates without assumptions on the values of the main reactor antineutrino fluxes and the data of the Gallium source experiments with free detector efficiencies. The corrections to the reactor neutrino fluxes and the Gallium detector efficiencies are obtained from the fit of the data. In particular, we confirm the indication in favor of the need for a recalculation of the U235 reactor antineutrino flux found in previous studies assuming the absence of neutrino oscillations.
The gallium anomaly revisited Kostensalo, J.; Suhonen, J.; Giunti, C. ...
Physics letters. B,
08/2019, Letnik:
795
Journal Article
Recenzirano
Odprti dostop
The gallium anomaly, i.e. the missing electron-neutrino flux from 37Ar and 51Cr electron-capture decays as measured by the GALLEX and SAGE solar-neutrino detectors, has been among us already for ...about two decades. We present here a new estimate of the significance of this anomaly based on cross-section calculations using nuclear shell-model wave functions obtained by exploiting recently developed two-nucleon interactions. The gallium anomaly of the GALLEX and SAGE experiments is found to be smaller than that obtained in previous evaluations, decreasing the significance from 3.0σ to 2.3σ. This result is compatible with the recent indication in favor of short-baseline ν¯e disappearance due to small active-sterile neutrino mixing obtained from the combined analysis of the data of the NEOS and DANSS reactor experiments.
A
bstract
We present the results of a new analysis of the data of the MiniBooNE experiment taking into account the additional background of photons from ∆
+
/
0
decay proposed in ref. 1 and ...additional contributions due to coherent photon emission, incoherent production of higher mass resonances, and incoherent non-resonant nucleon production. We show that the new background can explain part of the MiniBooNE low-energy excess and the statistical significance of the MiniBooNE indication in favor of short-baseline neutrino oscillation decreases from 5
.
1
σ
to 3
.
6
σ
. We also consider the implications for short-baseline neutrino oscillations in the 3+1 active-sterile neutrino mixing framework. We show that the new analysis of the MiniBooNE data indicates smaller active-sterile neutrino mixing and may lead us towards a solution of the appearance-disappearance tension in the global fit of short-baseline neutrino oscillation data.
A
bstract
We present new constraints on three different models, the so-called universal,
B − L
and
L
μ
− L
τ
models, involving a yet to be observed light vector
Z
′ mediator, by exploiting the recent ...observation of coherent elastic neutrino-nucleus scattering (CE
ν
NS) in argon and cesium-iodide performed by the COHERENT Collaboration. We compare the results obtained from a combination of the above data sets with the limits derived from searches in fixed target, accelerator, solar neutrino and reactor CE
ν
NS experiments, and with the parameter region that could explain the anomalous magnetic moment of the muon. We show that for the universal and the
B − L
models, the COHERENT data allow us to put stringent limits in the light vector mediator mass,
M
Z
′
, and coupling,
g
Z
′
, parameter space.
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