The single largest background to future $\bar{ν_μ}\to \bar{ν_e}$ ($ν_μ\to ν_e$) oscillation searches is neutral current (NC) $π^{0}$ production. MiniBooNE, which began taking antineutrino data in January 2006, has the world's largest sample of reconstructed $π^{0}$'s produced by antineutrinos. These neutral pions are primarily produced through the $Δ$ resonance but can also be created through ``coherent production.'' The latter process is the coherent sum of glancing scatters of antineutrinos off a neutron or proton, in which the nucleus is kept intact but a $π^{0}$ is created. A signature of this process is a $π^{0}$ which is highly forward-going. It is advantageous to study coherent production using antineutrinos rather than neutrinos because the ratio of coherent to resonant scattering is enhanced in antineutrino running. The first measurement of NC coherent $π^{0}$ production in the MiniBooNE antineutrino data is discussed here.
We discuss the nuclear interactions of neutrinos versus those of antineutrinos, a relevant comparison for CP violation experiments in the neutrino sector. We consider the MiniBooNE quasielastic-like double differential neutrinos and antineutrinos cross sections which are flux dependent and hence specific to the MiniBooNE set-up. We combine them introducing their sum and their difference. We show that the last combination can bring a general information, which can be exploited in other experiments, on the nuclear matrix elements of the axial vector interference term. Our theoretical model repro…
The MiniBooNE experiment has reported results from the analysis of $ν_e$ and $\bar ν_e$ appearance searches, which show an excess of signal-like events at low reconstructed neutrino energies, with respect to the expected background. A significant component of this background comes from photon emission induced by (anti)neutrino neutral current interactions with nucleons and nuclei. With an improved microscopic model for these reactions, we predict the number and distributions of photon events at the MiniBooNE detector. Our results are compared to the MiniBooNE in situ estimate and to other theo…
Understanding the charged current quasielestic (CCQE) neutrino-nucleus interaction is important for precision studies of neutrino oscillations. The theoretical description of the interaction depends on the combination of a nuclear model with the knowledge of form factors. While the former has received considerable attention, the latter, in particular the axial form factor, is implemented using the historical dipole model. Instead, we use a model-independent approach, presented in a previous study, to analyze the muon antineutrino CCQE mineral oil data published by the MiniBooNE collaboration. …
Can neutrino-induced photon production explain the low energy excess in MiniBooNE?
这份报告总结了我们对MiniBooNE中中性电流(NC)诱导的光子产生的研究,这是由本实验中的低能量过剩所激发的[A. A. Aquilar-Arevalo et al.(MiniBooNE Collaboration),Phys. Rev. Lett. 98,231801(2007); 103,111801(2009)]。提出了两个反常光子- $Z$玻色子-矢量介子耦合的NC光子产生可能解释这种过剩。然而,我们在中微子和反中微子运行中计算的事件数与以前的MiniBooNE估计是基于他们的π介子生产测量一致。在我们以前的工作中讨论的各种核效应,包括核子费米运动,泡利阻塞,和$Δ$共振加宽的核,考虑。用保守的方法研究了由于两个反常项和核效应引起的不确定度。
In this work we study the $Σπ$ and $Λπ$ production off free nucleons driven by the strangeness-changing weak charged current. We calculate the total cross sections for all possible channels and estimate the flux-averaged total cross sections for experiments like MiniBooNE, SciBooNE, T2K, and Minerva. The model is based on the lowest order effective SU(3) chiral Lagrangians in the presence of an external weak charged current and contains Born and the lowest-lying decuplet resonant mechanisms that can contribute to these reaction channels. We also compare and discuss our results with others foll…
We carry out an ab initio calculation of the neutrino flux-folded inclusive cross sections, measured on $^{12}$C by the MiniBooNE and T2K collaborations in the charged-current quasielastic (CCQE) regime. The calculation is based on realistic two- and three-nucleon interactions, and on a realistic nuclear electroweak current with one-and two-nucleon terms that are constructed consistently with these interactions and reproduce low-energy electroweak transitions. Numerically exact quantum Monte Carlo methods are utilized to compute the nuclear weak response functions, by fully retaining many-body…
Neutrino induced coherent charged pion production on nuclei, $\overlineν_μA\toμ^\pmπ^\mp A$, is a rare inelastic interaction in which the four-momentum squared transfered to the nucleus is nearly zero, leaving it intact. We identify such events in the scintillator of MINERvA by reconstructing |t| from the final state pion and muon momenta and by removing events with evidence of energetic nuclear recoil or production of other final state particles. We measure the total neutrino and antineutrino cross sections as a function of neutrino energy between 2 and 20 GeV and measure flux integrated diff…
We present the results of a new analysis of the data of the MiniBooNE experiment taking into account the additional background of photons from $Δ^{+/0}$ decay proposed in arXiv:1909.08571 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 $5.1σ$ to $3.6σ$. We also consider the implic…
We report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be $2.6^{+1.2}_{-1.0}(stat)^{+0.3}_{-0.4}(syst) \times 10^{-38} \textrm{cm}^{2}/\textrm{Ar}$ for neutrinos at a mean energy of $9.6$ GeV and $5.5^{+2.6}_{-2.1}(stat)^{+0.6}_{-0.7}(syst) \times 10^{-39} \textrm{cm}^{2}/\textrm{Ar}$ for antineutrinos at a mean energy of $3.6$ GeV.
The MiniBooNE experiment at Fermilab reports results from an analysis of $ν_e$ appearance data from $12.84 \times 10^{20}$ protons on target in neutrino mode, an increase of approximately a factor of two over previously reported results. A $ν_e$ charged-current quasielastic event excess of $381.2 \pm 85.2$ events ($4.5 σ$) is observed in the energy range $200<E_ν^{QE}<1250$~MeV. Combining these data with the $\bar ν_e$ appearance data from $11.27 \times 10^{20}$ protons on target in antineutrino mode, a total $ν_e$ plus $\bar ν_e$ charged-current quasielastic event excess of $460.5 \pm 99.0$ e…
The 96.4 day exposure of a 3 kg ultra-low noise germanium detector to the high flux of antineutrinos from a power nuclear reactor is described. A very strong preference ($p<1.2\times10^{-3}$) for the presence of a coherent elastic neutrino-nucleus scattering (CE$ν$NS) component in the data is found, when compared to a background-only model. No such effect is visible in 25 days of operation during reactor outages. The best-fit CE$ν$NS signal is in good agreement with expectations based on a recent characterization of germanium response to sub-keV nuclear recoils. Deviations of order 60\% from t…
We report the best limit on coherent elastic scattering of electron antineutrinos emitted from a nuclear reactor off germanium nuclei. The measurement was performed with the CONUS detectors positioned at 17.1m from the 3.9GWth reactor core of the nuclear power plant in Brokdorf, Germany. The antineutrino energies of less than 10 MeV assure interactions in the fully coherent regime. The analyzed dataset includes 248.7 kgd with the reactor turned on and background data of 58.8 kgd with the reactor off. With a quenching parameter of k = 0.18 for germanium, we determined an upper limit on the numb…
The MiniBooNE experiment at Fermilab reports a total excess of $638.0 \pm 132.8$ electron-like events ($4.8 σ$) from a data sample corresponding to $18.75 \times 10^{20}$ protons-on-target in neutrino mode, which is a 46\% increase in the data sample with respect to previously published results, and $11.27 \times 10^{20}$ protons-on-target in antineutrino mode. The additional statistics allow several studies to address questions on the source of the excess. First, we provide two-dimensional plots in visible energy and cosine of the angle of the outgoing lepton, which can provide valuable input…
Discrimination of parametrizations for nuclear effects in neutrino scattering through comparisons of low (~ 700 MeV) and medium (~ 3 GeV) energy cross-section data
The nuGeN experiment is aimed to investigate neutrino properties using antineutrinos from the reactor of the Kalinin Nuclear Power Plant. The experimental setup is located at about 11 meters from the center of the 3.1 GWth reactor core. Scattering of the antineutrinos from the reactor is detected with low energy threshold high purity germanium detector. Passive and active shieldings are used to suppress all kinds of backgrounds coming from surrounding materials and cosmic radiation. The description of the experimental setup together with the first results is presented. The data taken in regime…