Proceedings of the talk presented at the Conference New Trends in High-Energy Physics (experiment, phenomenology, theory), Alushta, Crimea, Ukraine, September 3 - 10, 2011
The latest oscillation results obtained in the off-axis accelerator neutrino experiment T2K are presented. In the data sample, corresponding to 1.43 x 10^20 protons on target, 6 electron neutrino candidate events pass the selection criteria, while the expected number of background events for sin^2 2θ_{13}=0 is 1.5 \pm 0.3 (syst.). The probability to observe six or more candidate events due to background is 0.7%, equivalent to 2.5-sigma significance. In the muon neutrino disappearance analysis the obtained atmospheric oscillation parameters are consistent with results from the Super-Kamiokande and MINOS experiments.
Double Chooz experiment will search for a disappearance of the reactor neutrinos from Chooz reactor cores in Ardenne, France, in order to detect the yet unknown neutrino oscillation angle θ13. The far detector was completed in 2010 and data-taking has started in spring 2011. Status of data-taking is presented and some performance plots from physics data are shown in this paper for the first time. Also the prospect of experimental sensitivity is presented, in light of recent indication from T2K for a non-zero θ13 value.
T2K is a long-baseline neutrino oscillation experiment taking data since 2010. A neutrino beam is produced at the J-PARC accelerator in Japan and is sampled at a Near Detector complex 280 m from the neutrino production point and at the far detector, Super-Kamiokande, located 295 km from the source. Beams predominantly composed of muon neutrinos or muon anti-neutrinos have been produced by changing the currents in the magnetic focusing horns. This presentation will show the most recent T2K oscillation results obtained from a combined analysis of the entire available data set in the muon neutrin…
In order to make precision measurements of GeV-scale neutrino oscillations a detailed understanding of both GeV-scale neutrino-nucleon scattering cross sections and nuclear effects are essential. To achieve this, many of the latest analyses at the T2K off-axis near detector (ND280) complement existing results by utilising new techniques to measure muon neutrino charged-current interactions without pions in the final state (CC0$π$ interactions). These techniques include water subtraction to obtain a double-differential cross section on oxygen and measurements of differential cross sections usin…
Thank to the stable operation at intense beam power, T2K data with neutrino-mode operation almost doubled in one year. A number of critical improvements to the oscillation analysis have been introduced and resulted in an unprecedented level of sensitivity in searching for CP violation in the neutrino sector. T2K firstly reports that the CP-conserving values of parameter $δ_{CP}$ in the PMNS mixing matrix fall out of its 2$σ$ C.L. measured range.
We re-evaluate neutrino mixing patterns according to the latest T2K result for a larger mixing angle $θ_{13}$, and find that the PMNS mixing matrix has larger deviations from bimaximal (BM) and tribimaximal (TB) mixing patterns than previously expected. We also find that several schemes connecting PMNS and CKM mixing matrices can accommodate the latest T2K result nicely. As necessary updates to former works, we make new triminimal expansions of PMNS mixing matrix based on BM and TB mixing patterns. We also propose a new mixing pattern with a self-complementary relation between the mixing angle…
In this paper, we have analysed the latest data from NO$ν$A and T2K with the Lorentz invariance violation along with the standard oscillation hypothesis. We have found that the NO$ν$A data cannot distinguish between the two hypotheses at $1\, σ$ confidence level. T2K data and the combined data analysis excluded standard oscillation at $1\, σ$. All three cases do not have any hierarchy sensitivity when analysed with LIV. There is a mild tension between the two experiments, when analysed with LIV, as $θ_{23}$ at \nova best-fit is at higher octant but the same for T2K is at lower octant. NO$ν$A h…
Recent neutrino oscillation results have evoked renewed interest in sterile neutrino oscillation models. This paper reviews the data from MiniBooNE and short-baseline reactor antineutrino experiments within the context of sterile neutrinos. The results are incorporated into combined fits to test the viability of sterile neutrino oscillation models, which are later expanded to address matter effects. Finally, future experiments that can resolve the questions that have been raised are discussed.
Neutrino oscillation results from several experiments and sources are discussed. Recent results from solar neutrino measurements by Super-Kamiokande and Borexino, atmospheric neutrino measurements from Super-Kamiokande, and accelerator neutrino measurements by MINOS and OPERA are the main topics of this document.
This is the report from the Snowmass NF01 topical group and colleagues on the current status and expected future progress to understand the three-flavor neutrino oscillation picture.
T2K is a long-baseline neutrino oscillation experiment using a $ν_μ$ beam produced at the J-PARC facility. Neutrinos are detected at a Near Detector complex (ND280) and at the Far Detector (Super-Kamiokande). The most recent oscillation results presented by T2K are described in these proceedings. With these data T2K has produced the first constraints on $δ_{CP}$, excluding CP conserving values at 2$σ$ and the world best measurement of the $θ_{23}$ mixing angle.
The bicycle model of Lorentz noninvariant neutrino oscillations without neutrino masses naturally predicts maximal mixing and a 1/E dependence of the oscillation argument for muon-neutrino to tau-neutrino oscillations of atmospheric and long-baseline neutrinos, but cannot also simultaneously fit the data for solar neutrinos and KamLAND. Within the Standard Model Extension, we examine all 19 possible structures of the effective Hamiltonian for Lorentz noninvariant oscillations of massless neutrinos that naturally have a 1/E dependence at high neutrino energy. Due to the lack of any evidence for…
A virtual graphical construction is made to show the difference between neutrino and anti-neutrino oscillations in the presence of CP violation with CPT conservation.
The T2K (Tokai to Kamioka) experiment is a long-baseline accelerator neutrino oscillation experiment. Intense muon neutrino and antineutrino beams are produced at the J-PARC accelerator complex situated in Tokai. After 280 metres the beam goes through the set of two near detectors: INGRID and ND280, where the beam parameters before oscillations are measured and neutrino cross-sections are studied. After another 295 km, the distance corresponding to the first oscillation maximum, the neutrino beam passes through the Super-Kamiokande far detector. Comparison of the beam characteristics in the ne…
A magnetized large-volume liquid scintillator might be used as a tracking detector with charge identification to measure high-energy neutrinos. I consider neutrino oscillations for a beam from a low-energy neutrino factory to such a detector for the baseline CERN-Pyhasalmi, with the length of 2288 km. The range to study the oscillation parameters extends to $\sin^2 2θ_{13}\sim 10^{-4}$ for reasonable assumptions for the detector and the beam.
The neutrino wave packet localization in short-baseline neutrino oscillation experiments, such as MiniBooNE, is investigated. It is shown that the transition from localization to delocalization may be observed for large neutrino mass splitting of order 1 eV, e.g., in theories with sterile neutrinos.
The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show that the very high statistics atmospheric neutrino data can be used to obtain precise measurements of the main oscillation parameters.
The T2K collaboration has recently reported their results, which gives the best-fit values of the atmospheric mixing angle $\sin^2 θ_{23} = 0.53$ and the Dirac CP-violating phase $δ= -1.89$ for normal neutrino mass ordering. We give a possible theoretical origin of such values based on the $μ$-$τ$ reflection symmetry. It has been found that the breaking of such symmetry using one-loop renormalization-group equations (RGEs) in the framework of minimal supersymmetric standard model can fit well with the latest T2K results and the recent global fits. To make a quantitative analysis, we have inclu…
The Nobel prize in physics 2015 has been awarded "... for the discovery of neutrino oscillations which show that neutrinos have mass". While SuperKamiokande (SK), indeed, has discovered oscillations, SNO observed effect of the adiabatic (almost non-oscillatory) flavor conversion of neutrinos in the matter of the Sun. Oscillations are irrelevant for solar neutrinos apart from small $ν_e$ regeneration inside the Earth. Both oscillations and adiabatic conversion do not imply masses uniquely and further studies were required to show that non-zero neutrino masses are behind the SNO results. Phenome…
We study neutrino oscillations in a medium of dark matter which generalizes the standard matter effect. A general formula is derived to describe the effect of various mediums and their mediators to neutrinos. Neutrinos and anti-neutrinos receive opposite contributions from asymmetric distribution of (dark) matter and anti-matter, and thus it could appear in precision measurement of neutrino or anti-neutrino oscillations. Furthermore, the standard neutrino oscillation can occur from the symmetric dark matter effect even for massless neutrinos.
A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations and effective 2-flavour approximations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on ν_μ\leftrightarrow ν_τoscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.
We show that, despite appearances, a theoretical approach to neutrino oscillation in which the neutrino and its interaction partners are entangled yields the standard result for the neutrino oscillation wavelength. We also shed some light on the question of why plane-wave approaches to the neutrino oscillation problem can yield the correct oscillation wavelength even though they do not explicitly account for the localization of the neutrino source and the detector.
In this contribution we discuss the future of the global long-baseline neutrino oscillation program. The case is made that our current lack of understanding of neutrino-nucleus interactions is a serious challenge which will need to be met with new experimental initiatives in neutrino scattering.
