Future Oscillation Experiments Research Articles

Search for neutral-current induced single photon production at the ND280 near detector in T2K

Neutrino neutral-current (NC) induced single photon production is a sub-leading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the fine-grained detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron–positron pairs, we achieved 95% pure gamma ray sample from protons-on-targets neutrino mode data. We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at cm2 (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals.

Neutrinophilic nonstandard interactions

We construct UV-complete models for non-standard neutrino interactions mediated by a sub-GeV gauge boson Z' coupled to baryon number $B$ or $B-L$. A flavor-dependent Z' coupling to neutrinos is induced by mixing a U(1)'-charged Dirac fermion with the active neutrinos, naturally suppressing flavor violation or non-universality of the charged leptons to the loop level. We show that these models can give rise to large flavor-conserving as well as flavor-violating non-standard neutral-current neutrino interactions potentially observable in current or future oscillation experiments such as DUNE without being in conflict with other constraints such as neutrino scattering or lepton-flavor-violating decays. In particular, the LMA-Dark solution to the solar-neutrino anomaly can be obtained for $U(1)_B$, but not for $U(1)_{B-L}$.

Quantum oscillation as diagnostics of pseudogap state in underdoped cuprates

The Fermi surface in underdoped cuprates is reconstructed by the charge density wave (CDW) order in the pseudogap phase. Theoretical proposals can be divided into two classes: one assumes the underlying Fermi surface without CDW as a conventional large surface; the other assumes small hole-like Fermi pockets. In both scenarios, we theoretically study the quantum oscillation and find three evenly spaced peaks in the oscillation spectra. The central dominant peak is induced by the CDW order. Its effective mass is strongly enhanced as the CDW vanishes in agreement with experiments. But the two scenarios have different understandings of the subdominant satellite peaks. In the large-surface scenario they are induced by the interlayer tunneling between the bilayer CuO2 planes. Their effective masses are also enhanced with descreasing CDW. In the small-pocket scenario one of the subdominant peaks comes from the original small Fermi pockets of the pseudogap state. Its effective mass is nearly independent of the CDW strength and increases monotonically with the doping. We propose future quantum oscillation experiments to test these different predictions and thus to clarify the underlying Fermi surface structure of the pseudogap state.

The MOMENT to search for CP violation

In this letter, we analyze for the first time the physics reach in terms of sensitivity to leptonic CP violation of the proposed MuOn-decay MEdium baseline NeuTrino beam (MOMENT) experiment, a novel neutrino oscillation facility that would operate with neutrinos from muon decay. Apart from obtaining a sufficiently intense flux, the bottlenecks to the physics reach of this experiment will be achieving a high enough suppression of the atmospheric background and, particularly, attaining a sufficient level of charge identification. We thus present our results as a function of these two factors. As for the detector, we consider a very massive Gd-doped Water Cherenkov detector. We find that MOMENT will be competitive with other currently planned future oscillation experiments if a charge identification of at least 80 % can be achieved at the same time that the atmospheric background can be suppressed by at least a factor of ten. We also find a large synergy of MOMENT with the current generation of neutrino oscillation experiments, T2K and NOvA, which significantly enhances its final sensitivity.

Non standard neutrino interactions: current status and future prospects

Neutrino oscillations have become well-known phenomena; the measurements of neutrino mixing angles and mass squared differences are continuously improving. Future oscillation experiments will eventually determine the remaining unknown neutrino parameters, namely, the mass ordering, normal or inverted, and the CP-violating phase. On the other hand, the absolute mass scale of neutrinos could be probed by cosmological observations, single beta decay as well as by neutrinoless double beta decay experiments. Furthermore, the last one may shed light on the nature of neutrinos, Dirac or Majorana, by measuring the effective Majorana mass of neutrinos. However, the neutrino mass generation mechanism remains unknown. A well-motivated phenomenological approach to search for new physics, in the neutrino sector, is that of non-standard interactions. In this short review, the current constraints in this picture, as well as the perspectives from future experiments, are discussed.

Neutrino Interactions

I summarize the most interesting questions and the current status of data and theory for interactions of neutrinos with energies relevant for current and future accelerator-based oscillation experiments.

Optimization of neutrino oscillation facilities for large θ 13

Abstract Up to now, future neutrino beam experiments have been designed and optimized in order to look for CP violation, θ 13 and the mass hierarchy under the conservative assumption that θ 13 is very small. However, the recent results from T2K and MINOS favor a θ 13 which could be as large as 8°. In this work, we propose a re-optimization for neutrino beam experiments in case this hint is confirmed. By switching from the first to the second oscillation peak, we find that the CP discovery potential of future oscillation experiments would not only be enhanced, but it would also be less affected by systematic uncertainties. In order to illustrate the effect, we present our results for a Super-Beam experiment, comparing the results obtained at the first and the second oscillation peaks for several values of the systematic errors. We also study its combination with a β-beam facility and show that the synergy between both experiments would also be enhanced due to the larger L/E. Moreover, the increased matter effects at the longer baseline also significantly improve the sensitivity to the mass hierarchy.

Resolving the octant degeneracy by neutrino oscillation experiments

We discuss how and to what extent the degeneracy associated with θ 23 , if it's not maximal, can be resolved by future oscillation experiments which utilize conventional neutrino beam from accelerator and/or reactor neutrinos.

Low energy cross section measurements in the FNAL Booster beamline: MiniBooNE and SciBooNE

Until recently, the state of low energy cross section measurements with neutrinos has been limited by low statistics and large flux uncertainties. With new and upcoming results from MiniBooNE and K2K, we already see substantial improvements in what we can measure. The proposed near term future experiment of placing the fine-grained K2K SciBar detector in the Fermilab Booster beamline (SciBooNE) will provide important cross section information for future oscillation experiments, such as T2K.

Future Precision Neutrino Oscillation Experiments and Theoretical Implications

Future neutrino oscillation experiments will lead to precision measurements of neutrino mass splittings and mixings. The flavour structure of the lepton sector will therefore at some point become better known than that of the quark sector. This article discusses the realistic potential of future oscillation experiments on the basis of detailed simulations with an emphasis on experiments which can be done in about ten years. In addition, some theoretical implications for neutrino mass models will be briefly discussed.

Physics prospects of future neutrino oscillation experiments in Asia

The three neutrino model has 9 physical parameters, 3 neutrino masses, 3 mixing angles and 3 CP violating phases. Among them, neutrino oscillation experiments can probe 6 parameters: 2 mass squared differences, 3 mixing angles, and 1 CP phase. The experiments performed so far determined the magnitudes of the two mass squared differences, the sign of the smaller mass squared difference, the magnitudes of two of the three mixing angles, and the upper bound on the third mixing angle. The sign of the larger mass squared difference (the neutrino mass hierarchy pattern), the magnitude of the third mixing angle and the CP violating phase, and a two-fold ambiguity in the mixing angle that dictates the atmospheric neutrino oscillation should be determined by future oscillation experiments. In this talk, I introduce a few ideas of future long baseline neutrino oscillation experiments which make use of the super neutrino beams from J-PARC (Japan Proton Accelerator Research Complex) in Tokai village. We examine the potential of HyperKamiokande (HK), the proposed 1 Mega-ton water Cerenkov detector, and then study the fate and possible detection of the off-axis beam from J-PARC in Korea. We also show that very long baseline experiments with higher energy beams from J-PARC and a water Cerenkov calorimeter detector (BAND) proposed in Beijing can resolve the neutrino mass hierarchy, and lift all the degeneracies in the three neutrino model parameters.

Leptonic unitarity triangle andCPviolation

The area of the unitarity triangle is a measure of $\mathrm{CP}$ violation. We introduce the leptonic unitarity triangles and study their properties. We consider the possibility of reconstructing the unitarity triangle in future oscillation and nonoscillation experiments. A set of measurements is suggested which will, in principle, allow us to measure all sides of the triangle, and consequently to establish $\mathrm{CP}$ violation. For different values of the $\mathrm{CP}$-violating phase ${\ensuremath{\delta}}_{D},$ the required accuracy of measurements is estimated. The key elements of the method are the determination of $|{U}_{e3}|$ and studying the ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{-}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ survival probability in the oscillations driven by the solar mass splitting $\ensuremath{\Delta}{m}_{\mathrm{sun}}^{2}.$ We suggest additional astrophysical measurements which may help to reconstruct the triangle. The method of the unitarity triangle is complementary to the direct measurements of $\mathrm{CP}$ asymmetry. It requires mainly studies of the survival probabilities and processes where oscillations are averaged or the coherence of the state is lost.

Report on SPY results: Secondary particle yields from 450 GeV/c protons on beryllium

Measurements of π ± and K ± production rates from 450 GeV/c protons on beryllium targets were performed in the low momenta range down to 7 GeV/c where no data exist. Preliminary results on K ± π ± production ratios of great importance for neutrino flux calculations at present and future oscillation experiments are presented.

Neutrino mass and lepton mixing hierarchies and future oscillation experiments

Future experiments searching for neutrino oscillations are discussed on the assumption of the existence of a hierarchy in the neutrino masses. Different scenarios for the hierarchy of coupling among lepton families are considered. Relations and inequalities among transition probabilities are derived. The inequalities follow the pattern in the hierarchy of coupling among lepton generations. Simpson's 17 keV neutrino is discussed. It is shown that if such a heavy neutrino exist, the probability of the transition v e→ v τ will not exceed approximately 2×10 −2 independently of the nature (Dirac or Marjorana) and the number of the neutrino mass eigenstates.