Long-baseline Accelerator Experiments Research Articles

Smallness of matter effects in long-baseline muon neutrino disappearance

Current long-baseline accelerator experiments, NOvA and T2K, are making excellent measurements of neutrino oscillations and the next generation of experiments, DUNE and HK, will make measurements at the O(1%) level of precision. These measurements are a combination of the appearance channel which is more challenging experimentally but depends on many oscillation parameters, and the disappearance channel which is somewhat easier and allows for precision measurements of the atmospheric mass splitting and the atmospheric mixing angle. It is widely recognized that the matter effect plays a key role in the appearance probability, yet the effect on the disappearance probability is surprisingly small for these experiments. Here we investigate both exactly how small the effect is and show that it just begins to become relevant in the high statistics regime of DUNE. Published by the American Physical Society 2024

The ProtoDUNE Photon Detection System: technology validation and performance

DUNE is a long-baseline accelerator experiment currently in construction at Fermilab and SURF (South Dakota). The science objectives of DUNE include the search for CP violationin the leptonic sector and the identification of the neutrino mass hierarchy, along with theobservation of supernova neutrino bursts and proton decay.The Far Detector consists of four modules located deep underground, three of those instrumented with Liquid Argon TPCs and equipped with the DUNE Photon Detection System (PDS). The PDS is based on a novellight trapping technology that greatly enhances the DUNE physics reach,improving vertex identification, energy resolution and providing the trigger for non-beam events.Following a first run of data taking (from 2018 to 2020), the PDS of the two prototypes of the Far Detector located at CERN Neutrino Platform, ProtoDUNE-HD and ProtoDUNE-VD, is currently being reinstalled in order to implement the final design of the first (Horizontal Drift) and second (Vertical Drift) module.This paper presents the latest results of the PDS from test facilities and the status of the installation in ProtoDUNE in view of its second run. The most important achievements of the Vertical Drift PDS are reported, with emphasis on the new SiPM configuration and cold electronics, the custom WaveLength Shifting bars, and the latest generation of the dichroic filter designed for ProtoDUNE-VD.

Solar parameters in long-baseline accelerator neutrino oscillations

Long-baseline (LBL) accelerator neutrino oscillation experiments, such as NOvA and T2K in the current generation, and DUNE-LBL and HK-LBL in the coming years, will measure the remaining unknown oscillation parameters with excellent precision. These analyses assume external input on the so-called “solar parameters,” θ12 and Delta {m}_{21}^2 , from solar experiments such as SNO, SK, and Borexino, as well as reactor experiments like KamLAND. Here we investigate their role in long-baseline experiments. We show that, without external input on Delta {m}_{21}^2 and θ12, the sensitivity to detecting and quantifying CP violation is significantly, but not entirely, reduced. Thus long-baseline accelerator experiments can actually determine Delta {m}_{21}^2 and θ12, and thus all six oscillation parameters, without input from any other oscillation experiment. In particular, Delta {m}_{21}^2 can be determined; thus DUNE-LBL and HK-LBL can measure both the solar and atmospheric mass splittings in their long-baseline analyses alone. While their sensitivities are not competitive with existing constraints, they are very orthogonal probes of solar parameters and provide a key consistency check of a less probed sector of the three-flavor oscillation picture. Furthermore, we also show that the true values of Delta {m}_{21}^2 and θ12 play an important role in the sensitivity of other oscillation parameters such as the CP violating phase δ.

Revealing Neutrino Oscillations Unknowns with Reactor and Long-Baseline Accelerator Experiments

Reactor and accelerator-based neutrino experiments have played a critical role in the understanding of neutrino oscillations and are currently dominating the high-precision measurements of neutrino oscillation parameters. The discovery of a non-zero θ13 by the reactor experiments has opened the possibility of observing CP violation in the lepton sector by long-baseline accelerator experiments. The current knowledge of the neutrino oscillation parameters will be expanded upon in the near future through more precise measurements, including the discovery of the neutrino mass ordering and the CP-violating phase. This review summarizes the distinct and complementary approach of reactor and accelerator-based neutrino experiments to measure neutrino oscillations. The main scientific achievements of the Double Chooz reactor neutrino experiment and the science program to be developed by the DUNE long-baseline neutrino experiment with the world’s most intense neutrino beam are presented in this article. Spain has strongly contributed to these results and will continue to play a prominent role in the neutrino oscillation program in the coming years.

Astroparticle physics in DUNE with the X-ARAPUCA detectors

DUNE is a long-baseline accelerator experiment in construction at Fermilab and SURF (South Dakota). The scientific program encompasses the investigation of long-baseline neutrino oscillation, with a focus on the study of the CP violation and neutrino mass hierarchy, along with high sensitivity searches for rare events, such as the observation of supernova neutrino bursts and the search for proton decay. The DUNE far detector consists of four liquid Argon TPCs located deep underground, paired with a Photon Detection System. In the present article we will discuss the role of the PDS in the search of the aforementioned rare events and the latest results in terms of technological achievements obtained by the PDS Consortium.

Time Projection Chambers instrumented with resistive MicroMegas for the SAND near detector of DUNE

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino accelerator experiment aiming for precise measurements of the neutrino oscillation parameters. DUNE will include a near detector complex regrouping three different detectors among which SAND (System for on-Axis Neutrino Detection) that will be the only one permanently on the neutrino beam axis in charge of monitoring in detail the emitted neutrino beam and its stability through time, a crucial characteristic to realize accurate oscillation measurements at the percent level. SAND will reuse the superconducting magnet and the electromagnetic calorimeter of the KLOE experiment. We will describe in the following the proposal of using, as inner tracker of SAND, a large 3D matrix of 1.5cm side scintillator cubes (3DST) surrounded by 3 gaseous Time Projection Chambers. This setup allows to realize accurate beam monitoring combining the 3DST unprecedented capability of neutron detection and energy measurement with the high precision momentum resolution for charged particles offered by the TPCs. The proposed TPC design allows to reach spatial resolutions of a few hundreds of micrometers using 1 cm pads by deploying the resistive MicroMegas technology for the charge readout.

Nonstandard Neutrino Interactions as a Solution to the NOνA and T2K Discrepancy.

The latest data of the two long-baseline accelerator experiments NOνA and T2K, interpreted in the standard three-flavor scenario, display a discrepancy. A mismatch in the determination of the standard CP phase δ_{CP} extracted by the two experiments is evident in the normal neutrino mass ordering. While NOνA prefers values close to δ_{CP}∼0.8π, T2K identifies values of δ_{CP}∼1.4π. Such two estimates are in disagreement at more than 90%C.L. for 2degrees of freedom. We show that such a tension can be resolved if one hypothesizes the existence of complex neutral-current nonstandard interactions (NSIs) of the flavor changing type involving the e-μ or the e-τ sectors with couplings |ϵ_{eμ}|∼|ϵ_{eτ}|∼0.2. Remarkably, in the presence of such NSIs, both experiments point towards the same common value of the standard CP phase δ_{CP}∼3π/2. Our analysis also highlights an intriguing preference for maximal CP violation in the nonstandard sector with the NSI CP phases having best fit close to ϕ_{eμ}∼ϕ_{eτ}∼3π/2, hence pointing towards imaginary NSI couplings.

Neutrino oscillations: recent results and future prospects

A brief review of recent results on neutrino oscillations from accelerator and reactor experiments is presented. Emphasis is placed on the indication of CP violation in neutrino oscillations obtained in long-baseline accelerator experiments. The latest results of a search for a sterile neutrino are discussed and the nearest-term prospects for long and short-baseline oscillation experiments are outlined.

Fuzzy dark matter and nonstandard neutrino interactions

We discuss novel ways in which neutrino oscillation experiments can probe dark matter. In particular, we focus on interactions between neutrinos and ultra-light ("fuzzy") dark matter particles with masses of order $10^{-22}$ eV. It has been shown previously that such dark matter candidates are phenomenologically successful and might help ameliorate the tension between predicted and observed small scale structures in the Universe. We argue that coherent forward scattering of neutrinos on fuzzy dark matter particles can significantly alter neutrino oscillation probabilities. These effects could be observable in current and future experiments. We set new limits on fuzzy dark matter interacting with neutrinos using T2K and solar neutrino data, and we estimate the sensitivity of reactor neutrino experiments and of future long-baseline accelerator experiments. These results are based on detailed simulations in GLoBES. We allow the dark matter particle to be either a scalar or a vector boson. In the latter case, we find potentially interesting connections to models addressing various $B$ physics anomalies.

Recent results from the T2K experiment

Recent results of the analysis of 2:23×1021 POT data collected by the T2K long-baseline neutrino accelerator experiment are presented in this paper. It is shown that T2K is able to constrain the CP-violating phase δCP in the lepton sector with 2σ significance. Nearest plans for improving the sensitivity to δCP are also given.

Precision neutrino experiments vs the Littlest Seesaw

We study to what extent upcoming precision neutrino oscillation experiments will be able to exclude one of the most predictive models of neutrino mass and mixing: the Littlest Seesaw. We show that this model provides a good fit to current data, predicting eight observables from two input parameters, and provide new assessments of its predictions and their correlations. We then assess the ability to exclude this model using simulations of upcoming neutrino oscillation experiments including the medium-distance reactor experiments JUNO and RENO-50 and the long-baseline accelerator experiments DUNE and T2HK. We find that an accurate determination of the currently least well measured parameters, namely the atmospheric and solar angles and the CP phase δ, provide crucial independent tests of the model. For θ13 and the two mass-squared differences, however, the model’s exclusion requires a combination of measurements coming from a varied experimental programme. Our results show that the synergy and complementarity of future experiments will play a vital role in efficiently discriminating between predictive models of neutrino flavour, and hence, towards advancing our understanding of neutrino oscillations in the context of the flavour puzzle of the Standard Model.

Long-baseline neutrino accelerator experiments: results and prospects

Recent results from long-baseline neutrino experiments are presented. Prospects for determining the mass hierarchy and observing CP violation in neutrino oscillations are discussed.

Sterile neutrino oscillations: the global picture

Abstract Neutrino oscillations involving eV-scale neutrino mass states are investigated in the context of global neutrino oscillation data including short and long-baseline accelerator, reactor, and radioactive source experiments, as well as atmospheric and solar neutrinos. We consider sterile neutrino mass schemes involving one or two mass-squared differences at the eV2 scale denoted by 3+1, 3+2, and 1+3+1. We discuss the hints for eV-scale neutrinos from $ \mathop{{{v_e}}}\limits^{{\left( - \right)}} $ disappearance (reactor and Gallium anomalies) and $ \mathop{{{v_{\mu }}}}\limits^{{\left( - \right)}}\to \mathop{{{v_e}}}\limits^{{\left( - \right)}} $ appearance (LSND and MiniBooNE) searches, and we present constraints on sterile neutrino mixing from $ \mathop{{{v_{\mu }}}}\limits^{{\left( - \right)}} $ and neutral-current disappearance data. An explanation of all hints in terms of oscillations suffers from severe tension between appearance and disappearance data. The best compatibility is obtained in the 1+3+1 scheme with a p-value of 0.2% and exceedingly worse compatibilities in the 3+1 and 3+2 schemes.

Identifying the neutrino mass ordering with INO and NOvA

The relatively large value of $\theta_{13}$ established recently by the Daya Bay reactor experiment opens the possibility to determine the neutrino mass ordering with experiments currently under construction. We investigate synergies between the NOvA long-baseline accelerator experiment with atmospheric neutrino data from the India-based Neutrino Observatory (INO). We identify the requirements on energy and direction reconstruction and detector mass for INO necessary for a significant sensitivity. If neutrino energy and direction reconstruction at the level of 10% and 10 degree can be achieved by INO a determination of the neutrino mass ordering seems possible around 2020.

Investigation of neutrino oscillations in the T2k long-baseline accelerator experiment

High-sensitivity searches for transitions of muon neutrinos to electron neutrinos are the main task of the T2K (Tokai-to-Kamioka) second-generation long-baseline accelerator neutrino experiment. The present article is devoted to describing basic principles of T2K, surveying experimental apparatuses that it includes, and considering in detail the muon-range detector (SMRD) designed and manufactured by a group of physicists from the Institute of Nuclear Research (Russian Academy of Sciences, Moscow). The results of the first measurements with a neutrino beam are presented, and plans for the near future are discussed.

Evidence ofθ13>0from global neutrino data analysis

The neutrino mixing angle theta(13) is at the focus of current neutrino research. From a global analysis of the available oscillation data in a 3-neutrino framework, we previously reported [Phys. Rev. Lett. 101, 141801 (2008)] hints in favor of theta(13)>0 at the 90 % C.L. Such hints are consistent with the recent indications of nu(mu)-->nu(e) appearance in the T2K and MINOS long-baseline accelerator experiments. Our global analysis of all the available data currently provides >3 sigma evidence for nonzero theta(13), with 1-sigma ranges sin^2 theta(13) = 0.021+-0.007 or 0.025+-0.007, depending on reactor neutrino flux systematics. Updated ranges are also reported for the other 3-neutrino oscillation parameters (delta m^2, sin^2 theta(12)) and (Delta m^2, sin^2 theta(23)).

Constraints onθ13from a three-flavor oscillation analysis of reactor antineutrinos at KamLAND

We present new constraints on the neutrino oscillation parameters $/textyen Delta m^{2}_{21}$, $/textyen theta_{12}$, and $/textyen theta_{13}$ from a three-flavor analysis of solar and KamLAND data. The KamLAND data set includes data acquired following a radiopurity upgrade and amounts to a total exposure of $3.49 \textyen times 10^{32}$ target-proton-year. Under the assumption of {\textyen it CPT} invariance, a two-flavor analysis (/textyen mbox{$\textyen theta_{13} = 0$}) of the KamLAND and solar data yields the best-fit values $\textyen tan^{2} \textyen theta_{12} = 0.444^{+0.036}_{-0.030}$ and $\textyen Delta m^{2}_{21} = 7.50^{+0.19}_{-0.20} \textyen times 10^{-5} ~ {\textyen rm eV}^{2}$; a three-flavor analysis with $\textyen theta_{13}$ as a free parameter yields the best-fit values $\textyen tan^{2} \textyen theta_{12} = 0.452^{+0.035}_{-0.033}$, $\textyen Delta m^{2}_{21} = 7.50^{+0.19}_{-0.20} \textyen times 10^{-5} ~ {\textyen rm eV}^{2}$, and $\textyen sin^{2} \textyen theta_{13} = 0.020^{+0.016}_{-0.016}$. This $\textyen theta_{13}$ interval is consistent with other recent work combining the CHOOZ, atmospheric and long-baseline accelerator experiments. We also present a new global $\textyen theta_{13}$ analysis, incorporating the CHOOZ, atmospheric and accelerator data, which indicates $\textyen sin^{2} \textyen theta_{13} = 0.009^{+0.013}_{-0.007}$. A nonzero value is suggested, but only at the 79\textyen% C.L.

Исследование нейтринных осцилляций в ускорительных экспериментах с длинной базой

Исследование нейтринных осцилляций в ускорительных экспериментах с длинной базой

Accelerator neutrino experiments: New results and perspectives

The current status of neutrino long-baseline accelerator experiments and new results obtained in these experiments are presented. Prospects for near-future program are also discussed.

Reconciling results of LSND, MiniBooNE and other experiments with soft decoherence

We propose an explanation of the LSND signal via quantum-decoherence of the mass states, which leads to damping of the interference terms in the oscillation probabilities. The decoherence parameters as well as their energy dependence are chosen in such a way that the damping affects only oscillations with the large (atmospheric) $\Delta m^2$ and rapidly decreases with the neutrino energy. This allows us to reconcile the positive LSND signal with MiniBooNE and other null-result experiments. The standard explanations of solar, atmospheric, KamLAND and MINOS data are not affected. No new particles, and in particular, no sterile neutrinos are needed. The LSND signal is controlled by the 1-3 mixing angle $\theta_{13}$ and, depending on the degree of damping, yields $0.0014 < \sin^2\theta_{13} < 0.034$ at $3\sigma$. The scenario can be tested at upcoming $\theta_{13}$ searches: while the comparison of near and far detector measurements at reactors should lead to a null-result a positive signal for $\theta_{13}$ is expected in long-baseline accelerator experiments. The proposed decoherence may partially explain the results of Gallium detector calibrations and it can strongly affect supernova neutrino signals.