Neutrino Oscillation Parameters Research Articles

Improving time and position resolutions of RPC detectors using time over threshold information

INO-ICAL is a proposed underground experiment to study the oscillation parameters of neutrinos by detecting those produced in the atmospheric air showers. The Iron CALorimeter (ICAL) is to have 151 layers of iron plates stacked vertically corresponding to a height of ∼14.5 m, with active detector elements inserted between the iron layers. The iron layers will be magnetized with a maximum magnetic field of 1.5 T to enable the measurement of the charge and momentum of the μ - (or μ +) produced by ν μ (or ν̅ μ ) interactions inside the detector throughout the operation. Resistive Plate Chambers (RPCs) have been chosen as the active detector elements as they are amenable to large area coverage, as well as due to their high particle detection efficiency, long-term performance and low cost of production. The major factors that weigh in on the physics potential of the ICAL detector are the efficiency, position resolution and time resolution of the large area RPCs. A prototype detector called mini-ICAL (with 11 iron layers) was commissioned in order to understand the engineering challenges in building the large-scale electromagnet and its ancillary systems, and also to study the performance of the RPC detectors and readout electronics developed by the INO collaboration. As part of the performance study of the RPC detectors, an attempt is made to improve their position and time resolutions. The designed position resolution for the ICAL detector is of the order of 1 cm and the required time resolution is ∼1 ns. Even a small improvement in the position and time resolution will help to improve the measurements of momentum and directionality of the neutrinos in the ICAL detector. In ICAL detector simulation, where muons traverse in all directions with on average 20 RPC layers, a 30 % improvement in position resolution results in ∼10 % improvement in the momentum resolution at 3 GeV. Due to large iron materials in between two RPCs, the resolution is dominated by the effect of multiple scattering at this momentum. Also for a muon with 10 layer hit, the charge ambiguity reduces from 0.04 % to 0.001 % when the time resolution improves from 1 ns to 0.7 ns. The Time-over-Threshold (ToT) of the RPC pulses is recorded by the readout electronics. ToT is a measure of the pulse width and consequently the pulse amplitude. This information is used to improve the time and position resolution of RPCs and consequently INO's physics potential.

Inverse seesaw in modular symmetry

We make an investigation of modular group in inverse seesaw framework. Modular symmetry is advantageous because it reduces the usage of extra scalar fields significantly. Moreover, the Yukawa couplings are expressed in terms of Dedekind eta functions, which also have a q expansion form, generally utilized to achieve numerical simplicity. Our proposed model includes six heavy fermion superfields i.e., , and a weighton. The study of neutrino phenomenology becomes simplified and effective by the usage of modular symmetry, which provides us a well defined mass structure for the lepton sector. Here, we observe that all the neutrino oscillation parameters, as well as the effective electron neutrino mass in neutrinoless double beta decay can be successfully accommodated in this model. We also briefly discuss the lepton flavor violating decays ℓ i → ℓ j γ, the collider bound on Z′ mass and comment on non-unitarity of lepton mixing matrix.

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.

Fermion spectrum with normal neutrino mass ordering in a nonrenormalizable [formula omitted] model based on [formula omitted] symmetry

We construct a nonrenormalizable B−L model with Σ(18)×Z2 symmetry that can explain the observed SM quark mass and mixing pattern as well as the neutrino oscillation data with normal mass ordering in which the best-fit values of the large atmospheric neutrino mixing angle θ23 and the Dirac CP-violating phase δCP are located in the higher octant and third quadrant, respectively. The smallness of the active neutrino mass is generated from type I-seesaw mechanism with only one SU(2)L Higgs doublet. In numerical analysis, we consider the neutrino oscillation parameters, including two neutrino mass squared differences Δm212,Δm312, three mixing angles s122,s132,s232 and one Dirac CP violating phase δ, as input parameters and find out the other undetermined neutrino parameters including the sum of neutrino masses, the effective neutrino mass 〈mee〉 and three free parameters α,ω12 and ω22. The sum of neutrino masses and the effective neutrino masses are respectively predicted to be Σmν=76.7meV and 〈mee〉=13.0meV which are well consistent with the recent experimental constraints. The quark masses are in good agreement with the recent experimental data while the quark mixings are consistent with the recent constraints on the CKM matrix.

Effects of gravitational lensing on neutrino oscillation in gamma -spacetime

We study the effects of gravitational lensing on neutrino oscillations in the gamma -spacetime which describes a static, axially-symmetric and asymptotically flat solution of the Einstein’s field equations in vacuum. Using the quantum-mechanical treatment for relativistic neutrinos, we calculate the phase of neutrino oscillations in this spacetime by considering both radial and non-radial propagation. We show the dependence of the oscillation probability on the absolute neutrino masses, which in the two-flavour case also depends upon the sign of mass squared difference, in sharp contrast with the well-known results of vacuum oscillation in flat spacetime. We also show the effects of the deformation parameter gamma on neutrino oscillations and reproduce previously known results for the Schwarzschild metric. We then extend these to a more realistic three flavours neutrino scenario and study the effects of the parameter gamma and the lightest neutrino mass while using best fit values of neutrino oscillation parameters.

JUNO Oscillation Physics

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton multi-purpose liquid scintillator detector with an expected energy resolution, under construction in a 700 m underground laboratory in the south of China (Jiangmen city, Guangdong province). The exceptional energy resolution and the massive fiducial volume of the JUNO detector offer great opportunities for addressing many essential topics in neutrino and astroparticle physics. JUNO’s primary goals are to determine the neutrino mass ordering and precisely measure the related neutrino oscillation parameters. With six years of data taking with reactor antineutrinos, JUNO can determine the mass ordering at a 3-4σ significance and the neutrino oscillation parameters sin2 θ 12, , and to a precision of better than 0.6%. In addition, the atmospheric neutrino and solar neutrino measurement at JUNO can also provide complementary and important information for neutrino oscillation physics. This work focuses on the oscillation physics of JUNO, which includes measurement and analysis of the reactor neutrinos, the atmospheric neutrinos, and the solar neutrinos. With the delicate energy response calibration and event reconstruction potential, JUNO will make a world-leading measurement on the neutrino oscillation parameters and neutrino mass ordering in the near future.

Exploring NSI using oscillation dip and valley in atmospheric neutrino experiments

We present a new approach to probe flavor-changing neutral-current non-standard neutrino interaction parameter εμτ using the oscillation dip and valley features. We use the simulated up/down ratio of reconstructed muons events at the proposed Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory to demonstrate that in presence of NSI parameter ε μτ, the oscillation dip location shifts and oscillation valley bends. Utilizing the charge identification capability of ICAL, the opposite shifts in the oscillation dip locations and the contrast in the oscillation valley curvatures for μ− and μ+ can be used to place 90% C.L. bounds of about 2% on |εμτ| using 500 kt• yr exposure. In our procedure, we take care of statistical fluctuations, systematic errors, and uncertainties in neutrino oscillation parameters.

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.

20-inch photomultiplier tube timing study for JUNO

Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator neutrino detector now under construction at Jiangmen, Guangdong, China for determination of neutrino mass ordering with 3% energy resolution at 1 MeV, a precise measurement of neutrino oscillation parameters, and other neutrino physics. The central detector is made up of a 35.4-meter diameter acrylic sphere which contains 20 kton of liquid scintillator and is surrounded by about 18k 20-inch photomultiplier tubes (PMTs). The PMTs performance is one of the JUNO’s key successes to reach the high resolution goal. In this study, the PMT characteristic and its timing related responses were determined via the PMT generated signals, extracted from the PMT in a scanning station system. About 2,400 of micro-channel plate PMTs (MCP-PMTs) and dynode PMTs were analyzed for their responses with LED source such as rise time, fall time, transit time spread (TTS), gain, etc., which relate to photon incident on different positions of PMT’s glass surface. Furthermore, we also observed the fluctuation of PMT performance under magnetic field which can decrease the PMT photon detection efficiency (PDE).

Evolution of neutrino mass-mixing parameters in matter with non-standard interactions

We explore the role of matter effect in the evolution of neutrino oscillation parameters in the presence of lepton-flavor-conserving and lepton-flavor-violating neutral-current non-standard interactions (NSI) of the neutrino. We derive simple approximate analytical expressions showing the evolution of mass-mixing parameters in matter with energy in the presence of standard interactions (SI) and SI+NSI (considering both positive and negative values of real NSI parameters). We observe that only the NSI parameters in the (2,3) block, namely εμτ and (γ − β) ≡ (εττ− εμμ) affect the modification of θ23. Though all the NSI parameters influence the evolution of θ13, εeμ and εeτ show a stronger impact at the energies relevant for DUNE. The solar mixing angle θ12 quickly approaches to ∼ 90° with increasing energy in both SI and SI+NSI cases. The change in ∆ {m}_{21,m}^2 is quite significant as compared to ∆ {m}_{31,m}^2 both in SI and SI+NSI frameworks for the energies relevant for DUNE baseline. Flipping the signs of the NSI parameters alters the way in which mass-mixing parameters run with energy. We demonstrate the utility of our approach in addressing several important features related to neutrino oscillation such as: a) unraveling interesting degeneracies between θ23 and NSI parameters, b) estimating the resonance energy in presence of NSI when θ13 in matter becomes maximal, c) figuring out the required baselines and energies to have maximal matter effect in νμ → νe transition in the presence of different NSI parameters, and d) studying the impact of NSI parameters εμτ and (γ − β) on the νμ → νμ survival probability.

Constraining CPT violation with Hyper-Kamiokande and ESSnuSB

CPT invariance is one of the most fundamental symmetries in nature and it plays a major role in the formulation of Quantum Field Theory. Although no definitive signal of CPT violation has been observed so far, there are many reasons to carefully investigate various low-energy phenomena that can provide better probes to test CPT symmetry. In this context, neutrino experiments are expected to provide more stringent bounds on CPT invariance violation when compared to the existing bounds from the Kaon system. In this work, we investigate the sensitivity of the upcoming long-baseline experiments: Hyper Kamiokande (T2HK, T2HKK), ESSnuSB and DUNE to constrain the CPT violating parameters $\Delta(\delta_{CP})$, $\Delta(m^2_{31})$ and $\Delta(\sin^2 \theta_{23})$, which characterize the difference between neutrino and antineutrino oscillation parameters. Further, we analyse neutrino and antineutrino data independently and constrain the oscillation parameters governing them by considering the combination of these experiments (DUNE+T2HKK and DUNE+ESSnuSB). In addition, assuming CPT symmetry is violated in nature, we study the individual ability of the aforementioned experiments to establish CPT violation. We found that the experiments Hyper-K (T2HK, T2HKK) and ESSnuSB, along with DUNE, will be able to establish CPT violation in their proposed run-times.

Future prospects in neutrino physics

Neutrino physics has come a long way and made great strides in the past decades. We discuss the prospects of what more can be learned in this field in the forthcoming neutrino oscillation facilities. We will mostly focus on the potential of the long-baseline experiments and the atmospheric neutrino experiments. Sensitivity of these experiments to standard neutrino oscillation parameters will be presented. We will also discuss the prospects of new physics searches at these facilities.

From Daya Bay experiment to Jiangmen Underground Neutrino Observatory experiment

Currently, the neutrino oscillation phenomenon is of research interest in particle physics. The discovery of the neutrino oscillation phenomenon confirmed that neutrinos have a minute mass, which is an important way to explore new physics beyond the standard model. The Daya Bay reactor neutrino experiment is an underground experiment that studies short-baseline reactor neutrino oscillations. It uses the far and near-identical detectors to reduce the detector uncertainty and the reactor neutrino expected flux uncertainty to measure the anti-neutrino rate and energy spectrum. The Daya Bay experiment released the latest neutrino oscillation parameters $\sin^{2}2\theta_{13}$ and $|\Delta$$m^{2}_{32}|$ in 2018, which used 1958 days of data. The $\sin^{2}2\theta_{13}$ had the highest measurement precision to date, which reached 3.4$%$, and the precision of $|\Delta$$m^{2}_{32}|$ was 2.8$%$, which was comparable with that of the accelerator-based experiments, such as MINOS, No$\nu$A and T2K. The accurate measurement of $\theta_{13}$ will be helpful to the next-generation of neutrino experiments that will determine the neutrino mass ordering and measure the CP-violating phase. Jiangmen Underground Neutrino Observatory (JUNO) is a multipurpose neutrino experiment that is under construction. The main scientific aim of JUNO is to determine the neutrino mass ordering by measuring the neutrino energy spectrum with a resolution of 3$%$ at 1 MeV and a $~\ge$ 1$%$ energy linearity. The neutrino mass ordering can be measured with a significance 3–4$\sigma$ based on six years of data that has been collected. In addition, JUNO will make a significant contribution to the precise measurement of neutrino oscillation parameters and the study of supernova neutrinos, solar neutrinos, atmospheric neutrinos, geoneutrinos, and nucleon decay.

Impact of improved energy resolution on DUNE sensitivity to neutrino non-standard interactions

The full physics potential of the next-generation Deep Underground Neutrino Experiment (DUNE) is still being explored. In particular, there have been some recent studies on the possibility of improving DUNE’s neutrino energy reconstruction. The main motivation is that a better determination of the neutrino energy in an event-by-event basis will translate into an improved measurement of the Dirac C P phase and other neutrino oscillation parameters. To further motivate studies and improvements on the neutrino energy reconstruction, we evaluate the impact of energy resolution at DUNE on an illustrative new physics scenario, viz. non-standard interactions (NSI) of neutrinos with matter. We show that a better energy resolution in comparison to the ones given in the DUNE conceptual and technical design reports may significantly enhance the experimental sensitivity to NSI, particularly when degeneracies are present. While a better reconstruction of the first oscillation peak helps disentangling standard C P effects from those coming from NSIs, we find that the second oscillation peak also plays a nontrivial role in improving DUNE’s sensitivity.

Physics potential of the combined sensitivity of T2K-II, NOνA extension, and JUNO

Leptonic \textit{CP} violation search, neutrino mass hierarchy determination, and the precision measurement of oscillation parameters for a unitary test of the leptonic mixing matrix are among the major targets of the ongoing and future neutrino oscillation experiments. The work explores the physics reach for these targets by around 2027, when the third generation of the neutrino experiments starts operation, with a combined sensitivity of three experiments: T2K-II, NO$\nu$A extension, and JUNO. It is shown that a joint analysis of these three experiments can conclusively determine the neutrino mass hierarchy. Also, at certain values of \emph{true} \dcp, it provides closely around a $5\sigma$ confidence level (C.L.) to exclude \textit{CP}-conserving values and more than a $50\%$ fractional region of \emph{true} $\delta_{\text{CP}}$ values can be explored with a statistic significance of at least a $3\sigma$ C.L. Besides, the joint analysis can provide unprecedented precision measurements of the atmospheric neutrino oscillation parameters and a great offer to solve the $\theta_{23}$ octant degeneracy in the case of nonmaximal mixing.

The physics potentials of JUNO

The Jiangmen Underground Neutrino Observatory(JUNO) is a 20 kton liquid scintillator neutrino experiment under construction in a 700 m deep underground in Southern China. The experiment has been designed to reach the energy resolution of 3% at 1 MeV for the neutrino mass ordering determination with the PMT photocathode coverage >75%.The central detector is installed with 17 612 20-inch PMTs and 25 600 3-inch PMTs. Besides the main physics goal, JUNO will also contribute to various other areas. These include measuring neutrino oscillation parameters to the sub-percent precision, detecting geo, solar, atmospheric neutrinos, and monitoring the neutrino sky for transient phenomena such as supernovae explosion. Besides, the detector will be a perfect observatory for proton decay searches.

Multiscalar B − L model with Σ(18) symmetry for neutrino mass and mixing

We construct a non-renormalizable [Formula: see text] model based on [Formula: see text] symmetry, whereby, neutrino mass ordering and the tiny neutrino masses are explained at tree level via type I seesaw mechanism. The model can reproduce the recent observed neutrino oscillation data in which neutrino oscillation parameters including three mixing angles [Formula: see text], Dirac CP phase plus neutrino squared-mass splittings [Formula: see text] get the best-fit values for both Normal ordering (NO) and Inverted ordering (IO). The Majorana phases are predicted to be [Formula: see text] for NO, [Formula: see text] for IO and [Formula: see text] for both NH and IO. The sum of neutrino mass and the effective neutrino mass are, respectively, predicted to be [Formula: see text] for NO while [Formula: see text] for IO and [Formula: see text] for NO while [Formula: see text] for IO which are well compatible with the most recent experimental constraints.

Vertex and energy reconstruction in JUNO with machine learning methods

The Jiangmen Underground Neutrino Observatory (JUNO) is an experiment designed to study neutrino oscillations. Determination of neutrino mass ordering and precise measurement of neutrino oscillation parameters sin2θ12, Δm212 and Δm312 are the main goals of the experiment. A rich physical program beyond the oscillation analysis is also foreseen. The ability to accurately reconstruct particle interaction events in JUNO is of great importance for the success of the experiment.In this work we present several machine learning approaches applied to the vertex and the energy reconstruction. Multiple models and architectures were compared and studied, including Boosted Decision Trees (BDT), Deep Neural Networks (DNN), a few kinds of Convolution Neural Networks (CNN), based on ResNet and VGG, and a Graph Neural Network based on DeepSphere. The models of BDT and DNN are trained with aggregated information, pre-calculated from PMT signal, while the others are trained with PMT-wise measured information from 17600 PMTs.Based on a study, carried out using the dataset, generated by the official JUNO software, we demonstrate that machine learning approaches achieve the necessary level of accuracy for reaching the physical goals of JUNO: σE=3% at Evis=1MeV for the energy and σx,y,z=10cm at Evis=1MeV for the position.

Muon reconstruction with a convolutional neural network in the JUNO detector

The Jiangmen Underground Neutrino Observatory (JUNO) is designed to determine the neutrino mass ordering and measure neutrino oscillation parameters. A precise muon reconstruction is crucial to reduce one of the major backgrounds induced by cosmic muons. This article proposes a novel muon reconstruction method based on convolutional neural network (CNN) models. In this method, the track information reconstructed by the top tracker is used for network training. The training dataset is augmented by applying a rotation to muon tracks to compensate for the limited angular coverage of the top tracker. The muon reconstruction with the CNN model can produce unbiased tracks with performance that spatial resolution is better than 10 cm and angular resolution is better than 0.6 degrees. By using a GPU accelerated implementation a speedup factor of 100 compared to existing CPU techniques has been demonstrated.

Quantum Gravity Effects on Oscillation Parameters in a Four Flavor Framework

We consider the effects of Planck scale operators on four flavour neutrino mixings. Quantum gravity (Planck scale effects) leads to an effective SU(2)L × U(1) invariant dimension-5 Lagrangian involving, neutrino and Higgs fields. On symmetry breaking, this operator gives rise to correction to the neutrino masses and mixing.We investigate the effect of higher dimensional operators coming from Planck scale Physics on neutrino oscillation parameters in a four flavor framework. We find that most of the parameters are not altered by this effect but we get the interesting result that for certain values of the Majoranna phases, the 𝜃23 (the atmospheric neutrino mixing angle) goes significantly above 45 degrees. Hence these values of the Majoranna phases are disallowed by data.