Nucleon Decay Research Articles

Measurement of the absolute efficiency of the X-ARAPUCA photon detector for the DUNE Far Detector 1

The DUNE far detector has been designed to detect photons and electrons generated by the charged products of the interaction of neutrinos with a massive liquid argon (LAr) target. The photon detection system (PDS) of the first DUNE far detector (FD1) is composed of 6000 photon detection units, named X-ARAPUCA. The detection of the prompt light pulse generated by the particle energy release in LAr will complement and boost the DUNE LAr Time Projection Chamber. It will improve the non-beam events tagging and enable at low energies the trigger and the calorimetry of the supernova neutrinos. The X-ARAPUCA is an assembly of several components. Its photon detection efficiency (PDE) depends on the design of the assembly, on the grade of the individual components and on their coupling. The X-ARAPUCA PDE is one of the leading parameters for the PDS sensitivity, that in turn determines the sensitivity of the DUNE for the detection of core-collapse supernova within the galaxy and for nucleon decay searches. In this work we present the final assessment of the absolute PDE of the FD1 X-ARAPUCA baseline design, measured in two laboratories with independent methods and setups. Preliminary results were reported in Palomares (JINST 18(02):C02064, https://doi.org/10.1088/1748-0221/18/02/C02064, 2023). One hundred sixty units of these X-ARAPUCA devices have been deployed in the NP04 facility at the CERN Neutrino Platform, the 1:20 scale FD1 prototype, and will be operated during the year 2024. The assessed value of the PDE is a key parameter both in the NP04 and in the DUNE analysis and reconstruction studies.

A Generic Analysis of Nucleon Decay Branching Fractions in Flipped SU(5) Grand Unification

In flipped SU(5) grand unified theories, the partial decay lifetimes of certain nucleon decay channels depend generically on an unknown unitary matrix, which arises when left-handed lepton fields are embedded into anti-fundamental representations of SU(5). This dependency is particularly relevant when the neutrino mass matrix has a generic structure, introducing uncertainty in the prediction of nucleon decay branching fractions within flipped SU(5). In this paper, we demonstrate that this uncertainty can be parametrized using two parameters, which can be determined by measuring the partial lifetimes of p→π0e+, p→π0μ+, and n→π0ν¯. In addition, we establish upper limits on the ratios of the decay widths of these channels, offering a potential method to test flipped SU(5) in future nucleon decay experiments.

Baryon-number-violating nucleon decays in ALP effective field theories

The search for baryon-number-violating (BNV) nucleon decay is an intriguing probe of new physics beyond the SM in future neutrino experiments with enhanced sensitivity. The dark sector states such as an axion or axion-like particle (ALP) can induce nucleon decays with distinct signature and kinematics from the conventional nucleon decays. In this work, we study the ALP effective field theories (EFTs) with baryon number violation and the impact of light ALP on BNV nucleon decays. We revisit the dimension-8 BNV operators in the extended EFTs with an ALP field a respecting shift symmetry. The low-energy EFT operators with |∆(B – L)| = 2 and |∆(B – L)| = 0 are matched to the baryon chiral perturbation theory. We obtain the effective chiral Lagrangian and the BNV interactions between ALP and baryons/mesons. The ALP interactions lead to two-body baryon decays B → ℓ (or ν) a and three-body nucleon decays N → M ℓ (or ν) a. We obtain the constraints on the UV scale from the invisible Λ0 decay search at BESIII, the invisible neutron decay search at KamLAND and proton decay search at Super-K. We also show the projections of some other baryon/nucleon decays and present the distinct distributions of kinematic observable.

The DUNE Far Detector Vertical Drift Technology. Technical Design Report

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including themystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model.The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolutionrequired to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise.In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D.Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered.This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals.

Baryon number violation involving tau leptons

Baryon number violation is our most sensitive probe of physics beyond the Standard Model, especially through the study of nucleon decays. Angular momentum conservation requires a lepton in the final state of such decays, kinematically restricted to electrons, muons, or neutrinos. We show that operators involving taus, which are at first sight too heavy to play a role in nucleon decays, still lead to clean nucleon decay channels with tau neutrinos. While many of them are already constrained from existing two-body searches such as p → π+ν, other operators induce many-body decays such as p→ηπ+ν¯τ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ p\ o {\\eta \\pi}^{+}{\\overline{\ u}}_{\ au } $$\\end{document} and n → K+π−ντ that have never been searched for.

Model-independent estimates for loop-induced baryon-number-violating nucleon decays

Baryon number is an accidental symmetry of the Standard Model (SM) Lagrangian that so far has been measured to be exactly preserved, although it is expected to be violated at higher energies. In this work we compute order-of-magnitude estimates for the matching contributions of generic ultraviolet models to effective operators that generate nucleon decay processes. This is done in a systematic and automated way using operators constructed from SM fields up to dimension nine and working in a framework that has proved useful in the study of lepton-number violation. For each of the operators we derive estimates for the rates of different nucleon-decay channels. These allow us to establish model-independent lower bounds on the underlying new-physics scale and identify potential correlations between the various decay modes. The results are most relevant for families of models that generate the considered operator. This analysis is especially timely given the expected future sensitivities in numerous experiments such as Hyper-K, DUNE, JUNO and THEIA.

Enhancement of the DUNE FD1 X-ARAPUCA Photon Detection Efficiency and upgrade of the FD2 Photon Collector

The Photon Detection System (PDS) of the first two DUNE far detectors (FD1 and FD2) is composed of 6000 and 672 photon detection units respectively, named X-Arapuca, of different size and geometry. The PDS will complement and boost the DUNE LArTPC for the detection of non beam events: the prompt light detection will improve their tagging, and at low energies it will enable the trigger and the calorimetry of the supernova neutrinos. The X-Arapuca unit is an assembly of several components: its Photon Detection Efficiency (PDE) depends both on the design of the assembly and on the grade and the coupling of the individual components. The X-Arapuca PDE is the driver of the Photon Detection System sensitivity, that in turn determines the sensitivity of the DUNE physics reach for the detection of core-collapse supernova within the galaxy and for nucleon decay searches. In this work we present an update of the absolute PDE of the FD1 X-Arapuca baseline design, measured in laboratory: 160 units of this are deployed in the scale 1:20 FD1 prototype hosted in the NP04 cryostat at the CERN neutrino platform. Further we show how to change the baseline design of the FD1 X-Arapuca, allowing to double its PDE. Finally we review a few selected features of the photon collector of the sixteen FD2 X-Arapuca recently deployed for the FD2 scale 1:20 prototype at CERN in the NP02 cryostat, and of the last six units that integrate the latest advancements.

Pulse shape discrimination technique for diffuse supernova neutrino background search with JUNO

Pulse shape discrimination (PSD) is widely used in particle and nuclear physics. Specifically in liquid scintillator detectors, PSD facilitates the classification of different particle types based on their energy deposition patterns. This technique is particularly valuable for studies of the diffuse supernova neutrino background (DSNB), nucleon decay, and dark matter searches. This paper presents a detailed investigation of the PSD technique, applied in the DSNB search performed with the Jiangmen Underground Neutrino Observatory (JUNO). Instead of using conventional cut-and-count methods, we employ methods based on boosted decision trees and neural networks and compare their capability to distinguish the DSNB signals from the atmospheric neutrino neutral-current background events. The two methods demonstrate comparable performance, resulting in a 50–80% improvement in signal efficiency compared to a previous study performed for JUNO (An et al. [JUNO] in J Phys G 43(3):030401, 2016). Moreover, we study the dependence of the PSD performance on the visible energy and final state composition of the events and find a significant dependence on the presence/absence of 11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{11}$$\\end{document}C. Finally, we evaluate the impact of the detector effects (photon propagation, PMT dark noise, and waveform reconstruction) on the PSD performance.

PocketWATCH: design and operation of a multi-use test bed for water Cherenkov detector components in pure and gadolinium loaded water

The PocketWATCH facility is a unique multi-purpose test bed designed to replicate the conditions of large water Cherenkov detectors. Housed at the University of Sheffield, the facility consists of a light-tight 2000 L ultrapure water tank with purification and temperature control systems. Water temperature, resistivity, and UV attenuation in the tank are monitored and shown to be stable over time. The system is also shown to be compatible with a solution of 0.2% gadolinium sulfate, allowing further utility in testing equipment bound for the next generation neutrino and nucleon decay water Cherenkov particle detectors. The relevant water quality parameters are shown to be stable whilst running in Gd-mode, thereby providing a suitable test bed for hardware development in a realistic, ex situ environment.

Tension between neutrino masses and gauge coupling unification in natural grand unified theories

The natural grand unified theories (GUT) solve various problems of the supersymmetric GUT and give realistic quark and lepton mass matrices under the natural assumption that all terms allowed by the symmetry are introduced with O(1) coefficients. However, because of the natural assumption, it is difficult to achieve the gauge coupling unification without tuning, while keeping neutrino masses at realistic values. In this paper, we try to avoid this tension between the neutrino masses and the gauge coupling unification, by introducing suppression factors for several terms. These suppression factors can be understood by approximate symmetries in some of the solutions. We show that one of the most important results in the natural GUT scenario, that the nucleon decay mediated by superheavy gauge fields is enhanced due to a smaller unification scale while the nucleon decay mediated by superheavy colored Higgs is suppressed, may change in those models proposed in this paper. Published by the American Physical Society 2024

Hyper-Kamiokande construction status and prospects

The Hyper-Kamiokande (Hyper-K) project is the world’s leading international neutrino and nucleon decay experiment comprising a next-generation underground water Cherenkov detector and upgraded Japan Proton Accelerator Research Complex (J-PARC) neutrino beam. It will provide an enormous potential to discover the leptonic charge-parity violation, to investigate the Grand Unified Theory by proton decay exploration, and to determine the neutrino mass ordering. Further, Hyper-K will significantly enhance the capability to observe solar neutrinos and neutrinos from other astronomical sources in comparison with its predecessors. After the budget approval in January 2020, the Hyper-K project officially began, and the operation is expected to start in 2027. The excavations of a 2.0 km long access tunnel and the tunnels for the detector facility have been completed. In October 2022 it was started the excavation of one of the world’s largest underground caverns to suite the HK detector. This article discusses the status and the prospects of the Hyper-K detector construction.

The Influence of Velocity-dependent Correction Factor on Proton Decay Reactions in Massive White Dwarfs

Twenty-five typical massive white dwarfs (WDs) are selected and the proton decay reaction catalyzed by magnetic monopoles (MMs) for these WDs is discussed. A velocity-dependent correction factor strongly affects the cross-section. We find that a strong suppression controls the monopole catalysis of nucleon decay by the correction factor. The maximum number of MMs is captured and the luminosity can be 2.235 × 1021 and 1.7859 × 1032erg s−1 (e.g., for the O+Ne core mass WD J055631.17+130639.78). The luminosities of most massive WDs agree well with the observations at relatively low temperatures (e.g., T 6 = 0.1), but can be three and two orders of magnitude higher than those of the observations for model (I) and (II) at relatively high temperatures (e.g., T 6 = 10), respectively. The luminosities of model (I) are about one order of magnitude higher than those of model (II). Since we consider the effect of the number of MMs captured on the mass–radius relation and the suppression of the proton decay by the correction factor, the study by model (II) may be an improved estimation.

Dark-Matter-Induced Nucleon Decay Signals in Mesogenesis.

We introduce and study the first class of signals that can probe the dark matter in mesogenesis, which will be observable at current and upcoming large volume neutrino experiments. The well-motivated mesogenesis scenario for generating the observed matter-antimatter asymmetry necessarily has dark matter charged under the baryon number. Interactions of these particles with nuclei can induce nucleon decay with kinematics differing from spontaneous nucleon decay. We calculate the rate for this process and develop a simulation of the signal that includes important distortions due to nuclear effects. We estimate the sensitivity of DUNE, Super-Kamiokande, Hyper-Kamiokande, and JUNO to this striking signal.

Revisiting renormalization group equations of the SMEFT dimension-seven operators

In this work, we revisit the renormalization group equations (RGEs) of dimension-seven (dim-7) operators in the Standard Model effective field theory (SMEFT) resulting from mixing among dim-7 operators themselves by means of the background field method. Adopting a recently proposed physical basis for dim-7 operators, we achieve the explicit RGEs of all non-redundant dim-7 operators in the SMEFT for the first time. Together with those originating from the dim-5 and dim-6 operators, these results constitute the complete RGEs of dim-7 operators, and hence can be exploited to study full RG-running effects on some lepton- or baryon-number-violating processes involving dim-7 operators in the SMEFT, such as neutrino masses, neutrinoless double beta decay, meson and nucleon decays. We perform an analysis of the structure and perturbative power counting of the obtained one-loop anomalous dimension matrix, which is consistent with a non-renormalization theorem and the naive dimension analysis. Additionally, a partial check on some results is carried out by means of different tools and quantum field gauges.

A possible critical heating from decay reaction and new upper limit of the magnetic monopole flux for the supermassive white dwarfs

We present the new upper limit of the magnetic monopole (MM) flux and discuss three MM models of the heating resource for supermassive white dwarfs (WDs) by considering the effect of temperature on thermonuclear reaction and mass radius relation of WDs based on the catalytic nuclear decay by MM. We discuss the luminosity and compared it with the observations to apply to 25 supermassive WDs. We find the maxnium of the number of MM captured can be 9.6943×1011\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.6943\ imes 10^{11}$$\\end{document}, and 9.0671×1011\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.0671\ imes 10^{11}$$\\end{document} for O+Ne core high mass WDs (e.g., WD J055631.17+130639.78), and C+O core high mass WDs (e.g., WD J055631.17+130639.78), respectively. The luminosities increase with the increasing of the temperature and are agreed well with the observations for model (III). The differences are no more than one, and three orders of magnitude higher than observations for model (III), and (I, II), respectively. Finaly, we find that the maxnium of the upper limits of the MM flux ϕm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi _{m}$$\\end{document} due to RC effect can be 9.1071×10-15\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.1071\ imes 10^{-15}$$\\end{document}, and 2.7670×10-14\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2.7670\ imes 10^{-14}$$\\end{document} for O+Ne and C+O core high mass WDs, respectively. Our results are about one and two orders of magnitude higher than those of Abbasi et al. (EPJC 69:361, 2010) (Albert et al. in JHEP 07:054, 2017) for O+Ne, and C+O core mass WDs, respectively, and can be about three and four orders of magnitude higher than those of Aartsen et al. (EPJC 76:133, 2016) (Ic40, Ic86), respectively. Our results show that the monopole-catalyzed nucleon decay could prevent WDs from cooling down into a stellar graveyard by keeping them hot.

Muon energy reconstruction for applications in neutrino astronomy in the DUNE far detector

DUNE (Deep Underground Neutrino Experiment) is a proposed long-baseline neutrino oscillation experiment located in the United States. The main physics objectives of DUNE are to measure neutrino oscillations and interactions, search for nucleon decay, observe supernova neutrino bursts and beyond Standard Model (BSM) effects. The DUNE far detector will be located 4850 feet underground at the Sanford Underground Research Facility in Lead, South Dakota. It will house the world's largest liquid-argon time projection chambers (TPC). The DUNE far detector can detect high-energy leptons that arise from interactions of cosmogenic neutrinos and search for neutrinos originating from the decay of weakly-interactive massive particles (WIMPs) annihilations occurring inside the Sun. Selecting upward-going muons reduces the background from cosmic-ray muons. The muon energy is estimated from the electromagnetic showers accompanying the muon, a technique that allows energy reconstruction up to a few hundred TeV.

Rescattering effects in nucleon-to-meson form factors and application to tau-lepton-induced proton decay

Nucleon decays put extremely stringent bounds on baryon-number-violating interactions. However, in case the corresponding operators involve only τ leptons, the direct two-body decays, e.g., p→π0τ+, are kinematically not allowed and nucleon decay can only proceed via an off-shell τ, leading to p→π0ℓ+νℓν¯τ. To calculate such processes, the momentum dependence of the form factors for nucleon-to-meson transitions, which describe the hadronization of the underlying process at the quark level, is needed. In this work, we point out new isospin and Fierz relations among such proton–kaon matrix elements and calculate the momentum dependence of the nucleon-to-meson form factors from the universal final-state interactions in terms of pion–nucleon or kaon–nucleon scattering phase shifts. We use these results to derive novel limits on the Wilson coefficients of the baryon-number-violating dimension-6 operators involving a τ lepton, which were previously unconstrained.

A study on nuclear binding energy and beta decay energy using deep neural networks

The Artificial Neural Network (ANN) is one of the innovative methods for predicting the structural and dynamic properties of atomic nuclei. In this work, we employed machine learning based on the Deep Neural Network (DNN) technique to find the ground state binding energy and beta decay energy of various nuclei. 3560 experimental nuclear data sets have been used for training and validating the DNN model. Neutron number (N), proton number (Z), the pairing term (δ), a magic number greater than or equal to N and Z, asymmetry factor (a) and promiscuity factor (P) are used as input parameters. The Rectified Linear Unit (ReLU) function and Mean Absolute Error (MAE) are used as activation and Loss functions for the training process. We perform the predictions of ground state binding energy per nucleon and beta decay energies in Zinc and Promethium isotopes using the DNN model, which is in good agreement with experimental results.

The neutrino emissivity and the cooling energy resources by magnetic monopole in white dwarfs

Some typical low mass and high mass white dwarfs (WDs) are selected and the neutrino emissivity and the cooling energy resources problems are discussed. We present three models (I, II, III) to investigate the number of magnetic monopole (MM) captured, the luminosity, and the neutrino emissivity based on the MM catalytic nuclear decay. Model (I) mainly considers the effect of compression factor on thermonuclear cross section and ignores the effect of mass radius relationship on luminosity and neutrino emissivity. Model (II) only considers the effect of mass radius relationship at zero temperature on the number of MMs captured, the luminosities and the neutrino emissivity. Model (III) discusses the equation of state of the plasma and considers the effect of the number of MMs captured on the mass radius relationship, then investigates the number of MMs captured, the luminosities and the neutrino emissivity. Firstly, we find that the maximum of the number of captured MMs and the luminosities of these WDs can be 1.313×1029, and 2.083×1036ergss−1, respectively. Secondly, the luminosities due to MM catalytic nuclear decay for models (I, III) are agreed well with the observations, but the luminosities for model (II) are higher than the observations. Finally, the maximum of the neutrino emission rates of these WDs can be 1.626×1038s−1. The neutrino emission may not influence the structure and the evolution of the WDs. However, the monopole-catalyzed nucleon decay process may be regarded as a mechanism for keeping WDs hot.

Photodetection and electronic system for the Hyper-Kamiokande Water Cherenkov detectors

Hyper-Kamiokande is a next-generation neutrino experiment built in Japan and is scheduled to become operational in 2027. It will be the world’s largest underground water Cherenkov detector instrumented with three kinds of photomultipliers (PMTs): 20- and 3- inch PMTs, supplemented with multi-PMTs. The physics program of the Hyper-Kamiokande experiment will address the most important, unsolved questions in physics, including CP violation in neutrino oscillations and nucleon decay. An overview of the experiment is presented, emphasizing photo-sensors and electronics.