Proton Decay Research Articles

Gauge and scalar boson mediated proton decay in a predictive SU(5) GUT model

Gauge and scalar boson mediated proton decay in a predictive SU(5) GUT model

Predictive Dirac neutrino spectrum with strong CP solution in SU(5)L × SU(5)R unification

We develop a grand unified theory of matter and forces based on the gauge symmetry SU(5)L × SU(5)R with parity interchanging the two factor groups. Our main motivation for such a construction is to realize a minimal GUT embedding of left-right symmetric models that provide a parity solution to the strong CP problem without the axion. We show how the gauge couplings unify with an intermediate gauge symmetry SU(3)cL × SU(2)2L × U(1)L × SU(5)R, and establish its consistency with proton decay constraints. The model correctly reproduces the observed fermion masses and mixings and leads to naturally light Dirac neutrinos with their Yukawa couplings suppressed by a factor MI/MG, the ratio of the intermediate scale to the GUT scale. We call this mechanism type II-Dirac seesaw. Furthermore, the model predicts δCP = ±(130.4±1.2)° and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${m}_{{\ u }_{1}}$$\\end{document} = (4.8 – 8.4) meV for the Dirac CP phase and the lightest neutrino mass. We demonstrate how the model solves the strong CP problem via parity symmetry.

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.

Heavy baryon decays into light meson and dark baryon within LCSR

We studied the decays of Heavy baryon into a pseudoscalar meson and a dark baryon in the recently developed B-Mesogenesis scenario, where the two types of effective Lagrangians proposed by the scenario are both considered. The decay amplitudes of Λb0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _b^0$$\\end{document} are calculated by light-cone sum rules using its light-cone distribution amplitudes. The decay amplitudes of Ξb0,±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Xi _b^{0,\\pm }$$\\end{document} are related with those of Λb0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _b^0$$\\end{document} through a flavor SU(3) analysis. The uncertainties of threshold parameter and the Borel parameter are both considered in the numerical calculation. The values of effective coupling constants in the B-Mesogenesis are taken as their upper limits that obtained from our previous study on the inclusive decay. The upper limits of the decay branching fractions are presented as functions of the dark baryon mass.

Testing realistic SO(10) SUSY GUTs with proton decay and gravitational waves

Testing realistic SO(10) SUSY GUTs with proton decay and gravitational waves

Flipped SU(5): unification, proton decay, fermion masses and gravitational waves

We study supersymmetric (SUSY) flipped SU(5) × U(1) unification, focussing on its predictions for proton decay, fermion masses and gravitational waves. We performed a two-loop renormalisation group analysis and showed that the SUSY flipped SU(5) model predicts a high GUT scale MGUT> 1016 GeV. We also investigated the restrictions on the MB−L scale which is associated with the U(1)χ breaking scale. We found that the MB−L scale can vary in a broad region with negligible or little effect on the value of MGUT. Proton decay in this model is induced by dimension-6 operators only. The dimension-5 operator induced by SUSY contribution is suppressed due to the missing partner mechanism. We found that the partial decay width p → π0e+ is high suppressed, being at least one order of magnitude lower than the future Hyper-K sensitivity. We also studied fermion (including neutrino) masses and mixings which can also influence proton decay. We presented two scenarios of flavour textures to check the consistency of the results with fermion masses and mixing. The B − L gauge breaking leads to the generation of cosmic strings. The B − L scale here is not constrained by gauge coupling unification. If this scale is very close that of GUT breaking, strings can be unstable due to the decay to monopole-antimonople pair. Such metastable strings can be used to explain the NANOGrav signals of stochastic gravitational wave background, which may be interpreted here as resulting from the decay of metastable cosmic strings.

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.

Neutrino charge radius and electromagnetic dipole moments via scalar and vector leptoquarks

The one-loop contribution of scalar and vector leptoquarks (LQs) to the electromagnetic properties (NEPs) of massive Dirac neutrinos is presented via an effective Lagrangian approach. For the contribution of gauge LQs to the effective neutrino charge radius defined in Bernabeu et al. (Phys Rev Lett 89:101802, 2002. https://doi.org/10.1103/PhysRevLett.89.101802 [Erratum: Phys Rev Lett 89:229902 (2002)]), we considered a Yang–Mills scenario and used the background field method for the calculation. Analytical results for nonzero neutrino mass are presented, which can be useful to obtain the NEPs of heavy neutrinos, out of which approximate expressions are obtained for light neutrinos. For the numerical analysis we concentrate on the only renormalizable scalar and vector LQ representations that do not need extra symmetries to forbid tree-level proton decay. Constraints on the parameter space consistent with current experimental data are then discussed and it is found that the scalar R~2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\widetilde{R}}_2$$\\end{document} and the vector U1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$U_1$$\\end{document} representations could yield the largest LQ contributions to the NEPs: for LQ couplings to both left- and right handed neutrinos of the order of O(1) and a LQ mass of 1.5-2 TeV, the magnetic dipole moment (MDM) of a Dirac neutrino with a mass in the eV scale can be of the order of 10-9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-9}$$\\end{document}–10-10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-10}$$\\end{document}μB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _B$$\\end{document}, whereas its neutrino electric dipole moment (EDM) can reach values as high as 10-20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-20}$$\\end{document}–10-19\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-19}$$\\end{document} ecm. On the other hand, the effective NCR can reach values up to 10-35\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-35}$$\\end{document} cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document} even if LQs do not couple to right-handed neutrinos, in which case the EDM vanishes and the contribution to the MDM would be negligible.

Inflation, superheavy metastable strings and gravitational waves in non-supersymmetric flipped SU(5)

Motivated by the NANOGrav 15 year data and other recent investigations of stochastic gravitational background radiation based on pulsar timing arrays, we show how superheavy strings survive inflation but the slightly heavier monopoles do not in a non-supersymmetric hybrid inflation model based on flipped SU(5). With the dimensionless string tension parameter Gμ ∼ 10-6, the gravitational wave spectrum emitted by the strings, which are metastable due to breaking caused by monopole-antimonopole quantum mechanical tunneling, is compatible with the latest NANOGrav measurement as well as the advanced LIGO-VIRGO third run data. The string network undergoes about 30 e-foldings of inflation which suppresses the spectrum in the LIGO-VIRGO frequency range. With the symmetry breaking chain SU(5)×U(1) X → SU(3) c ×SU(2) L ×U(1) Z ×U(1) X → SU(3) c ×SU(2) L ×U(1) Y , the estimated proton lifetime is of order 1036-1037 yrs.

Systematic study of two proton radioactivity within the effective liquid drop model

In this study, we investigated two-proton radioactivity using the effective liquid drop model with varying mass asymmetry shapes and effective inertia coefficients (VMAS-EFF). Gaudin’s expression term for Coulomb potential energy is replaced in the current study’s calculation of potential energy. The VMAS-EFF combination predicts the half-life with the lowest standard deviation ( σ =1.03) compared to other models and previous constant mass asymmetry with Werner-inertial Wheeler’s coefficient combinations. The lowest standard deviation value indicates that the VMAS-EFF combination is suitable for reproducing the experimental data. We extended the half-life predictions to another 54 nuclei and compared them with six theoretical model predictions and two empirical formula predictions. The present work also investigated the decay possibilities using quantum tunnelling by computing the driving potential (V-Q) for various states of angular momentum l = 0, 2, 3, and 4. Found that 6Be, 6B, 8C, 12O,15,16Ne, 19Mg, 22Si, 26S, 30Ar 38,39Ti, 40V, 42Cr, 45Fe, 48,49Ni, 54Zn, 58,59,60Ge and 64Se nuclei have a high chance of emission for two protons, while 7B, 10N, 14F, 17Na, 24P, 28Cl,32K, 34Ca, 36,37Sc, 44Mn, 47Co, 52Cu, 56,57,58Ga, 61,62As nuclei have a lower chance for two proton than one proton decay. The computation of separation energy findings agree well with the driving potential findings.

Gauge coupling unification in a minimal non-supersymmetric E6 GUT

We consider a minimal renormalizable non-supersymmetric [Formula: see text] Grand Unified Theory using fundamental representation 27 for fermions and scalars. The scalar with adjoint representation 78 is also taken for direct breaking of [Formula: see text] to SM. The proposed model, guided by TeV-scale vector-like fermions and scalar leptoquark, offers successful gauge unification even in the absence of any intermediate symmetry. Embedded with threshold corrections, it is shown to be compatible with the present experimental limit on proton decay lifetime. The unique feature of the model shows that the GUT threshold corrections to the unification mass is controlled by superheavy gauge bosons only, thereby minimizing the uncertainty of the GUT predictions. The scalar leptoquark and vector-like fermions residing in 27 representation can explain flavor physics anomalies like [Formula: see text] as reported by the LHCb collaboration and the muon anomalous magnetic moment reported by the recent muon [Formula: see text] experiment at Fermilab. The model can also predict a sub-eV scale neutrino at one-loop level via exchange of W and Z gauge bosons through MRIS mechanism.

Spectroscopic analysis of hidden-charm pentaquarks

In this work, the multiquark approach is used to analyze the spectroscopy of hidden-charm pentaquark states, motivated by recent discoveries at the LHCb collaboration. Using the SU(3) flavor representation, pentaquarks having J P = 5/2− are arranged into 10 (decuplet) of the SU(3) flavor multiplets. The masses of pentaquarks are calculated using the extension of the Gursey–Radicati mass formula and the effective mass scheme. Also, we calculated the magnetic moments of the hidden-charm pentaquarks using the effective mass and shielded charge technique. Further, we suggested the possible production modes for J P = 5/2− pentaquarks from the decay of bottom baryons, which consist of pentaquark states as intermediate states. Our results for masses demonstrate reasonable agreement with the available data and our analysis for both masses and magnetic moments may be useful for future experimental studies.

Integrative Modulation of Magnetic Resonance Transverse and Longitudinal Relaxivity in a Cell-Viable Bimagnetic Ensemble, γ-Fe2O3@ZnFe2O4.

The potential application of magnetic nanosystems as magnetic resonance imaging (MRI) contrast agents has been thoroughly investigated. This work seeks to attain robust MRI-contrast efficiency by designing an interacting landscape of a bimagnetic ensemble of zinc ferrite nanorods and maghemite nanoparticles, γ-Fe2O3@ZnFe2O4. Because of competing spin clusters and structural anisotropy triggered by isotropic γ-Fe2O3 and anisotropic ZnFe2O4, γ-Fe2O3@ZnFe2O4 undergoes the evolution of cluster spin-glass state as evident from the critical slowing down law. Such interacting γ-Fe2O3@ZnFe2O4 with spin flipping of 1.2 × 10-8 s and energy barrier of 8.2 × 10-14 erg reflects enhanced MRI-contrast signal. Additionally, γ-Fe2O3@ZnFe2O4 is cell-viable to noncancerous HEK 293 cell-line and shows no pro-tumorigenic activity as observed in MDA-MB-231, an extremely aggressive triple-negative breast cancer cell line. As a result, γ-Fe2O3@ZnFe2O4 is a feasible option for an MRI-contrast agent having longitudinal relaxivity, r1, of 0.46 s-1mM-1 and transverse relaxivity, r2, of 15.94 s-1mM-1, together with r2/r1 of 34.65 at 1.41 T up to a modest metal concentration of 0.1 mM. Hence, this study addresses an interacting isotropic/anisotropic framework with faster water proton decay in MR-relaxivity resulting in phantom signal amplification.

Dilepton production in proton-proton reaction at 4.5 GeV with the HADES spectrometer

Spectra of dileptons emitted in hadron collisions are important tool to study electromagnetic decays of resonances and the validity of the Vector Meson Dominance model. Furthermore, they provide reference spectra for the hot and dense (heavy-ion A+A collisions) and cold nuclear matter (p+A collisions). In February 2022, proton-proton reactions at 4.5 GeV beam kinetic energy were measured by HADES experiment. The aim of the analysis is to study the specific channels that produced dileptons, such as baryonic resonance Dalitz decays (Δ/N* → Ne+e−) and vector meson decays (ρ/ω/φ→ e+e−). In addition, the investigations of dielectron production above the φ meson mass will be enabled. In this contribution, different steps of the e+e− pair reconstruc tion are discussed.

Description of the Proton-Decaying 0_{2}^{+} Resonance of the α Particle.

The recent precise experimental determination of the monopole transition form factor from the ground state of ^{4}He to its 0_{2}^{+} resonance via electron scattering has reinvigorated discussions about the nature of this first excited state of the α particle. The 0_{2}^{+} state has been traditionally interpreted in the literature as the isoscalar monopole resonance (breathing mode) or, alternatively, as a particle-hole shell-model excitation. To better understand the nature of this state, which lies only ∼410  keV above the proton emission threshold, we employ the coupled-channel representation of the no-core Gamow shell model. By considering the [^{3}H+p], [^{3}He+n], and [^{2}H+^{2}H] reaction channels, we explain the excitation energy and monopole form factor of the 0_{2}^{+} state. We argue that the continuum coupling strongly impacts the nature of this state, which carries characteristics of the proton decay threshold.

TRAPPED HOT DARK MATTER IN THE SHELL AROUND THE COMPACT OBJECT

The model of the compact object is considered, being alternate to the black hole. In the model, the accreting protons decay at the Planck scale into positrons and hypothetical Planck neutrinos. The energy of the particles is split in two modes, low and high. The electrons, positrons and Planck neutrinos with the high energy move away. The electrons and positrons with the low energy form the compact object. The Planck neutrinos with the low energy form the shell around the compact object. The Planck neutrinos moving away may be interpreted as the hot dark matter (HDM). The Planck neutrinos in the shell around the compact object may be interpreted as the trapped hot dark matter (THDM). In a recent paper, the concept of the free fall pressure was introduced. In the effective gravity, including the Newton gravity and the free fall pressure, the THDM is hidden for the massive particles but makes deflection of the massless particles. The THDM can be seen in the gravitational interaction of two shells. The gravitational interaction of the galaxies in the Virgo cluster (M60, M87, M84, M86, M49) is studied. The motion of the galaxies is defined by the THDM masses in the shells around the compact objects in the centres of the galaxies, the stellar masses of the galaxies and the HDM mass in the galaxies. The velocities of M60 and M49 toward M87 are estimated to be 678 km s−1 and 445 km s−1 which are 66% and 59% of the observational values respectively.

Comparison of Ring Current Proton Losses Between Contributions From Scattering by Field Line Curvature and EMIC Waves

AbstractAlthough both the field line curvature (FLC) and electromagnetic ion cyclotron (EMIC) waves are recognized to contribute importantly to the loss of energetic protons in the Earth's ring current, their quantitative differences in scattering ring current protons are still not fully understood. In this study, using a realistic, nondipolar magnetic field model, we perform a detailed analysis of the scattering effects of ring current protons and the resultant proton lifetimes due to FLC and EMIC waves at different L‐shells under different levels of geomagnetic activity. We find that compared with EMIC wave‐driven scattering, FLC scattering has a stronger dependence on L‐shell and geomagnetic activity. Pitch angle scattering efficiency due to FLC enhances significantly as proton energy increases. In contrast, scattering by H+ band EMIC waves tends to be weaker with increasing proton energy, while the scattering rates by He+ band EMIC waves increase first and then decrease. The results of proton lifetime against pitch angle scattering show that EMIC wave‐driven scattering dominates the loss of ring current protons at lower L‐shells (L < 6), especially during geomagnetically quiet conditions. During geomagnetically active conditions at L ≥ 6, EMIC wave‐driven scattering dominates at lower proton energies, while FLC scattering dominates at higher proton energies. This study improves the current understanding of the relative contributions of scattering by FLC and EMIC waves to the Earth's ring current proton dynamics.

Investigating Zcs(3985) and Zcs(4000) exotic states in [formula omitted] decays

We study the Zcs(3985) and Zcs(4000) exotic states in the decays of Λb baryons through a molecular scenario. In the final state interaction, the Λb→Λc+Ds(⁎)− decays are followed by the Λc+Ds(⁎)− to Zcs−p rescatterings via exchange of a D(⁎) meson. We predict a branching fraction of (3.1−2.6+1.4)×10−4 for Λb→Zcs−p, which can be measured in the Λb→J/ψK(⁎)−p decay. This study proposes a new approach to test the molecular model, and guides future experimental searches for the Zcs(3985) and Zcs(4000).

Scattering amplitudes of fermions on monopoles

We consider scattering processes involving massless fermions and ’t Hooft-Polyakov magnetic monopoles in a minimal SU(2) model and in the Grand Unified SU(5) theory. We construct expressions for on-shell amplitudes for these processes in the J = 0 partial wave using the spinor helicity basis consisting of single-particle and pairwise helicities. These processes are unsuppressed and are relevant for the monopole catalysis of proton decay. The amplitudes for the minimal processes involving a single fermion scattering on a monopole in the initial state and half-fermion solitons in the final state are presented for the first time and are used to obtain the amplitudes for processes involving more fermions in the initial state and integer fermion numbers in the final state. A number of such anomalous and non-anomalous processes, along with their amplitude expressions, are written down for the SU(5) GUT model.

How Long Does the Hydrogen Atom Live?

It is possible that the proton is stable while atomic hydrogen is not. This is the case in models with new particles carrying baryon number which are light enough to be stable themselves, but heavy enough so that proton decay is kinematically blocked. Models of new physics that explain the neutron lifetime anomaly generically have this feature, allowing for atomic hydrogen to decay through electron capture on a proton. We calculate the radiative hydrogen decay rate involving the emission of a few hundred keV photon, which makes this process experimentally detectable. In particular, we show that the low energy part of the Borexino spectrum is sensitive to radiative hydrogen decay, and turn this into a limit on the hydrogen lifetime of order 1030s or stronger. For models where the neutron mixes with a dark baryon, χ, this limits the mixing angle to roughly 10−11, restricting the n→χγ branching to 10−4, over a wide range of parameter space.