We investigate the potential of future neutrino experiments, DUNE and Hyper-Kamiokande, to probe magnetic monopoles via Callan-Rubakov (CR) processes. We consider both relativistic and non-relativistic monopoles and focus on two primary detection signatures: high-energy antiproton production and proton decay catalysis. For relativistic monopoles, our analysis of the CR process indicates antiproton production with energies near 900 GeV and we find that both experiments can provide limits on the fluxes an order of magnitude below the Parker bound (approximately Φ ≲ 10 cm s sr ). For non-relativistic monopoles, we recast the experimental sensitivity to proton decay catalysis and obtain upper limits on the monopole flux of Φ ≲ 2.3 × 10 cm s sr for Hyper-Kamiokande and Φ ≲ 1.1 × 10 cm s sr for DUNE.

Spain

Pablo Candela

United Kingdom

Valentin Khoze

Jessica Turner

Monopoles at future neutrino detectors

We use recent evidence of TeV neutrino events from the most significant astrophysical sources detected by IceCube – NGC 1068, TXS 0506+056, PKS 1424+240– to constrain the local and global overdensity of relic neutrinos and to explore potential new neutrino self-interactions. Assuming a relic neutrino overdensity, such high-energy neutrinos have travelled considerable distances through a sea of relic neutrinos and could have undergone scattering, altering their observed flux on Earth. Considering only Standard Model interactions, we constrain the relic overdensity to <math altimg='si1.svg'><mi>&#951;</mi><mo>&#8804;</mo><mn>2</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></math> at the 90% confidence level, assuming the sum of neutrino masses saturates the cosmological bound, <math altimg='si2.svg'><msub><mrow><mo>&#8721;</mo></mrow><mrow><mi>i</mi></mrow></msub><msub><mrow><mi>m</mi></mrow><mrow><mi>i</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0.13</mn></math> eV. We demonstrate that this limit improves for larger neutrino masses and study how it depends on the scale of the overdensity region. Considering new interactions between TeV-scale neutrinos and relic neutrinos, mediated by a light boson, we probe couplings of approximately <math altimg='si3.svg'><mi>g</mi><mo>&#8764;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn></mrow></msup></math> with current data for a boson mass around the MeV scale. We demonstrate that this limit improves with larger neutrino masses and the scale of the overdensity region.

Jack Franklin

Ivan Martinez-Soler

Yuber F. Perez-Gonzalez

Probing the cosmic neutrino background and new physics with TeV-scale astrophysical neutrinos

We investigate a class of leptogenesis scenarios in which the sector containing the lightest right-handed neutrino establishes kinetic equilibrium at a temperature $$ {T}_{N_1} $$ > $\textit{T}$ , where $\textit{T}$ is the temperature of the Standard Model sector. We study the reheating processes which realise this “hot leptogenesis” and the conditions under which kinetic and chemical equilibrium can be maintained. We derive and solve two sets of evolution equations, depending on the presence of chemical equilibrium within the hot sector, and numerically solve these for benchmark scenarios. We compare the viable parameter space of this model with standard leptogenesis scenarios with a thermal initial condition and find that hot leptogenesis resolves the neutrino and Higgs mass fine-tuning problems present in the standard scenario.

United States

Michael Baker

Ansh Bhatnagar

Djuna Croon

Hot leptogenesis

We investigate the properties of domain walls arising from non-Abelian discrete symmetries, which we refer to as non-Abelian domain walls. We focus on $\textit{S}$ , one of the most commonly used groups in lepton flavour mixing models. The spontaneous breaking of $\textit{S}$ leads to distinct vacua preserving a residual $\textit{Z}$ or $\textit{Z}$ symmetry. Five types of domain walls are found, labelled as SI, SII, TI, TII, and TIII, respectively, the former two separating $\textit{Z}$ vacua and the latter three separating $\textit{Z}$ vacua. We highlight that SI, TI and TIII may be unstable for some regions of the parameter space and decay to stable domain walls. Stable domain walls can collapse and release gravitational radiation for a suitable size of explicit symmetry breaking. A symmetry-breaking scale of order 100 TeV may explain the recent discovery of nanohertz gravitational waves by PTA experiments. For the first time, we investigate the properties of these domain walls, which we obtain numerically with semi-analytical formulas applied to compute the tension and thickness across a wide range of parameter space. We estimate the resulting gravitational wave spectrum and find that, thanks to their rich vacuum structure, non-Abelian domain walls manifest in a very interesting and complex phenomenology.

China

Bowen Fu

Stephen King

Luca Marsili

Italy

Silvia Pascoli

Ye-Ling Zhou

Non-Abelian domain walls and gravitational waves

We present a comprehensive analysis of a supersymmetric SO(10) grand unified theory, which is broken to the Standard Model via the breaking of two intermediate symmetries. The spontaneous breaking of the first intermediate symmetry, <math><mrow><mi>B</mi><mo>−</mo><mi>L</mi></mrow></math>, leads to the generation of cosmic strings and right-handed neutrino masses and further to an observable cosmological background of gravitational waves and generation of light neutrino masses via type-I seesaw mechanism. Supersymmetry breaking manifests as sparticle masses below the <math><mi>B</mi><mo>−</mo><mi>L</mi></math> breaking but far above the electroweak scale due to proton decay limits. This naturally pushes the <math><mi>B</mi><mo>−</mo><mi>L</mi></math> breaking scale close to the grand unified theory scale, leading to the formation of metastable cosmic strings, which can provide a gravitational wave spectrum consistent with the recent pulsar timing arrays observation. We perform a detailed analysis of this model using two-loop renormalization group equations, including threshold corrections, to determine the symmetry-breaking scale consistent with the recent pulsar timing arrays signals such as NANOGrav 15-year data and testable by the next-generation limits on proton decay from Hyper-K and JUNO. Simultaneously, we find the regions of the model parameter space that can predict the measured quark and lepton masses and mixing, baryon asymmetry of our Universe, a viable dark matter candidate and can be tested by a combination of neutrinoless double beta decay searches and limits on the sum of neutrinos masses.

Stephen F. King

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

We investigate how superradiance affects the generation of baryon asymmetry in a universe with rotating primordial black holes, considering a scenario where a scalar boson is coupled to the heavy right-handed neutrinos. We identify the regions of the parameter space where the scalar production is enhanced due to superradiance. This enhancement, coupled with the subsequent decay of the scalar into right handed neutrinos, results in the non-thermal creation of lepton asymmetry. We show that successful leptogenesis is achieved for masses of primordial black holes in the range of order O(0.1 g) − O(10 g) and the lightest of the heavy neutrino masses, M  N  ~ O(1012) GeV. Consequently, regions of the parameter space, which in the case of Schwarzchild PBHs were incompatible with viable leptogenesis, can produce the observed matter-antimatter asymmetry.

Poland

Anish Ghoshal

Yuber Perez-Gonzalez

Superradiant leptogenesis

It remains a possibility that neutrinos are pseudo-Dirac states, such that a generation is composed of two maximally mixed Majorana neutrinos separated by a very small mass difference. We explore the physics potential of the JUNO experiment in constraining this possibility using the measurement of solar neutrinos. In particular, we investigate cases where one or three sterile states are present in addition to the active states. We consider two scenarios: one where JUNO’s energy threshold allows for the measurement of <math><mi>p</mi><mi>p</mi></math> solar neutrinos, and the case where JUNO can only measure <math><mrow><mmultiscripts><mrow><mi>Be</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>7</mn></mrow></mmultiscripts></mrow></math> neutrinos and above. We find that JUNO will be able to constrain pseudo-Dirac mass splittings of <math><mi>δ</mi><msup><mi>m</mi><mn>2</mn></msup><mo>≳</mo><mn>2.9</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>13</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mn>2</mn></msup></math> for the scenario including <math><mi>p</mi><mi>p</mi></math> solar neutrinos, and <math><mi>δ</mi><msup><mi>m</mi><mn>2</mn></msup><mo>≳</mo><mn>1.9</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>12</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mn>2</mn></msup></math> when the measurement only considers <math><mrow><mmultiscripts><mrow><mi>Be</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>7</mn></mrow></mmultiscripts></mrow></math> monochromatic neutrinos, at the <math><mn>3</mn><mi>σ</mi></math> C.L. Thus, including <math><mi>p</mi><mi>p</mi></math> neutrinos will be crucial for JUNO to improve current constraints on the pseudo-Dirac scenario from solar neutrinos.

JUNO as a probe of the pseudo-Dirac nature using solar neutrinos

Many cosmological phenomena lead to the production of primordial black holes in the early Universe. These phenomena often create a population of black holes with extended mass and spin distributions. As these black holes evaporate via Hawking radiation, they can modify various cosmological observables, lead to the production of dark matter, modify the number of effective relativistic degrees of freedom, <math><msub><mi>N</mi><mi>eff</mi></msub></math>, source a stochastic gravitational wave background and alter the dynamics of baryogenesis. We consider the Hawking evaporation of primordial black holes that feature nontrivial mass and spin distributions in the early Universe. We demonstrate that the shape of such a distribution can strongly affect most of the aforementioned cosmological observables. We outline the numerical machinery we use to undertake this task. We also release a new version of FRISBHEE that handles the evaporation of primordial black holes with an arbitrary mass and spin distribution throughout cosmic history.

Andrew Cheek

Lucien Heurtier

Evaporation of primordial black holes in the early Universe: Mass and spin distributions

We consider a minimal non-supersymmetric SO(10) Grand Unified Theory (GUT) model that can reproduce the observed fermionic masses and mixing parameters of the Standard Model. We calculate the scales of spontaneous symmetry breaking from the GUT to the Standard Model gauge group using two-loop renormalisation group equations. This procedure determines the proton decay rate and the scale of U(1) B−L  breaking, which generates cosmic strings and the right-handed neutrino mass scales. Consequently, the regions of parameter space where thermal leptogenesis is viable are identified and correlated with the fermion masses and mixing, the neutrinoless double beta decay rate, the proton decay rate, and the gravitational wave signal resulting from the network of cosmic strings. We demonstrate that this framework, which can explain the Standard Model fermion masses and mixing and the observed baryon asymmetry, will be highly constrained by the next generation of gravitational wave detectors and neutrino oscillation experiments which will also constrain the proton lifetime.

CERN

A predictive and testable unified theory of fermion masses, mixing and leptogenesis

We explore the interplay between light primordial black holes (PBH) and high-scale baryogenesis, with a particular emphasis on leptogenesis. We first review a generic baryogenesis scenario where a heavy particle, <math><mrow><mi>X</mi></mrow></math>, with mass, <math><msub><mi>M</mi><mi>X</mi></msub></math>, produced solely from PBH evaporation decays to generate a baryon asymmetry. We show that the viable parameter space is bounded from above by <math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mi>X</mi></mrow></msub><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>17</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> and increases with decreasing <math><msub><mi>M</mi><mi>X</mi></msub></math>. We demonstrate that regions of the leptogenesis parameter space, where the lightest right-handed neutrino (RHN) mass <math><msub><mi>M</mi><msub><mi>N</mi><mn>1</mn></msub></msub><mo>≳</mo><msup><mn>10</mn><mn>15</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and neutrino mass scale <math><msub><mi>m</mi><mi>ν</mi></msub><mo>≳</mo><mn>0.1</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>, excluded in standard cosmology due to <math><mi>Δ</mi><mi>L</mi><mo>=</mo><mn>2</mn></math> washout processes, become viable with the assistance of light PBHs. This scenario of PBH-assisted leptogenesis occurs because the PBHs radiate RHNs via Hawking evaporation late in the Universe’s evolution when the temperature of the thermal plasma is low relative to the RHN mass. Subsequently, these RHNs can decay and produce a lepton asymmetry while the washout processes are suppressed.