This study presents a radiative three-loop model for neutrino mass generation, employing an asymmetric Yukawa coupling between two new scalar <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>2</mn><msub><mo stretchy="false">)</mo><mi>L</mi></msub></math> doublets and vectorlike lepton doublets. Dark matter candidates arise from one of the scalar doublets and contribute to neutrino mass generation through the mass splitting between its neutral components. The singly charged scalars are also essential for neutrino mass, with the charged states of the two doublets mixing with one another. A single generation of vectorlike leptons yields two nonzero neutrino masses as a consequence of the asymmetric Yukawa combinations entering the neutrino mass matrix. The model is tested against dark matter phenomenology, neutrino mass and mixing data, and the charged lepton flavor-violating process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo stretchy="false">→</mo><mi>e</mi><mi>γ</mi></math>, showing compatibility with current bounds and leading to experimentally accessible predictions.

United Arab Emirates

Mohamed Amin Loualidi

Salah Nasri

Chile

Maximiliano A. Rivera

Radiative neutrino mass generation and dark matter through vectorlike leptons

In this paper, we explore the use of advanced machine learning (ML) techniques to enhance the sensitivity of double Higgs boson searches in the <inline-formula><tex-math id='TM0002' notation='LaTeX'>$ HH \rightarrow b\bar{b}\gamma \gamma$</tex-math></inline-formula> decay channel at <inline-formula><tex-math id='TM0003' notation='LaTeX'>$\sqrt{s} =$</tex-math></inline-formula> 13.6 TeV. Two ML models are implemented and compared: a tree-based classifier using XGBoost, and a geometry-based graph neural network classifier (GNN). We show that the geometrical model outperforms the traditional XGBoost classifier, improving the expected 95% CL upper limit on the double Higgs boson production cross section&#160;by 28%. Our results are compared to the latest ATLAS experiment results, showing significant improvement of both the upper limit and Higgs boson self-coupling ( <inline-formula><tex-math id='TM0004' notation='LaTeX'>$\kappa _{\lambda }$</tex-math></inline-formula>) constraints.

not found

Mohamed Belfkir

Boosting Sensitivity to <italic>HH</italic> &#8594; <italic>bb&#772;&#947;&#947;</italic> with Graph Neural Networks and XGBoost

Addressing the fermion flavor structures using modular invariance is a challenging task in the framework of quark-lepton unification. Building on recent applications of modular symmetry in nonsupersymmetric models, we propose the first renormalizable <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>5</mn><mo stretchy="false">)</mo></math> grand unified theory incorporating level 3 nonholomorphic modular symmetry, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="normal">Γ</mi><mn>3</mn></msub><mo>≃</mo><msub><mi>A</mi><mn>4</mn></msub></math>. This framework constrains Yukawa couplings to polyharmonic Maaß forms, significantly reducing the number of free parameters while enhancing the predictive power of the models. We present a comprehensive analysis of fermion masses and mixing while tackling key grand unified theory (GUT) queries such as gauge coupling unification and proton decay. Beyond the minimal <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>5</mn><mo stretchy="false">)</mo></math> framework, the Higgs sector incorporates the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>4</mn><msub><mn>5</mn><mi>H</mi></msub></math> dimensional Higgs field crucial in differentiating the masses of down quarks and charged leptons, and the fermion sector is extended with three right-handed neutrinos enabling neutrino masses via the type-I seesaw mechanism. We analyze two benchmark models with distinct modular weight and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mn>4</mn></msub></math> charge assignments. The predicted effective Majorana mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mrow><mi>β</mi><mi>β</mi></mrow></msub></math> values align with current neutrinoless double-beta decay experiments, and the effective neutrino mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>β</mi></msub></math> is within the reach of future beta decay searches. The predicted sum of neutrino masses, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∑</mo><msub><mi>m</mi><mi>i</mi></msub></math>, satisfies the upper bound set by recent cosmological observations. The gauge coupling unification is achieved through a light scalar triplet <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϕ</mi><mn>3</mn></msub><mo>∼</mo><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mn>3</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>/</mo><mn>3</mn><mo stretchy="false">)</mo></math> and a scalar octet <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϕ</mi><mn>5</mn></msub><mo>∼</mo><mo stretchy="false">(</mo><mn>8</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>1</mn><mo>/</mo><mn>2</mn><mo stretchy="false">)</mo></math> belonging to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>4</mn><msub><mn>5</mn><mi>H</mi></msub></math> Higgs, while proton decay constraints require that the contribution of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>4</mn><msub><mn>5</mn><mi>H</mi></msub></math> Higgs to the up-quark mass matrix remains highly suppressed.

Morocco

Mohamed Miskaoui

Nonholomorphic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mn>4</mn></msub></math> modular invariance for fermion masses and mixing in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>5</mn><mo stretchy="false">)</mo></math> GUT

Modular invariance has recently paved the way for promising new directions in flavor model building. Motivated by this development, we present in this work the first implementation of the <inline-formula><tex-math id='TM0002' notation='LaTeX'>$S_3$</tex-math></inline-formula> modular symmetry within the Pati&#8211;Salam unification framework, addressing the flavor structure of quarks and leptons. Assigning left- and right-handed matter fields as <inline-formula><tex-math id='TM0003' notation='LaTeX'>$S_3$</tex-math></inline-formula> doublets or singlets, we propose three benchmark models that achieve compelling fits to 16 observables including charged fermion mass ratios and flavor mixing parameters. Light neutrino masses arise via the type-I seesaw mechanism, and neutrino oscillation parameters are explored in light of the latest NuFIT v6.0 results. All models favor a normal neutrino mass ordering, with the atmospheric mixing angle lying in the lower octant. For models I and III, the effective Majorana mass <inline-formula><tex-math id='TM0004' notation='LaTeX'>$m_{\beta \beta }$</tex-math></inline-formula> is within the reach of upcoming neutrinoless double-beta decay experiments, while it is too small to be detected in model II. Predicted leptonic <italic>CP</italic>-violating phases and the sum of the active neutrino masses span wide but distinctive ranges, enabling future experiments to test and differentiate the proposed models.

Fermion Masses and Mixing in Pati–Salam Unification with <italic>S</italic> 3 Modular Symmetry

The Zee-Babu model is a minimal realization of radiative neutrino mass generation mechanism at the two-loop level. We study the phenomenology of this model at future multi-TeV muon colliders. After imposing all theoretical and low-energy experimental constraints on the model parameters, we find that the Zee-Babu states are expected not to reside below the TeV scale, making it challenging to probe them at the LHC. We first analyze the production rates for various channels, including multi singly charged and/or doubly charged scalars at muon colliders. For concreteness, we study several benchmark points that satisfy neutrino oscillation data and other constraints and find that most channels have large production rates. We then analyze the discovery reach of the model using two specific channels: the pair production of singly and doubly charged scalars. For the phenomenologically viable scenarios considered in this study, charged scalars with masses up to <math><mrow><mi>O</mi><mo>(</mo><mn>3</mn><mi>–</mi><mn>4</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> can be probed for the center-of-mass energy of 10 TeV and total luminosity of <math><mrow><mn>10</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>ab</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>.

South Korea

Adil Jueid

Bangladesh

Talal Ahmed Chowdhury

Italy

Switzerland

Shaikh Saad

Probing Zee-Babu states at muon colliders

In this work, we delve into the often overlooked cosmological implications of the spontaneous breaking of the non-Abelian discrete groups, specifically focusing on the formation of domain walls in the case of <math><msub><mi>S</mi><mn>4</mn></msub></math> flavor symmetry. In particular, we investigate three interesting breaking patterns of the <math><msub><mi>S</mi><mn>4</mn></msub></math> group and study the structure of the domain walls in the broken phase for three possible residual symmetries. The presentation of domain walls in the case of multiple vacua is usually complicated, which therefore implies that most of the analyses only approximate their presentation. Here, we propose a subtle way to represent the <math><msub><mi>S</mi><mn>4</mn></msub></math> domain wall networks by presenting the vacua in each breaking pattern as vectors with their components corresponding to their coordinates in the flavon space. Then, through the properties of the obtained vectors, we find that the domain wall networks can be represented by Platonic or Archimedean solids where the vertices represent the degenerate vacua while the edges correspond to the domain walls that separate them. As an illustration, we propose a type-II seesaw model that is based on the <math><msub><mi>S</mi><mn>4</mn></msub></math> flavor symmetry, and study its phenomenological implications on the neutrino sector. To solve the domain wall problem within this toy model, we consider an approach based on high-dimensional effective operators induced by gravity that explicitly break the structure of the induced vacua favoring one vacuum over the others.

Mohamed Amine Ouahid

Cosmological domain walls from the breaking of <math><msub><mi>S</mi><mn>4</mn></msub></math> flavor symmetry

We investigate the prospects of probing the doubly-charged scalars of the minimal Left-Right Symmetric model (MLRSM) at a muon collider. We assess its capability by studying the production of doubly-charged scalars and their subsequent decay into four charged lepton final states containing the same-charge lepton pairs. We find that the channels with same-charge electron and muon pairs, i.e., (<math><msup><mrow><mi>e</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>∓</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>∓</mo></mrow></msup></math> and its charge conjugated pairs), have the largest sensitivity due to the lowest Standard Model background. Besides, we show that the possibility of using fully polarized initial muon beams in the muon collider can enhance the detection sensitivity of doubly-charged scalars of the MLRSM. Furthermore, we show that one can put exclusion limits on the magnitudes of triplet Yukawa couplings that are directly related to the neutrino sector of the MLRSM for the mass range <math><mn>1.1</mn><mo>−</mo><mn>5</mn></math> TeV of the doubly-charged scalars.

United States

Doubly-charged scalars of the minimal left-right symmetric model at muon colliders

A series of pulsar timing arrays (PTAs) recently observed gravitational waves at the nanohertz frequencies. Motivated by this remarkable result, we present a novel class of Pati-Salam models that give rise to a network of metastable cosmic strings, offering a plausible explanation for the observed PTA data. Additionally, we introduce a hybrid inflationary scenario to eliminate magnetic monopoles that arise during the subsequent phase transitions from the Pati-Salam symmetry to the Standard Model gauge group. The resulting scalar spectral index is compatible with Planck data, and the tensor-to-scalar ratio is anticipated to be extremely small. Moreover, we incorporate a nonthermal leptogenesis to generate the required baryon asymmetry in our framework. Finally, the gravitational wave spectra generated by the metastable cosmic strings not only correspond to signals observed in recent PTAs, including NANOGrav, but are also within the exploration capacity of both present and future ground- and space-based experiments.

China

Waqas Ahmed

Gravitational waves from metastable cosmic strings in the Pati-Salam model in light of new pulsar timing array data

Abstract The search for dark matter (DM) candidates at high-energy colliders is one of the most promising avenues to understand the nature of this elusive component of the universe. Several searches at the Large Hadron Collider (LHC) have strongly constrained a wide range of simplified models. The combination of the bounds from the LHC with direct-detection experiments exclude the most minimal scalar-singlet DM model. To address this, lepton portal DM models are suitable candidates where DM is predominantly produced at lepton colliders since the DM candidate only interacts with the lepton sector through a mediator that carries a lepton number. In this work, we analyze the production of DM pairs in association with a Higgs boson decaying into two bottom quarks at future muon colliders in the framework of the minimal lepton portal DM model. It is found that the usual cut-based analysis methods fail to probe heavy DM masses for both the resolved (where the decay products of the Higgs boson can be resolved as two well-separated small-R jets) and the merged (where the Higgs boson is clustered as one large-R jet) regimes. We have then built a search strategy based on boosted-decision trees (BDTs). We have optimized the hyperparameters of the BDT model to both have a high signal-to-background ratio and to avoid overtraining effects. We have found very important enhancements of the signal significance with respect to the cut-based analysis by factors of 8–50 depending on the regime (resolved or merged) and the benchmark points. Using this BDT model on a 1D parameter space scan, we found that future muon colliders with  TeV and  can exclude DM masses up to 1 TeV at the 95% confidence level.

Boosting dark matter searches at muon colliders with machine learning: The mono-Higgs channel as a case study

We revisit the bottom and <math><mi>τ</mi></math> Yukawa coupling unification in the supersymmetric 4-2-2 model and present for the first time the sbottom-neutralino coannihilation scenario consistent with the bottom and <math><mi>τ</mi></math> Yukawa coupling unification. In addition, we present gluino-neutralino, stop-neutralino, stau-neutralino, chargino-neutralino, and A-resonance scenario and show that all such solutions are consistent with existing experimental collider constraints, Planck 2018 dark matter relic density bounds as well as direct and indirect bounds on neutralino-nucleons scattering cross sections. It is shown that in the sbottom-neutralino coannihilation scenario, the sbottom mass is between 1.2 to 3.5 TeV, whereas in the case of gluino-neutralino, stop-neutralino, the gluino mass can be between 1 to 3 TeV and the stop mass in the range of 1 to 3.5 TeV. Moreover, in the case of a coannihilation scenario, the stau and chargino masses can be as heavy as 3.5 TeV, while the A-resonance solutions are in the range of 0.5 to 3.5 TeV. We anticipate that some part of the parameter space will be accessible in the supersymmetry searches at LHC run 3 and beyond.