Heavy right-handed neutrinos are highly motivated due to their connection with the origin of neutrino masses via the seesaw mechanism. If the right-handed neutrino Majorana mass is at or below the weak scale, direct experimental discovery of these states is possible in laboratory experiments. However, there is no basis to expect right-handed neutrinos to be so light since the Majorana mass is a technically natural parameter and could comfortably reside at any scale, including at scales far above the weak scale. Here we explore the possibility that the right-handed neutrino Majorana mass originates from electroweak symmetry breaking. Working within an effective theory with two Higgs doublets, a nonzero lepton number is assigned to the bilinear operator built from the two Higgs fields, which is then coupled to the right-handed neutrino mass operator. In tandem with the neutrino Yukawa coupling, following electroweak symmetry breaking a seesaw mechanism operates, generating the light Standard Model neutrino masses along with right-handed neutrinos with masses below the electroweak scale. This scenario leads to novel phenomenology in the Higgs sector, which may be probed at the LHC and at future colliders. There are also interesting prospects for neutrinoless double beta decay and lepton flavor violation. We also explore some theoretical aspects of the scenario, including the technical naturalness of the effective field theory and ultraviolet completions of the right-handed neutrino Majorana mass.

We present an alternative framework to establish the neutrino mass scale from the Higgs mechanism in a minimalist approach, which does not introduce new scalar bosons or extend the symmetry group of the standard model (SM). A nonstandard form of the Higgs Lagrangian, constructed via the inverse problem of calculus of variations, is proposed. Only one dimensionful parameter in the TeV scale is incorporated into the SM Lagrangian. The multiplicative Lagrangian model of the Higgs field plays an essential role in explaining the vast mass difference between charged fermions and Dirac neutrinos, while the Yukawa couplings for these two groups of particles naturally fall within the same scale. On the other hand, if the neutrino mass term has both Dirac and Majorana components, the mass of the mostly right-handed neutrinos in the Type-I seesaw mechanism can range from the keV scale up to slightly below the grand unification scale without requiring extremely small Yukawa couplings outside the SM regime. Furthermore, we discuss the potential of this mechanism to explain the hierarchical structure in the Yukawa couplings between firstand third-generation particles.

A bstract It is common practice to explain deviations between data and Standard-Model (SM) predictions by postulating new particles at the TeV scale ad-hoc. This approach becomes much more convincing, if one successfully embeds the postulated particles into a UV completion which addresses other conceptual or phenomenological shortcomings of the SM. We present a study of an SO(10) grand unified theory which contains scalar leptoquark fields employed to explain the “flavour anomalies” in b → s and b → c decays. We find that the additional degrees of freedom improve the renormalization-group (RG) evolution of the SM parameters. In particular, the light leptoquarks modify the RG evolution of the Yukawa couplings such that successful bottom-tau unification becomes possible in a minimal SO(10) GUT with only a 126-plet coupling to fermions. If we amend the Yukawa interaction of the minimal one-generation model with a second fermion multiplet and small flavor-violating terms, we find the flavour violation in the leptoquark couplings growing with the RG evolution while it stays small in the Yukawa interaction of the SM Higgs boson. By employing mass splittings among the members of the 126 -plet one can increase the effect and obtain large flavor violation in leptoquark couplings from tiny perturbations at the GUT scale, because the flavour-conserving limit is an unstable initial condition for the RG equations.

Extensions of the Standard Model including Higgs doublets giving mass to neutrinos with Yukawa couplings comparable to the ones of electrically charged fundamental fermions offer the possibility of low energy tests due to the small vacuum expectation value of a component of the added Higgs doublet. We discuss the possibility of modulating the neutrino mass with properly designed electroweak and thermal cavities. Although the estimate of the effect precludes any positive detection in the foreseeable future, this discussion should also further motivate the development of high-intensity, pulsed, low-energy, monoenergetic neutrino beams.

We present new state-of-the-art predictions for Standard Model Higgs boson production in association with a bottom-quark pair ( b\bar bH b b ‾ H ). Updated cross sections are computed in accordance with the recommendations of the LHC Higgs Working Group, including the use of the PDF4LHC21 set of parton distribution functions, with a center-of-mass energy of 13.6 TeV. For the total inclusive cross section, we provide matched predictions of the massless five-flavour scheme (5FS) and the massive four-flavour scheme (4FS) at the fixed-order level. We further present recently obtained simulations matched with parton showers in both flavour schemes within the SM, and also discuss them in the context of potential BSM scenarios. In the massless scheme, we compare different NNLO+PS predictions obtained through the MiNNLOPS and GENEVA generators. In addition, the role of 4FS predictions is studied as a background to HH H H searches, considering both the top-quark and bottom-quark Yukawa contributions to b\bar bH b b ‾ H production. Finally, we analyse the sensitivity of the Higgs transverse momentum spectrum to light-quark Yukawa couplings in the diphoton decay channel based on MiNNLOPS simulations.

We investigate a grand unification inspired version of the minimal supersymmetric standard model (MSSM) based on a left-right symmetric 4 − 2 − 2 gauge group, incorporating Yukawa coupling unification and current phenomenological constraints. Utilizing a split soft supersymmetry-breaking parameter space motivated by flavor symmetries, we analyze the implications of recent results from ATLAS, CMS, LHCb, and dark matter direct detection experiments. Our numerical scans, conducted with and heno, identify viable low-energy regions consistent with third-generation Yukawa unification, the observed Higgs boson mass, dark matter relic density, and flavor observables such as B → X s γ , B s → μ + μ − and B u → τ ν τ . Our findings suggest that while current bounds severely constrain much of the MSSM-like parameter space, substantial regions remain experimentally viable and testable in the ongoing LHC run and next-generation dark matter experiments.

Abstract This article presents a comprehensive exposition on deriving the interaction potential between point-like particles within the framework of a scalar field. The Yukawa interaction energy, as well as the Coulomb interaction as a particular case, is obtained purely through classical arguments, without invoking field quantization, and directly from the field sources, with no need for artifacts such as the work-on-sources concept. Furthermore, we adopt an approach grounded in the language of classical field theory and based solely on dynamical equations, avoiding the use of analytic tools such as the Lagrangian and Hamiltonian density formalisms, in the hope that this exposition will help beginners appreciate the role of fields in mediating interactions and spark their interest in classical field theory. We also hope this approach is accessible, comprehensive, and self-contained for undergraduate physics students in the final year of a typical program. We recover a general formula that enables the calculation of the interaction energy between arbitrary stationary source distributions, not necessarily point-like, whose interaction is mediated by the scalar field. As an exercise for interested readers, we suggest investigating additional physical systems using the same framework employed in this work.

The Large Hadron Collider (LHC) offers a unique opportunity to investigate \mathcal{CP} 𝒞 𝒫 violation in the Yukawa coupling between the Higgs boson and the top quark by studying Higgs production in association with top quarks; this is of fundamental importance, seeing that the \mathcal{CP} 𝒞 𝒫 properties of the Higgs boson are yet to measure with high precision. To address this, the focus of this work has been an extension of the simplified template cross-section (STXS) framework, devised to be sensitive to \mathcal{CP} 𝒞 𝒫 effects. Our study focused on \mathcal{CP} 𝒞 𝒫 -sensitive observables across multiple Higgs decay channels, comparing their performances. The result indicates that the most efficient extension of the current binning used in the STXS framework, which currently uses the Higgs boson’s transverse momentum p_{T,H} p T , H , requires adding one further split using \mathcal{CP} 𝒞 𝒫 -sensitive observables. Between these observables, one of the best is the Collins-Soper angle |\cos\theta^*| | cos θ * | , a variable derived from momenta information of the top quarks. We have investigated the improvement brought by our two-dimensional STXS setup and compared it to the currently employed methodologies, finding an increase in performances at an integrated luminosity of 300 \mathrm{ fb}^{-1} 300 f b − 1 . Moreover, our results highlight that this advantage seems to be present also at 3000 \mathrm{ fb}^{-1} 3000 f b − 1 .

Abstract We study the augmentation of the Standard Model (SM) with another SU(2) Higgs doublet and right-handed neutrinos. The second Higgs doublet (Φ2) is defined to be odd under the Z2 symmetry, and hence, the lightest stable neutral particle from the additional doublet becomes the cold dark matter candidate. The right-handed neutrino field coupled to the Higgs field provides non-zero mass for the neutrinos. The inert doublet field coupled non-minimally to gravity as $\zeta _2 \Phi _2^\dagger \Phi _2 R$ also acts as an inflaton field. The inflationary bounds restrict the interaction couplings as $\lambda _2/\zeta _2^2 \approx 4\times 10^{-10}$. After inflation ends, the scalar bosonic degrees of freedom from the inert doublet can contribute to the electroweak phase transition. The strongly first-order phase transition bound, i.e., $\frac{\phi _{+}(T_c)}{T_c} \ge 1.0$ restricts the bare mass parameter of the additional doublet to m22 = 400.0 GeV, demanding GUT scale perturbative unitarity for YN = 0.01. The right-handed neutrino effect is studied here only through the running of Yukawa coupling, i.e. YN. The running of Yukawa coupling for different values at the electroweak scale restricts the perturbative unitarity at different scales, and effects the strength of phase transition. The increase in YN reduces the strength of phase transition, and it is no longer satisfied even for vanishing bare mass parameter. The Planck scale perturbative unitarity allows for the first-order phase transition, $\frac{\phi _{+}(T_c)}{T_c} \ge 0.6$, until m22 = 70.0 GeV for YN = 0.01, and none of the mass values satisfies the first-order phase transition for YN = 0.4. The thermal corrections also affect the probability of tunneling from the false vacuum to the true vacuum, and hence, the finite temperature stability of the electroweak vacuum has been studied including the finite-temperature effects.

We investigate a scale-invariant general two-Higgs-doublet model with explicit C P violation. Using the Gildener-Weinberg method, we analyze the Higgs mass spectrum and couplings at the one-loop level, focusing on C P violation originating from both the Higgs potential and the Yukawa sector. We show that, due to the flatness condition, both C P -even and C P -odd mixings between the 125 GeV Higgs boson and the heavier Higgs states arise only radiatively. As a result, the Higgs couplings to gauge bosons and fermions remain Standard Model-like, in agreement with current LHC constraints. We also find that the magnitude of C P violation from the Higgs potential depends on the new complex Yukawa couplings and heavy Higgs masses, due to the flatness condition. In the case where only an additional top Yukawa coupling ( ρ t t ) is present, the electron electric dipole moment is directly proportional to Im ρ t t 2 . Furthermore, a nontrivial cancellation region can occur for a specific Higgs mass spectrum. We extend our analysis to scenarios with an additional complex electron Yukawa coupling, identifying the conditions under which the electron electric dipole moment is suppressed or vanishes.

In this work, I discuss neutron stars with hyperons and antikaon condensate. To fix their coupling constants with the vector mesons of the quantum hadrodynamics, I use a unified scheme imposing that the Yukawa coupling is an invariant under SU(3) and SU(6) groups. Combining with the G-parity, I show that some expected results of the kaon and antikaon interaction with the nucleus are reobtained. In the same sense, the naive quark-isospin counting rule is restored in the SU(6) limit. Furthermore, the G-parity combined with the SU(3) gives us a clear picture of the role played by each meson in the kaon condensation. Numerical results show that the presence of antikaons severely compromises the stiffening of the equation of state by breaking the SU(6) symmetry.

Misalignment dynamics of scalar condensates with Yukawa coupling: Particle and entropy production

In this paper, we investigate the production of Majorana fermionic dark matter (DM) via the Higgs portal, considering both freeze-in and freeze-out mechanisms during and after the postinflationary reheating phase. We assume that the Universe is reheated through the decay of the inflaton ( ϕ ) into a pair of fermions f and f ¯ via the interaction y ϕ f ¯ f , where y is the dimensionless Yukawa coupling. Our analysis focuses on how the nonstandard evolution of the Hubble expansion rate and the thermal bath temperature during reheating influence DM production. Additionally, we examine the impact of electroweak symmetry breaking (EWSB), distinguishing between scenarios where DM freeze-in or freeze-out occurs before or after EWSB. We further explore the viable DM parameter space and its compatibility with current and future detection experiments, including XENONnT, LUX-ZEPLIN, XLZD, and collider searches. Moreover, we incorporate constraints from the Lyman- α bound to ensure consistency with small-scale structure formation.

A bstract The top-quark Yukawa coupling is extracted from the distribution of the top-quark pair ( $$ t\overline{t} $$ t t ¯ ) invariant mass in proton-proton collisions using 140 fb − 1 of data at $$ \sqrt{s}=13 $$ s = 13 TeV collected in 2015–2018 by the ATLAS experiment at the Large Hadron Collider. In the region near the production threshold, the $$ t\overline{t} $$ t t ¯ invariant mass spectrum is sensitive to electroweak virtual corrections, including contributions from Higgs boson exchange, thereby providing sensitivity to the top-quark Yukawa coupling. This is the first measurement in ATLAS that aims to obtain this coupling exploiting this approach. The $$ t\overline{t} $$ t t ¯ system is reconstructed in the single-lepton final state, requiring exactly one isolated electron or muon and at least four jets with at least two identified as originating from b -quarks. The measured Yukawa coupling is found to be in good agreement with the Standard Model prediction. An upper limit on the top-quark Yukawa coupling strength of Y t < 2 . 1 relative to the Standard Model prediction is observed at 95% confidence level, consistent with the expected sensitivity.

A bstract We investigate a possibility of electroweak symmetry non-restoration (SNR) below the Twin electroweak scale (~ TeV) within the Twin Higgs model. We focus on supersymmetric extensions with light sfermions where SNR is driven by mirror symmetry breaking in the Yukawa couplings. The inclusion of light scalars not only stabilizes the electroweak scale, but also extends SNR into new regions of the parameter space and enables a first-order phase transition. When this model is augmented with right-handed neutrinos with unbroken B′ − L′ in the twin sector, the number of dark relativistic degrees of freedom can be reduced to the level consistent with the constraints from CMB data. The SNR in the supersymmetric Twin Higgs framework can naturally be integrated with minimal axiogenesis, offering a simultaneous explanation for the origin of baryon asymmetry and dark matter and the resolution of the strong CP problem that is consistent with astrophysical constraints.

A bstract The Cutkosky cutting rules establish a direct connection between the imaginary parts of loop amplitudes and physical observables such as decay rates and cross sections, providing heuristic insights into the underlying processes. This work lays a robust theoretical foundation for the application of cutting rules in solid-state systems involving instantaneous dark matter (DM)–electron Yukawa interaction as well as the Coulomb potential. The cutting rules are formulated using the single-electron wavefunctions and corresponding energy eigenvalues obtained from the Kohn-Sham equations within density functional theory (DFT). This framework is not only of considerable theoretical interest but also holds significant practical relevance for studying DM phenomenology in condensed matter systems.

A bstract In the framework of non-holomorphic modular invariance approach, we have systematically constructed all minimal lepton models based on the non-holomorphic $${A}_{5}{\prime}$$ modular symmetry from a bottom-up approach. In these models, the Yukawa couplings are described by polyharmonic Maaß forms of integer weights at level N = 5. Under the assumption of Majorana neutrinos, both the Weinberg operator and the type-I seesaw mechanism are considered for neutrino mass generation. All minimal models are found to be based on generalized CP (gCP) symmetry, and each of them depends on five real dimensionless parameters and two overall scales. Through a comprehensive numerical scanning, we obtain 6 (4) phenomenologically viable Weinberg operator models and 94 (76) phenomenologically viable seesaw models for normal (inverted) ordering neutrino masses. For each viable model, we present predictions for key lepton properties, such as lepton masses, CP violation phases, mixing angles, effective Majorana mass for neutrinoless double beta decay and the kinematical mass in beta decay. Furthermore, we provide detailed numerical analysis for two representative models to illustrate our results.

A bstract Recently, Qu and Ding, have proposed a formalism where modular invariance is extended to non-supersymmetric scenario considering Yukawa couplings as non-holomorphic functions of modules field τ . Adopting this formalism in this work, we propose a Type-III seesaw model as a unified framework to explain lepton masses and mixing and baryogenesis via leptogenesis. χ 2 analysis is performed to fit the neutrino oscillation data from NuFIT 6.0 leading to a normal hierarchical pattern of neutrino masses and constrained CP phases. Furthermore, we analyze the generation of the observed baryon asymmetry of the Universe via thermal leptogenesis where the decays of the lightest fermion triplet Σ 1 into lepton-Higgs final states produce a CP asymmetry ε CP . The complex modules τ is responsible for the CP asymmetry produced during leptogenesis. The washout processes dominated by gauge scatterings and inverse decays are studied through the full set of Boltzmann equations. The resulting B − L asymmetry, Y B − L ~ 10 −9 successfully reproduces the baryon-to-photon ratio demonstrating the model’s capability to link low-energy neutrino data with the baryogenesis. The strong gauge-mediated washout of fermion triplets necessitates a leptogenesis scale of $$\mathcal{O}$$ (10 12 GeV) ensuring compatibility with both the Davidson-Ibarra bound and the thermal history of the Universe. Future pursuits remain open to the exploration of novel avenues aimed at lowering the energy scale associated with leptogenesis.

A bstract The excess in $$ t\to b\overline{b}c $$ t → b b ¯ c observed by ATLAS points towards a charged Higgs boson with a mass around 130 GeV, consistent with the expectations from the B anomalies, i.e. $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ and b → sℓ + ℓ − data. As a non-minimal flavour structure is required for an explanation of these observables, this points towards a two-Higgs-doublet model with generic Yukawa couplings. Such a scenario predicts a sizable cross section for the pair production of the charged Higgs at the Large Hadron Collider, which can be tested by recasting SM di-Higgs searches. While the predicted event rate is even higher than the one of SM Higgs pair production, the smaller efficiency (w.r.t. SM Higgs pair production) reduces the signal yield. Nonetheless, dedicated searches can probe most of the interesting parameter space and lead to a discovery with Run-3 or High-Luminosity LHC data.

Abstract We propose a simple and unified framework that simultaneously explains the origins of light Dirac neutrino masses, asymmetric dark matter (ADM), and the baryon asymmetry of the Universe. The model is based on an extended $U(1)_X$ Froggatt–Nielsen-like mechanism, which naturally generates suppressed Yukawa couplings and realizes a Dirac seesaw for neutrino masses. An additional $\mathbb {Z}_4$ symmetry stabilizes the dark sector, where chiral fermions charged under $\mathbb {Z}_4$ serve as ADM candidates. Leptogenesis occurs through the out-of-equilibrium decays of heavy Dirac neutrinos, where the generated asymmetry is shared between the visible and dark sectors due to exact lepton-number conservation. The same suppression mechanism that explains the smallness of neutrino masses also determines the GeV-scale ADM mass. Numerical studies demonstrate that a fully asymmetric DM scenario is realized, consistent with relic abundance, Big Bang nucleosynthesis, and direct detection constraints. This framework provides an experimentally testable connection between neutrino physics, dark matter, and baryogenesis within an anomaly-free setup.