Search

The vanishing of the Higgs quartic coupling at a high energy scale may be explained by Intermediate Scale Supersymmetry, where supersymmetry breaks at (109-1012) GeV. The possible range of supersymmetry breaking scales can be narrowed down by precise measurements of the top quark mass and the strong coupling constant. On the other hand, nuclear recoil experiments can probe Higgsino or sneutrino dark matter up to a mass of 1012 GeV. We derive the correlation between the dark matter mass and precision measurements of standard model parameters, including supersymmetric threshold corrections. The dark matter mass is bounded from above as a function of the top quark mass and the strong coupling constant. The top quark mass and the strong coupling constant are bounded from above and below respectively for a given dark matter mass. We also discuss how the observed dark matter abundance can be explained by freeze-out or freeze-in during a matter-dominated era after inflation, with the inflaton condensate being dissipated by thermal effects.

The vanishing of the Higgs quartic coupling of the Standard Model at high energies may be explained by spontaneous breaking of Higgs Parity. Taking Higgs Parity to originate from the Left-Right symmetry of the SO(10) gauge group, leads to a new scheme for precision gauge coupling unification that is consistent with proton decay. We compute the relevant running of couplings and threshold corrections to allow a precise correlation among Standard Model parameters. The scheme has a built-in solution for obtaining a realistic value for mb/mτ , which further improves the precision from gauge coupling unification, allowing the QCD coupling constant to be predicted to the level of 1% or, alternatively, the top quark mass to 0.2%. Future measurements of these parameters may significantly constrain the detailed structure of the theory. We also study an SO(10) embedding of quark and lepton masses, showing how large neutrino mixing is compatible with small quark mixing, and predict a normal neutrino mass hierarchy. The strong CP problem may be explained by combining Higgs Parity with space-time parity.

Flavour mixing and CP violation as measured in weak decays and mixing of neutral mesons are a fundamental tool to test the Standard Model and to search for new physics. New analyses performed at the LHC experiment open an unprecedented insight into the Cabibbo–Kobayashi–Maskawa metrology and new evidence for rare decays. Important progress has also been achieved in theoretical calculations of several hadronic quantities with a remarkable reduction of the uncertainties. This improvement is essential since previous studies of the Unitarity Triangle did show that possible contributions from new physics, if any, must be tiny and could easily be hidden by theoretical and experimental errors. Thanks to the experimental and theoretical advances, the Cabibbo–Kobayashi–Maskawa picture provides very precise Standard Model predictions through global analyses. We present here the results of the latest global Standard Model analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice Quantum Chromo-Dynamics and phenomenological calculations. [ABSTRACT FROM AUTHOR]

Abstract Leptonic CP violation is yet to be confirmed as an additional source of CP violation in fundamental interactions. We study the case where leptonic CP violation is spontaneous and is induced by the mixing with a heavy charged vector-like lepton (VLL). We show that the non-decoupling of this VLL is linked with the presence of CP violation and its coupling with the SM leptons are partly fixed from the SM Yukawas. Due to the large leptonic mixing angles, these couplings are typically of the same order and there is no flavor preference. Strong but not definitive constraints come from charged lepton flavor violating processes because the VLL can decouple from one or two leptonic flavors in very special points of parameter space. These special points are very sensitive to the neutrino Majorana phases.

Abstract We investigate the flavour alignment conditions that New Physics (NP) models need to satisfy in order to address the (g − 2) μ anomaly and, at the same time, be consistent with the tight bounds from μ → eγ and τ → μγ. We analyse the problem in general terms within the SMEFT, considering the renormalisation group evolution of all the operators involved. We show that semileptonic four-fermion operators, which are likely to generate a sizeable contribution to the (g − 2) μ anomaly, need to be tightly aligned to the lepton Yukawa couplings and the dipole operators in flavour space. While this tuning can be achieved in specific NP constructions, employing particular dynamical assumptions and/or flavour symmetry hypotheses, it is problematic in a wide class of models with broken flavour symmetries, such as those proposed to address both charged- and neutral-current B anomalies. We quantify this tension both in general terms, and in the context of explicit NP constructions.

Abstract Properly separating and subtracting renormalons in the framework of the op- erator product expansion (OPE) is a way to realize high precision computation of QCD effects in high energy physics. We propose a new method (FTRS method), which enables to subtract multiple renormalons simultaneously from a general observable. It utilizes a property of Fourier transform, and the leading Wilson coefficient is written in a one-parameter integral form whose integrand has suppressed (or vanishing) renormalons. The renormalon subtraction scheme coincides with the usual principal-value prescription at large orders. We perform test analyses and subtract the O Λ QCD 4 $$ \mathcal{O}\left({\Lambda}_{\mathrm{QCD}}^4\right) $$ renormalon from the Adler function, the O Λ QCD 2 $$ \mathcal{O}\left({\Lambda}_{\mathrm{QCD}}^2\right) $$ renormalon from the B → X u l ν ¯ $$ \overline{\nu} $$ decay width, and the O $$ \mathcal{O} $$ (ΛQCD) and O Λ QCD 2 $$ \mathcal{O}\left({\Lambda}_{\mathrm{QCD}}^2\right) $$ renormalons from the B, D meson masses. The analyses show good consistency with theoretical expectations, such as improved convergence and scale dependence. In particular we obtain Λ ¯ $$ \overline{\Lambda} $$ FTRS = 0.495 ± 0.053 GeV and ( μ π 2 $$ {\mu}_{\pi}^2 $$ )FTRS = −0.12 ± 0.23 GeV2 for the non-perturbative parameters of HQET. We explain the formulation and analyses in detail.

Abstract We consider the possibility that the neutral-current B anomalies are due to radiative corrections generated by Yukawa interactions of quarks and leptons with new vector-like quark and lepton electroweak doublets and new Standard Model singlet scalars. We show that the restricted interactions needed can result from an underlying Abelian family symmetry and that the same symmetry can give rise to an acceptable pattern of quark and charged lepton masses and mixings, providing a bridge between the non-universality observed in the B-sector and that of the fermion mass matrices. We construct two simple models, one with a single singlet scalar in which the flavour changing comes from quark and lepton mixing and one with an additional scalar in which the flavour changing can come from both fermion and scalar mixing. We show that for the case the new quarks are much heavier than the new leptons and scalars the B anomalies can be due to box diagrams with couplings in the perturbative regime consistent with the bounds coming from $$ {B}_s-{\overline{B}}_s $$ B s − B ¯ s , $$ K-\overline{K} $$ K − K ¯ and $$ D-\overline{D} $$ D − D ¯ mixing as well as other lepton family number violating processes. The new states can be dark matter candidates and, in the two scalar model with a light scalar of O(60) GeV and vector-like lepton of O(100) GeV, there can be a simultaneous explanation of the B-anomalies, the muon anomalous magnetic moment and the dark matter abundance.

Abstract Motivated by the reported discrepancies between experimental data and Standard Model predictions for the branching ratios of the color-allowed decays B ¯ $$ \overline{B} $$ 0 → D (*)+ K − and B ¯ s 0 $$ {\overline{B}}_s^0 $$ → D s ∗ + π − $$ {D}_s^{\left(\ast \right)+}{\pi}^{-} $$ , we study final-state rescattering effects on B ¯ $$ \overline{B} $$ (s) → D s ∗ P $$ {D}_{(s)}^{\left(\ast \right)}P $$ and B ¯ $$ \overline{B} $$ (s) → D (s) V, where P(V) is a light pseudoscalar (vector) meson. We consider quasi-elastic rescatterings in the framework of SU(3) and U(3) flavor symmetries, and find that the effects cannot explain the measured branching ratios of the color-allowed and color-suppressed decays simultaneously. We also perform global fits to the B ¯ $$ \overline{B} $$ (s) → D s ∗ P $$ {D}_{(s)}^{\left(\ast \right)}P $$ and B ¯ $$ \overline{B} $$ (s) → D (s) V data, allowing for new physics contributions to the Wilson coefficient a 1 associated with the color-allowed tree amplitudes. It is shown that the fits prefer a downward shift of O $$ \mathcal{O} $$ (10%) in a 1 even in the presence of the quasi-elastic rescattering contributions.

Abstract The determination of |V ub | in inclusive semileptonic B → X u ℓν decays will be among the pivotal tasks of Belle II. In this paper we study the potential and limitations of machine-learning approaches that attempt to reduce theory uncertainties by extending the experimentally accessible fiducial region of the B → X u ℓν signal into regions where the B → X c ℓν background is dominant. We find that a deep neural network trained on low-level single particle features offers modest improvement in separating signal from background, compared to BDT set-ups using physicist-engineered high-level features. We further illustrate that while the signal acceptance of such a deep neural network deteriorates in kinematic regions where the signal is small, such as at high hadronic invariant mass, neural networks which exclude kinematic features are flatter in kinematics but less inclusive in the sampling of exclusive hadronic final states at fixed kinematics. The trade-off between these two set-ups is somewhat Monte Carlo dependent, and we study this issue using the multipurpose event generator Sherpa in addition to the widely used B-physics tool EvtGen.

Abstract We determine the full set of coefficients for the completely general 4-loop gauge and 3-loop Yukawa β-functions for the most general renormalizable four-dimensional theories. Using a complete parametrization of the β-functions, we compare the general form to the specific β-functions of known theories to constrain the unknown coefficients. The Weyl consistency conditions provide additional constraints, completing the determination.

Abstract A non-supersymmetric renormalizable SO(10) model is investigated for its viability in explaining the observed fermion masses and mixing parameters along with the baryon asymmetry produced via thermal leptogenesis. The Yukawa sector of the model consists of complex 10 H and 126 ¯ H $$ {\overline{126}}_H $$ scalars with a Peccei-Quinn like symmetry and it leads to strong correlations among the Yukawa couplings of all the standard model fermions including the couplings and masses of the right-handed (RH) neutrinos. The latter implies the necessity to include the second lightest RH neutrino and flavor effects for the precision computation of leptogenesis. We use the most general density matrix equations to calculate the temperature evolution of flavoured leptonic asymmetry. A simplified analytical solution of these equations, applicable to the RH neutrino spectrum predicted in the model, is also obtained which allows one to fit the observed baryon to photon ratio along with the other fermion mass observables in a numerically efficient way. The analytical and numerical solutions are found to be in agreement within a factor of O 1 $$ \mathcal{O}(1) $$ . We find that the successful leptogenesis in this model does not prefer any particular value for leptonic Dirac and Majorana CP phases and the entire range of values of these observables is found to be consistent. The model specifically predicts (a) the lightest neutrino mass m v 1 $$ {m}_{v_1} $$ between 2–8 meV, (b) the effective mass of neutrinoless double beta decay m ββ between 4–10 meV, and (c) a particular correlation between the Dirac and one of the Majorana CP phases.

Abstract We compute the leading terms of the spectral action for a noncommutative geometry model that has no fermion doubling. The spectral triple describing it, which is chiral and allows for CP-symmetry breaking, has the Dirac operator that is not of the product type. Using Wick rotation we derive explicitly the Lagrangian of the model from the spectral action for a flat metric, demonstrating the appearance of the topological θ-terms for the electroweak gauge fields.

Abstract The Nelson-Barr (NB) mechanism to solve the strong CP problem assumes CP conservation, arranges vanishing θ ¯ $$ \overline{\theta} $$ at tree-level and requires vector-like quarks (VLQs) to transmit the CP breaking to the SM. We analyze the flavor constraints coming from the presence of one such down type VLQ of NB type by performing a global fit on the relevant flavor observables. A comparison is made to the case of one generic VLQ. We find that the allowed parameter space for the VLQ Yukawa couplings and the mixing to the SM are confined to a region much smaller than in the generic case, making the NB case falsifiable in principle.

Abstract We report a set of exact formulae for computing Dirac masses, mixings, and CP-violation parameter(s) from 3×3 Yukawa matrices Y valid when YY † → U † YY † U under global U 3 Q L $$ \mathrm{U}{(3)}_{Q_L} $$ flavour symmetry transformations U. The results apply to the Standard Model Effective Field Theory (SMEFT) and its ‘geometric’ realization (geoSMEFT). We thereby complete, in the Dirac flavour sector, the catalogue of geoSMEFT parameters derived at all orders in the 2 H † H $$ \sqrt{2\left\langle {H}^{\dagger }H\right\rangle } $$ /Λ expansion. The formalism is basis-independent, and can be applied to models with decoupled ultraviolet flavour dynamics, as well as to models whose infrared dynamics are not minimally flavour violating. We highlight these points with explicit examples and, as a further demonstration of the formalism’s utility, we derive expressions for the renormalization group flow of quark masses, mixings, and CP-violation at all mass dimension and perturbative loop orders in the (geo)SM(EFT) and beyond.

Abstract We propose a twin Pati-Salam (PS) theory of flavour broken to the G 4321 gauge group at high energies, then to the Standard Model at low energies, yielding a TeV scale vector leptoquark U 1 μ $$ {U}_1^{\mu } $$ (3, 1, 2/3) which has been suggested to address the lepton universality anomalies R K ∗ $$ {R}_{K^{\left(\ast \right)}} $$ and R D ∗ $$ {R}_{D^{\left(\ast \right)}} $$ in B decays. Quark and lepton masses are mediated by vector-like fermions, with personal Higgs doublets for the second and third families, which may be replaced by a two Higgs doublet model (2HDM). The twin PS theory of flavour successfully accounts for all quark and lepton (including neutrino) masses and mixings, and predicts a dominant coupling of U 1 μ $$ {U}_1^{\mu } $$ (3, 1, 2/3) to the third family left-handed doublets. However the predicted mass matrices, assuming natural values of the parameters, are not consistent with the single vector leptoquark solution to the R D ∗ $$ {R}_{D^{\left(\ast \right)}} $$ anomaly, given its current value.

Abstract In this work, we revisit the non-minimally coupled Higgs Inflation scenario and investigate its observational viability in light of the current Cosmic Microwave Background, Baryon Acoustic Oscillation and type Ia Supernovae data. We explore the effects of the Coleman-Weinberg approximation to the Higgs potential in the primordial universe, connecting the predictions for the Lagrangian parameters at inflationary scales to the electroweak observables through Renormalization Group methods at two-loop order. Initially, we find that electroweak scale measurements may be dissonant to the limits obtained from the cosmological data sets used in the analysis. Specifically, an ≈ 8σ-discrepancy between the inflationary parameters and the value of the Monte Carlo reconstructed top quark mass is found. However, considering the most recent results obtained by the CMS Collaboration from differential cross-section measurements of the top quark production a good agreement is obtained.

Abstract We present the first and complete dispersion relation analysis of the inner radiative corrections to the axial coupling constant g A in the neutron β-decay. Using experimental inputs from the elastic form factors and the spin-dependent structure function g 1, we determine the contribution from the γW-box diagram to a precision better than 10 −4. Our calculation indicates that the inner radiative corrections to the Fermi and the Gamow-Teller matrix element in the neutron β-decay are almost identical, i.e. the ratio λ = g A /g V is almost unrenormalized. With this result, we predict the bare axial coupling constant to be g ∘ A = − 1.2754 13 exp 2 RC $$ {\overset{\circ }{g}}_A=-1.2754{(13)}_{\mathrm{exp}}{(2)}_{\mathrm{RC}} $$ based on the PDG average λ = −1.2756(13).

Abstract We propose an extension of the three-Higgs-doublet model (3HDM), where the Standard Model (SM) particle content is enlarged by the inclusion of two inert SU2L scalar doublets, three inert and two active electrically neutral gauge singlet scalars, charged vector like fermions and Majorana neutrinos. These additional particles are introduced to generate the SM fermion mass hierarchy from a sequential loop suppression mechanism. In our model the top and exotic fermion masses appear at tree level, whereas the remaining fermions get their masses radiatively. Specifically, bottom, charm, tau and muon masses appear at 1-loop; the masses for the light up, down and strange quarks as well as for the electron at 2-loop and masses for the light active neutrinos at 3-loop. Our model successfully accounts for SM fermion masses and mixings and accommodates the observed Dark Matter relic density, the electron and muon anomalous magnetic moments, as well the constraints arising from charged Lepton Flavor Violating (LFV) processes. The proposed model predicts charged LFV decays within the reach of forthcoming experiments.

Abstract Parity solutions to the strong CP problem are a compelling alternative to approaches based on Peccei-Quinn symmetry, particularly given the expected violation of global symmetries in a theory of quantum gravity. The most natural of these solutions break parity at a low scale, giving rise to a host of experimentally accessible signals. We assess the status of the simplest parity-based solution in light of LHC data and flavor constraints, highlighting the prospects for near-future tests at colliders, tabletop experiments, and gravitational wave observatories. The origin of parity breaking and associated gravitational effects play crucial roles, providing new avenues for discovery through EDMs and gravity waves. These experimental opportunities underline the promise of generalized parity, rather than Peccei-Quinn symmetry, as a robust and testable solution to the strong CP problem.

Abstract We describe a method to numerically compute multi-loop integrals, depending on one dimensionless parameter x and the dimension d, in the whole kinematic range of x. The method is based on differential equations, which, however, do not require any special form, and series expansions around singular and regular points. This method provides results well suited for fast numerical evaluation and sufficiently precise for phenomenological applications. We apply the approach to four-loop on-shell integrals and compute the coefficient function of eight colour structures in the relation between the mass of a heavy quark defined in the MS ¯ $$ \overline{\mathrm{MS}} $$ and the on-shell scheme allowing for a second non-zero quark mass. We also obtain analytic results for these eight coefficient functions in terms of harmonic polylogarithms and iterated integrals. This allows for a validation of the numerical accuracy.

Abstract In this paper, we apply reinforcement learning to the problem of constructing models in particle physics. As an example environment, we use the space of Froggatt-Nielsen type models for quark masses. Using a basic policy-based algorithm we show that neural networks can be successfully trained to construct Froggatt-Nielsen models which are consistent with the observed quark masses and mixing. The trained policy networks lead from random to phenomenologically acceptable models for over 90% of episodes and after an average episode length of about 20 steps. We also show that the networks are capable of finding models proposed in the literature when starting at nearby configurations.

Abstract Motivated by the intriguing discrepancies in b → sℓℓ transitions, the fermion mass problem, and a desire to preserve the accidental symmetries of the Standard Model (SM), we extend the SM by an anomalous U(1) X gauge symmetry where X = Y 3 + a(L μ − Lτ)/6. The heavy Z′ boson associated with spontaneously breaking U(1) X at the TeV scale mediates the b → sℓℓ anomalies via O 9 μ ~ 1 Λ 2 s ¯ γ ρ P L b μ ¯ γ ρ μ $$ {\mathcal{O}}_9^{\mu}\sim \frac{1}{\Lambda^2}\left(\overline{s}{\gamma}_{\rho }{P}_Lb\right)\left(\overline{\mu}{\gamma}^{\rho}\mu \right) $$ . We show that this model, which features mixed gauge anomalies involving U(1) X and hypercharge, can be made anomaly-free for any a ∈ ℤ by integrating in a pair of charged fermions whose masses naturally reside somewhere between 1 and 30 TeV. The gauge symmetry permits only the third family Yukawas at the renormalisable level, and so the light quark masses and mixings are controlled by accidental U(2)3 flavour symmetries which we assume are minimally broken alongside U(1) X . The lepton sector is not governed by U(2) symmetries, but rather one expects a nearly diagonal charged lepton Yukawa with m e,μ « m τ . The model does not explain the hierarchy m e « m μ , but it does possess high quality lepton flavour symmetries that are robust to the heavy physics responsible for generating m e,μ . We establish the viability of these models by checking agreement with the most important experimental constraints. We comment on how the model could also explain neutrino masses and the muon g − 2.

Abstract Electric dipole moments are sensitive probes of new phases in the Higgs Yukawa couplings. We calculate the complete two-loop QCD anomalous dimension matrix for the mixing of CP-odd scalar and tensor operators and apply our results for a phenomenological study of CP violation in the bottom and charm Yukawa couplings. We find large shifts of the induced Wilson coefficients at next-to-leading-logarithmic order. Using the experimental bound on the electric dipole moments of the neutron and mercury, we update the constraints on CP-violating phases in the bottom and charm quark Yukawas.

Abstract The K → μ + μ − decay is often considered to be uninformative of fundamental theory parameters since the decay is polluted by long-distance hadronic effects. We demonstrate that, using very mild assumptions and utilizing time-dependent interference effects, ℬ(K S → μ + μ − ) ℓ=0 can be experimentally determined without the need to separate the ℓ = 0 and ℓ = 1 final states. This quantity is very clean theoretically and can be used to test the Standard Model. In particular, it can be used to extract the CKM matrix element combination ∣ V ts V td sin β + β s ∣ ≈ ∣ A 2 λ 5 η ¯ ∣ $$ \mid {V}_{ts}{V}_{td}\sin \left(\beta +{\beta}_s\right)\mid \approx \mid {A}^2{\lambda}^5\overline{\eta}\mid $$ with hadronic uncertainties below 1%.

Abstract Solutions of the Strong CP Problem based on the spontaneous breaking of CP must feature a non-generic structure and simultaneously explain a coincidence between a priori unrelated CP-even and CP-odd mass scales. We show that these properties can emerge from gauge invariance and a CP-conserving, but otherwise generic, physics at the Planck scale. In our scenarios no fundamental scalar is introduced beyond the Standard Model Higgs doublet, and CP is broken at naturally small scales by a confining non-abelian dynamics. This approach is remarkably predictive: robustness against uncontrollable UV corrections to the QCD topological angle requires one or more families of vector-like quarks below a few 10’s of TeV, hence potentially accessible at colliders. Because CP violation is communicated to the SM at these super-soft scales, our solution of the Strong CP Problem is not spoiled by the presence of heavy new states motivated by other puzzles in physics beyond the Standard Model. In addition, these models generically predict a dark sector that may lead to interesting cosmological signatures.

Abstract We analyze the Nelson-Barr approach to the Strong CP Problem. We derive the necessary conditions in order to simultaneously reproduce the CKM phase and the quark masses. Then we quantify the irreducible contributions to the QCD topological angle, namely the corrections arising from loops of the colored fermion mediators that characterize these models. Corrections analytic in the couplings first arise at 3-loop order and are safely below current bounds; non-analytic effects are 2-loop order and decouple as the mediators exceed a few TeV. We discuss collider, electroweak, and flavor bounds and argue that most of the parameter space above the TeV scale is still allowed in models with down-type mediators, whereas other scenarios are more severely constrained. With two or more families of mediators the dominant experimental bound is due to the neutron electric dipole moment.

Abstract We point out that hints of deviations from unitarity in the first row of the CKM matrix may be explained by the presence of a single vector-like top. We study how the stringent experimental constraints arising from CP Violation in the kaon sector and from meson mixing such as D 0 ‐ D ¯ 0 , K 0 ‐ K ¯ 0 $$ {D}^0\hbox{-} {\overline{D}}^0,{K}^0\hbox{-} {\overline{K}}^0 $$ and B d , s 0 ‐ B ¯ d , s 0 $$ {B}_{d,s}^0\hbox{-} {\overline{B}}_{d,s}^0 $$ can be satisfied in the proposed framework. In order for the deviations from unitarity to be of the required size while keeping the theory perturbative, the new top quark should have a mass m T ≲ 7 TeV which could be probed in upcoming experiments at the energy frontier.

Abstract To extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V ub |, we have re-analyzed all the available inputs (data and theory) on the B → πℓν decays including the newly available inputs on the form-factors from light cone sum rule (LCSR) approach. We have reproduced and compared the results with the procedure taken up by the Heavy Flavor Averaging Group (HFLAV), while commenting on the effect of outliers on the fits. After removing the outliers and creating a comparable group of data-sets, we mention a few scenarios in the extraction of |V ub |. In all those scenarios, the extracted values of |V ub | are higher than that obtained by HFLAV. Our best results for |V ub | exc. are (3.94 ± 0.14) × 10 −3 and 3.93 − 0.15 + 0.14 $$ \left({3.93}_{-0.15}^{+0.14}\right) $$ × 10 −3 in frequentist and Bayesian approaches, respectively, which are consistent with that extracted from inclusive decays |V ub | inc. within 1 σ confidence interval.

Abstract Higgs boson production in association with a charm-quark jet proceeds through two different mechanisms — one that involves the charm Yukawa coupling and the other that involves direct Higgs coupling to gluons. The interference of the two contributions requires a helicity flip and, therefore, cannot be computed with massless charm quarks. In this paper, we consider QCD corrections to the interference contribution starting from charm-gluon collisions with massive charm quarks and taking the massless limit, m c → 0. The behavior of QCD cross sections in that limit differs from expectations based on the canonical QCD factorization. This implies that QCD corrections to the interference term necessarily involve logarithms of the ratio M H /m c whose resummation is currently unknown. Although the explicit next-to-leading order QCD computation does confirm the presence of up to two powers of ln(M H /m c ) in the interference contribution, their overall impact on the magnitude of QCD corrections to the interference turns out to be moderate due to a cancellation between double and single logarithmic terms.

Abstract Recent measurements of the Higgs-muon coupling are directly probing muon mass generation for the first time. We classify minimal models with a one-loop radiative mass mechanism and show that benchmark models are consistent with current experimental results. We find that these models are best probed by measurements of (g − 2) μ , even when taking into account the precision of Higgs measurements expected at future colliders. The current (g − 2) μ anomaly, if confirmed, could therefore be a first hint that the muon mass has a radiative origin.

Abstract We present a determination of the charm quark mass in lattice QCD with three active quark flavours. The calculation is based on PCAC masses extracted from N f = 2 + 1 flavour gauge field ensembles at five different lattice spacings in a range from 0.087 fm down to 0.039 fm. The lattice action consists of the O(a) improved Wilson-clover action and a tree-level improved Symanzik gauge action. Quark masses are non-perturbatively O(a) improved employing the Symanzik-counterterms available for this discretisation of QCD. To relate the bare mass at a specified low-energy scale with the renormalisation group invariant mass in the continuum limit, we use the non-pertubatively known factors that account for the running of the quark masses as well as for their renormalisation at hadronic scales. We obtain the renormalisation group invariant charm quark mass at the physical point of the three-flavour theory to be M c = 1486(21) MeV. Combining this result with five-loop perturbation theory and the corresponding decoupling relations in the MS ¯ $$ \overline{\mathrm{MS}} $$ scheme, one arrives at a result for the renormalisation group invariant charm quark mass in the four-flavour theory of M c(N f = 4) = 1548(23) MeV, where effects associated with the absence of a charmed, sea quark in the non-perturbative evaluation of the QCD path integral are not accounted for. In the MS ¯ $$ \overline{\mathrm{MS}} $$ scheme, and at finite energy scales conventional in phenomenology, we quote m c MS ¯ $$ {m}_{\mathrm{c}}^{\overline{\mathrm{MS}}} $$ ( m c MS ¯ $$ {m}_{\mathrm{c}}^{\overline{\mathrm{MS}}} $$ ; N f = 4) = 1296(19) MeV and m c MS ¯ $$ {m}_{\mathrm{c}}^{\overline{\mathrm{MS}}} $$ (3 GeV; N f = 4) = 1007(16) MeV for the renormalised charm quark mass.

Abstract Although the 125 GeV Higgs boson discovered at the LHC is often heralded as the origin of mass, it may not in fact be the origin of Yukawa couplings. In alternative models, Yukawa couplings may instead arise from a seesaw type mechanism involving the mixing of Standard Model (SM) chiral fermions with new vector-like fermions, controlled by the vacuum expectation value (VEV) of a new complex Higgs singlet field 〈Φ〉. For example, the largest third family (t, b) quark Yukawa couplings may be forbidden by a U(1)′ gauge or global symmetry, broken by 〈Φ〉, and generated effectively via mixing with a vector-like fourth family quark doublet (T, B). Such theories predict a new physical Higgs singlet ϕ, which we refer to as the Yukon, resulting from 〈Φ〉, in the same way that the Higgs boson h 0 results from 〈H〉. In a simplified model we discuss the prospects for discovering the Yukon ϕ in gluon-gluon fusion production, with (t, b) and (T, B) quarks in the loops, and decaying in the channels ϕ → γγ, Zγ and ϕ → tT → tth 0, ttZ. The potential for discovery of the Yukon ϕ is studied at present or future hadron colliders such as the LHC (Run 3), HL-LHC, HE-LHC and/or FCC. For example, we find that a 300–350 GeV Yukon ϕ could be accessed at LHC Run 3 in the di-photon channel in the global model, providing a smoking gun signature of the origin of Yukawa couplings. The tth 0, ttZ channels are more involved and warrant a more sophisticated analysis.

Abstract We propose a 3+1 Higgs Doublet Model based on the ∆(27) family symmetry supplemented by several auxiliary cyclic symmetries leading to viable Yukawa textures for the Standard Model fermions, consistent with the observed pattern of fermion masses and mixings. The charged fermion mass hierarchy and the quark mixing pattern is generated by the spontaneous breaking of the discrete symmetries due to flavons that act as Froggatt-Nielsen fields. The tiny neutrino masses arise from a radiative seesaw mechanism at one loop level, thanks to a preserved Z 2 1 $$ {Z}_2^{(1)} $$ discrete symmetry, which also leads to stable scalar and fermionic dark matter candidates. The leptonic sector features the predictive cobimaximal mixing pattern, consistent with the experimental data from neutrino oscillations. For the scenario of normal neutrino mass hierarchy, the model predicts an effective Majorana neutrino mass parameter in the range 3 meV ≲ m ββ ≲ 18 meV, which is within the declared range of sensitivity of modern experiments. The model predicts Flavour Changing Neutral Currents which constrain the model, for instance, μ → e nuclear conversion processes and Kaon mixing are found to be within the reach of the forthcoming experiments.

Abstract We compute the O(α s ) corrections to the Wilson coefficients of the dimension five operators in inclusive semileptonic B decays in the limit of a massless final quark. Our calculation agrees with reparametrization invariance and with previous results for the total width and improves the constraints on the shape functions that enter those decays.

Abstract We study the determination of the top-quark mass using leptonic observables in t-channel single top-quark production at the LHC. We demonstrate sensitivity of transverse momentum of the charged lepton on the input top-quark mass. We present predictions at next-to-next-to-leading order (NNLO) in QCD with narrow width approximation and structure function approach. Further corrections due to parton shower and hadronization, non-resonant and non-factorized contributions are discussed. To reduce impact of SM backgrounds we propose to use the charge weighted distribution for the measurement, i.e., differences between distributions of charged lepton with positive and negative charges. By modeling both signal and background processes, we found the projections for (HL-)LHC to be promising, with a total theoretical uncertainty on the extracted top-quark mass of about 1 ∼ 2 GeV.

Abstract Precision measurements of the Higgs couplings are, for the first time, directly probing the mechanism of fermion mass generation. The purpose of this work is to determine to what extent these measurements can distinguish between the tree-level mechanism of the Standard Model and the theoretically motivated alternative of radiative mass generation. Focusing on the third-family, we classify the minimal one-loop models and find that they fall into two general classes. By exploring several benchmark models in detail, we demonstrate that a radiative origin for the tau-lepton and bottom-quark masses is consistent with current observations. While future colliders will not be able to rule out a radiative origin, they can probe interesting regions of parameter space.

Abstract Triple heavy vector boson production, pp → VVV (V = W, Z), has recently been observed for the first time. We propose that precision measurements of this process provide an excellent probe of the first generation light quark Yukawa couplings. Modified quark interactions with the off-shell Higgs in this process lead to a rapid growth of the partonic cross sections with energy, which manifests in an enhanced p T distribution of the final state leptons and quarks. We quantify this effect and estimate the present and future 2σ sensitivity to the up, down, and strange Yukawas. In particular, we find that HL-LHC can reach O 400 $$ \mathcal{O}(400) $$ sensitivity to the down Yukawa relative to the Standard Model value, improving the current sensitivity in this process by a factor of 10, and which can be further improved to O 30 $$ \mathcal{O}(30) $$ at FCC-hh. This is competitive with and complementary to constraints from global fits and other on-shell probes of the first generation Yukawas. The triboson sensitivity at HL-LHC corresponds to probing dimension-6 SMEFT operators suppressed by an O 1 $$ \mathcal{O}(1) $$ TeV scale, similarly to other LHC Higgs probes.

Abstract We combine SU(5) Grand Unified Theories (GUTs) with A 4 modular symmetry and present a comprehensive analysis of the resulting quark and lepton mass matrices for all the simplest cases. Classifying the models according to the representation assignments of the matter fields under A 4, we find that there are seven types of SU(5) models with A 4 modular symmetry. We present 53 benchmark models with the fewest free parameters. The parameter space of each model is scanned to optimize the agreement between predictions and experimental data, and predictions for the masses and mixing parameters of quarks and leptons are given at the best fitting points. The best fit predictions for the leptonic CP violating Dirac phase, the lightest neutrino mass and the neutrinoless double beta decay parameter when displayed graphically are observed to cover a wide range of possible values, but are clustered around particular regions, allowing future neutrino experiments to discriminate between the different types of models.

Abstract Precision studies of the Higgs boson at future e + e − colliders can help to shed light on fundamental questions related to electroweak symmetry breaking, baryogenesis, the hierarchy problem, and dark matter. The main production process, e + e − → HZ, will need to be controlled with sub-percent precision, which requires the inclusion of next-to-next-to-leading order (NNLO) electroweak corrections. The most challenging class of diagrams are planar and non-planar double-box topologies with multiple massive propagators in the loops. This article proposes a technique for computing these diagrams numerically, by transforming one of the sub-loops through the use of Feynman parameters and a dispersion relation, while standard one-loop formulae can be used for the other sub-loop. This approach can be extended to deal with tensor integrals. The resulting numerical integrals can be evaluated in minutes on a single CPU core, to achieve about 0.1% relative precision.

Abstract Precision measurements in allowed nuclear beta decays and neutron decay are reviewed and analyzed both within the Standard Model and looking for new physics. The analysis incorporates the most recent experimental and theoretical developments. The results are interpreted in terms of Wilson coefficients describing the effective interactions between leptons and nucleons (or quarks) that are responsible for beta decay. New global fits are performed incorporating a comprehensive list of precision measurements in neutron decay, superallowed 0+ → 0+ transitions, and other nuclear decays that include, for the first time, data from mirror beta transitions. The results confirm the V-A character of the interaction and translate into updated values for V ud and g A at the 10 −4 level. We also place new stringent limits on exotic couplings involving left-handed and right-handed neutrinos, which benefit significantly from the inclusion of mirror decays in the analysis.

Abstract The vanishing of the Higgs quartic coupling at a high energy scale may be explained by Intermediate Scale Supersymmetry, where supersymmetry breaks at (109-1012) GeV. The possible range of supersymmetry breaking scales can be narrowed down by precise measurements of the top quark mass and the strong coupling constant. On the other hand, nuclear recoil experiments can probe Higgsino or sneutrino dark matter up to a mass of 1012 GeV. We derive the correlation between the dark matter mass and precision measurements of standard model parameters, including supersymmetric threshold corrections. The dark matter mass is bounded from above as a function of the top quark mass and the strong coupling constant. The top quark mass and the strong coupling constant are bounded from above and below respectively for a given dark matter mass. We also discuss how the observed dark matter abundance can be explained by freeze-out or freeze-in during a matter-dominated era after inflation, with the inflaton condensate being dissipated by thermal effects.

Abstract We propose a theory of quark and lepton mass and mixing with non-universal Z′ couplings based on a 5d Standard Model with quarks and leptons transforming as triplets under a new gauged SO(3) isospin. In the 4d effective theory, the SO(3) isospin is broken to U(1)′, through a S 1/(ℤ2 × ℤ 2 t $$ {\mathrm{\mathbb{Z}}}_2^t $$ ) orbifold, then subsequently dynamically broken, resulting in a massive Z′. Quarks and leptons in the 5d bulk appear as massless modes, with zero Yukawa couplings to the Higgs on the brane, and zero couplings to Z′, at leading order, due to the U(1)′ symmetry. However, after the U(1)′ breaking, both Yukawa couplings and non-universal Z′ couplings are generated by heavy Kaluza-Klein exchanges. Hierarchical quark and lepton masses result from a hierarchy of 5d Dirac fermion masses. Neutrino mass and mixing arises from a novel type Ib seesaw mechanism, mediated by Kaluza-Klein Dirac neutrinos. The non-universal Z′ couplings may contribute to semi-leptonic B decay ratios which violate μ − e universality. In this model such couplings are related to the corresponding quark and lepton effective Yukawa couplings.

Abstract Measurements of electroweak precision observables at future electron-position colliders, such as the CEPC, FCC-ee, and ILC, will be sensitive to physics at multi-TeV scales. To achieve this sensitivity, precise predictions for the Standard Model expectations of these observables are needed, including corrections at the three- and four-loop level. In this article, results are presented for the calculation of a subset of three-loop mixed electroweak-QCD corrections, stemming from diagrams with a gluon exchange and two closed fermion loops. The numerical impact of these corrections is illustrated for a number of applications: the prediction of the W-boson mass from the Fermi constant, the effective weak mixing angle, and the partial and total widths of the Z boson. Two alternative renormalization schemes for the top-quark mass are considered, on-shell and MS ¯ $$ \overline{\mathrm{MS}} $$ .

Low energy observables involving the Standard Model fermions which arechirality-violating, such as anomalous electromagnetic moments, necessarilyinvolve an insertion of the Higgs in order to maintain $SU(2) \times U(1)$gauge invariance. As the result, the properties of the Higgs boson measured atthe LHC impact our understanding of the associated low-energy quantities. Weillustrate this feature with a discussion of the electromagnetic moments of the$\tau$-lepton, as probed by the rare decay $H \rightarrow \tau^+ \tau^-\gamma$. We assess the feasibility of measuring this decay at the LHC, and showthat the current bounds from lower energy measurements imply that $13~\rm{TeV}$running is very likely to improve our understanding of new physics contributingto the anomalous magnetic moment of the tau.

Low energy observables involving the Standard Model fermions which are chirality-violating, such as anomalous electromagnetic moments, necessarily involve an insertion of the Higgs in order to maintain SU(2) × U(1) gauge invariance. As the result, the properties of the Higgs boson measured at the LHC impact our understanding of the associated low-energy quantities. We illustrate this feature with a discussion of the electromagnetic moments of the τ -lepton, as probed by the rare decay H → τ+τ−γ. We assess the feasibility of measuring this decay at the LHC, and show that the current bounds from lower energy measurements imply that 13 TeV running is very likely to improve our understanding of new physics contributing to the anomalous magnetic moment of the tau.

Abstract We extend the framework of modular invariant supersymmetric theories to encompass invariance under more general discrete groups Γ, that allow the presence of several moduli and make connection with the theory of automorphic forms. Moduli span a coset space G/K, where G is a Lie group and K is a compact subgroup of G, modded out by Γ. For a general choice of G, K, Γ and a generic matter content, we explicitly construct a minimal Kähler potential and a general superpotential, for both rigid and local N $$ \mathcal{N} $$ = 1 supersymmetric theories. We also specialize our construction to the case G = Sp(2g, ℝ), K = U(g) and Γ = Sp(2g, ℤ), whose automorphic forms are Siegel modular forms. We show how our general theory can be consistently restricted to multi-dimensional regions of the moduli space enjoying residual symmetries. After choosing g = 2, we present several examples of models for lepton and quark masses where Yukawa couplings are Siegel modular forms of level 2.

Abstract In this paper, a model inspired by Grand Unification principles featuring three generations of vector-like fermions, new Higgs doublets and a rich neutrino sector at the low scale is presented. Using the state-of-the-art Deep Learning techniques we perform the first phenomenological analysis of this model focusing on the study of new charged vector-like leptons (VLLs) and their possible signatures at CERN’s Large Hadron Collider (LHC). In our numerical analysis we consider signal events for vector-boson fusion and VLL pair production topologies, both involving a final state containing a pair of charged leptons of different flavor and two sterile neutrinos that provide a missing energy. We also consider the case of VLL single production where, in addition to a pair of sterile neutrinos, the final state contains only one charged lepton. We propose a novel method to identify missing transverse energy vectors by comparing the detector response with Monte-Carlo simulated data. All calculated observables are provided as data sets for Deep Learning analysis, where a neural network is constructed, based on results obtained via an evolutive algorithm, whose objective is to maximise either the accuracy metric or the Asimov significance for different masses of the VLL. Taking into account the effect of the three analysed topologies, we have found that the combined significance for the observation of new VLLs at the high-luminosity LHC can range from 5.7σ, for a mass of 1.25 TeV, all the way up to 28σ if the VLL mass is 200 GeV. We have also shown that by the end of the LHC Run-III a 200 GeV VLL can be excluded with a confidence of 8.8 standard deviations. The results obtained show that our model can be probed well before the end of the LHC operations and, in particular, providing important phenomenological information to constrain the energy scale at which new gauge symmetries emergent from the considered Grand Unification picture can be manifest.