Search

In this paper, we derive a simplified formula of electric dipole moments (EDMs) of a fermion. In the Standard Model, it is well-known that non-trivial cancellations between some rainbow-type diagrams induced by W boson exchanges occur in the calculation of the neutron EDM at the two-loop level due to the gauge symmetry. The fermion self-energy and the vertex correction are related through the Ward-Takahashi identity, and this relation causes the exact cancellation of the EDM. We derive EDM formulas for a more general setup by introducing the form factors for the fermion self-energy and the vertex correction so that the derived formulas can be applicable to a larger class of models. We conclude that the non-zero EDM contributions are induced from rainbow-type diagrams with the chirality flipping effects for internal fermions. We also discuss the other possible generalization of the EDM calculation which is applicable to the other classes of models. [ABSTRACT FROM AUTHOR]

In this paper, we examine the leptonic flavor invariants in the minimal see-saw model (MSM), in which only two right-handed neutrino singlets are added into the Standard Model in order to accommodate tiny neutrino masses and explain cosmological matter-antimatter asymmetry via leptogenesis mechanism. For the first time, we calculate the Hilbert series (HS) for the leptonic flavor invariants in the MSM. With the HS we demonstrate that there are totally 38 basic flavor invariants, among which 18 invariants are CP-odd and the others are CP-even. Moreover, we explicitly construct these basic invariants, and any other flavor invariants in the MSM can be decomposed into the polynomials of them. Interestingly, we find that any flavor invariants in the effective theory at the low-energy scale can be expressed as rational functions of those in the full MSM at the high-energy scale. Practical applications to the phenomenological studies of the MSM, such as the sufficient and necessary conditions for CP conservation and CP asymmetries in leptogenesis, are also briefly discussed. [ABSTRACT FROM AUTHOR]

In this paper we propose a new reconstruction method to explore the low mass region in the associated production of top-quark pairs (t t ¯ ) with a generic scalar boson (ϕ) at the LHC. The new method of mass reconstruction shows an improved resolution of at least a factor of two in the low mass region when compared to previous methods, without the loss of sensitivity of previous analyses. It turns out that it also leads to an improvement of the mass reconstruction of the 125 GeV Higgs for the same production process. We use an effective Lagrangian to describe a scalar with a generic Yukawa coupling to the top quarks. A full phenomenological analysis was performed, using Standard Model background and signal events generated with MadGraph5_aMC@NLO and reconstructed using a kinematic fit. The use of CP-sensitive variables allows then to maximize the distinction between CP-even and CP-odd components of the Yukawa couplings. Confidence Levels (CLs) for the exclusion of ϕ bosons with mixed CP (both CP-even and CP-odd components) were determined as a function of the top Yukawa couplings to the ϕ boson. The mass range analysed starts slightly above the ϒΥ mass up to 40 GeV, although the analysis can be used for an arbitrary mass. If no new light scalar is found, exclusion limits at 95% CL for the absolute value of the CP-even and CP-odd Yukawa are derived. Finally, we analyse how these limits constrain the parameter space of the complex two-Higgs doublet model (C2HDM). [ABSTRACT FROM AUTHOR]

For a number of years, there has been a certain inconsistency among the measurements of the branching ratios and CP asymmetries of the four B → π K decays ( B → π K, B → π K, B → π K, B → π K). In this paper, we re-examine this B → π K puzzle. We find that the key unknown parameter is | C /T |, the ratio of color-suppressed and color-allowed tree amplitudes. If this ratio is large, | C /T | = 0 .5, the SM can explain the data. But if it is small, | C /T | = 0 .2, the SM cannot explain the B → π K puzzle -new physics (NP) is needed. The two types of NP that can contribute to B → π K at tree level are Z bosons and diquarks. Z models can explain the puzzle if the Z couples to right-handed uū and/or $$ d\overline{d} $$ , with g ≠ g. Interestingly, half of the many Z models proposed to explain the present anomalies in b → sμ μ decays have the required Z couplings to uū and/or $$ d\overline{d} $$ . Such models could potentially explain both the b → sμ μ anomalies and the B → π K puzzle. The addition of a color sextet diquark that couples to ud can also explain the puzzle. [ABSTRACT FROM AUTHOR]

Beyond the Standard Model (SM) extensions usually include extended Higgs sectors. Models with singlet or doublet fields are the simplest ones that are compatible with the ρ parameter constraint. The discovery of new non-SM Higgs bosons and the identification of the underlying model requires dedicated Higgs properties analyses. In this paper, we compare several Higgs sectors featuring 3 CP-even neutral Higgs bosons that are also motivated by their simplicity and their ability to solve some of the flaws of the SM. They are: the SM extended by a complex singlet field (CxSM), the singlet extension of the 2-Higgs-Doublet Model (N2HDM), and the Next-to-Minimal Supersymmetric SM extension (NMSSM). In addition, we analyse the CP-violating 2-Higgs-Doublet Model (C2HDM), which provides 3 neutral Higgs bosons with a pseudoscalar admixture. This allows us to compare the effects of singlet and pseudoscalar admixtures. Through dedicated scans of the allowed parameter space of the models, we analyse the phenomenologically viable scenarios from the view point of the SM-like Higgs boson and of the signal rates of the non-SM-like Higgs bosons to be found. In particular, we analyse the effect of singlet/pseudoscalar admixture, and the potential to differentiate these models in the near future. This is supported by a study of couplings sums of the Higgs bosons to massive gauge bosons and to fermions, where we identify features that allow us to distinguish the models, in particular when only part of the Higgs spectrum is discovered. Our results can be taken as guidelines for future LHC data analyses, by the ATLAS and CMS experiments, to identify specific benchmark points aimed at revealing the underlying model. [ABSTRACT FROM AUTHOR]

We compute the hadronic matrix elements of the four-quark operators relevant for $$ {K}^0-{\overline{K}}^0 $$ mixing beyond the Standard Model. Our results are from lattice QCD simulations with n = 2 + 1 flavours of domain-wall fermion, which exhibit continuum-like chiral-flavour symmetry. The simulations are performed at two different values of the lattice spacing ( a ∼ 0 .08 and a ∼ 0 .11 fm) and with lightest unitary pion mass ∼ 300 MeV. For the first time, the full set of relevant four-quark operators is renormalised non-perturbatively through RI-SMOM schemes; a detailed description of the renormalisation procedure is presented in a companion paper. We argue that the intermediate renormalisation scheme is responsible for the discrepancies found by different collaborations. We also study different normalisations and determine the matrix elements of the relevant four-quark operators with a precision of ∼ 5% or better. [ABSTRACT FROM AUTHOR]

Since the standard model contribution is virtually absent, any observation of direct CP violation in the Cabibbo-favored charmed meson decays would be evidence of new physics. In this paper, we conduct a quantitative study on direct CP violation in D0 → K−π+, Ds+ → ηπ+ and Ds+ → η′π+ decays in the SU(2)L ×SU(2)R ×U(1)B−L gauge extension of the standard model. In the model, direct CP violation arises mainly from the interference between the decay amplitude coming from the SM left-left current operators and that from the right-right current operators induced by WR+ gauge boson exchange. Interestingly, the strong phase between the two amplitudes is evaluable, since it stems from difference in QCD corrections to the left-left and right-right current operators, which is a short-distance QCD effect given by ∼αsMWL2/4πlogMWR2/MWL2. We assess the maximal direct CP violation in the above decays in the SU(2)L × SU(2)R × U(1)B−L model. Additionally, we present a correlation between direct CP violation in these modes and one in K → ππ decay parametrized by ϵ′, since WR+ gauge boson has a sizable impact on the latter. [ABSTRACT FROM AUTHOR]

Scalar triplet extensions of the Standard Model provide an interesting playground for the explanation of neutrino mass suppression through the type-II seesaw mechanism. Propelled by the possible connections with leptonic CP violation, we explore under which conditions spontaneous CP violation can arise in models with extra scalar triplets. The minimal model satisfying such conditions requires adding two such triplets to the SM field content. For this model, the scalar mass spectrum in both the CP-conserving and spontaneous CP-violating scenarios is studied. In the former case, a decoupling limit for the new scalars can be achieved, while this is not the case when CP is spontaneously broken. In particular, we show that the existence of two light neutral scalars with masses below a few tenths of GeVs is unavoidable in the CP-violating case. Using matrix theory theorems, we derive upper bounds for the masses of those light scalars and briefly examine whether they can still be experimentally viable. Other interesting features of the scalar mass spectrum are discussed as, e.g., the existence of relations among the charged and neutral scalar masses. [ABSTRACT FROM AUTHOR]

We study a simplified model of flavoured Majorana dark matter in the Dark Minimal Flavour Violation framework. The model extends the Standard Model by a dark matter flavour triplet and a scalar mediator, through which the new dark fermions couple to right-handed up-type quarks. This interaction is governed by a new coupling matrix λ which is assumed to constitute the only new source of flavour and CP violation. We analyse the parameter space of this model by using constraints from collider searches, D0− D ¯ 0 mixing, cosmology and direct dark matter searches. Throughout our study, we point out crucial differences between the Majorana and Dirac dark matter cases. After performing a combined analysis within the context of all the experimental constraints mentioned above, we analyse which flavour for the dark matter particle is preferred by experimental data. We further investigate if this model is capable of explaining the large measured value of the direct CP asymmetry ∆ A CP dir in charm decays. We find that significant enhancements with respect to the Standard Model expectation are compatible with all constraints, and even the central value of the measurement can be reached. We also advertise the flavour-violating final state with two same-sign top quarks produced in association with missing transverse energy as a smoking-gun signature for flavoured Majorana dark matter at the LHC. [ABSTRACT FROM AUTHOR]

We investigate rare decays of Higgs via exchange of two almost degenerate heavy on-shell Majorana neutrinos Nj (j = 1, 2): Γ± = Γ(h → νkNj→ νkℓ±π∓), and into the open quark channels Γ± = Γ(h → νkNj→ νkℓ±UD), where UD are two jets of open quarks ( U ¯ D , or U D ¯ , where U = u, c and D = d, s). The related CP violation asymmetry ACP = (Γ−− Γ+)/(Γ− + Γ+) is studied in detail. We take into account the N1-N2 overlap and oscillation effects. We can see that for certain, presently acceptable, range of input parameters, such decays with open quark channels, and their asymmetries, could be detected in the International Linear Collider (ILC). [ABSTRACT FROM AUTHOR]

Charged current semi-leptonic decays of B-meson are important for a precise determination of the CKM elements. The CKM elements |Vub| and |Vcb| show a discrepancy between the exclusive and inclusive determinations. These determinations are however masked with hadronic and other uncertainties, and thus can't be unambiguously taken as implying new physics. In the present study, we propose a new observable: the ratio of these two CKM elements, R V ≡ V ub V cb , which is found to receive negligible corrections due to hadronic as well as QED effects. Interestingly, RV as constructed from exclusive determinations of |Vub| and |Vcb| agrees quite well with that constructed from the inclusive determinations of these CKM elements. Hence, we propose that RV is a better and cleaner observable, and can serve as an excellent tool for the test of the Standard Model. We also provide an example of its probing power. [ABSTRACT FROM AUTHOR]

The measured branching fractions of B-mesons into leptonic final states derived by the LHCb, Belle and BaBar collaborations hint towards the breakdown of lepton flavour universality. In this work we take at face value the so-called R D ∗ observables that are defined as the ratios of neutral B-meson charged-current decays into a D(*)-meson, a charged lepton and a neutrino final state in the tau and light lepton channels. A well-studied and simple solution to this charged current anomaly is to introduce a scalar leptoquark S1 that couples to the second and third generation of fermions. We investigate how S1 can also serve as a mediator between the Standard Model and a dark sector. We study this scenario in detail and estimate the constraints arising from collider searches for leptoquarks, collider searches for missing energy signals, direct detection experiments and the dark matter relic abundance. We stress that the production of a pair of leptoquarks that decays into different final states (i.e. the commonly called "mixed" channels) provides critical information for identifying the underlying dynamics, and we exemplify this by studying the tτbν and the resonant S1 plus missing energy channels. We find that direct detection data provides non-negligible constraints on the leptoquark coupling to the dark sector, which in turn affects the relic abundance. We also show that the correct relic abundance can not only arise via standard freeze-out, but also through conversion-driven freeze-out. We illustrate the rich phenomenology of the model with a few selected benchmark points, providing a broad stroke of the interesting connection between lepton flavour universality violation and dark matter. [ABSTRACT FROM AUTHOR]

The goal of this work is to find the simplest UV completion of Accidental Composite Dark Matter Models (ACDM) that can dynamically generate an asymmetry for the DM candidate, the lightest dark baryon (DCb), and simultaneously annihilate the symmetric component. In this framework the DCb is a bound state of a confining SU(N)DC gauge group, and can interact weakly with the visible sector. The constituents of the DCb can possess non-trivial charges under the Standard Model gauge group. The generation of asymmetry for such candidate is a two-flavor variation of the out-of-equilibrium decay of a heavy scalar, with mass Mϕ ≳ 1010 GeV. Below the scale of the scalars, the models recover accidental stability, or long-livedness, of the DM candidate. The symmetric component is annihilated by residual confined interactions provided that the mass of the DCb mDCb ≲ 75 TeV. We implement the mechanism of asymmetry generation, or a variation of it, in all the original ACDM models, managing to generate the correct asymmetry for DCb of masses in this range. For some of the models found, the stability of the DM candidate is not spoiled even considering generic GUT completions or asymmetry generation mechanisms in the visible sector. [ABSTRACT FROM AUTHOR]

New-physics (NP) constraints on first-generation quark-lepton interactions are particularly interesting given the large number of complementary processes and observables that have been measured. Recently, first hints for such NP effects have been observed as an apparent deficit in first-row CKM unitarity, known as the Cabibbo angle anomaly, and the CMS excess in q q ¯ → e+e−. Since the same NP would inevitably enter in searches for low-energy parity violation, such as atomic parity violation, parity-violating electron scattering, and coherent neutrino-nucleus scattering, as well as electroweak precision observables, a combined analysis is required to assess the viability of potential NP interpretations. In this article we investigate the interplay between LHC searches, the Cabibbo angle anomaly, electroweak precision observables, and low-energy parity violation by studying all simplified models that give rise to tree-level effects related to interactions between first-generation quarks and leptons. Matching these models onto Standard Model effective field theory, we derive master formulae in terms of the respective Wilson coefficients, perform a complete phenomenological analysis of all available constraints, point out how parity violation can in the future be used to disentangle different NP scenarios, and project the constraints achievable with forthcoming experiments. [ABSTRACT FROM AUTHOR]

In the context of lepton flavor universality violation (LFUV) studies, we fully derive a general tensor formalism to investigate the role that left- and right-handed neutrino new-physics (NP) terms may have in b → cτ ν ¯ τ transitions. We present, for several extensions of the Standard Model (SM), numerical results for the Λb → Λcτ ν ¯ τ semileptonic decay, which is expected to be measured with precision at the LHCb. This reaction can be a new source of experimental information that can help to confirm, or maybe rule out, LFUV presently seen in B ¯ meson decays. The present study analyzes observables that can help in distinguishing between different NP scenarios that otherwise provide very similar results for the branching ratios, which are our currently best hints for LFUV. Since the τ lepton is very short-lived, we consider three subsequent τ-decay modes, two hadronic πντ and ρντ and one leptonic μ ν ¯ μντ, which have been previously studied for B ¯ → D(*) decays. Within the tensor formalism that we have developed in previous works, we re-obtain the expressions for the differential decay width written in terms of visible (experimentally accessible) variables of the massive particle created in the τ decay. There are seven different τ angular and spin asymmetries that are defined in this way and that can be extracted from experiment. Those asymmetries provide observables that can help in constraining possible SM extensions. [ABSTRACT FROM AUTHOR]

We perform a detailed analysis of flavour changing neutral current processes in the charm sector in the context of 331 models. As pointed out recently, in the case of Z′ contributions in these models there are no new free parameters beyond those already present in the Bd,s and K meson systems analyzed in the past. As a result, definite ranges for new Physics (NP) effects in various charm observables could be obtained. While generally NP effects turn out to be small, in a number of observables they are much larger than the tiny effects predicted within the Standard Model. In particular we find that the branching ratio of the mode D0→ μ+μ−, despite remaining tiny, can be enhanced by 6 orders of magnitude with respect to the SM. We work out correlations between this mode and rare Bd,s and K decays. We also discuss neutral charm meson oscillations and CP violation in the charm system. In particular, we point out that 331 models provide new weak phases that are a necessary condition to have non-vanishing CP asymmetries. In the case of ∆ACP, the difference between the CP asymmetries in D0→ K+K− and D0→ π+π−, we find that agreement with experiment can be obtained provided that two conditions are verified: the phases in the ranges predicted in 331 models and large hadronic matrix elements. [ABSTRACT FROM AUTHOR]

We analyze rare charm baryon decays within the standard model and beyond. We identify all null test observables in unpolarized Λc→ pℓ+ℓ−, ℓ = e, μ decays, and study the new physics sensitivities. We find that the longitudinal dilepton polarization fraction FL is sensitive to electromagnetic dipole couplings C 7 ′ , and to the right-handed 4-fermion vector coupling C 9 ′ . The forward-backward asymmetry, AFB, due to the GIM-suppression a standard model null test already, probes the left-handed axialvector 4-fermion coupling C10; its CP–asymmetry, A FB CP probes CP-violating phases in C10. Physics beyond the standard model can induce branching ratios of dineutrino modes Λc→ pν ν ¯ up to a few times 10−5, and one order of magnitude smaller if lepton flavor universality is assumed, while standard model rates are negligible. Charged lepton flavor violation allows for striking signals into e±μ∓ final states, up to 10−6 branching ratios model-independently, and up to order 10−8 in leptoquark models. Related three-body baryon decays Ξc→ Σℓℓ, Ξc→ Λℓℓ and Ωc→ Ξℓℓ offer similar opportunities to test the standard model with |∆c| = |∆u| = 1 transitions. [ABSTRACT FROM AUTHOR]

The recent experimental status, including the confirmation of the muon g − 2 anomaly at Fermilab, indicates a Beyond Standard Model (BSM) satisfying the following properties: 1) it enhances the g − 2 2) suppresses flavor violations, such as μ → eγ, 3) suppresses CP violations, such as the electron electric dipole moment (EDM). In this letter, I show that the eigenbasis of the mass matrix and higher dimensional photon operators can be automatically aligned if the masses of heavy leptons are generated radiatively together with the g − 2. As a result, the muon g − 2 is enhanced but the EDM of the electron and μ → eγ rate are naturally suppressed. Phenomenology and applications of the mechanism to the B-physics anomalies are argued. [ABSTRACT FROM AUTHOR]

We propose a framework where a phase transition associated with a gauge symmetry breaking that occurs (not far) above the electroweak scale sets a stage for baryogenesis similar to the electroweak baryogenesis in the Standard Model. A concrete realization utilizes the breaking of SU(2)R× U(1)X→ U(1)Y. New chiral fermions charged under the extended gauge symmetry have nonzero lepton numbers, which makes the B − L symmetry anomalous. The new lepton sector contains a large flavor-dependent CP violation, similar to the Cabibbo-Kobayashi-Maskawa phase, without inducing sizable electric dipole moments of the Standard Model particles. A bubble wall dynamics associated with the first-order phase transition and SU(2)R sphaleron processes generate a lepton asymmetry, which is transferred into a baryon asymmetry via the ordinary electroweak sphaleron process. Unlike the Standard Model electroweak baryogenesis, the new phase transition can be of the strong first order and the new CP violation is not significantly suppressed by Yukawa couplings, so that the observed asymmetry can be produced. The model can be probed by collider searches for new particles and the observation of gravitational waves. One of the new leptons becomes a dark matter candidate. The model can be also embedded into a left-right symmetric theory to solve the strong CP problem. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

We develop an efficient method for solving transport equations, particularly in the context of electroweak baryogenesis. It provides fully-analytical results under mild approximations and can also test semi-analytical results, which are applicable in more general cases. Key elements of our method include the reduction of the second-order differential equations to first order, representing the set of coupled equations as a block matrix of the particle densities and their derivatives, identification of zero modes, and block decomposition of the matrix. We apply our method to calculate the baryon asymmetry of the Universe (BAU) in a Standard Model effective field theory framework of complex Yukawa couplings to determine the sensitivity of the resulting BAU to modifications of various model parameters and rates, and to estimate the effect of the commonly-used thin-wall approximation. [ABSTRACT FROM AUTHOR]

We study the phenomenology of the minimal (2, 2) inverse-seesaw model supplemented with Abelian flavour symmetries. To ensure maximal predictability, we establish the most restrictive flavour patterns which can be realised by those symmetries. This setup requires adding an extra scalar doublet and two complex scalar singlets to the Standard Model, paving the way to implement spontaneous CP violation. It is shown that such CP-violating effects can be successfully communicated to the lepton sector through couplings of the scalar singlets to the new sterile fermions. The Majorana and Dirac CP phases turn out to be related, and the active-sterile neutrino mixing is determined by the active neutrino masses, mixing angles and CP phases. We investigate the constraints imposed on the model by the current experimental limits on lepton flavour-violating decays, especially those on the branching ratio BR(μ → eγ) and the capture rate CR(μ − e, Au). The prospects to further test the framework put forward in this work are also discussed in view of the projected sensitivities of future experimental searches sensitive to the presence of heavy sterile neutrinos. Namely, we investigate at which extent upcoming searches for μ → eγ, μ → 3e and μ − e conversion in nuclei will be able to test our model, and how complementary will future high-energy collider and beam-dump experiments be in that task. [ABSTRACT FROM AUTHOR]

To address the long-standing (g − 2)μ anomaly via a light boson, in ref. [1] we proposed to extend the standard model (SM) by the local (B − L)23, under which only the second and third generations of fermions are charged. It predicts an invisible Z′ with mass O 100 MeV, and moreover it has flavor-changing neutral current (FCNC) couplings to the up-type quarks at tree level. Such a Z′, via KL→ π0 + Z′(→ v v ¯ ) at loop level, may be a natural candidate to account for the recent KOTO anomaly. In this article, we investigate this possibility, to find that Z′ can readily do this job if it is no longer responsible for the (g − 2)μ anomaly. We further find that both anomalies can be explained with moderate tuning of the CP violation, but may contradict the B meson decays. [ABSTRACT FROM AUTHOR]

General flavor changing Goldstone boson (GB) interactions with fermions from a spontaneous global U(1)G symmetry breaking are discussed. This GB may be the Axion, solving the strong QCD CP problem, if there is a QCD anomaly for the assignments of quarks U(1)G charge. Or it may be the Majoron, producing seesaw Majorana neutrino masses by lepton number violation, if the symmetry breaking scale is much higher than the electroweak scale. It may also, in principle, play the roles of Axion and Majoron simultaneously as far as providing solution for the strong CP problem and generating a small Majorana neutrino masses are concerned. Great attentions have been focused on flavor conserving GB interactions. Recently flavor changing Axion and Majoron models have been studied in the hope to find new physics from rare decays in the intensity frontier. In this work, we will provide a systematic model building aspect study for flavor changing neutral current (FCNC) GB interactions in the fermion sectors, or separately in the quark, charged lepton and neutrino sectors and will identify in detail the sources of FCNC interactions in a class of beyond standard model with a spontaneous global U(1)G symmetry breaking. We also provide a general proof of the equivalence of using physical GB components and GB broken generators for calculating GB couplings to two gluons and two photons, and discuss some issues related to spontaneous CP violation models. Besides, we will also provide some details for obtaining FCNC GB interactions in several popular models, such as the Type-I, -II, -III seesaw and Left-Right symmetric models, and point out some special features in these models. [ABSTRACT FROM AUTHOR]

We discuss the testability of CP-violating phases at future lepton colliders for the scenario which satisfies electric dipole moment data by destructive interferences among several phases. We consider the general but aligned two Higgs doublet model which has the CP-violating phases in the Higgs potential and the Yukawa interaction. The Yukawa interaction terms are aligned to avoid flavor changing neutral currents at tree level. The Higgs potential is also aligned such that the coupling constants of the lightest Higgs boson with the mass of 125 GeV to the Standard Model (SM) particles are the same as those of the SM at tree level. We investigate the azimuthal angle distribution of the hadronic decay of tau leptons arising from production and decay of the extra Higgs bosons, which contains information of the CP-violating phases. From the signal and background simulation, we find that the scenario with finite CP-violating phases can be distinguished from CP conserving one at future lepton colliders like the International Linear Collider. [ABSTRACT FROM AUTHOR]

We consider a 5D extension of the DFSZ axion model that addresses both the axion quality and fermion mass hierarchy problems, and predicts flavour-dependent, off-diagonal axion-fermion couplings. The axion is part of a 5D complex scalar field charged under a U(1)PQ symmetry that is spontaneously broken in the bulk, and is insensitive to explicit PQ breaking on the UV boundary. Bulk Standard Model fermions interact with two Higgs doublets that can be localized on the UV boundary or propagate in the bulk to explain the fermion masses and mixings. When the Higgs doublets are localized on the UV boundary, they induce flavour diagonal couplings between the fermions and the axion. However, when the Higgs doublets propagate in the bulk, the overlap of the axion and fermion profiles generates flavour off-diagonal couplings. The effective scale of these off-diagonal couplings in both the quark and lepton sectors can be as small as 1011 GeV, and therefore will be probed in future precision flavour experiments. [ABSTRACT FROM AUTHOR]

The CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the CP -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant CP -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the CP properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the t t ¯ H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone. [ABSTRACT FROM AUTHOR]

In this Addendum we rewrite the neutrino mixing angles and mass squared differences in matter given in our original paper, [1], in a notation that is more conventiona for the reader. Replacing the usual neutrino mixing angles and mass squared differences in the expressions for the vacuum oscillation probabilities with these matter mixing angles and mass squared differences gives an excellent approximation to the oscillation probabilities in matter. Comparisons for T2K & T2HK, NOvA, T2HKK and DUNE are also given for neutrinos and anti-neutrinos, disappearance and appearance channels, and for both normal and inverted orderings. [ABSTRACT FROM AUTHOR]

The μτ-reflection symmetric neutrino mass matrix can accommodate all known neutrino mixing angles, with maximal atmospheric angle fixed, and predicts all the unknown CP phases of the lepton sector but is unable to predict the absolute neutrino mass scale. Here we present a highly predictive scenario where μτ-reflection is combined with a discrete abelian symmetry to enforce a texture-zero in the mass matrix of the heavy right-handed neutrinos that generate the light neutrino masses. Such a restriction reduces the free parameters of the low energy theory to zero and the absolute neutrino mass scale is restricted to few discrete regions, three in the few meV range and one extending up to around 30 meV. The heavy neutrino sector is dependent only on two free parameters which are further restricted to small regions from the requirement of successful leptogenesis. Mass degenerate heavy neutrinos are possible in one case but there is no resonant enhancement of the CP asymmetry. [ABSTRACT FROM AUTHOR]

We explore models and phenomenology of a photophobic axion-like particle (ALP), an axion whose coupling to photons is maximally suppressed without fine-tuning of the underlying parameters. We demonstrate that photophobia can be a natural UV property of ALP models and determine the irreducible coupling of photophobic ALPs to photons induced by violations of the axion shift symmetry. The signatures of photophobic axions are radically different from those of typical ALPs and are of particular interest for collider-based experiments, for which Standard Model triboson measurements provide a significant probe at higher masses. A variety of terrestrial and astrophysical measurements constrain the parameter space of photophobic ALPs, though bounds are typically much weaker compared to typical ALPs. We discuss implications for particle production relaxion models based on photophobic ALPs, finding that they are in mild tension with existing experimental constraints. [ABSTRACT FROM AUTHOR]

Light sterile neutrinos can be probed in a number of ways, including electroweak decays, cosmology and neutrino oscillation experiments. At long-baseline experiments, the neutral-current data is directly sensitive to the presence of light sterile neutrinos: once the active neutrinos have oscillated into a sterile state, a depletion in the neutral-current data sample is expected since they do not interact with the Z boson. This channel offers a direct avenue to probe the mixing between a sterile neutrino and the tau neutrino, which is currently only weakly constrained by current data from SuperK, IceCube and NOvA, however, these constrains will continue to improve as more data is collected by these experiments. In this work, we study the potential of the DUNE experiment to constrain the mixing angle which parametrizes this mixing, θ34, through the observation of neutral-current events at the far detector. We find that DUNE will be able to improve significantly over current constraints thanks to its large statistics and excellent discrimination between neutral- and charged-current events. [ABSTRACT FROM AUTHOR]

The QCD axion is one of the most compelling solutions of the strong CP problem. There are major current efforts into searching for an ultralight, invisible axion, which is believed to be the only phenomenologically viable realization of the QCD axion. Visible axions with decay constants at or below the electroweak scale are believed to have been long excluded by laboratory searches. Considering the significance of the axion solution to the strong CP problem, we revisit experimental constraints on QCD axions in the O(10 MeV) mass window. In particular, we find a variant axion model that remains compatible with existing constraints. This model predicts new states at the GeV scale coupled hadronically, and a variety of low-energy axion signatures, such as rare meson decays, nuclear de-excitations via axion emission, and production in e+e- annihilation and fixed target experiments. This reopens the possibility of solving the strong CP problem at the GeV scale. [ABSTRACT FROM AUTHOR]

We explore the phenomenology of a unique three-Higgs-doublet model based on the single CP symmetry of order 4 (CP4) without any accidental symmetries. The CP4 symmetry is imposed on the scalar potential and Yukawa interactions, strongly shaping both sectors of the model and leading to a very characteristic phenomenology. The scalar sector is analyzed in detail, and in the Yukawa sector we list all possible CP4-symmetric structures which do not run into immediate conflict with experiment, namely, do not lead to massless or mass-degenerate quarks nor to insufficient mixing or CP -violation in the CKM matrix. We show that the parameter space of the model, although very constrained by CP4, is large enough to comply with the electroweak precision data and the LHC results for the 125 GeV Higgs boson phenomenology, as well as to perfectly reproduce all fermion masses, mixing, and CP violation. Despite the presence of flavor changing neutral currents mediated by heavy Higgs scalars, we find through a parameter space scan many points which accurately reproduce the kaon CP -violating parameter ϵ as well as oscillation parameters in K and B mesons. Thus, CP4 offers a novel minimalistic framework for building models with very few assumptions, sufficient predictive power, and rich phenomenology yet to be explored. [ABSTRACT FROM AUTHOR]

We investigate the consequences of a generalized ℤ × ℤ symmetry on a scaling neutrino Majorana mass matrix. It enables us to determine definite analytical relations between the mixing angles θ and θ , maximal CP violation for the Dirac type and vanishing for the Majorana type. Beside the other testable predictions on the low energy neutrino parameters such as ββ decay matrix element | M | and the light neutrino masses m , the model also has intriguing consequences from the perspective of leptogenesis. With the assumption that the required CP violation for leptogenesis is created by the decay of lightest ( N ) of the heavy Majorana neutrinos, only τ -flavored leptogenesis scenario is found to be allowed in this model. For a normal (inverted) ordering of light neutrino masses, θ is found be less (greater) than its maximal value, for the final baryon asymmetry Y to be in the observed range. Besides, an upper and a lower bound on the mass of N have also been estimated. Effect of the heavier neutrinos N on final Y has been worked out subsequently. The predictions of this model will be tested in the experiments such as nEXO, LEGEND, GERDA-II, T2K, NO νA, DUNE etc. [ABSTRACT FROM AUTHOR]

We discuss the phenomenology of right-handed charged currents in the frame-work of the Standard Model Effective Field Theory, in which they arise due to a single gauge-invariant dimension-six operator. We study the manifestations of the nine complex couplings of the W to right-handed quarks in collider physics, flavor physics, and low-energy precision measurements. We first obtain constraints on the couplings under the assumption that the right-handed operator is the dominant correction to the Standard Model at observable energies. We subsequently study the impact of degeneracies with other Beyond-the-Standard-Model effective interactions and identify observables, both at colliders and low-energy experiments, that would uniquely point to right-handed charged currents. [ABSTRACT FROM AUTHOR]

We derive sufficient conditions that guarantee a robust solution of the strong CP problem in theories with spontaneous CP violation, and introduce a class of models satisfying these requirements. In the simplest scenarios the dominant contribution to the topological angle arises at 3-loop order in the Standard Model Yukawa couplings. A variety of new realizations are obtained on a warped extra dimension, which can dynamically generate a CKM phase of the right size as well as the Planck-TeV hierarchy. Experimental signatures of this approach to the strong CP problem include a characteristic pattern of flavor violation and vector-like partners of the top and/or bottom quarks. [ABSTRACT FROM AUTHOR]

The three-site Pati-Salam gauge model provides a consistent description for the hints of lepton-flavor non-universality observed in B decays, connecting the present pattern of “anomalies” to the origin of the Standard Model Yukawa couplings. We present here a detailed analysis of the model predictions for a series of low-energy observables, mainly in B and τ physics. The model is in good agreement with present data and predicts a well-defined pattern of non-standard effects in low-energy observables that could allow us to test it in the near future. Particularly interesting are the predictions of large τ → μ Lepton Flavor Violating processes, such as τ → μγ, τ → 3μ, B → Kτ μ, and Bs → τ μ. Also μ → 3e, μ → eγ, and KL → μe decays could be not far from the present exclusion bounds, although this conclusion is more model dependent. [ABSTRACT FROM AUTHOR]

A Z2 symmetry that extends the weak interaction, SU(2)L → SU(2)L ×SU(2)′, and the Higgs sector, H(2) → H(2, 1) + H′(1, 2), yields a Standard Model quartic coupling that vanishes at scale v′ = 〈H′〉 ≫ 〈H〉. Near v′, theories either have a “prime” sector, or possess “Left-Right” (LR) symmetry with SU(2)′ = SU(2)R. If the Z2 symmetry incorporates spacetime parity, these theories can solve the strong CP problem. The LR theories have all quark and lepton masses arising from operators of dimension 5 or more, requiring Froggatt-Nielsen structures. Two-loop contributions to θ¯ are estimated and typically lead to a neutron electric dipole moment of order 10−27e cm that can be observed in future experiments. Minimal models, with gauge group SU(3) × SU(2)L × SU(2)L × U(1)B−L, have precise gauge coupling unification for v′ = 1010±1 GeV, successfully correlating gauge unification with the observed Higgs mass of 125 GeV. With SU(3) × U(1)B−L embedded in SU(4), the central value of the unification scale is reduced from 1016−17 GeV to below 1016 GeV, improving the likelihood of proton decay discovery. Unified theories based on SO(10) × CP are constructed that have H + H′ in a 16 or 144 and generate higher-dimensional flavor operators, while maintaining perturbative gauge couplings. [ABSTRACT FROM AUTHOR]

The light sterile neutrino, if it exists, will give additional contribution to matter effect when active neutrinos propagate through terrestrial matter. In the simplest 3+1 scheme, three more rotation angles and two more CP-violating phases in lepton mixing matrix make the interaction complicated formally. In this work, the exact analytical expressions for active neutrino oscillation probabilities in terrestrial matter, including sterile neutrino contribution, are derived. It is pointed out that this set of formulas contain information both in matter and in vacuum, and can be easily tuned by choosing related parameters. Based on the generic exact formulas, we present oscillation probabilities of typic medium and long baseline experiments. Taking NOνA experiment as an example, we show that in particular parameter space sterile neutrino gives important contribution to terrestrial matter effect, and Dirac phases play a vital role. [ABSTRACT FROM AUTHOR]

The Standard Model prediction for ϵ′/ϵ based on recent lattice QCD results exhibits a tension with the experimental data. We solve this tension through WR+ gauge boson exchange in the SU(2)L × SU(2)R × U(1)B−L model with ‘charge symmetry’, whose theoretical motivation is to attribute the chiral structure of the Standard Model to the spontaneous breaking of SU(2)R × U(1)B−L gauge group and charge symmetry. We show that MWR<58 TeV is required to account for the ϵ′/ϵ anomaly in this model. Next, we make a prediction for the neutron EDM in the same model and study a correlation between ϵ′/ϵ and the neutron EDM. We confirm that the model can solve the ϵ′/ϵ anomaly without conflicting the current bound on the neutron EDM, and further reveal that almost all parameter regions in which the ϵ′/ϵ anomaly is explained will be covered by future neutron EDM searches, which leads us to anticipate the discovery of the neutron EDM. [ABSTRACT FROM AUTHOR]

In this work we consider a minimal version of the scotogenic model capable of accounting for an electron electric dipole moment within experimental sensitivity reach in addition to providing a dark matter candidate and radiatively generating neutrino masses. The Standard Model is minimally extended by two sterile fermions and one inert scalar doublet, both having odd parity, while the Standard Model particles have an even parity, imposed by a ℤ2 symmetry. The neutrino Yukawa couplings provide additional sources of CP violation, and thus a possible impact on electric dipole moments of charged leptons. This model provides two possible dark matter candidates (one bosonic and one fermionic) and our results show that, independently of the ordering of the generated light neutrino spectrum, one can have sizeable electron electric dipole moment within ACME sensitivity reach in the case of fermionic dark matter candidate. [ABSTRACT FROM AUTHOR]