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Showing papers on "Pseudoscalar published in 2021"


Journal ArticleDOI
TL;DR: In this paper, the authors considered an extension of the Standard Model with a complex hypercharge zero triplet scalar and showed the performance of such a scalar at the LHC and MATHUSLA.
Abstract: In this study we consider an extension of the Standard Model with a complex hypercharge zero triplet scalar. In this scenario one of the charged Higgs bosons remains purely triplet and does not couple to the fermions, making it elusive at colliders. Also the physical pseudoscalar is a pure triplet and this purity makes it a suitable dark matter candidate without the need of discrete symmetries, unlike other extensions. The bounds from relic density and direct dark matter search experiments select its mass to be $\ensuremath{\sim}1.35--1.60\text{ }\text{ }\mathrm{TeV}$. The pure triplet charged Higgs gives rise to displaced signatures and their sensitivity at LHC and MATHUSLA have been studied. The prospects at present and future hadron/muon colliders of such exotic scalars are pointed out by calculating their productions cross section and dominant decay modes. We present also the expected reach for the triplet states at a multi-TeV muon collider.

46 citations


Journal ArticleDOI
TL;DR: In this article, the nucleon axial and induced pseudoscalar form factors were computed using three ensembles of gauge configurations, generated with dynamical light quarks with mass tuned to approximately their physical value.
Abstract: We compute the nucleon axial and induced pseudoscalar form factors using three ensembles of gauge configurations, generated with dynamical light quarks with mass tuned to approximately their physical value. One of the ensembles also includes the strange and charm quarks with their mass close to physical. The latter ensemble has large statistics and finer lattice spacing and it is used to obtain final results, while the other two are used for assessing volume effects. The pseudoscalar form factor is also computed using these ensembles. We examine the momentum dependence of these form factors as well as relations based on pion pole dominance and the partially conserved axial-vector current hypothesis.

41 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss the possibilities of extracting the constraints on New Physics by using the current data on the leptonic and semileptonic decays of pseudoscalar mesons.
Abstract: We discuss the possibilities of extracting the constraints on New Physics by using the current data on the leptonic and semileptonic decays of pseudoscalar mesons In doing so we use a general low energy Lagrangian that besides the vector and axial operators also includes the (pseudo-)scalar and tensor ones In obtaining constraints on New Physics couplings, we combine the experimental information concerning several decay modes with the accurate and precise lattice QCD results for the hadronic matrix elements We propose to study new observables that can be extracted from the angular analysis of the semileptonic decays and discuss their values both in the Standard Model and in some specific scenarios of physics beyond the Standard Model

31 citations


Journal ArticleDOI
TL;DR: In this paper, a symmetry-preserving Poincare-covariant quark+diquark Faddeev equation treatment of the nucleon was used to deliver parameter-free predictions for axial and induced pseudoscalar form factors, respectively.

23 citations


Journal ArticleDOI
TL;DR: In this article, a bottom-up holographic model for QCD in the Veneziano limit is proposed, where the backreaction of the quarks to the gluon dynamics is included.
Abstract: We initiate the study of Regge theory in a bottom-up holographic model for QCD in the Veneziano limit, where the backreaction of the quarks to the gluon dynamics is included. We determine the parameters of the model by carrying out a precise fit to the meson spectrum in QCD. The spectrum for spin-one and pseudoscalar mesons is well reproduced. We then generalise the model to incluce higher spin fields in the bulk trajectories dual to the Pomeron and meson Regge trajectories at the boundary. With this setting, we fit the masses of the mesons with spins J = 2, 3, and 4, as well as the experimental data of the total cross-sections σ(γγ → X), σ(γp → X) and σ(pp → X). For the cross sections we obtain a $$ {\chi}_{\mathrm{d}.\mathrm{o}.\mathrm{f}}^2 $$ of 0.74 for a total of 199 experimental points.

20 citations


Journal ArticleDOI
TL;DR: In this article, the authors explore the phenomenology of ultralight scalars in low-energy leptonic observables, and discuss the current limits on the diagonal couplings to charged leptons and consider processes in which the ultraligh scalar ϕ is directly produced, such as μ → eϕ, or acts as a mediator, as in τ → μμμ.
Abstract: Many new physics scenarios contain ultralight scalars, states which are either exactly massless or much lighter than any other massive particle in the model. Axions and majorons constitute well-motivated examples of this type of particle. In this work, we explore the phenomenology of these states in low-energy leptonic observables. After adopting a model independent approach that includes both scalar and pseudoscalar interactions, we briefly discuss the current limits on the diagonal couplings to charged leptons and consider processes in which the ultralight scalar ϕ is directly produced, such as μ → eϕ, or acts as a mediator, as in τ → μμμ. Contributions to the charged leptons magnetic and electric moments are studied as well.

19 citations


Journal ArticleDOI
TL;DR: In this article, the relation between dark matter and photon absorption via electronic excitations has been clarified and the sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments are presented.
Abstract: We revisit the calculation of bosonic dark matter absorption via electronic excitations. Working in an effective field theory framework and consistently taking into account in-medium effects, we clarify the relation between dark matter and photon absorption. As is well-known, for vector (dark photon) and pseudoscalar (axion-like particle) dark matter, the absorption rates can be simply related to the target material's optical properties. However, this is not the case for scalar dark matter, where the dominant contribution comes from a different operator than the one contributing to photon absorption, which is formally next-to-leading-order and does not suffer from in-medium screening. It is therefore imperative to have reliable first-principles numerical calculations and/or semi-analytic modeling in order to predict the detection rate. We present updated sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments.

18 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Dale Charles Abbott3, A. Abed Abud4  +2861 moreInstitutions (222)
TL;DR: The results of a search for new phenomena in final states with b-jets and missing transverse momentum using 139 fb−1 of proton-proton data collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the LHC are reported in this paper.
Abstract: The results of a search for new phenomena in final states with b-jets and missing transverse momentum using 139 fb−1 of proton-proton data collected at a centre-of-mass energy $$ \sqrt{s} $$ = 13 TeV by the ATLAS detector at the LHC are reported The analysis targets final states produced by the decay of a pair-produced supersymmetric bottom squark into a bottom quark and a stable neutralino The analysis also seeks evidence for models of pair production of dark matter particles produced through the decay of a generic scalar or pseudoscalar mediator state in association with a pair of bottom quarks, and models of pair production of scalar third-generation down-type leptoquarks No significant excess of events over the Standard Model background expectation is observed in any of the signal regions considered by the analysis Bottom squark masses below 1270 GeV are excluded at 95% confidence level if the neutralino is massless In the case of nearly mass-degenerate bottom squarks and neutralinos, the use of dedicated secondary-vertex identification techniques permits the exclusion of bottom squarks with masses up to 660 GeV for mass splittings between the squark and the neutralino of 10 GeV These limits extend substantially beyond the regions of parameter space excluded by similar ATLAS searches performed previously

18 citations


Journal ArticleDOI
TL;DR: In this article, a symmetry-preserving regularisation of a vector contact interaction (SCI) was proposed to describe the initial and final state baryons as quark+diquark composites, wherein the diquark correlations are fully dynamical, interacting with the photon as allowed by their quantum numbers.
Abstract: The $$\gamma ^{(*)}+p \rightarrow N(1535) \tfrac{1}{2}^-$$ transition is studied using a symmetry-preserving regularisation of a vector $$\,\otimes \,$$ vector contact interaction (SCI). The framework employs a Poincare-covariant Faddeev equation to describe the initial and final state baryons as quark+diquark composites, wherein the diquark correlations are fully dynamical, interacting with the photon as allowed by their quantum numbers and continually engaging in breakup and recombination as required by the Faddeev kernel. The presence of such correlations owes largely to the mechanisms responsible for the emergence of hadron mass; and whereas the nucleon Faddeev amplitude is dominated by scalar and axial-vector diquark correlations, the amplitude of its parity partner, the $$N(1535) \tfrac{1}{2}^-$$ , also contains sizeable pseudoscalar and vector diquark components. It is found that the $$\gamma ^{(*)}+p \rightarrow N(1535) \tfrac{1}{2}^-$$ helicity amplitudes and related Dirac and Pauli form factors are keenly sensitive to the relative strengths of these diquark components in the baryon amplitudes, indicating that such resonance electrocouplings possess great sensitivity to baryon structural details. Whilst SCI analyses have their limitations, they also have the virtue of algebraic simplicity and a proven ability to reveal insights that can be used to inform more sophisticated studies in frameworks with closer ties to quantum chromodynamics.

17 citations


Journal ArticleDOI
TL;DR: In this article, the authors performed a search for a new generic X boson which could be a scalar (S), pseudoscalar (P), vector (V), or an axial vector (A) particle produced in the 100-GeV electron scattering off nuclei, e^{-}Z→e^{ −}ZX, followed by its invisible decay in the NA64 experiment at CERN.
Abstract: We performed a search for a new generic X boson, which could be a scalar (S), pseudoscalar (P), vector (V), or an axial vector (A) particle produced in the 100 GeV electron scattering off nuclei, e^{-}Z→e^{-}ZX, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such a process was found in the full NA64 dataset of 2.84×10^{11} electrons on target. We place new bounds on the S, P, V, A coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment a_{e}, |Δa_{X}|≲10^{-15}-10^{-13} for the X mass region 1 MeV≲m_{X}≲1 GeV. These results are an order of magnitude more sensitive compared to the current accuracy on a_{e} from the electron g-2 experiments and recent high-precision determination of the fine structure constant.

17 citations


Journal ArticleDOI
TL;DR: In this article, a comprehensive analysis of form factors for two light pseudoscalar mesons induced by scalar, vector, and tensor quark operators is presented, based on a combination of unitarized chiral perturbation theory and dispersion relations.
Abstract: We present a comprehensive analysis of form factors for two light pseudoscalar mesons induced by scalar, vector, and tensor quark operators. The theoretical framework is based on a combination of unitarized chiral perturbation theory and dispersion relations. The low-energy constants in chiral perturbation theory are fixed by a global fit to the available data of the two-meson scattering phase shifts. Each form factor derived from unitarized chiral perturbation theory is improved by iteratively applying a dispersion relation. This study updates the existing results in the literature and explores those that have not been systematically studied previously, in particular the two-meson tensor form factors within unitarized chiral perturbation theory. We also discuss the applications of these form factors as mandatory inputs for low-energy phenomena, such as the semi-leptonic decays Bs → π+π−l+l− and the τ lepton decay τ → π−π0ντ, in searches for physics beyond the Standard Model.

Journal ArticleDOI
TL;DR: In this article, a light leptophilic boson (scalar or pseudoscalar) has been postulated to explain the muon g-2 anomaly and could be a portal to dark matter, but it is shown that such a hypothetical particle will be unambiguously ruled out or discovered via the Yukawa process at a lepton collider designed as a Higgs factory.
Abstract: A light leptophilic boson (scalar or pseudoscalar) has been postulated to explain the muon g-2 anomaly and could be a portal to dark matter. Realizing the leptophilic nature of a singlet boson in the framework of the two-Higgs-doublet-Model of type-X, we identify the parameter space viable for the explanation of the updated muon g-2 discrepancy. It is then shown that such a hypothetical particle will be unambiguously ruled out or discovered via the Yukawa process at a lepton collider designed as a Higgs factory.

Journal ArticleDOI
TL;DR: In this article, a simple extension to the Standard Model containing two gauge singlets, a Dirac fermion and a real pseudoscalar, was explored, and it was shown that in large regions of the parameter space, both singlets are stable without the necessity of additional symmetries.
Abstract: We explore a simple extension to the Standard Model containing two gauge singlets: a Dirac fermion and a real pseudoscalar. In large regions of the parameter space, both singlets are stable without the necessity of additional symmetries, then becoming a possible two-component dark matter model. We study the relic abundance production via freeze-out, with the latter determined by annihilations, conversions and semi-annihilations. Experimental constraints from invisible Higgs decay, dark matter relic abundance and direct/indirect detection are studied. We found three viable regions of the parameter space.

Journal ArticleDOI
TL;DR: In this article, the authors investigate the most general form of the one-dimensional Dirac Hamiltonian HD in the presence of scalar and pseudoscalar potentials, and construct a quasi-Hamiltonian K, defined as the square of HD, to explore the consequences.
Abstract: We investigate the most general form of the one-dimensional Dirac Hamiltonian HD in the presence of scalar and pseudoscalar potentials. To seek embedding of supersymmetry (SUSY) in it, as an alternative procedure to directly employing the intertwining relations, we construct a quasi-Hamiltonian K, defined as the square of HD, to explore the consequences. We show that the diagonal elements of K under a suitable approximation reflect the presence of a superpotential, thus proving a useful guide in unveiling the role of SUSY. For illustrative purposes, we apply our scheme to the transformed one-dimensional version of the planar electron Hamiltonian under the influence of a magnetic field. We generate spectral solutions for a class of isochronous potentials.

Journal ArticleDOI
Georges Aad1, Brad Abbott2, Dale Charles Abbott3, A. Abed Abud4  +2980 moreInstitutions (222)
TL;DR: In this article, a search for dark matter in the context of a two-Higgs-doublet model together with an additional pseudoscalar mediator, $a$, which decays into the dark-matter particles is presented.
Abstract: This paper presents a search for dark matter in the context of a two-Higgs-doublet model together with an additional pseudoscalar mediator, $a$, which decays into the dark-matter particles. Processes where the pseudoscalar mediator is produced in association with a single top quark in the 2HDM+$a$ model are explored for the first time at the LHC. Several final states which include either one or two charged leptons (electrons or muons) and a significant amount of missing transverse momentum are considered. The analysis is based on proton-proton collision data collected with the ATLAS experiment at $\sqrt{s} = 13$ TeV during LHC Run2 (2015-2018), corresponding to an integrated luminosity of 139 fb$^{-1}$. No significant excess above the Standard Model predictions is found. The results are expressed as 95% confidence-level limits on the parameters of the signal models considered.

Posted Content
TL;DR: In this article, the axial and pseudoscalar form factors obtained on each ensemble satisfy the PCAC relation once the lowest energy $N\pi$ excited state is included in the spectral decomposition of the correlation functions used for extracting the ground state matrix elements.
Abstract: We present high statistics results for the isovector nucleon charges and form factors using seven ensembles of 2+1-flavor Wilson-clover fermions. The axial and pseudoscalar form factors obtained on each ensemble satisfy the PCAC relation once the lowest energy $N\pi$ excited state is included in the spectral decomposition of the correlation functions used for extracting the ground state matrix elements. Similarly, we find evidence that the $N\pi\pi $ excited state contributes to the correlation functions with the vector current, consistent with the vector meson dominance model. The resulting form factors are consistent with the Kelly parameterization of the experimental electric and magnetic data. Our final estimates for the isovector charges are $g_{A}^{u-d} = 1.31(06)(05)_{sys}$, $g_{S}^{u-d} = 1.06(10)(06)_{sys}$, and $g_{T}^{u-d} = 0.95(05)(02)_{sys}$, where the first error is the overall analysis uncertainty and the second is an additional combined systematic uncertainty. The form factors yield: (i) the axial charge radius squared, ${\langle r_A^2 \rangle}^{u-d}=0.428(53)(30)_{sys}\ {\rm fm}^2$, (ii) the induced pseudoscalar charge, $g_P^\ast=7.9(7)(9)_{sys}$, (iii) the pion-nucleon coupling $g_{\pi {\rm NN}} = 12.4(1.2)$, (iv) the electric charge radius squared, ${\langle r_E^2 \rangle}^{u-d} = 0.85(12)(19)_{sys} \ {\rm fm}^2$, (v) the magnetic charge radius squared, ${\langle r_M^2 \rangle}^{u-d} = 0.71(19)(23)_{\rm sys} \ {\rm fm}^2$, and (vi) the magnetic moment $\mu^{u-d} = 4.15(22)(10)_{\rm sys}$. All our results are consistent with phenomenological/experimental values but with larger errors. Lastly, we present a Pade parameterization of the axial, electric and magnetic form factors over the range $0.04< Q^2 <1$ GeV${}^2$ for phenomenological studies.

Journal ArticleDOI
TL;DR: In this paper, the instanton-induced contributions to the hard block were explicitly calculated, and it was shown that they contribute substantially to the vector, scalar and gravitational form factors of the pseudoscalar and vector mesons, over a wide range of momentum transfer.
Abstract: The existing theory of hard exclusive QCD processes is based on two assumptions: (i) factorization into a hard block convoluted with the light front distribution amplitudes; (ii) use of perturbative gluon exchanges within the hard block. However, unlike deep inelastic scattering and jet physics, the characteristic momentum transfer $Q$ involved in the factorized block is not large enough for this theory to be phenomenologically successful. In this work, we revisit the latter assumption (ii), by explicitly calculating the instanton-induced contributions to the hard block, and show that they contribute substantially to the vector, scalar, and gravitational form factors of the pseudoscalar, scalar, and vector mesons, over a wide range of momentum transfer.

Journal ArticleDOI
TL;DR: In this paper, a light leptophilic boson (scalar or pseudoscalar) has been postulated to explain the muon g-2 anomaly and could be a portal to dark matter, but it is shown that such a hypothetical particle will be unambiguously ruled out or discovered via the Yukawa process at a lepton collider designed as a Higgs factory.
Abstract: A light leptophilic boson (scalar or pseudoscalar) has been postulated to explain the muon g-2 anomaly and could be a portal to dark matter. Realizing the leptophilic nature of a singlet boson in the framework of the two-Higgs-doublet-Model of type-X, we identify the parameter space viable for the explanation of the updated muon g-2 discrepancy. It is then shown that such a hypothetical particle will be unambiguously ruled out or discovered via the Yukawa process at a lepton collider designed as a Higgs factory.

Journal ArticleDOI
TL;DR: In this article, it is shown that depending on the nature of dark matter and the interaction involved, neutron stars can improve the sensitivity on the dark matter-nucleon scattering cross section by orders of magnitude.
Abstract: What if the dark matter-nucleon scattering cross section is too small to be detected by direct detection experiments? It is well known in the literature that some interactions lead to dark matter-nucleon scattering cross sections that can be velocity and momentum suppressed. We show that in case of bosonic dark matter the neutron star spectroscopy offers a possible detection. Firstly, we discuss the case of scalar dark matter with scalar, pseudoscalar and vector mediators. Later, we do this exercise for vector dark matter. We show that depending on the nature of dark matter and the interaction involved, neutron stars can improve the sensitivity on the dark matter-nucleon scattering cross section by orders of magnitude, representing a major step forward in the dark matter siege.

Journal ArticleDOI
TL;DR: In this paper, the meson family of η pseudoscalars is studied in the context of the AdS/QCD correspondence and the differential configurational entropy (DCE).

Journal ArticleDOI
TL;DR: In this paper, generalized neutrino interactions (GNI) were studied for neutrinos from electron-positron collisions, neutrini-electron scattering, and neutrinuclear deep inelastic scattering.
Abstract: We study generalized neutrino interactions (GNI) for several neutrino processes, including neutrinos from electron-positron collisions, neutrino-electron scattering, and neutrino deep inelastic scattering. We constrain scalar, pseudoscalar, and tensor new physics effective couplings, based on the standard model effective field theory at low energies. We have performed a global analysis for the different effective couplings. We also present the different individual constraints for each effective parameter (scalar, pseudoscalar, and tensor). Being a global analysis, we show robust results for the restrictions on the different GNI parameters and improve some of these bounds.

Journal ArticleDOI
TL;DR: In this paper, the lowest lying meson masses for SU(N) gauge theory in the large N limit (with Nf /N → 0) are given in units of the square root of the string tension, and with errors which account for both statistical and systematic errors.
Abstract: We present the result of our computation of the lowest lying meson masses for SU(N) gauge theory in the large N limit (with Nf /N → 0). The final values are given in units of the square root of the string tension, and with errors which account for both statistical and systematic errors. By using 4 different values of the lattice spacing we have seen that our results scale properly. We have studied various values of N (169, 289 and 361) to monitor the N-dependence of the most sensitive quantities. Our methodology is based upon a first principles approach (lattice gauge theory) combined with large N volume independence. We employed both Wilson fermions and twisted mass fermions with maximal twist. In addition to masses in the pseudoscalar, vector, scalar and axial vector channels, we also give results on the pseudoscalar decay constant and various remormalization factors.

Journal ArticleDOI
TL;DR: In this article, the authors study the collider phenomenology of color-octet scalars (sgluons) in supersymmetric models with Dirac gaugino masses that feature an explicitly broken R symmetry.
Abstract: In this work we study the collider phenomenology of color-octet scalars (sgluons) in supersymmetric models with Dirac gaugino masses that feature an explicitly broken R symmetry (R-broken models). We construct such models by augmenting minimal R-symmetric models with a fairly general set of supersymmetric and softly supersymmetry-breaking operators that explicitly break R symmetry. We then compute the rates of all significant two-body decays and highlight new features that appear as a result of R symmetry breaking, including enhancements to extant decay rates, novel tree- and loop-level decays, and improved cross sections of single sgluon production. We demonstrate in some detail how the familiar results from minimal R-symmetric models can be obtained by restoring R symmetry. In parallel to this discussion, we explore constraints on these models from the Large Hadron Collider. We find that, in general, R symmetry breaking quantitatively affects existing limits on color-octet scalars, perhaps closing loopholes for light CP-odd (pseudoscalar) sgluons while opening one for a light CP-even (scalar) particle. Qualitatively, however, we find that — much as for minimal R-symmetric models, despite stark differences in phenomenology — scenarios with broken R symmetry and two sgluons below the TeV scale can be accommodated by existing searches.

Journal ArticleDOI
TL;DR: In this paper, the authors investigate the most general form of the one-dimensional Dirac Hamiltonian in the presence of scalar and pseudoscalar potentials and construct a quasi-Hamiltonian to explore the consequences.
Abstract: We investigate the most general form of the one-dimensional Dirac Hamiltonian $H_D$ in the presence of scalar and pseudoscalar potentials. To seek embedding of supersymmetry (SUSY) in it, as an alternative procedure to directly employing the intertwining relations, we construct a quasi-Hamiltonian $\mathcal{K}$, defined as the square of $H_D$, to explore the consequences. We show that the diagonal elements of $\mathcal{K}$ under a suitable approximation reflects the presence of a superpotential thus proving a useful guide in unveiling the role of SUSY. For illustrative purpose we apply our scheme to the transformed one-dimensional version of the planar electron Hamiltonian under the influence of a magnetic field. We generate spectral solutions for a class of isochronous potentials.

Journal ArticleDOI
TL;DR: In this paper, the relation between dark matter and photon absorption via electronic excitations has been clarified and the sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments are presented.
Abstract: We revisit the calculation of bosonic dark matter absorption via electronic excitations. Working in an effective field theory framework and consistently taking into account in-medium effects, we clarify the relation between dark matter and photon absorption. As is well-known, for vector (dark photon) and pseudoscalar (axion-like particle) dark matter, the absorption rates can be simply related to the target material’s optical properties. However, this is not the case for scalar dark matter, where the dominant contribution comes from a different operator than the one contributing to photon absorption, which is formally next-to-leading-order and does not suffer from in-medium screening. It is therefore imperative to have reliable first-principles numerical calculations and/or semi-analytic modeling in order to predict the detection rate. We present updated sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments.

Posted Content
TL;DR: In this article, a quark+diquark approach to the nucleon bound-state problem in relativistic quantum field theory was used to deliver parameter-free predictions for the axial and induced pseudoscalar form factors.
Abstract: We use a continuum quark+diquark approach to the nucleon bound-state problem in relativistic quantum field theory to deliver parameter-free predictions for the nucleon axial and induced pseudoscalar form factors, $G_A$ and $G_P$, and unify them with the pseudoscalar form factor $G_5$ or, equivalently, the pion-nucleon form factor $G_{\pi NN}$. We explain how partial conservation of the axial-vector current and the associated Goldberger-Treiman relation are satisfied once all necessary couplings of the external current to the building blocks of the nucleon are constructed consistently; in particular, we fully resolve the seagull couplings to the diquark-quark vertices associated with the axial-vector and pseudoscalar currents. Among the results we describe, the following are worth highlighting. A dipole form factor defined by an axial charge $g_A=G_A(0)=1.25(3)$ and a mass-scale $M_A = 1.23(3) m_N$, where $m_N$ is the nucleon mass, can accurately describe the pointwise behavior of $G_A$. Concerning $G_P$, we obtain the pseudoscalar charge $g_p^\ast = 8.80(23)$, and find that the pion pole dominance approach delivers a reliable estimate of the directly computed result. Our computed value of the pion-nucleon coupling constant, $g_{\pi NN}/m_N =14.02(33)/{\rm GeV}$ is consistent with a Roy--Steiner-equation analysis of pion-nucleon scattering. We also observe a marked suppression of the size of the $d$-quark component relative to that of the $u$-quark in the ratio $g_A^d/g_A^u=-0.16(2)$, which highlights the presence of strong diquark correlations inside the nucleon -- both scalar and axial-vector, with the scalar diquark being dominant.

Posted Content
TL;DR: In this paper, the high-scale validity of a Type-X two Higgs doublet scenario was studied, which provides an explanation of the observed value of muon $(g-2)$.
Abstract: We study the high-scale validity of a Type-X two Higgs doublet scenario which provides an explanation of the observed value of muon $(g-2)$. This region admits of a pseudoscalar physical state, which is well below the observed 125-GeV scalar in mass. A second neutral scalar particle can be both above and below 125 GeV in such a scenario. Admissible regions in the parameter space are obtained by using the most recent data on muon $(g-2)$, theoretical constraints such as low-scale perturbativity and vacuum stability, and also all experimental constraints, including the available LHC results. Among other things, both the aforesaid orders of CP-even neutral scalar masses are included in our benchmark studies. Two-loop renormalisation group equations are used to predict the values of various couplings at high scales, and the regions in the space spanned by low-scale parameters, which retain perturbative unitarity as well as vacuum stability upto various scales are identified. We thus conclude that such a scenario, while successfully explaining the observed muon $(g-2)$, can be valid upto energy scales ranging from $10^{4}$ GeV to the Planck scale, thus opening up directions of thought on its ultraviolet completion.

Journal ArticleDOI
TL;DR: In this paper, the authors studied CP violation in photon self-interactions at low energy using superconducting radio frequency cavities and vacuum birefringence experiments, and proposed a method to isolate the CP-violating contribution to the photon selfinteractions using Superconducting Radio-Frequency cavities.
Abstract: In this paper we study CP violation in photon self-interactions at low energy. These interactions, mediated by the effective operator $FFF\tilde{F}$, where ($\tilde F$) $F$ is the (dual) electromagnetic field strength, have yet to be directly probed experimentally. Possible sources for such interactions are weakly coupled light scalars with both scalar and pseudoscalar couplings to photons (for instance, complex Higgs-portal scalars or the relaxion), or new light fermions coupled to photons via dipole operators. We propose a method to isolate the CP-violating contribution to the photon self-interactions using Superconducting Radio-Frequency cavities and vacuum birefringence experiments. In addition, we consider several theoretical and experimental indirect bounds on the scale of new physics associated with the above effective operator, and present projections for the sensitivity of the proposed experiments to this scale. We also discuss the implications of these bounds on the CP-violating couplings of new light particles coupled to photons.

Journal ArticleDOI
TL;DR: In this paper, the axial form factor of the proton axial structure was extracted from neutrino data using accelerator neutrinos of all energies, and the pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos with a few hundreds MeV of energy.
Abstract: We study the scattering of neutrinos on polarized and unpolarized free nucleons, and also the polarization of recoil particles in these scatters. In contrast to electromagnetic processes, the parity-violating weak interaction gives rise to large spin asymmetries at leading order. Future polarization measurements could provide independent access to the proton axial structure and allow the first extraction of the pseudoscalar form factor from neutrino data without the conventional partially conserved axial current (PCAC) ansatz and assumptions about the pion-pole dominance. The pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos of a few hundreds MeV of energy or with tau (anti)neutrinos. The axial form factor can be extracted from scattering measurements using accelerator neutrinos of all energies.

Journal ArticleDOI
TL;DR: In this paper, the Mellin moment of double parton distributions (DPDs) in the unpolarized proton was extracted in the framework of lattice QCD and the dependence of the DPD Mellin moments on quark flavor and quark polarization was investigated.
Abstract: We evaluate nucleon four-point functions in the framework of lattice QCD in order to extract the first Mellin moment of double parton distributions (DPDs) in the unpolarized proton. In this first study, we employ an nf = 2+1 ensemble with pseudoscalar masses of mπ = 355 MeV and mK = 441 MeV. The results are converted to the scale μ = 2 GeV. Our calculation includes all Wick contractions, and for almost all of them a good statistical signal is obtained. We analyze the dependence of the DPD Mellin moments on the quark flavor and the quark polarization. Furthermore, the validity of frequently used factorization assumptions is investigated.