Search

We review the recent progress made in using holographic QCD to study hadronic contributions to the anomalous magnetic moment of the muon, in particular the hadronic light-by-light scattering contribution, where the short-distance constraints associated with the axial anomaly are notoriously difficult to satisfy in hadronic models. This requires the summation of an infinite tower of axial vector mesons, which is naturally present in holographic QCD models, and indeed takes care of the longitudinal short-distance constraint due to Melnikov and Vainshtein. Numerically the results of simple hard-wall holographic QCD models point to larger contributions from axial vector mesons than assumed previously, while the predicted contributions from pseudo-Goldstone bosons agree nicely with data-driven approaches., Comment: Review article for Eur.Phys.J.C., topical selection "New Frontiers in Holographic Duality", 18 pages, 11 figures, 4 tables (v2: references updated, typo in table 2 corrected)

Theoretical models of the neutrino-induced meson production reaction are reviewed. The formulation of various approaches to the neutrino reactions in the resonance region is briefly discussed. The total cross-section, the distribution of charged lepton and pion are examined using the dynamical coupled channel (DCC) model. Possible test of the models of axial vector current in the resonance region is discussed.

A complete set of scalar products for vector, axial vector, scalar, and pseudoscalar currents of two massive fermions (lepton and nucleon) is reviewed. The scalar products are obtained for three physically different cases of the lepton spin and nucleon spin orientations. These expressions are needed at least for self-consistent calculations of cross sections for coherent (elastic) and incoherent (inelastic) interactions of massive neutral weakly interacting particles with nuclear targets utilized in the detectors intended for direct detection of galactic dark matter particles on Earth.

We consider nonperturbative vacuum polarization effects in the supercritical region for a planar Dirac–Coulomb system with a supercritical extended axially symmetric Coulomb source with a charge $$Z > Z_{{\rm cr},1}$$ and radius $$R_0$$ in the magnetic field with an axial-vector potential. We study the behavior of the vacuum charge and vacuum current densities, $$\rho_{\mathrm{VP}}(\vec r\,)$$ and $$\vec{j}_{\mathrm{VP}}(\vec r\,)$$ . We focus on the divergence in the theory corresponding to the renormalization and convergence of partial series for $$\rho_{\mathrm{VP}}(\vec r\,)$$ and $$\vec{j}_{\mathrm{VP}}(\vec r\,)$$ . We stress that in contrast to the vacuum charge density, the partial channels with large values of the third projection of the total angular momentum $$|m_j|$$ must be taken into account in calculating the vacuum current density in the presence of an external magnetic field localized in the range $$R_1>R_0$$ . We show that in the presence of a supercritical Coulomb source, the induced magnetic field can enhance the original magnetic field for certain values of parameters of the external vector potential.

Exact solutions of relativistic quasipotential equations in the configuration representation are found for the $$s$$ -state wave function for a composite system of two arbitrary-mass relativistic spinor quarks interacting via a Coulomb-like chromodynamic potential. Composite systems whose spinor structure corresponds to the pseudoscalar, pseudovector, and vector cases are considered. Quantization conditions for the energy levels of the meson $$s$$ -wave state are determined in the pseudoscalar, pseudovector, and vector cases. Expressions for the relativistic threshold resummation $$S$$ factor corresponding to a Coulomb-like chromodynamic potential are obtained for these spinor meson structures, and the properties of this factor are studied. New regularities in the behavior of the threshold $$S$$ factor are revealed. The present analysis is performed within the relativistic quasipotential approach based on the covariant Hamiltonian formulation of quantum field theory by means of the transition from the momentum representation in Lobachevsky space to the three-dimensional relativistic configuration representation for the case of a composite system of two arbitrary-mass relativistic spinor particles.

The $$(1+1)$$ ( 1 + 1 ) dimensional generalized model where vector and axial vector interaction get mixed up with different strength is considered. Imposing a chiral constraint, the model can be expressed in terms of chiral boson. Then the theoretical spectra of this model has been determined in both the Lagrangian and Hamiltonian formalism. It is found that the massless degrees of freedom disappears from the spectra and the photon acquires mass as well. Imposition of chiral constraint brings a disaster so far as Lorentz invariance is concerned. An attempt has been made here to show the physical Lorentz invariance explicitly using Poincaré algebra.

If dark matter has strong self-interactions, future astrophysical and cosmological observations, together with a clearer understanding of baryonic feedback effects, might be used to extract the velocity dependence of the dark matter scattering rate. To interpret such data, we should understand what predictions for this quantity are made by various models of the underlying particle nature of dark matter. In this paper, we systematically compute this function for fermionic dark matter with light bosonic mediators of vector, scalar, axial vector, and pseudoscalar type. We do this by matching to the nonrelativistic effective theory of self-interacting dark matter and then computing the spin-averaged viscosity cross section nonperturbatively by solving the Schrodinger equation, thus accounting for any possible Sommerfeld enhancement of the low-velocity cross section. In the pseudoscalar case, this requires a coupled-channel analysis of different angular momentum modes. We find, contrary to some earlier analyses, that nonrelativistic effects only provide a significant enhancement for the cases of light scalar and vector mediators. Scattering from light pseudoscalar and axial vector mediators is well described by tree-level quantum field theory., 22 pages, 6 figures

A linear manifold ${\mathcal K}_2$ of evolutionary equations for a pseudovector field on ${\Bbb R}^3$ is described. An infinitisimal shift of each equation is determined by a second-order differential operator of divergent type. All operators are invariant with respect to space translations in ${\Bbb R}^3$, relative to time translations, and they are transformed by covariant way relative to rotations of ${\Bbb R}^3$. It is proved that the linear space ${\mathcal M}_2 \subset {\mathcal K}_2$ of differential operators preserving solenoidal property and unimodularity of the field is one-dimensional and an explicit form of such operators is found.

Under improper transformations, the traditional transformation laws for cross products, the permutation tensor, and rotations are incorrect. For a cross product, using a counter-example the left-hand rule is proved wrong. The unique rule for a cross product is the right-hand rule. Coordinate systems have handedness, while a cross product is frame-indifference. Since the permutation tensor is defined as a triple product including a cross product, the law for the permutation tensor is false. For a rotation, its pseudovector representation is incorrect, because the mirror is an auxiliary device to produce the virtual image rather than a new coordinate system or reference frame. Keywords: Pseudovector, Cross product, Improper transformation, Handed coefficient, Permutation tensor

We report results of our recent works [S. Narison, Int. J. Mod. Phys. A33 (2018) no. 10, 1850045; S. Narison. Addendum: Int. J. Mod. Phys. A33 (2018) no. 10, 1850045; S. Narison, Phys. Lett . B802 (2020) 135221.] where the correlations between the c,b -quark running masses m‾c,b , the gluon condensate 〈αsG2〉 and the QCD coupling αs in the MS‾ -scheme from an analysis of the charmonium and bottomium spectra and the Bc -meson mass. We use optimized ratios of relativistic Laplace sum rules (LSR) evaluated at the μ -subtraction stability point where higher orders PT and D≤6−8 -dimensions nonperturbative condensates corrections are included. We obtain [S. Narison, Int. J. Mod. Phys. A33 (2018) no. 10, 1850045; S. Narison. Addendum: Int. J. Mod. Phys. A33 (2018) no. 10, 1850045.] αs(2.85)=0.262(9) and αs(9.50)=0.180(8) from the (pseudo)scalar Mχ0c(0b)−Mηc(b) mass-splittings at μ=2.85(9.50) GeV. The most precise result from the charm channel leads to αs(Mτ)=0.318(15) and αs(MZ)=0.1183(19)(3) in excellent agreement with the world average: αs(MZ)=0.1181(11) [For a review, see e.g: S. Bethke, Nucl. Part. Phys. Proc . 282–284 (2017)149; C. Patrignani et al. (Particle Data Group), Chin. Phys . C40, 100001 (2016) and 2017 update.]. Updated results from a global fit of the (axial-)vector and (pseudo)scalar channels using Laplace and Moments sum rules @ N2LO [S. Narison, Int. J. Mod. Phys. A33 (2018) no. 10, 1850045; S. Narison. Addendum: Int. J. Mod. Phys. A33 (2018) no. 10, 1850045.] combined with the one from MBc [S. Narison, Phys. Lett . B802 (2020) 135221.] lead to the new tentative QCD spetral sum rules (QSSR) average: m‾c(m‾c)|average=1266(6) MeV and m‾b(m‾b)|average=4196(8) MeV. The values of the gluon condensate 〈αsG2〉 from the (axial)-vector charmonium channels combined with previous determinations in Table 1, leads to the new QSSR average: [S. Narison, Int. J. Mod. Phys. A33 (2018) no. 10, 1850045; S. Narison. Addendum: Int. J. Mod. Phys. A33 (2018) no. 10, 1850045.] 〈αsG2〉|average=(6.35±0.35)×10−2 Ge4 . Our results clarify the (apparent) discrepancies between different estimates of 〈αsG2〉 from J/ψ sum rule but also shows the sensitivity of the sum rules on the choice of the μ -subtraction scale. As a biproduct, we deduce the Bc -decay constants fBc=371(17) MeV and fBc(2S)≤139(6) MeV.

We analyze all available experimental data on the $\nu_\mu$ and $\overline{\nu}_\mu$ total and differential cross sections of charged-current single pion production through the decay of intermediate nucleon and baryon resonances measured on hydrogen and deuterium targets in the accelerator experiments at ANL, BNL, FNAL, and CERN. These data are used to determine the current "resonance" axial-vector mass of the nucleon and to fine-tune the nonresonance non-interfering background contribution which described within the Rein-Sehgal approach. For this analysis, we revise the phenomenological model and the experimental dataset for the fits, modify the method of likelihood analysis compared to the previous study. The obtained model parameters coming in combination with a revised strategy for the normalization of the BW distributions are slightly different from the values used by default., Comment: 15 pages, 8 figures

The renormalized contribution of fermions to the curvature masses of vector and axial-vector mesons is derived with two different methods at leading order in the loop expansion applied to the (2+1)-flavor constituent quark-meson model. The corresponding contribution to the curvature masses of the scalar and pseudoscalar mesons, already known in the literature, is rederived in a transparent way. The temperature dependence of the curvature mass of various (axial-)vector modes obtained by decomposing the curvature mass tensor is investigated along with the (axial-)vector--(pseudo)scalar mixing. All fermionic corrections are expressed as simple integrals that involve at finite temperature only the Fermi-Dirac distribution function modified by the Polyakov-loop degrees of freedom. The renormalization of the (axial-)vector curvature mass allows us to lift a redundancy in the original Lagrangian of the globally symmetric extended linear sigma model, in which terms already generated by the covariant derivative were reincluded with different coupling constants., Comment: 22 pages, 3 figures, clarifications and references added, published version

As a first step towards a realistic phenomenological description of vector and axial-vector mesons in nuclear matter, we calculate the spectral functions of the $\rho$ and the $a_1$ meson in a chiral baryon-meson model as a low-energy effective realization of QCD, taking into account the effects of fluctuations from scalar mesons, nucleons, and vector mesons within the Functional Renormalization Group (FRG) approach. The phase diagram of the effective hadronic theory exhibits a nuclear liquid-gas phase transition as well as a chiral phase transition at a higher baryon-chemical potential. The in-medium $\rho$ and $a_1$ spectral functions are calculated by using the previously introduced analytically-continued FRG (aFRG) method. Our results show strong modifications of the spectral functions in particular near the critical endpoints of both phase transitions which may well be of relevance for electromagnetic rates in heavy-ion collisions or neutrino emissivities in neutron-star merger events., Comment: 16 pages, 10 figures

We evaluate the $a_1(1260) \to \pi \sigma (f_0(500))$ decay width from the perspective that the $a_1(1260)$ resonance is dynamically generated from the pseudoscalar-vector interaction and the $\sigma$ arises from the pseudoscalar-pseudoscalar interaction. A triangle mechanism with $a_1(1260) \to \rho \pi$ followed by $\rho \to \pi \pi$ and a fusion of two pions within the loop to produce the $\sigma$ provides the mechanism for this decay under these assumptions for the nature of the two resonances. We obtain widths of the order of $13-22$ MeV. Present experimental results differ substantially from each other, suggesting that extra efforts should be devoted to the precise extraction of this important partial decay width, which should provide valuable information on the nature of the axial vector and scalar meson resonances and help clarify the role of the $\pi\sigma$ channel in recent lattice QCD calculations of the $a_1$., Comment: 20 pages, 6 figures and 1 table

Estimating the contribution from axial-vector intermediate states to hadronic light-by-light scattering requires input on their transition form factors (TFFs). Due to the Landau-Yang theorem, any experiment sensitive to these TFFs needs to involve at least one virtual photon, which complicates their measurement. Phenomenologically, the situation is best for the $f_1(1285)$ resonance, for which information is available from $e^+e^-\to e^+e^- f_1$, $f_1\to 4\pi$, $f_1\to \rho \gamma$, $f_1\to \phi \gamma$, and $f_1\to e^+e^-$. We provide a comprehensive analysis of the $f_1$ TFFs in the framework of vector meson dominance, including short-distance constraints, to determine to which extent the three independent TFFs can be constrained from the available experimental input, a prerequisite for improved calculations of the axial-vector contribution to hadronic light-by-light scattering. In particular, we focus on the process $f_1\to e^+e^-$, evidence for which has been reported recently by SND for the first time, and discuss the impact that future improved measurements will have on the determination of the $f_1$ TFFs., Comment: 60 pages, 14 figures; v2: Appendix D on alternative $f_1 \to 4\pi$ mechanism added, references updated, version published in JHEP

The quasielastic production cross sections and polarizations of the hyperons induced by ${\bar\nu}_\mu$ on the free nucleon as well as from $^{40}$Ar in the sub-GeV energy region has been reviewed [1-5]. The effects of the second class currents in the axial vector sector with and without T-invariance as well as the effect of SU(3) symmetry breaking are also studied. We find that the cross sections and the various polarization components can effectively be used to determine the axial vector transition form factors in the strangeness sector and to test the validity of various symmetries of the weak hadronic currents like G-invariance, T-invariance and SU(3) symmetry. These hyperons decay dominantly into pions giving an additional contribution to the weak pion production induced by the antineutrinos. In the case of nuclear targets like $^{40}$Ar, this contribution is shown to be significant when compared with the pion production by the $\Delta$ excitations in the energy range of $E_{\bar{\nu}_{\mu}} \le 0.7$ GeV [1]. This study could be useful for the DUNE experiment where argon will be used as the target material and the electronic imaging of particles is possible and the particle tracks can be identified., Comment: 16 pages, 10 figures. arXiv admin note: substantial text overlap with arXiv:1807.08314

We propose to measure the $$\tau ^-\rightarrow K_1^-\nu _\tau \rightarrow (K^-\omega ) \nu _\tau \rightarrow (K^- \pi ^+\pi ^-\pi ^0)\nu _\tau \ $$ τ - → K 1 - ν τ → ( K - ω ) ν τ → ( K - π + π - π 0 ) ν τ decay in order to determine the $$K_1$$ K 1 axial vector mixing angle $$\theta _{K_1}$$ θ K 1 . We derive, for the first time, the differential decay rate formula for this decay mode. Using the obtained result, we perform a sensitivity study for the Belle (II) experiment. We will show that the $$K^-\pi ^+\pi ^-\pi ^0$$ K - π + π - π 0 spectrum of the $$\tau ^-\rightarrow K_1^-\nu _\tau \rightarrow (K^-\omega ) \nu _\tau \rightarrow (K^- \pi ^+\pi ^-\pi ^0)\nu _\tau \ $$ τ - → K 1 - ν τ → ( K - ω ) ν τ → ( K - π + π - π 0 ) ν τ decay can discriminate the two solutions $$\theta _{K_1}=\sim 30^{\circ }$$ θ K 1 = ∼ 30 ∘ or $$\sim 60^{\circ }$$ ∼ 60 ∘ observed in the other measurements.

We formulate a direct generalization of the Prigogine’s principle of minimum entropy production, according to a new isoperimetric variation principle by classical non-equilibrium thermodynamics. We focus our attention on the possible mathematical forms of constitutive equations. Our results show that the Onsager’s reciprocity relations are consequences of the suggested variation principle. Furthermore, we show by the example of the thermo-diffusion such reciprocity relations for diffusion tensor, which are missing in Onsager’s theory. Our theorem applied to the non-linear constitutive equations indicates the existence of dissipation potential. We study the forms of general reciprocity with the dissipation potential. This consideration results in a weaker condition than Li-Gyarmati-Rysselberhe reciprocity has. Furthermore, in the case of electric conductivity in the magnetic field, our theorem shows the correct dependence of the Onsager’s kinetic coefficient by the axial vector of magnetic induction. We show in general that the evolution criterion of the global entropy production is a Lyapunov-function, and so the final stationer state is independent of the initial, time-independent boundary conditions.

A simple, physically validated, model of charge-independence and charge-symmetry breaking is proposed for the pion-nucleon coupling constant. Within this model, the pion-nucleon coupling constants are assumed to be in direct proportion to the masses of nucleons and pions involved in the interaction. The charge dependence of the pion-nucleon coupling constants and low-energy parameters of nucleon-nucleon scattering in the 1S0 spin-singlet state is studied on the basis of Yukawa’s meson theory. By using the value of $$f_{pp\pi^0}^2=0.0749(7)$$ established reliably for the pseudovector pion-nucleon coupling constant, which characterizes the strength of the nuclear proton-proton interaction, the values of $$f_c^2=0.0802(7)$$ and $$f_0^2=0.0750(7)$$ were calculated for, respectively, the charged and neutral pion-nucleon coupling constants, along with the value of $$f_{nn\pi^0}^2=0.0751(7)$$, which characterizes the strength of the nuclear neutron-neutron interaction. The values calculated for the low-energy parameters of neutron-proton and neutron-neutron scattering with the aid of the above constants agree well with experimental data.

Resonance structure of the beta decay strength function Sβ(E) for GT β–-decay of halo nuclei 6He and 11Li is analyzed. Compare experimental total strength for β-transitions in $${{g_{V}^{2}} \mathord{\left/ {\vphantom {{g_{V}^{2}} {4\pi }}} \right. \kern-0em} {4\pi }}$$ units with the Ikeda sum rule (in $${{{{{\left( {g_{A}^{{{\text{eff}}}}} \right)}}^{2}}} \mathord{\left/ {\vphantom {{{{{\left( {g_{A}^{{{\text{eff}}}}} \right)}}^{2}}} {4\pi }}} \right. \kern-0em} {4\pi }}$$ units) one can determine the squared ratio of axial-vector and vector weak interaction constants value $${{\left( {{{g_{A}^{{{\text{eff}}}}} \mathord{\left/ {\vphantom {{g_{A}^{{{\text{eff}}}}} {{{g}_{V}}}}} \right. \kern-0em} {{{g}_{V}}}}} \right)}^{2}}$$. We obtained $${{\left( {{{g_{A}^{{{\text{eff}}}}} \mathord{\left/ {\vphantom {{g_{A}^{{{\text{eff}}}}} {{{g}_{V}}}}} \right. \kern-0em} {{{g}_{V}}}}} \right)}^{2}}$$ = 1.272 ± 0.010 for 6He and $${{\left( {{{g_{A}^{{{\text{eff}}}}} \mathord{\left/ {\vphantom {{g_{A}^{{{\text{eff}}}}} {{{g}_{V}}}}} \right. \kern-0em} {{{g}_{V}}}}} \right)}^{2}}$$ = 1.5 ± 0.2 for 11Li β–-decays. Quenching of the weak axial-vector constant $$g_{A}^{{{\text{eff}}}}$$ in halo nuclei is discussed.

We elaborate on the dichotomy between the description of the semileptonic decays of heavy hadrons on the one hand and the semileptonic decays of light hadrons such as neutron $\beta$ decays on the other hand. For example, almost without exception the semileptonic decays of heavy baryons are described in cascade fashion as a sequence of two two-body decays $B_1 \to B_2 + W_{\rm off-shell}$ and $W_{\rm off-shell} \to \ell + \nu_\ell$ whereas neutron $\beta$ decays are analyzed as true three-body decays $n \to p + e^- +\bar \nu_e$. Within the cascade approach it is possible to define a set of seven angular observables for polarized neutron $\beta$ decays as well as the longitudinal, transverse and normal polarization of the decay electron. We determine the dependence of the observables on the usual vector and axial vector form factors. In order to be able to assess the importance of recoil corrections we expand the rate and the $q^2$ averages of the observables up to NLO and NNLO in the recoil parameter $\delta=(M_n-M_p)/(M_n+M_p)= 0.689\cdot 10^{-3}$. Remarkably, we find that the rate and three of the four parity conserving polarization observables that we analyze are protected from NLO recoil corrections when the second class current contributions are set to zero., Comment: 22 pages, 5 figures and 2 tables

The width of the $$\tau\rightarrow\bar{K}^{0*}(892)\pi^-\nu_\tau$$ decay has been calculated within the extended Nambu-Jona-Lasinio model taking into account intermediate axial-vector, vector, and pseudoscalar mesons in the ground and first radially excited states. The splitting of the axial-vector intermediate state K1A into two physical mesons K1(1270) and K1(1400) caused by the mixing of axial-vector strange mesons from the 3P1 and 1P1 nonets has also been taken into account. The results are in satisfactory agreement with experimental data.

This work investigates the interaction of an axial vector-meson with nucleons in the AdS/QCD soft wall model. The axial vector fields have been determined inside the anti-de Sitter (AdS) space with the help of gauge fields with left and right chiral symmetries. In addition, a pseudoscalar field has been introduced inside the AdS space to break the chiral symmetry. A Lagrangian for these fields has been introduced inside the AdS space and the profile functions which are solutions of the equation of motion have been found. In accordance with AdS/CFT, the interaction constant of the axial vector-meson with the nucleons has been obtained as an integral over the additional dimension. The main task of this work was to find numerical values of the interaction constant of the axial vector-meson with the nucleons in the AdS/QCD soft wall model. With the help of the computer program Mathematica 7, these values were determined. A comparison of the theoretical and experimental data has revealed significant agreement of the results.

A new threshold resummation S-factor in quantum chromodynamics is obtained for a composite system of two relativistic spin-1/2 quarks having identical masses and interacting via a Coulomb-like chromodynamical potential. The pseudoscalar, vector, and pseudovector cases are considered. The present analysis is performed on the basis of the relativistic quasipotential approach in the Hamiltonian formulation of quantum field theory via a transition to the relativistic configuration representation for the case of a composite system formed by two relativistic particles of equal mass.

The widths of the τ → [ρ0(770), ρ0(1450)]π−ντ decays have been calculated within the extended Nambu—Jona-Lasinio model including both the ground and first radially excited intermediate meson states. The axial-vector channel with intermediate a1 mesons dominates. The values of the masses and total widths of the a1 meson recently obtained by the COMPASS and JPAC Collaborations have been taken into account.

The baryon axial vector current is computed in heavy baryon chiral perturbation theory in the large-${N}_{c}$ limit, where ${N}_{c}$ is the number of color charges. One-loop nonanalytic corrections of the order ${m}_{q}\mathrm{ln}{m}_{q}$ are comprised in the analysis, with contributions of both intermediate octet and decuplet baryon states, to all orders in the $1/{N}_{c}$ expansion of the axial vector current relevant for ${N}_{c}=3$. Theoretical expressions are obtained in the limit of vanishing decuplet-octet mass difference only, which allows one to carry out a full comparison with conventional heavy baryon chiral perturbation theory results for three flavors of light quarks and at the physical value ${N}_{c}=3$. Both approaches perfectly agree to all orders considered. Furthermore, a numerical analysis via a least-squares fit is performed in order to extract the values of the free parameters of the theory, using the experimental data available. The predictions of formalism are in good agreement with the experimental data.

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.

We present the first lattice-QCD determination of the form factors describing the semileptonic decays ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{*}(2595){\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}$ and ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{*}(2625){\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}$, where the ${\mathrm{\ensuremath{\Lambda}}}_{c}^{*}(2595)$ and ${\mathrm{\ensuremath{\Lambda}}}_{c}^{*}(2625)$ are the lightest charm baryons with ${J}^{P}={\frac{1}{2}}^{\ensuremath{-}}$ and ${J}^{P}={\frac{3}{2}}^{\ensuremath{-}}$, respectively. These decay modes provide new opportunities to test lepton flavor universality and also play an important role in global analyses of the strong interactions in $b\ensuremath{\rightarrow}c$ semileptonic decays. We determine the full set of vector, axial vector, and tensor form factors for both decays but only in a small kinematic region near the zero-recoil point. The lattice calculation uses three different ensembles of gauge-field configurations with $2+1$ flavors of domain-wall fermions, and we perform extrapolations of the form factors to the continuum limit and physical pion mass. We present Standard Model predictions for the differential decay rates and angular observables. In the kinematic region considered, the differential decay rate for the ${\frac{1}{2}}^{\ensuremath{-}}$ final state is found to be approximately 2.5 times larger than the rate for the ${\frac{3}{2}}^{\ensuremath{-}}$ final state. We also test the compatibility of our form-factor results with zero-recoil sum rules.

The nonlinear shift current, also known as the bulk photovoltaic current generated by linearly polarized light, has long been known to be absent in crystals with inversion symmetry. Here we argue that a nonzero shift current in centrosymmetric crystals can be activated by a photon-drag effect. Photon-drag shift current proceeds from a "shift current dipole" (a geometric quantity characterizing interband transitions) and manifests a purely transverse response in centrosymmetric crystals. This transverse nature proceeds directly from the shift-vector's pseudovector nature under mirror operation and underscores its intrinsic geometric origin. Photon-drag shift current can be greatly enhanced by coupling to polaritons and provides a new and sensitive tool to interrogate the subtle interband coherences of materials with inversion symmetry previously thought to be inaccessible via photocurrent probes. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version L.-K. S. gratefully acknowledges helpful conversations with Inti Sodemann. J. C. W. S. acknowledges support from the National Research Foundation (NRF), Singapore under its NRF fellowship program Award No. NRF-NRFF2016- 05, the Ministry of Education, Singapore under its MOE AcRF Tier 3 Grant No. MOE2018-T3-1-002, and a Nanyang Technological University start-up grant (Grant No. NTU-SUG). K. C. is supported by the MOST of China No. 2017YFA0303400, the Chinese Academy of Sciences No. QYZDJSSW-SYS001, No. XDB28000000 and No. XDPB22.

The transverse component of the axial-vector correlation function of quark fields is a natural starting object for lattice calculations of twist-3 nucleon parton distribution functions. In this work we derive the corresponding factorization expression in terms of twist-2 and twist-3 collinear distributions to one-loop accuracy. The results are presented both in position space, as the factorization theorem for Ioffe-time distributions, and in momentum space, for the axial-vector quasi- and pseudodistributions., Comment: 30 pages, 2 figures; v2: typos fixed, reference added matching published version

A symmetry-preserving treatment of a vector$\times$vector contact interaction is used to compute spectra of ground-state $J^P = 0^\pm, 1^\pm$ $(f\bar g)$ mesons, their partner diquark correlations, and $J^P=1/2^\pm, 3/2^\pm$ $(fgh)$ baryons, where $f,g,h \in \{u,d,s,c,b\}$. Results for the leptonic decay constants of all mesons are also obtained, including scalar and pseudovector states involving heavy quarks. The spectrum of baryons produced by this chiefly algebraic approach reproduces the 64 masses known empirically or computed using lattice-regularised quantum chromodynamics with an accuracy of 1.4(1.2)%. It also has the richness of states typical of constituent-quark models and predicts many baryon states that have not yet been observed. The study indicates that dynamical, nonpointlike diquark correlations play an important role in all baryons; and, typically, the lightest allowed diquark is the most important component of a baryon's Faddeev amplitude., Comment: 21 pages, 7 tables, 5 figures. arXiv admin note: text overlap with arXiv:1903.00160

We present a systematic study of the productions and decays of light axial vector mesons with $J^{PC}=1^{+\pm}$ in charmonium decays. In the quark model scenario, the two axial vector nonets are connected with each other by the Gell-Mann-Okubo mass relation through the mixing between two $K_1$ states (i.e. $K_1(1270)$ and $K_1(1400)$) with configurations of $^3P_1$ and $^1P_1$. The mixing angles between $f_1$ and $f_1'$ (i.e. $f_1(1285)$ and $f_1(1420)$), and between $h_1$ and $h_1'$ (i.e. $h_1(1170)$ and $h_1(1415)$) can be reliably constrained. We then introduce the intermediate $K^*\bar{K}+c.c.$ meson loop transitions in the description of the productions and decays of these axial vector mesons. The presence of the nearby $S$-wave $K^*\bar{K}+c.c.$ to which these axial vector mesons have strong coupling strengths, turns out to be crucial for understanding many puzzling questions related to their productions and decays. This is because that the $S$-wave $K^*\bar{K}+c.c.$ rescatterings by the kaon exchange satisfy the triangle singularity (TS) condition in some of these cases and the TS mechanism can introduce special interference effects in the exclusive decays of these light axial vector mesons., Revtex, 26 pages, 17 figures

We present the study of radiative tau decay (${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}\ensuremath{\gamma}$), computing the structure dependent contribution using light cone sum rules. This decay includes the same form factors as the radiative pion decay with the crucial difference that the momentum transfer squared, $t$, between the pion-photon system is positive, which makes these form factors timelike and also as $t$ can now take values up to ${m}_{\ensuremath{\tau}}^{2}$, it can produce real hadronic resonances. The analytical form for these form factors has been calculated using the light cone sum rules method and the invariant mass spectrum in the $\ensuremath{\pi}\ensuremath{-}\ensuremath{\gamma}$ system and the decay width are presented. The structure dependent parameter, $\ensuremath{\gamma}$, the ratio of the axial vector to vector form factor is found to be in good agreement with the experimental determination.

Motivated by the LHCb's very recent observation of exotic ${X}_{0}(2900)$ in the ${B}^{+}\ensuremath{\rightarrow}{D}^{+}{D}^{\ensuremath{-}}{K}^{+}$ process, for which could be a good open-charm $ud\overline{c}\overline{s}$ tetraquark candidate, we endeavor to investigate its possibility by means of QCD sum rules. In technique, four configurations of interpolating currents with ${J}^{P}={0}^{+}$ are studied for the $ud\overline{c}\overline{s}$ tetraquark state. In the end, mass values are calculated to be ${2.76}_{\ensuremath{-}0.23}^{+0.16}\text{ }\text{ }\mathrm{GeV}$ for the axial vector diquark-axial vector antidiquark configuration and ${2.75}_{\ensuremath{-}0.24}^{+0.15}\text{ }\text{ }\mathrm{GeV}$ for the scalar diquark-scalar antidiquark configuration, both of which are consistent with the experimental data $2.866\ifmmode\pm\else\textpm\fi{}0.007\ifmmode\pm\else\textpm\fi{}0.002\text{ }\text{ }\mathrm{GeV}$ of ${X}_{0}(2900)$ in view of the uncertainty. These results support that ${X}_{0}(2900)$ could be a ${0}^{+}$ tetraquark state with open-charm flavor.

We investigate the effects of non-Hermiticity on interacting fermionic systems. We do this by including non-Hermitian bilinear terms into the 3+1 dimensional Nambu--Jona-Lasinio (NJL) model. Two possible bilinear modifications give rise to $\mathcal{PT}$ symmetric theories; this happens when the standard NJL model is extended either by a pseudovector background field $ig \bar\psi\gamma_5 B_\mu \gamma^\mu \psi$ or by an antisymmetric-tensor background field $g \bar\psi F_{\mu\nu}\gamma^\mu \gamma^\nu \psi$. The three remaining bilinears are {\it anti}-$\mathcal{PT}$-symmetric in nature, $ig \bar\psi B_\mu \gamma^\mu \psi, ig\bar\psi \gamma_5 \psi$ and $ig\bar\psi {1}\psi$, so that the Hamiltonian then has no overall symmetry. The pseudovector $ig \bar\psi\gamma_5 B_\mu \gamma^\mu \psi$ and the vector $ig \bar\psi B_\mu \gamma^\mu \psi$ combinations, are, in addition, chirally symmetric. Thus, within this framework we are able to examine the effects that the various combinations of non-Hermiticity, $\mathcal{PT}$ symmetry, chiral symmetry and the two-body interactions of the NJL model have on the existence and dynamical generation of a real effective fermion mass (a feature which is absent in the corresponding modified massless free Dirac models) as well as on the masses of the composite particles, the pseudoscalar and scalar mesonic modes ($\pi$ and $\sigma$ mesons). Our findings demonstrate that $\mathcal{PT}$ symmetry is not necessary for real fermion mass solutions to exist, rather the two-body interactions of the NJL model supersede the non-Hermitian bilinear effects. The effects of chiral symmetry are evident most clearly in the meson modes, the pseudoscalar of which will always be Goldstone in nature if the system is chirally symmetric. Second solutions of the mesonic equations are also discussed., Comment: 15 pages, 7 figures

A new resummation of the S-factor of a composite system of two relativistic spin-1/2 particles of arbitrary masses interacting via a Coulomb-like chromodynamical potential is presented. The analysis is performed in the framework of a relativistic quasipotential approach based on the Hamiltonian formulation of the covariant quantum field theory in the relativistic configuration representation. The pseudoscalar, vector, and pseudovector systems are considered, and the behavior of the S-factor near the threshold and in the relativistic limit is investigated in detail. The spin dependence of the S-factors is discussed as well. It is argued that at the threshold the contribution of spins significantly reduces the Sommerfeld effect, while at ultrarelativistic velocities their role diminishes and the S-factor becomes basically the same as for the spinless systems. A connection between the new and previously obtained S-factors for spinless particles of arbitrary masses and for relativistic spinor particles of equal masses is established.

In the presence of a thermal medium or an external electro-magnetic field, neutrinos can interact with photon, mediated by the corresponding charged leptons (real or virtual). The effect of a medium or an electromagnetic field is two-fold—to induce an effective νγ vertex and to modify the dispersion relations of all the particles involved to render the processes kinematically viable. It has already been noted that, in a medium, neutrinos acquire an effective charge, which in the standard model of electroweak interaction comes from the vector type vertex of weak interaction. On the other hand, in a magnetized plasma, the axial vector part also starts contributing to the effective charge of a neutrino. This contribution corresponding to the axial vector part in the interaction Lagrangian is denoted as the axial polarisation tensor. In this note, we outline the calculation of the axial polarization tensor to odd and even powers in eB. We further show its gauge invariance properties. Finally, we infer upon the zero external momentum limit of this axial polarisation tensor.

In this work, we mainly explore the possibility of charged rho ($$\rho ^\pm $$ ρ ± ) superconductor in the presence of parallel magnetic field and rotation within three-flavor Nambu–Jona-Lasino model. By following similar schemes as in the previous studies of charged pion ($$\pi ^\pm $$ π ± ) superfluid, the $$\rho ^\pm $$ ρ ± superconductor is found to be favored for both choices of Schwinger phase in Minkowski and curved spaces. Due to the stability of the internal spin structure, charged rho begins to condensate at a smaller threshold of angular velocity than charged pion for the given large magnetic fields. Even the axial vector meson condensation is checked – the conclusion is that $$\rho ^\pm $$ ρ ± superconductor is the robust ground state at strong magnetic field and fast rotation, which actually sustains to very large angular velocity.

We present the package for the simulation of DM (Dark Matter) particles in fixed target experiments. The most convenient way of this simulation (and the only possible way in the case of beam-dump) is to simulate it in the framework of the program for tracing particles in the experimental setup. One of the most popular such programs is Geant4. Specifically, the package includes the processes of DM particles production via electron and muon bremsstrahlung off nuclei, resonant in-flight positron annihilation on atomic electrons and gamma to ALP (axion-like particles) conversion on nuclei. Four types of DM mediator particles are considered: vector, scalar, pseudoscalar and axial vector. In particular, for bremsstrahlung the total cross sections are calculated at exact tree level (ETL). The code handles both the case of invisible DM mediator decay and of visible decay into $e^+e^-$ (or into $\gamma \gamma$ in the case of ALP). The software consists of a collection of different classes, inheriting from the Geant4 framework classes, thus the expected use of this package is to include it in a Geant4-based code for the simulation of particles propagation and interaction in the detector. As an example of its usage, we discuss the results obtained from the simulation of a typical active beam-dump experiment, considering $5 \times 10^{12}$ 100 GeV electrons impinging on a lead/plastic scintillator active thick target, showing the expected sensitivity for the four types of DM mediator particles mentioned above., Comment: 10 pages, 4 figures

In this work we consider the axial-vector form factors of the nucleon in flavor-SU(2) and of the baryon octet in flavor-SU(3) Chiral Perturbation Theory. We include the Δ-isobar and the baryon decuplet as explicit degrees of freedom and focus on their consistent treatment in terms of chiral power counting. We employ the use of on-shell meson and baryon masses in the one-loop contributions to the axial-vector form factors. The convergence properties of such an approach are scrutinized. Our results are compared to the available flavor-SU(2) QCD lattice data.

We calculate masses of light and heavy mesons as well as baryons of negative parity containing $u,d,s,c$ and $b$ quarks. It is an extension of our previous work where we had studied the positive parity baryons. We adopt a quark-diquark picture of baryons where the diquarks are non-pointlike with a finite spatial extension. The mathematical foundation for this analysis is implemented through a symmetry-preserving Schwinger-Dyson equations treatment of a vector-vector contact interaction, which preserves key features of quantum chromodynamics, such as confinement, chiral symmetry breaking, axial vector Ward-Takahashi identity and low-energy Goldberger-Treiman relations. This treatment simultaneously describes mesons and provides attractive correlations for diquarks in the $\overline{3}$ representation. Employing this model, we compute the spectrum and masses of all spin-1/2 and spin-3/2 baryons of negative parity, supplementing our earlier evaluation of positive parity baryons, containing 1, 2 or 3 heavy quarks. In the process, we calculate masses of a multitude of mesons and corresponding diquarks. Wherever possible, we make comparisons of our results with known experimental observations as well as theoretical predictions of several models and approaches including lattice quantum chromodynamics, finding satisfactory agreement. We also make predictions for heavier states not yet observed in the experiment., Comment: 10 pages, 4 figures

Physical review / D 104(9), 094007 (2021). doi:10.1103/PhysRevD.104.094007, Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the axial-vector contributions to two-photon processes in the $\overline{\rm MS}$ scheme. This is the last missing element for the complete next-to-next-to-leading order (NNLO) calculation of the the pion transition form factor $\gamma^\ast\gamma\to \pi $ in perturbative QCD. The corresponding high-statistics measurement is planned by the Belle II collaboration and will allow one to put strong constraints on the pion light-cone distribution amplitude. The calculated NNLO corrections prove to be rather large and have to be taken into account. The same coefficient function determines the contribution of the axial-vector generalized parton distributions to deeply-virtual Compton scattering which is investigated at the JLAB 12 GeV accelerator, by COMPASS at CERN, and in the future will be studied at the Electron Ion Collider EIC., Published by Inst., Melville, NY

Accumulating evidence indicates that soft quark+quark (diquark) correlations play an important role in the structure and interactions of hadrons constituted from three or more valence-quarks; so, it is worth developing insights into diquark structure. Using a leading-order truncation of those equations needed to solve continuum two-valence-body bound-state problems, the leading-twist two-parton distribution amplitudes (DAs) of light-quark scalar and pseudovector diquarks are calculated. The diquark DAs are narrower and taller than the asymptotic profile that characterises mesons. Consequently, the valence quasiparticles in a diquark are less likely to carry a large light-front fraction of the system's total momentum than those in a meson. These features may both influence the form of baryon DAs and be transmitted to diquark distribution functions (DFs), in which case their impact will be felt, e.g. in the proton's $u$ and $d$ valence-quark DFs., Comment: 8 pages, 2 figures, 1 table. Accepted for publication in Eur. Phys. J. A (Lett)

Physical review / D 103(9), 094018 (2021). doi:10.1103/PhysRevD.103.094018, Evolution equations for leading twist operators in high orders of perturbation theory can be restored from the spectrum of anomalous dimensions and the calculation of the special conformal anomaly at one order less using conformal symmetry of QCD at the Wilson-Fisher critical point at non-integer $d=4-2\epsilon$ space-time dimensions. In this work we generalize this technique to axial-vector operators. We calculate the corresponding three-loop evolution kernels in Larin's scheme and derive explicit expressions for the finite renormalization kernel that describes the difference to the vector case to restore the conventional ${\overline{\mathrm{MS}}}$-scheme. The results are directly applicable to deeply-virtual Compton scattering and the transition form factor $\gamma^*\gamma\to\pi$., Published by Inst., Melville, NY

Whereas the theoretical results for the dominant contributions to hadronic light-by-light scattering coming from pseudoscalar meson exchange have converged over the past years, the various published estimates of the contribution due to axial vector meson exchange differ wildly. Since holographic AdS/QCD models have proved to provide rather good models of singly and doubly virtual pion transition form factors, which reproduce remarkably well the known low-energy data and also the asymptotic leading-order pQCD behavior, it is of interest to consider their predictions for axial vector transition form factors. Indeed, we find that these reproduce also very well existing data from the L3 experiment for $f_1\to\gamma\gamma^*$. Including the full infinite tower of axial vector mesons of the AdS/QCD models we moreover show that the Melnikov-Vainshtein short-distance constraint can be satisfied, while almost all existing models for hadronic light-by-light scattering fail to incorporate it. The contribution to $g-2$, which is dominated by the first few resonances, turns out to be significantly larger than estimated previously., Comment: 6 pages, 3 figures, 2 tables. Proceedings contribution for the 40th International Conference on High Energy physics - ICHEP2020, July 28 - August 6, 2020, Prague, Czech Republic (virtual meeting)

We evaluate the cross-section for gamma production by neutrinos through a meson exchange effect which derives from the concept of axial-vector mixing. The resulting cross-section leads to some increase of the gamma production cross-section by neutrinos, especially at low neutrino energies, which may influence the understanding of the low energy excess of electron-like events seen in the MiniBooNE experiment., Comment: 9 pages, 4 figures

The renormalization constant $Z_J$ of the flavor-singlet axial-vector current with a non-anticommuting $\gamma_5$ in dimensional regularization is determined to order $\alpha_s^3$ in QCD with massless quarks. The result is obtained by computing the matrix elements of the operators appearing in the axial-anomaly equation $\big[\partial_{\mu} J^{\mu}_{5} \big]_{R} = \frac{\alpha_s}{4 \pi}\, n_f\, {\displaystyle \mathrm{T}_{F}} \, \big[F \tilde{F} \big]_{R}$ between the vacuum and a state of two (off-shell) gluons to 4-loop order. Furthermore, through this computation, the conjectured equality between the $\overline{\mathrm{MS}}$ renormalization constant $Z_{F\tilde{F}}$ associated with the operator $\big[F \tilde{F} \big]_{R}$ and that of $\alpha_s$ is verified explicitly to hold true at 4-loop order. This equality automatically ensures a relation between the respective anomalous dimensions, $\gamma_{{\scriptscriptstyle J}} = \frac{\alpha_s}{4 \pi}\, n_f\, {\displaystyle \mathrm{T}_{F}} \, \gamma_{{\scriptscriptstyle FJ}} $, at order $\alpha_s^4$ given the validity of the axial-anomaly equation which was used to determine the non-$\overline{\mathrm{MS}}$ piece of $Z_J$ for the particular $\gamma_5$ prescription in use., Comment: 23 pages, 4 figures and 1 table, references updated, matched with the published version in JHEP

We present the result of our computation of the lowest lying meson masses for SU(N) gauge theory in the large $N$ limit (with $N_f/N\longrightarrow 0$). 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., Comment: 48 pages, 15 figures and 17 tables