Revisiting $$\gamma ^*\rightarrow \gamma \pi ^0\eta $$ near the $$\phi (1020)$$ using analyticity and the left-cut structure

Amplitudes of the form $$\gamma ^*(q^2)\rightarrow \gamma P_1P_2$$ γ ∗ ( q 2 ) → γ P 1 P 2 appear as sub-processes in the computation of the muon $$g-2$$ g - 2 . We test a proposed theoretical modelling against very precise experimental measurements by the KLOE collaboration at $$q^2=m^2_\phi $$ q 2 = m ϕ 2 . Starting from an exact, parameter-free dispersive representation for the S-wave satisfying QCD asymptotic constraints and Low’s soft photon theorem we derive, in an effective theory spirit, a two-channel Omnès integral representation which involves two subtraction parameters. The discontinuities along the left-hand cuts which, for timelike virtualities, extend both on the real axis and into the complex plane are saturated by the contributions from the light vector mesons. In the case of $$P_1P_2=\pi \eta $$ P 1 P 2 = π η , we show that a very good fit of the KLOE data can be achieved with two real parameters, using a T-matrix previously determined from $$\gamma \gamma $$ γ γ scattering data. This indicates a good compatibility between the two data sets and confirms the validity of the T-matrix. The resulting amplitude is also found to be compatible with the chiral soft pion theorem. Applications to the $$I=1$$ I = 1 scalar form factors and to the $$a_0(980)$$ a 0 ( 980 ) resonance complex pole are presented.

The impact of transverse Slavnov-Taylor identities on dynamical chiral symmetry breaking

We extend earlier studies of transverse Ward-Fradkin-Green-Takahashi identities in QED, their usefulness to constrain the transverse fermion-boson vertex and their importance for multiplicative renormalizability, to the equivalent gauge identities in QCD. To this end, we consider transverse Slavnov-Taylor identities that constrain the transverse quark-gluon vertex and derive its eight associated scalar form factors. The complete vertex can be expressed in terms of the quark’s mass and wave-renormalization functions, the ghost-dressing function, the quark-ghost scattering amplitude and a set of eight form factors. The latter parametrize the hitherto unknown nonlocal tensor structure in the transverse Slavnov-Taylor identity which arises from the Fourier transform of a four-point function involving a Wilson line in coordinate space. We determine the functional form of these eight form factors with the constraints provided by the Bashir-Bermudez vertex and study the effects of this novel vertex on the quark in the Dyson-Schwinger equation using lattice QCD input for the gluon and ghost propagators. We observe significant dynamical chiral symmetry breaking and a mass gap that leads to a constituent mass of the order of 500 MeV for the light quarks. The flavor dependence of the mass and wave-renormalization functions as well as their analytic behavior on the complex momentum plane is studied and as an application we calculate the quark condensate and the pion’s weak decay constant in the chiral limit. Both are in very good agreement with their reference values.

Anatomical studies on the leaf and stem of Tinospora formanii Udayan & Pradeep (Menispermaceae), an endemic species to Southern Western Ghats, Kerala, India

The anatomical studies on leaf and stem of T. formanii Udayan & Pradeep an endemic species to southern Western Ghats, Kerala, India was carried out focusing on its macroscopic, microscopic, maceration along with organoleptic evaluation. Distinguishing characters of the stem revealed the presence of calcium oxalate crystals, simple and compound starch grains and pitted lignified fibers. Leaf anatomy showed the anomocytic and paracytic stomata, pitted lignified fibers, spiral vessels, non-glandular small trichomes, C or half-moon shaped vascular bundle, surrounded with sclerenchymatous tissues and rosette and prism shaped calcium oxalate crystals. Whereas, maceration studies revealed the presence of spiral and scalar form vessel, fibers, calcium oxalate crystals, simple starch grains. These anatomical studies are vital in the present-day trade scenario not only helpful in the proper identification of the genuine materials in use but also to distinguish different species of Tinospora, where the stem and leaf are often admixed with other species of Tinospora in the crude drug markets.

The $$ \overline{B} $$ → π form factors from QCD and their impact on |Vub|

We revisit light-cone sum rules with pion distribution amplitudes to determine the full set of local $$ \overline{B} $$ B ¯ → π form factors. To this end, we determine all duality threshold parameters from a Bayesian fit for the first time. Our results, obtained at small momentum transfer q2, are extrapolated to large q2 where they agree with precise lattice QCD results. We find that a modification to the commonly used BCL parametrization is crucial to interpolate the scalar form factor between the two q2 regions. We provide numerical results for the form factor parameters — including their covariance — based on simultaneous fit of all three form factors to both the sum rule and lattice QCD results. Our predictions for the form factors agree well with measurements of the q2 spectrum of the semileptonic decay $$ {\overline{B}}^0\to {\pi}^{+}{\mathrm{\ell}}^{-}{\overline{\nu}}_{\mathrm{\ell}} $$ B ¯ 0 → π + ℓ − ν ¯ ℓ . From the world average of the latter we obtain |Vub| = (3.77 ± 0.15) · 10−3, which is in agreement with the most recent inclusive determination at the 1 σ level.

Chiral dynamics and S-wave contributions in $${\bar{B}}^0/D^0 \rightarrow \pi ^{\pm }\eta \ l^{\mp } \nu $$ decays

In this work, we analyze the semi-leptonic decays $$\bar{B}^0/D^0 \rightarrow (a_0(980)^{\pm }\rightarrow \pi ^{\pm }\eta ) l^{\mp } \nu $$ B ¯ 0 / D 0 → ( a 0 ( 980 ) ± → π ± η ) l ∓ ν within light-cone sum rules. The two and three-body light-cone distribution amplitudes (LCDAs) of the B meson and the only available two-body LCDA of the D meson are used. To include the finite-width effect of the $$a_0(980)$$ a 0 ( 980 ) , we use a scalar form factor to describe the final-state interaction between the $$\pi \eta $$ π η mesons, which was previously calculated within unitarized Chiral Perturbation Theory. The result for the decay branching fraction of the $$D^0$$ D 0 decay is in good agreement with that measured by the BESIII Collaboration, while the branching fraction of the $${\bar{B}}^0$$ B ¯ 0 decay can be tested in future experiments.

Simulation Studies of Control Systems for Doubly Fed Induction Generator Supplied by the Current Source Converter

The control system for a Doubly Fed Induction Generator (DFIG) supplied by a grid-connected Current Source Converter (CSC) is presented in this paper. Nonlinear transformation of DFIG model to the multi-scalar form is proposed. The nonlinear control strategy of active and reactive power of DFIG is realized by feedback linearization. In the proposed control scheme, the DFIG model and CSI parameters are included. Two Proportional-Integral (PI) controllers are dedicated for the control of the respective active and reactive powers. The control variables are the dc-link input voltage vector and the angular speed of the inverter output current. The proposed control approach is characterized by satisfactional dynamics and provides enhanced quality of the power transferred to the grid. In the simulation, evaluation of the characteristic operating states of the generator system, correctness of the feedback linearization and the dynamics of active and reactive power control loops are studied. Simulation results are adequately provided.

Relations between b → cτν decay modes in scalar models

As a consequence of the Ward identity for hadronic matrix elements, we find relations between the differential decay rates of semileptonic decay modes with the underlying quark-level transition b → cτν, which are valid in scalar models. The decay-mode dependent scalar form factor is the only necessary theoretical ingredient for the relations. Otherwise, they combine measurable decay rates as a function of the invariant mass-squared of the lepton pair q2 in such a way that a universal decay-mode independent function is found for decays to vector and pseudoscalar mesons, respectively. This can be applied to the decays $$ B\to {D}^{\ast}\tau v,{B}_s\to {D}_s^{\ast}\tau v,{B}_c\to J/\psi \tau v $$ B → D ∗ τv , B s → D s ∗ τv , B c → J / ψτv and B → Dτv, Bs → Dsτv, Bc → ηcτv, with implications for R(D(*)), $$ R\left({D}_s^{\left(\ast \right)}\right) $$ R D s ∗ , R(J/ψ), R(ηc), and ℬ(Bc → τv). The slope and curvature of the characteristic q2-dependence is proportional to scalar new physics parameters, facilitating their straight forward extraction, complementary to global fits.

Decoupled Scalar Approach for Aircraft Angular Motion Estimation Using a Gyro-Free Inertial Measurement Unit

In-flight aircraft angular motion estimation based on an all-accelerometers inertial measurement unit (IMU) is investigated in this study. The relative acceleration equation as the representative of a rigid-body kinematics is manipulated to present the state and measurement equations of the aircraft dynamics. A decoupled scalar form (DSF) of the system equations, as a free-singularity problem, is derived. Mathematical modeling and simulation of an aircraft dynamics, equipped with an all-accelerometers IMU, are employed to prepare measurement data. Taking into account the modeling of accelerometer error, the measurement data have been simulated as a real condition. Three extended Kalman filters (EKFs) are used in parallel to estimate aircraft angular motion. Performance of the estimation algorithm is assessed by Monte Carlo analysis. As a result, the presented decoupled scalar approach using a gyro-free IMU (GF-IMU) provides an uncorrelated estimate of the in-flight aircraft motion components.

Tau decays into two mesons: an overview

We review the state-of-the-art theoretical analyses of tau decays into a pair of mesons and a neutrino. The participant vector and scalar form factors, f+ (s) and f0(s), are described in the frame of Chiral Perturbation Theory with resonances supplemented by dispersion relations, and the physical parameters of the intermediate resonances produced in the decay are extracted through the pole position of f+,0(s) in the complex plane. As a side result, we also determine the low-energy observables associated to the form factors. We hope our study to be of interest for present and future experimental analyses of these decays.