Form Factors Of Pseudoscalar Mesons Research Articles

Analysis of the decay constants and form factors of pseudoscalar mesons in a dirac formalism

We investigate the weak leptonic and semileptonic decay widths of pseudoscalar light and heavy mesons in a Dirac formalism. We take relativistic-independent quark model of the form [Formula: see text], where [Formula: see text]. This is computed using the binding quark eigenfunction and taking the assumptions of a significant relationship between the quark and antiquark momenta inside the decaying meson in the rest frame. To calculate the decay constant [Formula: see text], decay width and branching fractions of pseudoscalar mesons, we employ the model parameters that we used earlier. The experimental findings and various similar models are in good agreement with our predictions such as [Formula: see text] and [Formula: see text]”. Finally, we calculate the form factors and branching fractions for the semileptonic [Formula: see text] decays [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]” and find reasonable agreement with the experimental results.

Transition Form Factors of Pseudoscalar Mesons and the Contribution of the Gluon Anomaly

The expressions for the transition form factors (TFFs) of pseudoscalar mesons are derived in the context of the anomaly sum rule approach based on the dispersion representation of the axial anomaly and hypothesis of the global quark-hadron duality. The obtained solutions take into account the π$^{0}$-η-η′ mixing and the contribution of the gluon anomaly. It is shown that this method allows one to describe the TFFs for spacelike and timelike photon virtualities. The contribution of the gluon anomaly is estimated.

Measurement of transition form factors in two-photon collisions at BESIII

The two-photon physics program of the BESIII Collaboration is mainly motivated by the need of new measurements of transition form factors as input for the Standard Model calculations of $ \mathop a\nolimits_\mu ^{HLbL} $, the hadronic light-by-light scattering contribution to the anomalous magentic moment of the muon. The large data sets acquired at BESIII allow to study the transition form factors of pseudoscalar mesons in the relevant region of momentum transfer for $ \mathop a\nolimits_\mu ^{HLbL} $. In this presentation the status of the respective measurements for π0,η and η’ mesons are discussed, and prospects for studies of multi-meson systems as well as of doubly-virtual transition form factors are given.

Two-photon Transition Form Factors of Pseudoscalar Mesons in the PHOKHARA and the EKHARA Generators

Two-photon Transition Form Factors of Pseudoscalar Mesons in the PHOKHARA and the EKHARA Generators

Form factors of pseudoscalar mesons in a model with unitarity and Regge exchanges

We consider the transition and electromagnetic pseudoscalar form factors in a wide range of energy-momentum transfer, s. We employ dispersion relations to connect the time-like and space-like region. We find that hadronic resonances give sizable contributions in the currently available range of s. For the asymptotic contribution, we propose a model that operates with reggeized fermion exchanges.

Axial anomaly, quark-hadron duality and transition form factors

We study the transition form factors of pseudoscalar mesons by means of anomaly sum rule — an exact relation which is a consequence of dispersive representation of axial anomaly. This sum rule (derived for the octet channel) and combined with the quark-hadron duality allows us to relate the transition form factors of η and η′ mesons. The notion of quark-hadron duality in connection with our approach is discussed and comparison with recent experimental data is done.

Form factors of pseudoscalar mesons

We consider the transition (${\ensuremath{\gamma}}^{*}{\ensuremath{\pi}}^{0}(\ensuremath{\eta},{\ensuremath{\eta}}^{\ensuremath{'}})\ensuremath{\rightarrow}\ensuremath{\gamma}$) and electromagnetic (${\ensuremath{\gamma}}^{*}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$) form factors in a wide range of energy-momentum transfer $s$. We employ dispersion relations to connect the timelike and spacelike regions. We discuss the role of resonances and QCD partonic contributions. We find that the former give sizable contributions in the currently available range of $s$ and for the latter we consider the role of Reggeized fermion exchange.

Pseudoscalar meson transition form factors in nonperturbative QCD approach

In this communication we discuss a few topics related to modern experimental data on physics of light pseudoscalar mesons. It includes the contribution of the pseudoscalar mesons to the muon anomalous magnetic moment (AMM), g − 2 , rare decays of light pseudoscalar mesons to a lepton pair, transition form factors of pseudoscalar mesons at large momentum transfer, the pion transversity form factor. Measuring the muon anomalous magnetic moment g − 2 and rare decays of light pseudoscalar mesons into a lepton pair P → l + l − serve as important test of the standard model. To reduce the theoretical uncertainty in the standard model predictions, the data on the transition form factors of light pseudoscalar mesons play significant role. Recently new data on behavior of these form factors at large momentum transfer was supplied by the BABAR collaboration. Within the nonlocal chiral quark model it is shown how to describe these data and how the meson distribution amplitude evolves as a function of the dynamical quark masses and meson masses.

HADRONIC FORM FACTORS: COMBINING QCD CALCULATIONS WITH ANALYTICITY

I discuss recent applications of QCD light-cone sum rules to various form factors of pseudoscalar mesons. In this approach both soft and hard contributions to the form factors are taken into account. Combining QCD calculation with the analyticity of the form factors, one enlarges the region of accessible momentum transfers.

Erratum: Extrapolations of lattice meson form factors [Phys. Rev. D74, 034514 (2006)

We use chiral perturbation theory to study the extrapolations necessary to make physical predictions from lattice QCD data for the electromagnetic form factors of pseudoscalar mesons. We focus on the quark mass, momentum, lattice spacing, and volume dependence and apply our results to simulations employing mixed actions of Ginsparg-Wilson valence quarks and staggered sea quarks. To determine charge radii at quark masses on the lattices currently used, we find that all extrapolations except the one to infinite volume make significant contributions to the systematic error.

Extrapolations of lattice meson form factors

We use chiral perturbation theory to study the extrapolations necessary to make physical predictions from lattice QCD data for the electromagnetic form factors of pseudoscalar mesons. We focus on the quark mass, momentum, lattice spacing, and volume dependence and apply our results to simulations employing mixed actions of Ginsparg-Wilson valence quarks and staggered sea quarks. To determine charge radii at quark masses on the lattices currently used, we find that all extrapolations except the one to infinite volume make significant contributions to the systematic error.

Exploring light-cone sum rules for pion and kaon form factors

We analyze the higher-twist effects and the SU(3)-flavour symmetry breaking in the correlation functions used to calculate form factors of pseudoscalar mesons in the QCD light-cone sum rule approach. It is shown that the Ward identities for these correlation functions yield relations between twist-4 two- and three-particle distribution amplitudes. In addition to the relations already obtained from the QCD equations of motions, we have found a new one. With the help of these relations, the twist-4 contribution to the light-cone sum rule for the pion electromagnetic form factor is reduced to a very simple form. Simultaneously, we correct a sign error in the earlier calculation. The updated light-cone sum rule prediction for the pion form factor at intermediate momentum transfers is compared with the recent Jefferson Lab data. Furthermore, from the correlation functions with strange-quark currents the kaon electromagnetic form factor and the $K\to \pi$ weak transition form factors are predicted with $O(m_s)\sim O(m_K^2)$ accuracy.

Charge form factors of pseudoscalar mesons.

The elastic charge form factors of the pion, kaon, D, and B mesons are calculated within a relativistic constituent quark model formulated on the light cone. Our parameter-free predictions agree well with the available data. The results are approximately independent of the assumed form of the light-cone wave function; in particular, they do not depend on the high momentum tail of the wave function for energies accessible to present experiments.

Low-energy expansion of meson form factors

We calculate the corrections to various low-energy theorems concerning the behaviour of the pseudoscalar meson form factors near t =0. In particular we discuss (i) the Ademollo-Gatto theorem, (ii) Sirlin's relation between the K l 3 form factor ƒ + K π (t) and the electromagnetic form factors, (iii) the Callan-Treiman relation, and (iv) the Dashen-Weinstein relation, which connects the slope λ 0 of ƒ 0 K π (t) with the ratio F K / F π . Furthermore, we point out a remarkable isospin breaking effect which is clearly visible in the experimental rates of the decays K + → π 0 e + ν , K 0 → π − e + ν .

Moving frame wave functions and e.m. form factors of pseudoscalar mesons

We pose and solve approximately the problem of deriving the moving frame wave functions (w.f.) of mesons from the p = 0 w.f.'s obtained in the framework of anisotropic chromo-dynamics (ACD). Such w.f.'s are then employed in the calculation of the e.m. form factors of pseudoscalar mesons. Good agreement with experiments is obtained.

Mesons in anisotropic chromodynamics: The electromagnetic form factors of pseudoscalars

The electromagnetic form factors of pseudoscalar mesons have been calculated in the ACD-theory of hadrons, by making use of meson wf's with momentum p ≠ 0 . The (approximate) solution of the p ≠ 0 problem is sketched, and the results for charged π's and K's EM form factors as well as for the K 0 charged radius are presented.

Gravitational Form Factors of Pseudoscalar Mesons, Stress-Tensor-Current Commutation Relations, and Deviations from Tensor- and Scalar-Meson Dominance

The low-momentum-transfer behavior of the gravitational form factors of the pseudoscalar mesons is derived, starting with the model-independent equal-time commutation relations between the stress tensor and the axial-vector current. The results indicate significant deviations from tensor-meson pole dominance and scalar-meson pole dominance of the matrix elements of the traceless part and the trace, respectively, of the stress tensor. An expression is derived for the stress-tensor-$\ensuremath{\epsilon}$-meson coupling in terms of ${g}_{{A}_{1}\ensuremath{\epsilon}\ensuremath{\pi}}$. With additional assumptions, a phenomenological result is obtained for the scale dimension of the pion field. Possible mechanisms are discussed which may give rise to large values of the rms radii of the form factors. As an example of additional phenomenological results obtainable from the scheme discussed here, a result is derived for the $f{A}_{1}\ensuremath{\pi}$ coupling.