arXiv subjects

Joachim Kambor

Publications and source records attributed to Joachim Kambor.

21 records · Page 2Linked to original sources

arXiv1996

Dispersive Approach to Semileptonic Form-Factors in Heavy-to-Light Meson Decays

We study the semileptonic decays of heavy mesons into light pseudoscalars by making use of dispersion relations. Constraints from heavy quark symmetry, chiral symmetry and perturbative QCD are implemented into a dispersive model for the form-factors. Large deviations from $B^*$-pole dominance are observed in $B\toπ\ellν$. We discuss the model prediction for this mode and its possible impact on the extraction of $|V_{ub}|$.

hep-ph↗

arXiv1995

Inverse-Moment Chiral Sum Rules

A general class of inverse-moment sum rules was previously derived by the authors in a chiral perturbation theory (ChPT) study at two-loop order of the isospin and hypercharge vector-current propagators. Here, we address the evaluation of the inverse-moment sum rules in terms of existing data and theoretical constraints. Two kinds of sum rules are seen to occur, those which contain as-yet undetermined ${\cal O}(q^6)$ counterterms and those free of such quantities. We use the former to obtain phenomenological evaluations of two ${\cal O}(q^6)$ counterterms. Light is shed on the important but difficult issue regarding contributions of higher orders in the ChPT expansion.

hep-ph↗

arXiv1995

Two-Loop Analysis of Vector Current Propagators in Chiral Perturbation Theory

We perform a calculation of the isospin and hypercharge vector current propagators ($Δ_{V33}^{μν}(q^2)$ and $Δ_{V88}^{μν}(q^2)$) to two loops in chiral perturbation theory. The analysis is carried out with straightforward Feynman diagram methods by making appropriate use of external vector sources. Counterterms from the ${\cal O}(q^6)$ chiral lagrangian, required to absorb divergences and scale dependence encountered at the two-loop level, are constructed. Our final results are finite, covariant, and scale-independent. Several applications are described, including a comparison of the two-loop isospin vector spectral function with data and the construction of new chiral sum rules.

hep-ph↗