arXiv subjects

J. Bijnens

Publications and source records attributed to J. Bijnens.

43 records · Page 3Linked to original sources

arXiv1994

$K_{l4}$ - Decays Beyond One Loop

The matrix elements for $K\rightarrow ππłν$ decays are described by four form factors $F,G,H$ and $R$. We complete previous calculations by evaluating $R$ at next-to-leading order in the low-energy expansion. We then estimate higher order contributions using dispersion relations and determine the low-energy constants $L_1,L_2$ and $L_3$ from data on $K_{e4}$ decays and on elastic pion scattering. Finally, we present predictions for the slope of the form factor $G$ and for total decay rates.

hep-ph↗

arXiv1993

Violations of Dashen's Theorem

The electromagnetic contribution to the $K^+ - K^0$ mass difference is calculated in the $1/N_c$ approach including the $SU(3)$ breaking contributions due to a non-zero strange quark mass. The short-distance contribution can be unambiguously determined in terms of the known parameters of the next-to-leading order chiral lagrangian. The long distance part is estimated using the $1/N_c$ approach by Bardeen et al. Relatively large corrections are found.

hep-ph↗

arXiv1993

Semileptonic $π$ and $K$ Decays and the Chiral Anomaly at One-loop

We calculate the $O(p^6)$ corrections to the anomalous form factors appearing in $π^+$, $K^+ \to e^+ νγ,\ μ^+νγ$ and $K_{l4}$ decays in Chiral Perturbation Theory. The relevant dimension $6$ terms of the lagrangian are evaluated assuming their saturation by the vector meson contribution.

hep-ph↗

arXiv1992

Radiative Semileptonic Kaon Decays

We evaluate the matrix elements for the radiative kaon decays $K^+ \to l^+ν_lγ$, $l^+ ν_l l'^+ l'^-$ and $K \to πl ν_lγ$ \ ($l,\ l' = e,μ$) to next-to-leading order in chiral perturbation theory. We calculate total rates and rates with several kinematical cuts and confront the results with existing data. Measurements at future kaon facilities will allow for a more detailed comparison between theory and experiment.

hep-ph↗

arXiv1992

Semileptonic Kaon Decays in Chiral Perturbation Theory

We present the matrix elements for the semileptonic kaon decays $K_{l2γ}$, $K_{l2l^+l^-}$, $K_{l2l'^+l'^-}$, $K_{l3}$, $K_{l3γ}$ and $K_{l4}$ at next-to-leading order in chiral perturbation theory and compare the predictions with experimental data. Monte Carlo event generators are used to calculate the corresponding rates at DAFNE. We discuss the possibilities to improve our knowledge of the low-energy structure of the Standard Model at this and similar machines.

hep-ph↗

arXiv1992

The Chiral Anomaly in Non-Leptonic Weak Interactions

The interplay between the chiral anomaly and the non-leptonic weak Hamiltonian is studied. The structure of the corresponding effective Lagrangian of odd intrinsic parity is established. It is shown that the factorizable contributions (leading in $1/N_C$) to that Lagrangian can be calculated without free parameters. As a first application, the decay $K^+ \ra π^+ π^0 γ$ is investigated.

hep-ph↗

arXiv1992

Two--Body Decays of $B_s$ Mesons

We have calculated the decay rates of the $B_s$ meson in a number of exclusive two--body decay channels using the Bauer--Stech--Wirbel model for current matrix elements. The influence of the free parameters of the model on the predictions is studied. The total branching ratio of the $B_s$ into final states which only contain stable charged particles is found to be about $10^{-3}$.

hep-ph↗