V. Baru

Towards a field theoretic understanding of NN → NNπ

Abstract.We study the production amplitude for the reaction NN → NNπ up to next-to-leading order in chiral perturbation theory using a counting scheme that takes into account the large scale introduced by the initial momentum. In particular, we investigate a subtlety that arises once the leading loop contributions are convoluted with the NN wave functions as demanded by the non-perturbative nature of the NN interaction. We show how to properly identify the irreducible contribution of loop diagrams in such type of reaction. The net effect of the inclusion of all next-to-leading-order loops is to enhance the leading rescattering amplitude by a factor of 4/3, bringing its contribution to the cross-section for pp → dπ+ close to the experimental value.

Flatté-like distributions and the a0(980)/f0(980) mesons

Abstract.We explore the features of Flatté-like parametrizations. In particular, we demonstrate that the large variation in the absolute values of the coupling constants to the πη (or ππ) and K¯ channels for the a0(980) and f0(980) mesons that one can find in the literature can be explained by a specific scaling behaviour of the Flatté amplitude for energies near the K¯ threshold. We argue that the ratio of the coupling constants can be much better determined from a fit to experimental data.

Dispersive and absorptive corrections to the pion–deuteron scattering length

Abstract We present a parameter-free calculation of the dispersive and absorptive contributions to the pion–deuteron scattering length based on chiral perturbation theory. We show that once all diagrams contributing to leading order to this process are included, their net effect provides a small correction to the real part of the pion–deuteron scattering length. At the same time the sizable imaginary part of the pion–deuteron scattering length is reproduced accurately.

Precision calculation of γd↦πnn within chiral perturbation theory

Abstract.The reaction γd↦π+nn is calculated up to order χ5/2 in chiral perturbation theory, where χ denotes the ratio of the pion to the nucleon mass. Special emphasis is put on the role of nucleon recoil corrections that are the source of contributions with fractional power in χ. Using the known near-threshold production amplitude for γp↦π+n as the only input, the total cross-section for γd↦π+nn is described very well. A conservative estimate suggests that the theoretical uncertainty for the transition operator amounts to 3% for the computed amplitude near threshold.

The role of nucleon recoil in low-energy antikaon-deuteron scattering

The effect of the nucleon recoil for the antikaon-deuteron scattering is investigated in the framework of the effective field theory. In particular, we concentrate on the calculation of the nucleon recoil effect for the double-scattering process. It is shown that the leading correction to the static term that emerges at order

Three-body Ddquer pion dynamics for the X(3872)

\xi^{{1/2}}_{}

Role of the Δ(1232) in pion–deuteron scattering at threshold within chiral effective field theory

with

Remarks on the study of the X(3872) from Effective Field Theory with Pion-Exchange Interaction

\xi

Heavy-quark spin symmetry partners of the X(3872) revisited

= MK/mN vanishes due to a complete cancellation of individually large contributions. The resulting recoil effect in this process is found to be of the order of 10-15% as compared to the static term. We also briefly discuss the application of the method in the calculations of the multiple-scattering diagrams.

Spin partners of the Z b (10610) and Z b (10650) revisited

We investigate the role played by the three-body