Isospin breaking in pion and $K_{e4}$ form factors - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2016

Isospin breaking in pion and $K_{e4}$ form factors

Résumé

Isospin breaking in the Kℓ4form factors induced by the difference between charged and neutral pion masses is discussed within a framework built on suitably subtracted dispersion representations. The Kℓ4form factors are constructed in an iterative way up to two loops in the low-energy expansion by implementing analyticity, crossing, and unitarity due to two-meson intermediate states. Analytical expressions for the phases of the two-loop form factors of the K± → π+π−e±νechannel are presented, allowing one to connect the difference of form-factor phase shifts measured experimentally (out of the isospin limit) and the difference of S- and P-wave ππ phase shifts studied theoretically (in the isospin limit). The dependence with respect to the two S-wave scattering lengths a00and a20in the isospin limit is worked out in a general way, in contrast 0 0 to previous analyses based on one-loop chiralperturbation theory. The results on the phases of the K± → π+π−e±νeform factors obtained by the NA48/2 collaboration at the CERN SPS are reanalysed including isospin-breaking correction to extract values for the scattering lengths a00and a02

Dates et versions

hal-03626616 , version 1 (31-03-2022)

Identifiants

Citer

V. Bernard, S. Descotes-Genon, M. Knecht. Isospin breaking in pion and $K_{e4}$ form factors. 11th Conference on Quark Confinement and the Hadron Spectrum, Sep 2014, St. Petersburg, Russia. pp.040011, ⟨10.1063/1.4938628⟩. ⟨hal-03626616⟩
16 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More