K_l3 form factors at order p^6 in chiral perturbation theory
| dc.creator | Post, P. | |
| dc.creator | Schilcher, K. | |
| dc.date | 2001-12-28 | |
| dc.date | 2002-03-27 | |
| dc.date.accessioned | 2026-07-07T10:52:33Z | |
| dc.date.available | 2026-07-07T10:52:33Z | |
| dc.description | This paper describes the calculation of the semileptonic K_l3 decay form factor at order p^6 of chiral perturbation theory which is the next-to-leading order correction to the well-known p^4 result achieved by Gasser and Leutwyler. At order p^6 the chiral expansion contains 1- and 2-loop diagrams which are discussed in detail. The irreducible 2-loop graphs of the sunset topology are calculated numerically. In addition, the chiral Lagrangian L^6 produces direct couplings with the W-bosons. Due to these unknown couplings, one can always add linear terms in q^2 to the predictions of the form factor f_-(q^2). For the form factor f_+(q^2), this ambiguity involves even quadratic terms. Making use of the fact that the pion electromagnetic form factor involves the same q^4 counter term, the q^4-ambiguity can be resolved. Apart from the possibility of adding an arbitrary linear term in q^2 our calculation shows that chiral perturbation theory converges very well in this application, as the O(p^6) corrections are small. Comparing the predictions of chiral perturbation theory with the recent CPLEAR data, it is seen that the experimental form factor f_+(q^2) is well described by a linear fit, but that the slope lambda_+ is smaller by about 2 standard deviations than the O(p^4) prediction. The unavoidable q^2 counter term of the O(p^6) corrections allows to bring the predictions of chiral perturbation theory into perfect agreement with experiment. | |
| dc.description | 32 pages, 7 figures | |
| dc.identifier | https://arxiv.org/abs/hep-ph/0112352 | |
| dc.identifier | http://arxiv.org/abs/hep-ph/0112352 | |
| dc.identifier | Eur.Phys.J.C25:427-443,2002 | |
| dc.identifier | doi:10.1007/s10052-002-0967-1 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/185195 | |
| dc.subject | High Energy Physics - Phenomenology | |
| dc.title | K_l3 form factors at order p^6 in chiral perturbation theory | |
| dc.type | text |