Implication of the running mass of the ρ^{0} meson for the dilepton mass spectrum and the μ^{+}μ^{}/e^{+}e^{} ratio in K^{+}>π^{+}l^{+}l^{} decays
Abstract
We make an attempt to resolve the discrepancy of the observed e^{+}e^{} mass spectrum in the K^{+}>π^{+}e^{+}e^{} decay with that predicted by meson dominance. To this end we investigate the properties of the ρ^{0} propagator. We use dispersion relations to evaluate the running mass m^{2}_{ρ}(t) of the ρ^{0} resonance without adjustable parameters. To improve the convergence of the dispersion integral, the momentum dependence of strong vertices is taken from the fluxtubebreaking model of Kokoski and Isgur. The obtained behavior of m^{2}_{ρ}(t) at small momentum squared t makes the K^{+}>π^{+}e^{+}e^{} form factor rise faster with increasing t than in the original meson dominance calculation and more in agreement with the published data. As a consequence, the meson dominance prediction of the μ^{+}μ^{}/e^{+}e^{} ratio changes slightly, from 0.224 to 0.236. We do not see any possibility to accommodate into the meson dominance approach an even steeper e^{+}e^{} spectrum, indicated by the preliminary data of the E865 Collaboration at BNL AGS.
 Publication:

Physical Review D
 Pub Date:
 September 1999
 DOI:
 10.1103/PhysRevD.60.053007
 arXiv:
 arXiv:hepph/9903216
 Bibcode:
 1999PhRvD..60e3007L
 Keywords:

 12.15.Ji;
 11.55.Fv;
 13.20.Eb;
 Applications of electroweak models to specific processes;
 Dispersion relations;
 Decays of K mesons;
 High Energy Physics  Phenomenology
 EPrint:
 13 pages, RevTeX, epsf.sty, 4 embedded figures