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B l 4 decays and the extraction of | V u b | </mml:…

2014; American Physical Society; Volume: 89; Issue: 5 Linguagem: Inglês

10.1103/physrevd.89.053015

1550-7998

Xian-Wei Kang, Bastian Kubis, C. Hanhart, Ulf-G. Meißner,

Black Holes and Theoretical Physics

The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| is not well determined yet. It can be extracted from both inclusive or exclusive decays, like B --> pi (rho) l nu-bar_l. However, the exclusive determination from B --> rho l nu-bar_l, in particular, suffers from a large model dependence. In this paper, we propose to extract |V_ub| from the four-body semileptonic decay B --> pi pi l nu-bar_l, where the form factors for the pion-pion system are treated in dispersion theory. This is a model-independent approach that takes into account the pi-pi rescattering effects, as well as the effect of the rho meson. We demonstrate that both finite-width effects of the rho meson as well as scalar pi-pi contributions can be considered completely in this way.