PT Journal
AU Guevara, A
   Lopez Castro, G
   Roig, P
TI Improved description of dilepton production in tau(-) -> nu(tau)P(- )decays
SO Physical Review D
JI Phys. Rev. D
PY 2022
BP 076007
EP 15pp
VL 105
IS 7
DI 10.1103/PhysRevD.105.076007
LA English
AB Recently, the Belle Collaboration reported the first measurements of the tau(-) -> nu(tau)pi(-) e(+) e(-) branching fraction and the spectrum of the pion-dielectron system. In an analysis previous to Belle's results, we evaluated this branching fraction which turned out to be compatible with that reported by Belle, although with a large uncertainty. This is the motivation to seek for improvement on our previous evaluation of tau(-) -> nu(tau)pi(-) l(+) l(-) decays (l = e, mu). In this paper we improve our calculation of the WP-gamma* vertex by including flavor-symmetry breaking effects in the framework of the resonance chiral theory. We impose QCD short-distance behavior to constrain most parameters and data on the pi(-) e(+) e(-) spectrum reported by the Belle Collaboration to fix the remaining free ones. As a result, improved predictions for the branching ratios and hadronic/leptonic spectra are reported, which are in good agreement with observations. Analogous calculations for the strangeness-changing tau(-) -> nu(tau) K- l(+) l(-) transitions are reported for the first time. Albeit one expects the m(pi mu+ mu- )spectrum to be measured in Belle-II and the observables with l = e can be improved, it is rather unlikely that the K channels can be measured due to the suppression factor vertical bar V-ud/V-us vertical bar(2) = 0.05.
ER