CPviolation in τ→3πντ

Abstract

We consider CP violating effects in the decays τ → (3π)ν τ where both the J P = 1 + resonance, a 1 , and J P = 0 − resonance, π ′ , can contribute. The interference between the a 1 and π ′ resonances can lead to enhanced CP-violating asymmetries whose magnitudes depend crucially on the π ′ decay constant,We make an estimate of f π ′ with a simplified chiral Lagrangian coupled to a massive pseudoscalar field, and we compare the estimates from the nonrelativistic quark model and from the QCD sum rule with the estimate from the 'mock' meson model. We then estimate quantitatively the size of CPviolating effects in a multi-Higgs-doublet model and scalar-leptoquark models. We find that, while CP-violating effects in the scalar-leptoquark models may require more than 10 10 τ leptons, CP-violating effects from the multi-Higgsdoublet model can be seen at the 2σ level with about 10 7 τ leptons using the chiral Lagrangian estimate of f π ′ = (1 ∼ 5) × 10 −3 GeV.

Search for nonstandard modelCPorTviolation at theτ-charm factory

“…As the result, at 2σ level ǫ ≃ 3 × 10 −2 is observable. This estimation agrees with the exact result of reference [18]. (3) Obviously the numerical result we obtained above is quite crude.…”

“…However, if one assumes that all the couplings λ and λ ′ are at the same size irrespective of the generation indexes, then much more stringent bounds exist. These bounds are obtained from experimental bounds of Br(K L → µe), Br(π → eν e (γ)), Br(π → µν µ (γ)) and Γ(µT i → eT i)/Γ(µT i → capture) [18]. They are generally about five order of magnitude smaller than the direct bounds.…”

“…CP violation effect in τ sector for the models are recently discussed extensively by some authors [18,22]. It is particularly interesting for generating a large d l .…”

“…A direct constraint on these parameters can be obtained through comparing the theoretical value Γ th (τ → πν τ ) = (2.480 ± 0.025) × 10 −13 GeV and the measurement value of Γ exp (τ → πν τ ) = (2.605 ± 0.093) × 10 −13 GeV [42]. Assuming that real and imaginary part of the coupling λλ ′ * are approximately equal, one has from τ → πν τ [18] |Im(…”

“…Hagiwara and Tanabashi [18] investigated the possibility that the large width-mass ratios of these resonances enhance CP-violation effects in the multi-Higgs extensions of the SM.…”