Improving the Kpi vector form factor through Kl3 constraints

Dispersive representation of the scalar and vector Kpi form factors for tau --> K pi nu_tau and K_{l3} decays

Recently, the tau --> K pi nu_tau decay spectrum has been measured by the Belle and BaBar collaborations. In this work, we present an analysis of such decays introducing a dispersive parametrization for the vector and scalar Kpi form factors. This allows for precise tests of the Standard Model. For instance, the determination of f_+(0)|V_{us}| from these decays is discussed. A comparison and a combination of these results with the analyses of the K_{l3} decays is also considered.

The Kpi vector form factor and constraints from Kl3 decays

The slope and curvature parameters of the $Kπ$ vector form factor, $F_+^{Kπ}$, are fitted to the data on $\tauKpi$ and $K_{l3}$ decays yielding $λ_+'=(25.49 \pm 0.31) \times 10^{-3}$ and $λ_+"= (12.22 \pm 0.14) \times 10^{-4}$. The pole position of the $K^*(892)^\pm$ is found to be at $m_{K^*(892)^\pm}= 892.0\pm 0.5$ MeV and $Γ_{K^*(892)^\pm}= 46.5 \pm1.1$ MeV. The phase-space integrals relevant for $K_{l3}$ analyses and the $P$-wave isospin-1/2 $Kπ$ phase-shift threshold parameters are also calculated.

从标量K Pi形状因子订购p^6手性耦合

Order p^6 chiral couplings from the scalar K Pi form factor

利用最近在耦合通道色散关系分析\cite{JOP01}中对标量KPi的形状因子F_0 ^KPi的测定结果，本文计算了零动量转移时F_0 ^KPi（t）的斜率和曲率。标量KPi形状因子的斜率和曲率的知识，以及最近在p^6阶手征微扰理论中计算出的F_0 ^KPi（t）的表达式，使得能够估计O（p^6）手征常数C_12 ^r =（0.3 +- 5.4）10^-7和（C_12 ^r + C_34 ^r）=（3.2 +- 1.5）10^-6。我们的研究结果还允许估计来自C_i对矢量形状因子F_+^KPi（0）的贡献，这对于精确测定来自K_13衰变的|V_us|是至关重要的。我们的结果F_+^KPi（0）|_C_i^r=-0.018 +-0.009，尽管有很大的不确定性，但与Leutwyler和Roos在20年前所做的估计完全一致。

Constraining the Kpi vector form factor by tau---> K pi nu_tau and K_l3 decay data

A subtracted dispersive representation of the $Kπ$ vector form factor, $F_+^{Kπ}$, is used to fit the Belle spectrum of $\tauKpi$ decays incorporating constraints from results on $K_{l3}$ decays. Through the use of three subtractions, the slope and curvature of $F_+^{Kπ}$ are obtained directly from the data yielding $λ_+'=(25.49 \pm 0.31) \times 10^{-3}$ and $λ_+"= (12.22 \pm 0.14) \times 10^{-4}$. The phase-space integrals relevant for $K_{l3}$ analyses are calculated. Additionally, from the pole position on the second Riemann sheet the mass and width of the $K^*(892)^\pm$ are found to be $m_…

Kpi form factors and final state interactions in D+ --> K- pi+ pi+ decays

We present a model for the decay D+ --> K- pi+ pi+. The weak interaction part of this reaction is described using the effective weak Hamiltonian in the factorisation approach. Hadronic final state interactions are taken into account through the Kpi scalar and vector form factors fulfilling analyticity, unitarity and chiral symmetry constraints. The model has only two free parameters that are fixed from experimental branching ratios. We show that the modulus and phase of the S wave thus obtained agree nicely with experiment up to 1.55 GeV. We perform Monte Carlo simulations to compare the predi…

K pi vector form factor constrained by tau ---> K pi nu_tau and K_l3 decays

Dispersive representations of the Kpi vector and scalar form factors are used to fit the spectrum of tau ---> K pi nu_tau obtained by the Belle collaboration incorporating constraints from results for K_l3 decays. The slope and curvature of the vector form factor are obtained directly from the data through the use of a three-times-subtracted dispersion relation. We find $λ_+'=(25.49 \pm 0.31) \times 10^{-3}$ and $λ_+"= (12.22 \pm 0.14) \times 10^{-4}$. From the pole position on the second Riemann sheet the mass and width of the $K^*(892)^{\pm}$ are found to be $m_{K^*(892)^\pm}=892.0\pm 0.5$~M…