Study of the resummation of chiral logarithms in the exponentiated expression for the pion form factor

2013

Eur. Phys. J. C

We propose a dispersive representation of the charged pion vector form factor that is consistent with chiral symmetry and fulfills the constraints imposed by analyticity and unitarity. Unknown parameters are fitted to the very precise data on τ − → π − π 0 ντ decays obtained by Belle, leading to a good description of the corresponding spectral function up to a ππ squared invariant mass s ≃ 1.5 GeV 2 . We determine the ρ(770) mass and width pole parameters and obtain the values of low energy observables. The significance of isospin breaking corrections is also discussed. For larger values of s, this representation is complemented with a phenomenological description to allow its implementation in the new TAUOLA hadronic currents.

Section: Low Energy Description Of Fmentioning

confidence: 92%

Dispersive representation of the pion vector form factor in τ→ππν τ decays

Dumm

2013

Eur. Phys. J. C

“…[66]. 34 Also the leading next-to-next-to-leading (NNLO) order terms [70,71] are reproduced [51,72]. 35 In RχT all nine mesons [ρ, K * , ω, (φ)] have the same mass in the N C → ∞ limit without taking into account SU (3) breaking.…”

Section: Theoretical Basis Of the Currents 71 Resonance Chiral Theormentioning

confidence: 99%

Resonance chiral Lagrangian currents andτdecay Monte Carlo

Shekhovtsova

Przedziński²,

et al. 2012

Phys. Rev. D

In the present paper we describe the set of form factors for hadronic τ decays based on Resonance Chiral Theory. The technical implementation of the form factors in FORTRAN code is also explained. It is shown how it can be installed into TAUOLA Monte Carlo program. Then it is rather easy to implement into software environments of not only Belle and BaBar collaborations but also for FORTRAN and C++ applications of LHC. The description of the current for each τ decay mode is complemented with technical numerical tests. The set is ready for fits, parameters to be used in fits are explained. Arrangements to work with the experimental data not requiring unfolding are prepared. Hadronic currents, ready for confrontation with the τ decay data, but not yet ready for the general use, cover more than 88 % of hadronic τ decay width.

“…We would like to stress that the Breit-Wigner model is consistent with χP T only at leading order, while the exponential parametrization (JPP) and the dispersive representation (BEJ) reproduce the chiral limit results up to next-to-leading order and including the dominant contributions at the next order [94].…”

Section: Different Form Factors According To Treatment Of Final-statementioning

confidence: 99%

τ − →K − η (′) ν τ decays in Chiral Perturbation Theory with resonances

Escribano

Gonzàlez-Solís

2013

J. High Energ. Phys.

Abstract:We have studied the τ − → K − η ( ) ν τ decays within Chiral Perturbation Theory including resonances as explicit degrees of freedom. We have considered three different form factors according to treatment of final-state interactions. In increasing degree of soundness: Breit-Wigner, exponential resummation and dispersive representation. We find that although the first one fails in accounting for the data on the Kη mode, the other two approaches provide good fits to them which are sensitive to the K (1410) pole parameters, that are determined to be M K = 1330 +27 −41 MeV and Γ K = 217 +68 −122 MeV. These values are competitive with the standard determination from τ − → (Kπ) − ν τ decays. The corresponding predictions for the τ − → K − η ν τ channel respect the current upper bound and hint to the discovery of this decay mode in the near future.