arXiv subjects

J. Kambor

Publications and source records attributed to J. Kambor.

9 recordsLinked to original sources

arXiv2001

Dispersion relations and soft pion theorems for K -> pi pi

We propose a new method to obtain the K -> pi pi amplitude from K -> pi which allows one to fully account for the effects of final state interactions. The method is based on a set of dispersion relations for the K -> pi pi amplitude in which the weak Hamiltonian carries momentum. The soft pion theorem, which relates this amplitude to the K -> pi amplitude, can be used to determine one of the two subtraction constants - the second constant is at present known only to leading order in chiral perturbation theory. We solve the dispersion relations numerically and express the result in terms of the unknown higher order corrections to this subtraction constant.

hep-ph↗

arXiv2001

A note on the dispersive treatment of K -> pi pi with the kaon off-shell

It has been recently suggested that it is possible to calculate the effect of final state interactions in K -> pi pi amplitudes by applying dispersive methods to the amplitude with the kaon off-shell. We critically reexamine the procedure, and point out the effects of the arbitrariness in the choice of the off-shell field for the kaon.

hep-ph↗

arXiv2000

The Strange Quark Mass From Flavor Breaking in Hadronic Tau Decays

The strange quark mass is extracted from a finite energy sum rule (FESR) analysis of the flavor-breaking difference of light-light and light-strange quark vector-plus-axial-vector correlators, using spectral functions determined from hadronic tau decay data. We point out problems for existing FESR treatments associated with potentially slow convergence of the perturbative series for the mass-dependent terms in the OPE over certain parts of the FESR contour, and show how to construct alternate weight choices which not only cure this problem, but also (1) considerably improve the convergence of the integrated perturbative series, (2) strongly suppress contributions from the region of s values where the errors on the strange current spectral function are still large and (3) essentially completely remove uncertainties associated with the subtraction of longitudinal contributions to the experimental decay distributions. The result is an extraction of m_s with statistical errors comparable to those associated with the current experimental uncertainties in the determination of the CKM angle, V_{us}. We find m_s(1 GeV)=158.6\pm 18.7\pm 16.3\pm 13.3 MeV (where the first error is statistical, the second due to that on V_{us}, and the third theoretical).

hep-ph↗

arXiv2000

Extracting m_s From Flavor Breaking in Hadronic Tau Decays

New finite energy sum rules (FESR's) for extracting m_s from hadronic tau decay data are constructed which (1) significantly reduce potential theoretical uncertainties present in existing sum rule analyses and (2) remove problems associated with both the poor convergence of the OPE representation of the longitudinal part of the $us$ vector and axial vector correlators and the large statistical errors in the $us$ spectral data above the K^* region.

hep-ph↗

arXiv1999

Low-energy photon-photon fusion into three pions in Generalized Chiral Perturbation Theory

The processes $γγ\toπ^0π^0π^0$ and $γγ\to π^+ π^- π^0$ are considered in Generalized Chiral Perturbation theory, in view of their potential sensitivity to the mechanism of spontaneous breaking of chiral symmetry and to various counterterms. The amplitudes are computed up to order ${\cal O}(p^6)$. The event production rates are estimated for the Daphne $ϕ$-Factory and for a future $τ$-Charm Factory.

hep-ph↗

arXiv1997

Report of the Working Group on Goldstone Boson Production and Decay

This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997. For the production aspects we discuss $π^0$ and $η$ production in nucleon-nucleon collisions and the behaviour of hadrons in various sum rules. For the decays we present a discussion on various $K$, $η$ and $π$ decay channels. Other aspects discussed are a new treatment of meson-meson scattering, the light-by-light contribution to the muon anomalous magnetic moment and progress in various aspects of the $p^6$ generating functional in the mesonic sector.

hep-ph↗

arXiv1995

Electromagnetic Corrections to the decays $η\to 3π$

We calculate the electromagnetic corrections to the decays $η\rightarrow 3π$ in next to leading order in the chiral expansion. We find that the corrections are small in accordance with Sutherland's theorem and modify neither rate nor the Dalitz plot distributions noticeably.

hep-ph↗

arXiv1995

Final State Interactions and Khuri-Treiman Equations in $η\to 3π$ decays

Using extended Khuri-Treiman equations, we evaluate the final state interactions due to two-pion rescatterings to the decays $η\to π^0 π^+ π^-$ and $η\to π^0 π^0 π^0$. As subtraction to the dispersion relation we take the one-loop chiral perturbation theory result of Gasser and Leutwyler. The calculated corrections are moderate and amount to about $14\%$ in the amplitude at the center of the decay region. A careful analysis of the errors inherent to our approach is given. As a consequence, the experimental rate of the decay can only be reproduced if the double quark mass ratio $Q^{-2}\equiv\frac{m_{d}-m_{u}} {m_{s}-{\hat m}} \cdot\frac{m_{d}+m_{u}}{m_{s}+{\hat m}}$ is increased from the usual value of $1/(24.1)^2$ to $1/(22.4 \pm 0.9)^2$. We have also calculated the ratio of the rates of the two decays and various Dalitz Plot parameters. In particular, the linear slope $a$ in the charged decay is different from the one-loop value and agrees better with experiment.

hep-ph↗

arXiv1993

K_S\rightarrow γγ, K_L\rightarrowπ^0γγ$ and Unitarity

Agreement between the experimental value $Γ(K_S\rightarrow γγ)$ and the number predicted via a one-loop chiral perturbation theory calculation has been cited as a success for the latter. On the other hand the one-loop prediction for the closely related process $K_L\rightarrow π^0γγ$ has been found to be a factor three below the experimental value. Using the inputs of unitarity and dispersion relations, we demonstrate the importance of higher order loop effects to both of these processes.

hep-ph↗