2,544 research outputs found

    The ΔI=1/2\Delta I=1/2 Rule for Kaons

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    We report on recent advances at understanding the ΔI=1/2\Delta I= 1/2 rule for kaons. We get reasonable matching between short-- and long--distances for scales between between 0.6 and 1.0 GeV and reproduce the ΔI=1/2\Delta I=1/2 rule huge enhancement in the chiral limit. A detailed analysis of the different contributions to the relevant octet and 27-plet couplings is done. For the B6(1/2)(μ)/[Nc]B_6^{(1/2)}(\mu) \equiv / [ {\Large|}_{N_c}] parameter, we get in the chiral limit B6(1/2)(μ)=2.2±0.5B_6^{(1/2)}(\mu) = 2.2 \pm 0.5 for scales μ[0.6,1.0]\mu \in [0.6, 1.0] GeV.Comment: 9 LaTeX pages, 2 ps figures included. Invited talk at QCD '99 High Energy Euro Conference on Quantum Chromodynamics, July 1999, Montpellier, France. Corrected eq. (16) and misprint

    Progress in KππK\to\pi\pi Decays

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    Recent work by J.~Prades and myself on KππK\to\pi\pi is described. The first part describes our method to connect in a systematic fashion the short-distance evolution with long-distance matrix-element calculations taking the scheme dependence of the short-distance evolution into account correctly. In the second part I show the results we obtain for the ΔI=1/2\Delta I=1/2 rule in the chiral limit.Comment: 4 pages, uses espcrc1.sty. Talk given at PANIC99, Uppsala 10-16 june 199

    A new global fit of the LirL^r_i at next-to-next-to-leading order in Chiral Perturbation Theory

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    A new fit is done to obtain numerical values for the order p4p^4 low-energy-constants LirL_i^r in Chiral Perturbation Theory. This includes both new data and new calculated observables. We take into account masses, decay constants, K4K_{\ell4}, ππ\pi\pi and πK\pi K scattering lengths and slopes and the slope of the pion scalar formfactor. We compare in detail where the changes w.r.t. to the 10 year old "fit 10" come from. We discuss several scenarios for estimating the order p6p^6 constants CirC_i^r and search for possible values of them that provide a good convergence for the ChPT series. We present two such sets. One big change is that the fits do not have the expected behaviour in the limit of large NcN_c as well as before.Comment: 41 pages, p^4 values of the l_i added, numerical values for f_+(0) in Kl3 added, a comparison with the LECS from Ecker et al., Phys. Lett. B692 (2010) 184 [arXiv:1004.3422 [hep-ph]] adde

    A Parametrization for K+π+πe+νK^+\to \pi^+\pi^- e^+\nu

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    We discuss various models and Chiral Perturbation Theory results for the Kl4K_{l4} form factors FF and GG. We check in how much a simple parametrization with a few parameters can be used to extract information from experiment.Comment: 19 pages, 14 figure

    Chiral Meson Physics at Two Loops

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    An overview of Chiral Perturbation Theory calculations in the mesonic sector at the two Loop level is given. Discussed in some detail are the partially quenched case relevant for lattice QCD, the general fitting procedures and ππ\pi\pi,πK\pi K scattering as well as the determination of VusV_{us} and K3K_{\ell3} decays.Comment: 7 pages, Invited plenary talk presented at the 19th European Few-Body conference, Groningen, The Netherlands, August 23-27, 200

    Chiral extrapolation and determination of low-energy constants from lattice data

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    We propose analytic approximations of chiral SU(3) amplitudes for the extrapolation of lattice data to the physical meson masses. The method allows the determination of NNLO low-energy constants in a controllable fashion. We test the approach with recent lattice data for the ratio F_K/F_pi of meson decay constants.Comment: 10 pages, 1 figure, matches version published in PLB: title enlarged, comments added, results unchange

    The Pseudoscalar Meson Mass to Two Loops in Three-Flavor Partially Quenched χ\chiPT

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    This paper presents a first study of the pseudoscalar meson masses to two loops, or NNLO, within the supersymmetric formulation of partially quenched chiral perturbation theory (PQχ\chiPT). The expression for the pseudoscalar meson mass in the case of three valence and three sea quarks with equal masses, but different from each other, is given to O(p6){\cal O}(p^6), along with a numerical analysis.Comment: 4 pages, one reference added, small changes in discussio

    Semileptonic π\pi and KK Decays and the Chiral Anomaly at One-loop

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    We calculate the O(p6)O(p^6) corrections to the anomalous form factors appearing in π+\pi^+, K+e+νγ, μ+νγK^+ \to e^+ \nu \gamma,\ \mu^+\nu\gamma and Kl4K_{l4} decays in Chiral Perturbation Theory. The relevant dimension 66 terms of the lagrangian are evaluated assuming their saturation by the vector meson contribution.Comment: 10 pages of LaTeX (+3 figures available on request

    Chiral logarithms to five loops

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    We investigate two specific Green functions in the framework of chiral perturbation theory. We show that, using analyticity and unitarity, their leading logarithmic singularities can be evaluated in the chiral limit to any desired order in the chiral expansion, with a modest calculational cost. The claim is illustrated with an evaluation of the leading logarithm for the scalar two-point function to five-loop order.Comment: 13 pages, 5 figure
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