Search results for "chiral Lagrangians"
showing 10 items of 31 documents
Orderp6chiral couplings from the scalarK form factor
2004
15 páginas, 2 tablas.-- arXiv:hep-ph/0401080v2
Chiral Perturbation Theory with tensor sources
2007
23 pages, 1 figure.-- ISI Article Identifier: 000249788800051.-- ArXiv pre-print available at: http://arxiv.org/abs/0705.2948
Charm mass dependence of the weak Hamiltonian in chiral perturbation theory
2004
Suppose that the weak interaction Hamiltonian of four-flavour SU(4) chiral effective theory is known, for a small charm quark mass m_c. We study how the weak Hamiltonian changes as the charm quark mass increases, by integrating it out within chiral perturbation theory to obtain a three-flavour SU(3) chiral theory. We find that the ratio of the SU(3) low-energy constants which mediate Delta I=1/2 and Delta I=3/2 transitions, increases rather rapidly with m_c, as \sim m_c ln (1/m_c). The logarithmic effect originates from "penguin-type" charm loops, and could represent one of the reasons for the Delta I=1/2 rule.
Axial resonances in the open and hidden charm sectors
2007
13 pages, 2 figures.-- PACS nrs.: 11.10.St, 11.80.Gw, 12.39.Hg, 12.39.Fe.-- ISI Article Identifier: 000249271600001.-- ArXiv pre-print available at: http://arxiv.org/abs/0704.2314
Oblique S and T Constraints on Electroweak Strongly-Coupled Models with a Light Higgs
2014
Using a general effective Lagrangian implementing the chiral symmetry breaking SU(2) L ⊗ SU(2) R → SU(2) L+R , we present a one-loop calculation of the oblique S and T parameters within electroweak strongly-coupled models with a light scalar. Imposing a proper ultraviolet behaviour, we determine S and T at next-to-leading order in terms of a few resonance parameters. The constraints from the global fit to electroweak precision data force the massive vector and axial-vector states to be heavy, with masses above the TeV scale, and suggest that the W + W − and ZZ couplings of the Higgs-like scalar should be close to the Standard Model value. Our findings are generic, since they only rely on so…
Towards a determination of the chiral couplings at NLO in 1/N-C: L-8(r)(μ) and C-38(r)(μ)
2007
14 pages.-- ISI Article Identifier: 000244120200039.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0610290
V-us determination from hyperon semileptonic decays
2005
16 páginas, 9 tablas.-- arXiv:hep-ph/0509045v2
Low-energy couplings of QCD from topological zero-mode wave functions
2003
By matching 1/m^2 divergences in finite-volume two-point correlation functions of the scalar or pseudoscalar densities with those obtained in chiral perturbation theory, we derive a relation between the Dirac operator zero-mode eigenfunctions at fixed non-trivial topology and the low-energy constants of QCD. We investigate the feasibility of using this relation to extract the pion decay constant, by computing the zero-mode correlation functions on the lattice in the quenched approximation and comparing them with the corresponding expressions in quenched chiral perturbation theory.
Towards a consistent estimate of the chiral low-energy constants
2006
Guided by the large-N_C limit of QCD, we construct the most general chiral resonance Lagrangian that can generate chiral low-energy constants up to O(p^6). By integrating out the resonance fields, the low-energy constants are parametrized in terms of resonance masses and couplings. Information on those couplings and on the low-energy constants can be extracted by analysing QCD Green functions of currents both for large and small momenta. The chiral resonance theory generates Green functions that interpolate between QCD and chiral perturbation theory. As specific examples we consider the VAP and SPP Green functions.
Vanishing chiral couplings in the large-Nc resonance theory
2007
5 pages, 2 figures.-- PACS nrs.: 12.39.Fe; 11.15.Pg; 12.38.-t.-- ISI Article Identifier: 000247625300022.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0611375