20,661 research outputs found
One loop predictions for the pion VFF in Resonance Chiral Theory
A calculation for the one-loop pion vector form-factor in Resonance Chiral
Theory is provided in this talk. The amplitude is computed up to
next-to-leading order in 1/Nc and, by means of high-energy constraints, we are
able to produce a prediction for the corresponding O(p4) Chiral Perturbation
Theory low energy constant L9(mu)=(7.6+- 0.6) 10^{-3} at the scale mu=770 MeV.Comment: 6 pages. Talk given at QCD@Work 2010 -International Workshop on QCD:
Theory and Experiment-, 20-23 June 2010, Martina Franca, Valle d'Itria
(Italy
V+A and V-A Correlators at Large NC: From OPE to Resonance Theory
The spin-1 correlators are analysed in this talk through a large NC resonance
theory. The matching to perturbative QCD and the first terms in the OPE
constrains the hadronic parameters. A further sum-rule analysis shows the wider
range of validity of the resonance description, which can help to discern the
proper structure of the QCD mass spectrum.Comment: 6 pages, 2 figures, proceedings of the talk given at HSQCD 2005, St.
Petersburg, Russia, September 20-24 200
QCD Correlators at Large NC
This talk explores the spin--1 correlators up to O(alpha_s) through a large
NC resonance theory. The phenomenological analyses of this kind must take these
corrections into account since they produce a larger impact than the first OPE
condensates. It is also necessary to separate low and high energy regimes;
fixing the parameters of the lightest multiplets through perturbative QCD
arguments is unfair and introduces errors in the determination of the
condensates and resonance parameters. This separation of regimes improves our
understanding of the Minimal Hadronical Approximation. The study at O(alpha_s)
already allows discerning between different hadronical models, where the
Regge-like mass spectrum shows the best agreement to phenomenology.Comment: 4 pages, 1 table and 2 figures. Proceedings of the talk given at the
International Conference on Quantum Chromodynamics, 2-9 July (2005),
Montpellier (France). To be published in Nucl. Phys. B (Proc. Suppl.
Electroweak chiral Lagrangians and the Higgs properties at the one-loop level
In these proceedings we explore the use of (non-linear) electroweak chiral
Lagrangians for the description of possible beyond the Standard Model strong
dynamics in the electroweak sector. Experimentally one observes an approximate
electroweak symmetry breaking pattern .
Quantum Chromodynamics shows a similar chiral structure and, in spite of the
differences (in the electroweak theory is gauged), it
has served for years as a guide for this type of studies. Examples of one-loop
computations in the low-energy effective theory and the theory including the
first vector and axial-vector resonances are provided, yielding, respectively,
predictions for and the oblique parameters
and .Comment: 6 pages, 2 eps figures. Proceedings of the 7th Edition of the
International Workshop on Quantum Chromodynamics -QCD@Work: Interantional
Workshop on QCD, Theory and Experiment- (16-19 June 2014, Giovinazzo, Italy
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