Quantum loops in the Resonance Chiral Theory: improving the vector form factor

Quantum loops in the Resonance Chiral Theory are needed to improve the implementation of non-perturbative QCD. Furthermore, the one-loop computations can predict chiral low-energy couplings at next-to-leading order, a very appealing task. We present a first calculation of the vector form factor of the pion at subleading order in the 1/N_C expansion. From the analysis of the result at large energies we justify the requirement of considering short-distance constraints from form factors with resonances in the final state. The long-distance limit of our results allows to get a next-to-leading order estimate of \ell_6.Comment: Talk given at the International Workshop e+e- Collisions from phi to J/psi, 27th February-2nd March (2006), Novosibirsk (Russia

Present Status of Chiral Perturbation Theory

The basic ideas and methods of chiral perturbation theory are briefly reviewed. I discuss the recent attempts to build an effective Lagrangian in the resonance region and summarize the known large-N_C constraints on the low-energy chiral couplings.Comment: 6 pages. Invited talk at the 10th International Symposium on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2004), Beijing, China, August 29 - September 4, 200

Form-factors and current correlators: chiral couplings L_10(mu) and C_87(mu) at NLO in 1/N(C)

Using the resonance chiral theory Lagrangian, we perform a calculation of the vector and axial-vector two-point functions at the next-to-leading order (NLO) in the 1/N(C) expansion. We have analyzed these correlators within the single-resonance approximation and have also investigated the corrections induced by a second multiplet of vector and axial-vector resonance states. Imposing the correct QCD short-distance constraints, one determines the difference of the two correlators Pi(t) = Pi_VV(t)- Pi_AA(t) in terms of the pion decay constant and resonance masses. Its low momentum expansion fixes then the low-energy chiral couplings L_10 and C_87 at NLO, keeping full control of their renormalization scale dependence. At mu_0=0.77 GeV, we obtain L_10(mu_0) = (-4.4 \pm 0.9)10^{-3} and C_87^r(mu_0)=(3.1 \pm 1.1)10^{-5}

Theoretical overview on tau physics

Precise measurements of the tau lepton properties provide stringent tests of the Standard Model structure and accurate determinations of its parameters. We overview the present status of a few selected topics: lepton universality, QCD tests and the determination of alpha_s, m_s and V_us from hadronic tau decays, and lepton flavor violation phenomena.Comment: Invited talk at the International Workshop on Tau-Charm Physics (Charm2006), Beijing, China, June 5-7, 2006. 8 pages, 2 figure

The Hadronic Light-by-Light Contribution to the Muon Anomalous Magnetic Moment: Where do we stand?

We review the status of the hadronic light-by-light contribution to the muon anomalous magnetic moment and critically compare recent calculations. We also study in detail which momentum regions the pi^0 exchange main contribution originates. We also argue that a_\mu^{light-by-light} = (11 \pm 4) \times 10^{-10} encompasses the present understanding of this contribution and comment on some directions to improve on that.Comment: 16 pages, 9 figure

One-loop Renormalization of Resonance Chiral Theory with Scalar and Pseudoscalar Resonances

The divergent part of the generating functional of the Resonance Chiral Theory is evaluated up to one loop when one multiplet of scalar an pseudoscalar resonances are included and interaction terms which couple up to two resonances are considered. Hence we obtain the renormalization of the couplings of the initial Lagrangian and, moreover, the complete list of operators that make this theory finite, at this order.Comment: 4 pages, no figures. Talk given at the High-Energy Physics International Conference on Quantum Chromodynamics, 2-9 July (2005), Montpellier (France). To appear in the Proceeding

Les Noves tecnologies i l'agricultura. Impacte a Catalunya

L'agricultura ha estat sempre una activitat innovadora per la necessitat de fer servir les millors tecnologies agronòmiques i els millors materials agrícoles per tenir un bon producte i un bon rendiment. Ha estat també una activitat oberta a l'entorn històric. En l'entorn globalitzat actual disposem també d'unes tecnologies noves que tenen un gran impacte sobre les varietats i les tècniques de conreu que es fan servir. Al mateix temps, sobretot a Europa, es busca la manera que el producte tingui el valor afegit més gran possible i per tant es desenvolupen diverses formes de producció que incorporen criteris geogràfics o de tradició, entre d'altres. En un país com el nostre cal trobar la manera que es faci possible la coexistència entre els diferents tipus d'agricultura que permetin respondre als reptes complexos que la nostra societat té davant seu.Agriculture has always been an innovative activity owing to the need to use the best agronomic technologies and the best agricultural materials to obtain good products and good yields. It has also been an activity open to its historic environment. In today’s globalized environment, we also have new technologies that have a great impact on the varieties we use and on cultivation techniques. At the same time, especially in Europe, people are looking for ways to give products the greatest added value so they are seeking to develop different production methods that include geographic or tradition-based criteria, among others. In a country like Catalonia, we must find ways to allow the coexistence of different types of agriculture responding to the complex challenges that our society is facing.La agricultura ha sido siempre una actividad innovadora por la necesidad de usar las mejores tecnologías agronómicas y los mejores materialesagrícolas para tener un buen producto y un buen rendimiento. Ha sido también una actividad abierta al entorno histórico. En el actual entorno globalizado disponemos también de unas tecnologías nuevas que tienen un gran impacto sobre las variedades y las técnicas de cultivo que se usan. Al mismo tiempo, sobre todo en Europa, se busca la manera de que el producto tenga el mayor valor añadido posible y por lo tanto se desarrollan formas diversas de producción que incorporan criterios geográficos o de tradición, entre otros. En un país como el nuestro hay que encontrar la manera de que se haga posible la coexistencia entre los diferentes tipos de agricultura que permitan responder a los retos complejos que nuestra sociedad tiene ante sí

Física i societat a la Catalunya de finals del segle XIX

¿Per què la demanda social respecte a la física es redueix en aquella època a l'astronomia i la meteorologia