K -> pi pi Phenomenology in the Presence of Electromagnetism

We describe the influence of electromagnetism on the phenomenology of K -> pi pi decays. This is required because the present data were analyzed without inclusion of electromagnetic radiative corrections, and hence contain several ambiguities and uncertainties which we describe in detail. Our presentation includes a full description of the infrared effects needed for a new experimental analysis. It also describes the general treatment of final state interaction phases, needed because Watson's theorem is no longer valid in the presence of electromagnetism. The phase of the isospin-two amplitude A_2 may be modified by 50% -> 100%. We provide a tentative analysis using present data in order to illustrate the sensitivity to electromagnetic effects, and also discuss how the standard treatment of epsilon'/epsilon is modified.Comment: 25 pages, 6 figure

Improved Determination of the Electroweak Penguin Contribution to epsilon'/epsilon in the Chiral Limit

We perform a finite energy sum rule analysis of the flavor ud two-point V-A current correlator, Delta Pi (Q^2). The analysis, which is performed using both the ALEPH and OPAL databases for the V-A spectral function, Delta rho, allows us to extract the dimension six V-A OPE coefficient, a_6, which is related to the matrix element of the electroweak penguin operator, Q_8, by chiral symmetry. The result for a_6 leads directly to the improved (chiral limit) determination epsilon'/epsilon = (- 15.0 +- 2.7) 10^{-4}. Determination of higher dimension OPE contributions also allows us to perform an independent test using a low-scale constrained dispersive analysis, which provides a highly nontrivial consistency check of the results.Comment: 17 pages, 4 figures, Revte

La Metodología y la Planificación en un sistema de educación abierta / distancia

Una metodología para establecer y operar un S.E.A.D. es un conjunto estructurado y secuenciado a realizar. Las metodologías cumplen una doble función: sirven para evaluar un S.E.A.D. ya existente. Habría una tercera función que sería la de transformación de un sistema educativo ya existente en un S.E.A.D. Estas metodologías suelen expresarse mediante un modelo normativo que constituye la conjunción teórica de todos los componentes, anticipando la realidad que quiere construirse asegurando el cumplimiento de las funciones de las partes. Ejemplos: la metodología P.A.L.S. de la Open University y el modelo normativo para los cursos de la U.N.A. en Venezuela. Un S.E.A.D. traduce o encarna la política de la institución que lo promueve, depende de la política educativa del país en que se halla; pero un S.E. A.D., además de poseer un carácter remedial, de corrección o supletorio, puede hallar su razón de ser en sí mismo ya que es el instrumento que, dentro de un enfoque de educación permanente, intenta brindar un acceso al saber a un gran número de personas. La determinación de la conveniencia de instaurar un S.E. A.D. viene marcada por el surgimiento de ciertas deficiéncias que aparecen en todo sistema educativo, como puede ser un alto número de sujetos sin oportunidades en una área del saber, o una escasez de docentes en determinada áreas. Estas carencias de todo sistema se convierten en elementos decisivos para la creación de un S.E.A.D. Ahora bien, la programación de un S.E.A.D. requiere una serie de condiciones como sería un sistema de transportes, un sistema de medios de comunicación, la disponibilidad de personal docente entrenado en técnicas de educación abierta / distancia, entre otros. La política de medios decide "el material instruccional" para un S.E.A.D. y puede optar entre dos alternativas: - un medio principal que suele ser el texto impreso acompañado de medios complementarios ; -o bien cuando desaparece la subordinación y se da una igualdad diferenciada de los medios. Finalmente, la política de medios decide la estructura de comunicación (T.V., centros, etc.). Habiendo establecido la finalidad y los medios de un S.E. A.D., se hace necesario precisar la población con la que se va a actuar. La información se obtiene mediante un encuesta aplicada sobre dicha población potencial, con lo que obtenemos el "perfil" del usuario. Por su parte, la política de la institución fija el "perfil del egresado" que es el conjunto de todas las características deseables que habrá de poseer al finalizar los cursos. La estructura organizativa de un S.E. A.D. puede centrarse en diversos modelos: 1. el enfoque de sistemas que organiza según el esquema input proceso-output; 2. el enfoque estructural que organiza sobre la base de áreas y funciones el enfoque por proyectos que crea una estructura ad boc de gran autonomía. Sobre la base de estos enfoques, o combinándolos, se procede a dotar de estructura organizativa a un S.E.A.D.A methodology to set and carry out a S.E.A.D. (System of open and distance education) is a structural and sequenced ensemble of actions to realize. The methodologies accomplish a double function: fust they serve to set-up, plan and organize a new S.E.A.D., and secondly, they serve to evaluate and abready existing S.E.A.D. There could be a third hnction which would be the transformation of an abready existing educational system in a S.E. A.D. These methodologies are usually expressed by means a normative model which constitute the theoretical conjunction of all the components, anticipating the reality which desires to be constructed, ensuring the accomplishment of the functions of the components. For example: the P. A.L.S. methodology of the Open University and the normative model for the courses of U.N.A. in Venezuela. A S.E.A.D. translates or incarnate the policy of the institution which promotes it, depending on the educational policy of the country; moreover, a S.E. A.D., besider possessing a remdial characteristic, of correction and supplemental, the reason for its existence can be found in its own self, since it is the instrument which, within the focus of permanent education, uies to open an acces to knowledge to a great number of persons. The determination of the convenience of restoring a S.E.A.D. is underlined by the arisal of certain defects in the whole educational system, as for example, the incrcased number of subjects without any opportunity in knowledge area, or, lack of teacheis in determined areas, etc. These deficiencies of the whole system are converted into decisive elements for the creation of a S.E.A.D. However, the prograrnming of a S.E.A.D. requires a series of conditions which could be trasnportation system, communication media system, the availability of the teaching force trained in the technics of openldistance education, among others . The policy of the means decide uthe instructional materials for a S.E.A.D. nad can be choose between tow alternatives: - a principal means which is usually a printed text acconpanied by complementary means; - or when subordination disappears and a differentiated equality among the means arises. Finally, the policy of the means decides the communication structure (T.V., centers, etc.) Having established the aims and the means of a S .E. A .D., it is necessary to indicate the population where it has to operate. The information is obtained through a survey applied on said potential population from which a ubirds eyeview~o f the user is obtained. For its side, the policy of institution fmes the "profile of the graduate" which is the totality of all the desired characteristies to be possessed at the end of the courses. The organizational structure of a S .E. A.D. can be centered in various models: I . The approach of the systems which organizes the "input-process-output" scheme. 2. The structural approach which organizes basing on the areas and functions. 3. The approach for projects which create and ad boc structure of great autonomy . On the basis of these approaches or combinating them, one procceds in giving and organizational structure to S.E.A.

Determination of <2pi_{I=2}|Q_{7,8}|K0> in the Chiral Limit

We reconsider the dispersive evaluation of the weak matrix elements in the chiral limit. The perturbative matching is accomplished fully within the scheme dependence used in the two loop weak OPE calculations. The effects of dimension eight (and higher dimension) operators are fully accounted for. We perform a numerical determination of the weak matrix elements using our dispersive sum rules fortified by constraints from the classical chiral sum rules. A careful assessment of the attendant uncertainties is given.Comment: 18 pages, 2 figure

How Magnetic is the Dirac Neutrino?

We derive model-independent, "naturalness" upper bounds on the magnetic moments \mu_\nu of Dirac neutrinos generated by physics above the scale of electroweak symmetry breaking. In the absence of fine-tuning of effective operator coefficients, we find that current information on neutrino mass implies that |\mu_\nu | < 10^(-14) Bohr magnetons. This bound is several orders of magnitude stronger than those obtained from analyses of solar and reactor neutrino data and astrophysical observations.Comment: 4 pages, 3 figures, Majorana case discussion corrected. References updated; replaced to match published versio

Magnetic Moments of Dirac Neutrinos

The existence of a neutrino magnetic moment implies contributions to the neutrino mass via radiative corrections. We derive model-independent "naturalness" upper bounds on the magnetic moments of Dirac neutrinos, generated by physics above the electroweak scale. The neutrino mass receives a contribution from higher order operators, which are renormalized by operators responsible for the neutrino magnetic moment. This contribution can be calculated in a model independent way. In the absence of fine-tuning, we find that current neutrino mass limits imply that $|\mu_\nu| < 10^{-14}$ Bohr magnetons. This bound is several orders of magnitude stronger than those obtained from solar and reactor neutrino data and astrophysical observations.Comment: 3 pages. Talk given at PANIC'0

The leading chiral electromagnetic correction to the nonleptonic Delta I = 3/2 amplitude in kaon decays

In kaon decay, electromagnetic radiative corrections can generate shifts in the apparent Delta I = 3/2 amplitude of order alpha A_0/A_2 ~ 22 alpha. In order to know the true Delta I = 3/2 amplitude for comparison with lattice calculations and phenomenology, one needs to subtract off this electromagnetic effect. We provide a careful estimate of the electromagnetic shift in the amplitude, which shows that it is smaller than naive expectations, with a fractional shift of delta A_2/A_2 = -0.016 +- 0.01.Comment: 13 pages, 5 figures Revised comments and titl

Model-dependent radiative corrections to tau- -> pi- pi0 nu revisited

The long-distance electromagnetic radiative corrections to tau- -> pi- pi0 nu are re-evaluated. A meson dominance model is used to describe the emission of real photons in this decay. Results obtained for the hadronic spectrum and the decay rate in photon inclusive reactions are compared with previous calculations based on the chiral resonance theory. Independent tests in tau -> pi pi nu gamma that can help to validate the predictions of one of the two models are briefly discussed.Comment: 5 pages, 4 figures, talk given by GLC at the 9th International Workshop on Tau Lepton Physics, Pisa (Italy), september 200

Tendencias actuales del pensamiento educacional en los Estados Unidos

Al iniciar este intento de perfilar las tendencias actuales del pensamiento educacional en los EE. UU. nos vemos precisados a señalar que una gran dificultad para llevarlo a cabo radica en el peligro de que el panorama a recomponer a distancia del escenario original vaya a pecar de inexacto. Pero esta no es la dificultad mayor. Más complejo aún es organizar, distribuir las escuelas, en la búsqueda de una mejor visión, bajo esquemas y rótulos que desfiguran o alteran la situación real. Pero no queda otra salida que acomodar, de alguna manera, la realidad al esquema.Universidad Nacional de La Plat