repositories = "DIAL - Dépôt Institutionnel de l'Académie Louvain" > : "UCL - SC/PHYS - Département de physique"

Found 701 documents, displaying page 2 of 71

Resonance propagation and threshold singularities

Description : We consider the problem of propagation of an unstable particle in the framework of Quantum Field Theory. Using unitarity, we show that a real renormalization constant free of threshold singularities naturally arises. Comment: 5 pages, no figures, revtex
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Trace anomalies and the Delta I = 1/2 rule

Description : Trace Anomaly Dominance in weak $K$-decays successfully reproduces the $\Delta I = {1\over 2}$ selection rule results, as observed in $K_S \to \pi\pi, K_L \to \pi\pi\pi, K_S \to \gamma\gamma$ and $K_L \to \pi^0 \gamma\gamma$. Comment: 10 pages, no figure
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Masses and widths of the rho+-,0 (770)

Description : Isospin violation in the $\rho(770)$ mass and width is considered within the $S$ matrix approach using combined fits to the $e^+e^- \to\pi^+\pi^-$ and $\tau^- \to \nu_{\tau}\pi^-\pi^0$ data performed by the ALEPH collaboration. We show that the pole position following from the parameters obtained fr...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Analytical behavior of positronium decay amplitudes

Description : Positronium annihilation amplitudes that are computed by assuming a factorization approximation with on-shell intermediate leptons do not exhibit good analytical behaviour. Using dispersion techniques, we find new contributions that interfere with the known results to restore analytical properties. ...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Parapositronium decay and dispersion relations

Description : Positronium decay rates are computed at the one-loop level, using convolution-type factorized amplitudes. The dynamics of this factorization is probed with dispersion relations, showing that unallowed approximations are usually made, and some ordre alpha^2 corrections missed. Further, we discuss the...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Binding energy corrections in positronium decays

Description : Positronium annihilation amplitudes that are computed by assuming a factorization approximation with on-shell intermediate leptons, do not exhibit good analytical behavior. We propose an ansatz which allows to include binding energy corrections and obtain the correct analytical and gauge invariance ...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

On electric fields in low temperature superconductors

Description : The manifestly Lorentz covariant Landau-Ginzburg equations coupled to Maxwell's equations are considered as a possible framework for the effective description of the interactions between low temperature superconductors and magnetic as well as electric fields. A specific experimental set-up, involvin...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Scaling fields in the two-dimensional Abelian sandpile model

Description : We consider the isotropic two-dimensional abelian sandpile model from a perspective based on two-dimensional (conformal) field theory. We compute lattice correlation functions for various cluster variables (at and off criticality), from which we infer the field-theoretic description in the scaling l...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

A New basis for QED bound state computations

Description : A simple method to compute QED bound state properties is presented, in which binding energy effects are treated non-perturbatively. It is shown that to take the effects of all ladder Coulomb photon exchanges into account, one can simply perform the derivative of standard QED amplitudes with respect ...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Soft photon spectrum in orthopositronium and vector quarkonium decays

Description : QED gauge invariance, when combined with analyticity, leads to constraints on the low energy end of the emitted photon spectra. This is known as Low's theorem. It is shown that the Ore-Powell result, as well as further developments for the orthopositronium differential decay rate, are in contradicti...
Repository : DIAL - Dépôt Institutionnel de l'Académie Louvain
Language(s) : English

Found 701 documents, displaying page 2 of 71