Search results for "Tree"

Quantum electrodynamics for vector mesons

2005

Quantum electrodynamics for $\rho$ mesons is considered. It is shown that, at tree level, the value of the gyromagnetic ratio of the $\rho^+$ is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference $M_{\rho^0}-M_{\rho^\pm}\sim 1 {\rm MeV}$ at tree order.

Charm-beauty meson bound states from B(B*)D(D*) and B(B*)D¯(D¯*) interaction

2017

We evaluate the $s$-wave interaction of pseudoscalar and vector mesons with both charm and beauty to investigate the possible existence of molecular $BD$, ${B}^{*}D$, $B{D}^{*}$, ${B}^{*}{D}^{*}$, $B\overline{D}$, ${B}^{*}\overline{D}$, $B{\overline{D}}^{*}$, or ${B}^{*}{\overline{D}}^{*}$ meson states. The scattering amplitude is obtained implementing unitarity starting from a tree level potential accounting for the dominant vector meson exchange. The diagrams are evaluated using suitable extensions to the heavy flavor sector of the hidden gauge symmetry Lagrangians involving vector and pseudoscalar mesons, respecting heavy quark spin symmetry. We obtain bound states at energies above 7 Ge…

The KK¯π decay of the f1(1285) and its nature as a K*K¯ − cc molecule

2016

We investigate the decay of f1(1285)→πKK¯ with the assumption that the f1(1285) is dynamically generated from the K*K¯+cc interaction. In addition to the tree level diagrams that proceed via f1(1285)→K*K+cc→πKK¯, we take into account also the final state interactions of KK¯→KK¯ and πK → πK. The partial decay width and mass distributions of f1(1285)→πKK¯ are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions are significantly different from phase space an…

Time Dependent Hartree-Fock and Beyond

1983

Quantum corrections to the Wigner crystal: A Hartree-Fock expansion

1993

The quantum corrections to the two-dimensional Wigner crystal, for filling \ensuremath{\nu}\ensuremath{\le}1/3, are discussed by using a Hartree-Fock expansion based on wave functions which are (i) related to one another by magnetic translations, (ii) orthonormal, and (iii) strongly localized. Such wave functions are constructed in terms of Gaussians that are localized at the sites of a triangular (Wigner) lattice and have a small overlap c. The ground-state energy per particle is calculated by an expansion in \ensuremath{\surd}\ensuremath{\nu} and in \ensuremath{\delta}\ensuremath{\equiv}${\mathit{c}}^{1/4}$, which is rapidly convergent and stable under the thermodynamical limit. In partic…

On the Multifractal Character of the Lorenz Attractor

1992

A detailed analysis of the Lorenz attractor in connection with generalized dimensions is presented in this work. Different methods have been employed to estimate these dimensions. Two of them are of standard type. A new method, based on the minimal spanning tree of the point distribution, is extensively tested in this work. It turns out that the Lorenz attractor is very appropriate for being analyzed through this technique, which produces a very clean estimate of the extrema scaling indices α min and α max . The different methods give qualitatively the same result: The Lorenz attractor has a multifractal character

Charge Distribution ofPb208and the Difference inρ(r)for Pb and Tl Investigated by by Elastic Electron Scattering

1976

Elastic electron-scattering cross sections from $^{208}\mathrm{Pb}$ have been measured for $0.5 {\mathrm{fm}}^{\ensuremath{-}1}lql2.24 {\mathrm{fm}}^{\ensuremath{-}1}$. The charge distribution for this nucleus is determined by a "model-independent" method; it exhibits a bump in the center of the nucleus which is also a characteristic feature of Hartree-Fock calculations. The influence of the $3s$ protons on $\ensuremath{\rho}(r)$ has been investigated by a difference measurement between lead and thallium isotones.

Lepton-number violation with quasi-Dirac neutrinos

1983

We investigate lepton-number violation in weak interactions with massive Dirac neutrinos. In the framework of a simple $\mathrm{SU}{(3)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ electroweak model we find that neutrinos naturally acquire only Dirac masses at tree level, and for an odd number of lepton families, one neutrino remains massless. After a spontaneous breakdown of symmetry we find that the SU(2)\ifmmode\times\else\texttimes\fi{}U(1) effective theory has lepton-number-violating currents which couple to the standard gauge bosons. Flavorconserving $|\ensuremath{\Delta}l|=2$ processes such as neutrinoless double-$\ensuremath{\beta}$ decay are forbidden in the simplest model,…

FFLO state in 1-, 2- and 3-dimensional optical lattices combined with a non-uniform background potential

2008

We study the phase diagram of an imbalanced two-component Fermi gas in optical lattices of 1-3 dimensions, considering the possibilities of the FFLO, Sarma/breached pair, BCS and normal states as well as phase separation, at finite and zero temperatures. In particular, phase diagrams with respect to average chemical potential and the chemical potential difference of the two components are considered, because this gives the essential information about the shell structures of phases that will occur in presence of an additional (harmonic) confinement. These phase diagrams in 1, 2 and 3 dimensions show in a striking way the effect of Van Hove singularities on the FFLO state. Although we focus o…

The loop-tree duality at work

2014

We review the recent developments of the loop-tree duality method, focussing our discussion on analysing the singular behaviour of the loop integrand of the dual representation of one-loop integrals and scattering amplitudes. We show that within the loop-tree duality method there is a partial cancellation of singularities at the integrand level among the different components of the corresponding dual representation. The remaining threshold and infrared singularities are restricted to a finite region of the loop momentum space, which is of the size of the external momenta and can be mapped to the phase-space of real corrections to cancel the soft and collinear divergences.