Search results for "Field theory"
showing 10 items of 1188 documents
Universality of the rho-meson coupling in effective field theory
2004
It is shown that both the universal coupling of the rho-meson and the Kawarabayashi-Suzuki-Riadzuddin-Fayyazuddin expression for the magnitude of its coupling constant follow from the requirement that chiral perturbation theory of pions, nucleons, and rho-mesons is a consistent effective field theory. The prerequisite of the derivation is that all ultraviolet divergences can be absorbed in the redefinition of fields and the available parameters of the most general effective Lagrangian.
Kaon Photo- and Electroproduction on Nucleons
1995
We extend previous models of kaon photo- and electroproduction in order to include all six isospin channels. It is found that the inclusion of the few available data for the reactions γp → K 0 Σ − in the fit leads to drastically reduced Born coupling constants g Λ and g Σ . The result suggests the need to include hadronic form factors in a gauge invariant fashion. It is also shown that the K 0 form factor can be seen in K 0 Λ electroproduction.
Crystal Fields in PrX3 (X=In, Tl, Pb, Sn) Intermetallic Compounds with Cu3Au Structure
1977
We have determined the crystal field splittings of Pr3+ in PrIn3, PrTl3, PrPb3, and PrSn3 by inelastic neutron scattering. The values of the deduced crystal field parameters are found to depend strongly on the constituent X, though all systems have nonmagnetic ground-states. The line widths in the different systems are compared.
Crystal field splitting of some rare earth intermetallic compounds with Cu3Au structure
1980
Inelastic neutron scattering studies were performed in the paramagnetic phases of several rare earth compounds that crystallize in the cubic Cu3Au structure: ErPb3, ErTl3, ErIn3, HoPb3, HoTl3, HoIn3, PrSn3, PrPb3, PrTl3, PrIn3, CeIn3, La1−c Pr c Tl3, and Pr(In0.5Tl0.5)3. The energies, widths and intensities of the crystal field excitations are determined and discussed in terms of interactions between the rare earth ions. Variations of the crystal field parameters are observed across the series.
s-wave charmed baryon resonances from a coupled-channel approach with heavy quark symmetry
2009
We study charmed baryon resonances which are generated dynamically within a unitary meson-baryon coupled channel model that treats the heavy pseudoscalar and vector mesons on equal footing as required by heavy-quark symmetry. It is an extension of recent SU(4) models with t-channel vector meson exchanges to a SU(8) spin-flavor scheme, but differs considerably from the SU(4) approach in how the strong breaking of the flavor symmetry is implemented. Some of our dynamically generated states can be readily assigned to recently observed baryon resonances, while others do not have a straightforward identification and require the compilation of more data as well as an extension of the model to d-w…
Limit on the production of a light vector gauge boson in $\phi $ mesondecays with the KLOE detector
2012
We present a new limit on the production of a light dark-force mediator with the KLOE detector at DAPHNE. This boson, called U, has been searched for in the decay phi --> eta U, U --> e+ e-, analyzing the decay eta --> pi0 pi0 pi0 in a data sample of 1.7 fb-1. No structures are observed in the e+e- invariant mass distribution over the background. This search is combined with a previous result obtained from the decay eta --> pi+ pi- pi0, increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of alpha'/alpha < 1.7x10^-5 for 30<M_U<400 MeV and alpha'/alpha < 8x10^-6 for the sub-region 50<M_U<210 MeV. This…
Software Modernization and Replacement Decision Making in Industry: A Qualitative Study
2006
Software modernization and replacement decisions are crucial to many organizations. They affect greatly to the success and well being of the organizations and their people. The decisions like that are usually presumed to be rational and based on facts. These decisions and how they are made tell much about the decision makers and the decision making tools available to them. Interviews of 29 software modernization decision makers or senior experts were analyzed in order to find out how the decisions were made and what models and tools were used. It turned out that decisions are not as rational as supposed. Intuition is the dominant factor in decision making. Formal software engineering orient…
Mass and width of the Delta resonance using complex-mass renormalization
2016
The pole mass and width of the Delta resonance are calculated in the relativistic chiral effective field theory approach. We choose a systematic power-counting procedure by applying the complex-mass scheme (CMS).
Quantum kinetic theory for fermions in temporally varying backrounds
2008
We derive quantum kinetic equations for fermions in a homogeneous time-dependent background in presence of decohering collisions, by use of the Schwinger-Keldysh CTP-formalism. The quantum coherence (between particles and antiparticles) is found to arise from new spectral solutions for the dynamical 2-point correlation function in the mean field limit. The physical density matrix $\rho$ and its dynamics is shown to be necessarily dependent on the extrenous information on the system, and expressions that relate $\rho$ to fundamental coherence functions and fermionic particle and antiparticle numbers are derived. For an interacting system we demonstrate how smooth decoherence effects are indu…
Kinetic transport theory with quantum coherence
2008
We derive transport equations for fermions and bosons in spatially or temporally varying backgrounds with special symmetries, by use of the Schwinger-Keldysh formalism. In a noninteracting theory the coherence information is shown to be encoded in new singular shells for the 2-point function. Imposing this phase space structure to the interacting theory leads to a a self-consistent equation of motion for a physcial density matrix, including coherence and a well defined collision integral. The method is applied e.g. to demonstrate how an initially coherent out-of-equlibrium state approaches equlibrium through decoherence and thermalization.