Search results for "Observables"
showing 10 items of 31 documents
Semileptonic decaysΛc+→Λℓ+νℓ(ℓ=e,μ)in the covariant quark model and comparison with the new absolute branching fraction measurements of Belle and BES…
2016
We present precise theoretical predictions for the absolute branching fractions of ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}(\ensuremath{\ell}=e,\ensuremath{\mu})$ decays in the covariant confined quark model. This study is motivated by two recent and accurate measurements of the absolute branching fractions of ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{e}^{+}{\ensuremath{\nu}}_{e}$ by the Belle Collaboration at the KE…
Pion Photo- and Electroproduction on the Proton
1999
Using a unitary isobar model a new operator for pion photo- and electroproduction has been developed for nuclear applications at photon equivalent energies up to 1 GeV. The model contains Born terms, vector mesons and nucleon resonances (P 33(1232), P 11(1440), D 13(1520), S 11(1535), F 15(1680), and D 33(1700)). Within this model we have obtained good agreement with the experimental data for pion photo- and electroproduction on the nucleon for both differential cross sections and polarization observables.
Dispersion theoretical analysis of the nucleon spin polarizabilities
1999
The spin polarizabilities of the nucleon have been calculated from pion photoproduction data using forward dispersion relations. The feasibility of an experimental determination of these structure constants is discussed by focusing on polarization observables of the reaction \( \vec{\gamma }\vec{p} \to \gamma p \)→ γ p.
Polarization observables for elastic electron scattering off a moving nucleon
2019
General expressions for all parity-conserving polarization observables of elastic electron-nucleon scattering in the one-photon exchange approximation are derived for a general frame of reference, i.e.\ not assumming scattering off a nucleon at rest and not specializing to a specific system of coordinates. Essentially, the given expressions are also valid for the inverse process, i.e.\ nucleon scattering off electrons.
Role of pion exchange inηmeson photoproduction on the deuteron
2015
Incoherent $\ensuremath{\eta}$ photoproduction on the deuteron is studied, with the main emphasis on the role of final-state interactions. In addition to the previously studied mechanisms of $NN$ and $\ensuremath{\eta}N$ rescatterings, the role of an intermediate pion exchange is considered in detail, where first a pion is photoproduced on one nucleon and then rescatters into an $\ensuremath{\eta}$ meson on the other, the spectator nucleon. It is found that the role of this pion-mediated contribution is comparable in size to that of $\ensuremath{\eta}N$ rescattering. Results for total and semi-inclusive differential cross sections and associated polarization observables are presented. In pa…
Photoproduction of η and η′ mesons with EtaMAID
2016
The unitary isobar model EtaMAID has been updated with an extended list of nucleon resonances, fitted to recent and new data for differential cross sections and polarization observables. The nonresonant background is described by Regge trajectories of ω,ρ and a 1 , b 1 mesons and in addition Regge cuts, where vector and axial vector mesons are exchanged together with Pomeron and f 2 mesons.
General formulae for polarization observables in deuteron electrodisintegration and linear relations
1993
Formal expressions are derived for all possible polarization observables in deuteron electrodisintegration with longitudinally polarized incoming electrons, oriented deuteron targets and polarization analysis of outgoing nucleons. They are given in terms of general structure functions which can be determined experimentally. These structure functions are Hermitean forms of theT-matrix elements which, in principle, allow the determination of allT-matrix elements up to an arbitrary common phase. Since the set of structure functions is overcomplete, linear relations among various structure functions exist which are derived explicitly.
Measurement of trilinear gauge boson couplings WWV, (V Z,gamma) in e(+)e(-) collisions at 189 GeV
2001
Measurements of the trilinear gauge boson couplings WWgamma and WWZ are presented using the data taken by DELPHI in 1998 at a centre-of-mass energy of 189 GeV and combined with DELPHI data at 183 GeV. Values are determined for Delta(g_1^Z) and Delta(kappa_gamma), the differences of the WWZ charge coupling and of the WWgamma dipole coupling from their Standard Model values, and for lambda_gamma, the WWgamma quadrupole coupling. A measurement of the magnetic dipole and electric quadrupole moment of the W is extracted from the results for Delta(kappa_gamma) and lambda_gamma. The study uses data from the final states jjlv, jjjj, lX, jjX and gammaX, where j represents a quark jet, l an identifie…
Regge phenomenology in π0 and η photoproduction
2017
The $\ensuremath{\gamma}N\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}N$ and $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\eta}N$ reactions at photon beam energies above 4 GeV are investigated within Regge models. The models include $t$-channel exchanges of vector ($\ensuremath{\rho}$ and $\ensuremath{\omega}$) and axial-vector (${b}_{1}$ and ${h}_{1}$) mesons. Moreover, Regge cuts of $\ensuremath{\rho}\mathbb{P},\phantom{\rule{0.28em}{0ex}}\ensuremath{\rho}{f}_{2},\phantom{\rule{0.28em}{0ex}}\ensuremath{\omega}\mathbb{P}$, and $\ensuremath{\omega}{f}_{2}$ are investigated. A good description of differential cross sections and polarization observables at photon beam energies fr…
Comparison of theory and experiment
1991
In this section we are finally going to confront experimental data on total cross section, angular distributions and polarization observables with theoretical results in order to establish the present status of our knowledge of this important process. We hope this will enable us to set directions and guidelines for future experimental and theoretical studies, which kind of experiments are needed and what accuracy should be aimed for, where theoretical studies should be extended, on what they should focus and whether some basic assumptions need to be modified. For the comparison we shall use mostly the data of experiments selected in sections 6.3 and 6.4, the relative quantities and the best…