Search results for "vector [form factor]"
showing 10 items of 770 documents
Photo- and electroproduction of eta mesons
1995
Eta photo- and electroproduction off the nucleon is investigated in an effective lagrangian approach that contains Born terms and both vector meson and nucleon resonance contributions. In particular, we review and develop the formalism for coincidence experiments with polarization degrees of freedom. The different response functions appearing in single and double polarization experiments have been studied. We will present calculations for structure functions and kinematical conditions that are most sensitive to details of the lagrangian, in particular with regard to contributions of nucleon resonances beyond the dominant $S_{11}$(1535) resonance.
Radiative decay into gamma-baryon of dynamically generated resonances from the vector-baryon interaction
2010
We study the radiative decay into gamma and a baryon of the SU(3) octet and decuplet of nine and ten resonances that are dynamically generated from the interaction of vector mesons with baryons of the octet and the decuplet, respectively. We obtain quite different partial decay widths for the various resonances, and for different charge states of the same resonance, suggesting that the experimental investigation of these radiative decays should bring much information on the nature of these resonances. For the case of baryons of the octet we determine the helicity amplitudes and compare them with experimental data when available.
Two-photon and one-photon–one-vector meson decay widths of thef0(1370),f2(1270),f0(1710),f2′(1525), andK2*(1430)
2010
We calculate the radiative decay widths, two-photon ($\ensuremath{\gamma}\ensuremath{\gamma}$) and one-photon--one-vector meson ($V\ensuremath{\gamma}$), of the dynamically generated resonances from vector-meson--vector-meson interaction in a unitary approach based on the hidden-gauge Lagrangians. In the present paper we consider the following dynamically generated resonances: ${f}_{0}(1370)$, ${f}_{0}(1710)$, ${f}_{2}(1270)$, ${f}_{2}^{\ensuremath{'}}(1525)$, ${K}_{2}^{*}(1430)$, two $\mathrm{\text{strangeness}}=0$ and $\mathrm{\text{isospin}}=1$ states, and two $\mathrm{\text{strangeness}}=1$ and $\mathrm{\text{isospin}}=1/2$ states. For the ${f}_{0}(1370)$ and ${f}_{2}(1270)$ we reproduc…
V P gamma radiative decay of resonances dynamically generated from the vector meson-vector meson interaction
2010
We evaluate the radiative decay into a vector, a pseudoscalar and a photon of several resonances dynamically generated from the vector-vector interaction. The process proceeds via the decay of one of the vector components into a pseudoscalar and a photon, which have an invariant mass distribution very different from phase space as a consequence of the two vector structure of the resonances. Experimental work along these lines should provide useful information on the nature of these resonances.
Photoproduction of theωmeson on the proton near threshold
2015
An experimental study of omega photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The gamma p -> omega p differential cross sections are measured from threshold to the incident-photon energy E-gamma = 1.40 GeV (W = 1.87 GeV for the center-of-mass energy) with 15-MeV binning in E-gamma and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the omega N scattering length alpha(omega p) is provided.
Analytical solution for the solid angle subtended at any point by an ellipse via a point source radiation vector potential
2010
An axially symmetric radiation vector potential is derived for a spherically symmetric point source. This vector potential is used to derive a line integral for the solid angle subtended at a point source by a detector of arbitrary shape and location. An equivalent line integral given previously by Asvestas for optical applications is derived using this formulation. The line integral can be evaluated in closed form for important cases, and the analytical solution for the solid angle subtended by an ellipse at a general point is presented. The solution for the ellipse was obtained by considering sections of a right elliptic cone. The general solution for the ellipse requires the solution of …
Vector meson-baryon dynamics in photoproduction reactions around 2 GeV
2014
We investigate the role of vector mesons and coupled-channel unitarization on photoproduction reactions off the proton at energies around 2 GeV. We explain the sudden drop on the γp → K 0 Σ + cross section, observed recently by the CBELSA/TAPS collaboration, by a delicate interference between amplitudes having K ∗ Λ and K ∗ Σ in- termediate states modulated by the presence of a nearby N ∗ resonance produced by our model, a feature that we have employed to predict its properties. We also show the impor- tance of coupled-channel unitarization in the γp → K ∗ 0 Σ + reaction, measured recently by CBELSA/TAPS and CLAS with conflicting results.
Observation ofη′→ωe+e−
2015
Based on a sample of eta' mesons produced in the radiative decay J/psi -> gamma eta' in 1.31 x 10(9) J/psi events collected with the BESIII detector, the decay eta' -> omega e(+)e(-) is observed for the first time, with a statistical significance of 8 sigma. The branching fraction is measured to be B(eta' -> omega e(+)e(-)) = (1.97 +/- 0.34(stat) +/- 0.17(syst)) x 10(-4), which is in agreement with theoretical predictions. The branching fraction of eta' -> omega gamma is also measured to be (2.55 +/- 0.03(stat) +/- 0.16(syst)) x 10(-2), which is the most precise measurement to date, and the relative branching fraction B(eta' -> omega e(+)e(-))/B(eta' -> omega gamma) is determined to be (7.7…
Higher nucleon resonances in exclusive(γ,πN)reactions on nuclei
1998
We report calculations for exclusive pion photoproduction on nuclei beyond the first resonance region in the distorted wave impulse approximation. The elementary operator contains contributions from the resonances $P_{33}(1232)$, $P_{11}(1440)$, $D_{13}(1520)$, $D_{33}(1740)$, $S_{11}(1535)$, $S_{11}(1650)$, and $F_{15}(1680)$, in addition to the usual Born plus vector meson contributions. It gives a good description of single pion photoproduction data up to about 1.1 GeV. Final state interactions are incorporated via optical potentials and are found to be substantial in the coincidence cross sections, but insensitive to the photon asymmetry. Clear signatures of possible medium modification…
Exclusive Vector Meson Production at the EIC
2020
We discuss how vector meson production at the future Electron Ion Collider can be used to probe non-linear dynamics in heavy nuclei. Additionally, the potential to study the evolution of proton and nuclear geometries with event-by-event fluctuations is illustrated.