Search results for "Vector"
showing 10 items of 2660 documents
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.
Pion Exchange Current Effects in ν μ + d → μ − +p + p
1986
The effect of pion exchange currents in the process νμ + d → μ− +p + p is estimated using realistic wave functions for the deuteron and closure over the final dinucleon states. Its implications on the determination of axial vector form factor FA(q2) are discussed.
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…
Study of annihilation at rest into ωηπ0
1994
Abstract We have studied p p annihilations at rest in liquid hydrogen into the final state ωηπ 0 where ω decays to π 0 γ . This reaction is dominated by the production of α 0 (980) and contributions from a 2 (1320) and b 1 0 (1235). Upper limits for the production of an axial vector h ′ 1 (1380) meson and vector mesons ω(1390), ω(1600), and φ(1680) decaying to ωη are given. The branching ratio of p p annihilation into ωηπ 0 was determined to be (0.68±0.01±0.05)%.
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.
Design and Calculations for the New ECRIS at KVI
2005
In this paper a brief description is given of the on‐going upgrade of the CAPRICE‐type ECRIS injector of the K=600 AGOR cyclotron at KVI. This upgrade is motivated by the new TRIμP program, which requires a significant increase of available beam intensity by up to two orders in magnitude. The upgrade follows the AECR design of the university of Jyvaskyla, which was originally pioneered at LBNL (USA). We will discuss the mechanical design and magnetic field calculations of the solenoidal and the permanent magnetic hexapole fields.
First Exploration of Neutron Shell Structure below Lead and beyond N=126
2020
The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical r process in producing nuclei heavier than A∼190. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in ^{207}Hg have been probed using the neutron-adding (d,p) reaction in inverse kinematics. The radioactive beam of ^{206}Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of ^{207}Hg marks a first step in improving our…
A simple two-detector method for precision intercomparisons of source strengths
1972
Abstract A two-detector method for comparing source strengths which largely eliminates errors due to uncertainties of geometric character is described. The simplest version of the method is based on the fact that, when a symmetric face-to-face geometry is being used, the change of the counting rate of one detector caused by the change of the position of the source is approximately compensated for by the change of the counting rate of the other detector. In a more versatile geometry, in which the axes of the detectors are slightly misaligned, the sum and the ratio of the two counting rates can be used in a simple manner to virtually eliminate uncertainties due to the shapes and horizontal po…
Effect of the tilt on the gyrotron operation
2013
The effect of the tilt of the electron beam axis on the gyrotron operation is investigated. It is commonly accepted that the tilt deteriorates the efficiency of cylindrical cavity gyrotrons. Our study showed that this deterioration can be mitigated by a proper displacement of the electron beam axis at the entrance. Also, in some cases, when the aftercavity interaction lowers the gyrotron efficiency, the tilt can reduce this interaction and, therefore, slightly increase the efficiency.