A Precise Measurement of the Neutron Magnetic Form Factor GMn in the Few-GeV2 Region

The neutron elastic magnetic form factor GMn has been extracted from quasielastic electron scattering data on deuterium with the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic coverage of the measurement is continuous from Q2=1 GeV2 to 4.8 GeV2. High precision was achieved by employing a ratio technique in which many uncertainties cancel, and by a simultaneous in-situ calibration of the neutron detection efficiency, the largest correction to the data. Neutrons were detected using the CLAS electromagnetic calorimeters and the time-of-flight scintillators. Data were taken at two different electron beam energies, allowing up to four semi-independent measurements of GMn to be made at each value of Q2. The dipole parameterization is found to provide a good description of the data over the measured Q2 range.Comment: 14 pages, 5 figures, revtex4, submitted to Physical Review Letters, Revised version has changes recommended by journal referee

First measurement of direct f0(980)f_0(980) photoproduction on the proton

We report on the results of the first measurement of exclusive $f_0(980)$ meson photoproduction on protons for $E_\gamma=3.0 - 3.8$ GeV and $-t = 0.4-1.0$ GeV$^2$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the $\pi^+ \pi^-$ channel by performing a partial wave analysis of the reaction $\gamma p \to p \pi^+ \pi^-$. Clear evidence of the $f_0(980)$ meson was found in the interference between $P$ and $S$ waves at $M_{\pi^+ \pi^-}\sim 1$ GeV. The $S$-wave differential cross section integrated in the mass range of the $f_0(980)$ was found to be a factor of 50 smaller than the cross section for the $\rho$ meson. This is the first time the $f_0(980)$ meson has been measured in a photoproduction experiment

Electroproduction of p \pi^{+} \pi^{-} off protons at 0.2<Q^{2}<0.6 GeV^{2} and 1.3<W<1.57 GeV with CLAS

This paper reports on the most comprehensive data set obtained on differential and fully integrated cross sections for the process $e p \to e' p \pi^{+} \pi^{-}$. The data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the so-far unexplored kinematic region of photon virtuality 0.2 $<$ $Q^{2}$ $<$ 0.6 GeV$^{2}$ and invariant mass of the final hadron system $W$ from 1.3 to 1.57 GeV. For the first time, nine independent 1-fold differential cross sections were determined in each bin of $W$ and $Q^{2}$ covered by the measurements. A phenomenological analysis of the data allowed us to establish the most significant mechanisms contributing to the reaction. The non-resonant mechanisms account for a major part of cross-sections. However, we find sensitivity to s-channel excitations of low-mass nucleon resonances, especially to the $N(1440)P_{11}$ and $N(1520)D_{13}$ states in kinematical dependencies of the 1-fold differential cross-sections

A new approach for analysis and evaluation of partial photoneutron reaction cross sections

There are well-known systematic disagreements in partial photoneutron reaction cross sections obtained using quasimonoenergetic annihilation photons in experiments based on neutron multiplicity sorting methods. Using newly proposed criteria we demonstrate that a large part of the systematic uncertainty comes from certain shortcomings of experimental methods of neutron multiplicity sorting. To develop methods of correction of data obtained in experiments a new approach to data evaluation was developed in which a combined model of photonuclear reactions is used to decompose experimental total neutron yield reaction cross sections into partial reaction contributions. Evaluated cross sections of partial photoneutron reactions obtained using this method show a good agreement with results of alternative experiments

Cadmium isotope photodesintigration

Section II. Experimental Investigations of Nuclear Reactions Mechanism

Multinucleon photonuclear reactions on 209 Bi: experiment and evaluation

Section II. Experimental Investigations of Nuclear Reactions Mechanism

Erratum: Photoneutron cross-section measurements in the 209Bi(γ,xn) reaction with a new method of direct neutron-multiplicity sorting [Phys. Rev. C 96, 044604 (2017)]

info:eu-repo/semantics/publishe