Search results for "Proton"
showing 10 items of 5886 documents
Polarization-transfer measurement to a large-virtuality bound proton in the deuteron
2017
Possible differences between free and bound protons may be observed in the ratio of polarization-transfer components, $P'_x/P'_z$. We report the measurement of $P'_x/P'_z$, in the $^2\textrm{H}(\vec{e},e^{\prime}\vec{p})n$ reaction at low and high missing momenta. Observed increasing deviation of $P'_x/P'_z$ from that of a free proton as a function of the virtuality, similar to that observed in \hefour, indicates that the effect in nuclei is due to the virtuality of the knock-out proton and not due to the average nuclear density. The measured differences from calculations assuming free-proton form factors ($\sim10\%$), may indicate in-medium modifications.
Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
2014
We present new data for angular distributions and on the cross section ratio of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.
Isomer-tagged differential-plunger measurements in proton-unbound 144Ho
2010
The lifetime of an excited state above a weakly populated isomer in the proton-unbound odd-odd nucleus 144Ho has been measured using the recoil distance Doppler shift method. This measurement represents the first differential-plunger lifetime measurement to utilize recoil-isomer tagging. The first excited I[pi]=(10+) state above the two-quasiparticle [pi]h11/2[circle times operator][nu]h11/2(8+) isomer was determined to have a lifetime of [tau]=6(1)�ps. Potential energy surface calculations, based on the configuration-constrained blocking method, predict the isomeric state to have [gamma]-soft triaxial-nuclear shape with [gamma][approximate]24�. The lifetime of the (10+) state can be unders…
ProjectileΔand target Roper excitation in thep(d,d′)Xreaction
2000
In this paper we compare a model that contains the mechanisms of $\ensuremath{\Delta}$ excitation in the projectile and Roper excitation in the target with experimental data from two ${(d,d}^{\ensuremath{'}})$ experiments on a proton target. The agreement of the theory with the experiment is fair for the data taken at ${T}_{d}=2.3$ GeV. The $\ensuremath{\Delta}$ excitation in the projectile is predicted close to the observed energy with the correct width. The theory, however, underpredicts by about 40% the cross sections measured at ${T}_{d} = 1.6$ GeV at angles where the cross section has fallen by about two orders of magnitude. The analysis done here allows us to extract an approximate st…
Compton scattering by the proton through θcms = 75° and 90° in the Δ-resonance region
1997
Abstract Differential cross sections for Compton scattering by the proton have been measured in the energy interval between 200 and 500 MeV at scattering angles of θcms = 75° and θcms = 90° using the CATS, the CATS/TRAJAN, and the COPP setups with the Glasgow Tagger at MAMI (Mainz). The data are compared with predictions from dispersion theory using photo-meson amplitudes from the recent VPI solution SM95. The experiment and the theoretical procedure are described in detail. It is found that the experiment and predictions are in agreement as far as the energy dependence of the differential cross sections in the Δ-range is concerned. However, there is evidence that a scaling down of the reso…
Direct URCA process in neutron stars with strong magnetic fields
1997
We calculate the emissivity for the direct URCA process in strongly magnetized, degenerate matter in neutron stars, under $\beta $-equilibrium. We show that, if the magnetic field is large enough for protons and electrons to be confined to the ground Landau levels, the field-free threshold condition on proton concentration no longer holds, and direct URCA reactions are open for an arbitrary proton concentration. Direct URCA process leads to an early phase of fast neutron star cooling. This circumstance allows us to constrain the initial magnetic field inside observed pulsars.
First observation of gamma-rays from the proton emitter 171Au
2003
Gamma-rays from the alpha- and proton-unstable nuclide 171Au have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2-) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.
Neutron and proton spectra from the decay ofΛhypernuclei
1997
We have determined the spectra of neutrons and protons following the decay of {Lambda} hypernuclei through the one- and two-nucleon-induced mechanisms. The momentum distributions of the primary nucleons are calculated and a Monte Carlo simulation is used to account for final state interactions. The shape of the proton spectrum is sensitive to the value of {Gamma}{sub n}/{Gamma}{sub p} the ratio of neutron- to proton-induced decay, and the available experimental information favors larger values than those predicted by the one-pion-exchange model. From the spectra we calculate the number of neutrons (N{sub n}) and protons (N{sub p}) per {Lambda} decay and show how the measurement of these qua…
In-beam spectroscopy at the proton-drip line. First observation of excited states in 106Sb and 107Sb
1994
Neutron deficient nuclei close to Sn-100 have been investigated in-beam using the NORDBALL detector array. A target of Fe-54 was bombarded with a beam of Ni-58 at 270 MeV. Evaporation residues were identified by detecting protons and alpha particles in a 4 pi charged particle multi-detector set-up and neutrons in a 1 pi neutron detector wall in coincidence with gamma rays. Excited states of the proton drip line nucleus Sb-106 and of Sb-107 were identified for the first time. The yrast level schemes constructed from gamma-gamma-particle coincidence and gamma-gamma angular correlation analysis are presented and discussed within the framework of the nuclear shell model.
Identification of excited states in119Ba
2000
Excited states have been identified in the very neutron-deficient ${}^{119}\mathrm{Ba}$ nucleus. Two bands have been observed, which are likely to be based on ${h}_{11/2}$ and ${(g}_{7/2}{d}_{5/2})$ neutron orbitals. Despite this being the first observation of excited states in ${}^{119}\mathrm{Ba},$ the bands extend to $(75/2)\ensuremath{\Elzxh}$ and $(79/2)\ensuremath{\Elzxh},$ respectively. The bands have been assigned to ${}^{119}\mathrm{Ba}$ using gamma-recoil and gamma--x-ray coincidences. Several quasiparticle alignments have been identified, involving neutron ${(h}_{11/2}{)}^{2}$ and proton ${(h}_{11/2}{)}^{2}$ aligned configurations. Furthermore, the bands show features which are r…