Search results for "Nucleon"
showing 10 items of 1041 documents
Comment on ‘‘Multinucleon mechanisms in (γ,N) and (γ,NN) reactions’’
1996
Recently, calculations of (\ensuremath{\gamma},NN) cross sections in the \ensuremath{\Delta}(1232) region have been reported by J. Ryckebusch et al. [Phys. Rev. C 49, 2704 (1994)]. However, these calculations use an unjustified ansatz for the \ensuremath{\Delta} propagation, which leads to an underestimation of the (\ensuremath{\gamma},NN) cross section in the resonance region for quasifree kinematics. \textcopyright{} 1996 The American Physical Society.
Electromagnetic polarizabilities of nucleons bound in 12C and 16O
1992
Abstract The polarizabilities of nucleons imbedded in 12C and 16O nuclei are measured via Compton scattering of 61 and 77 MeV photons, leading to α N = (11.5±0.8±2.1) × 10 −4 fm 3 and β N = (2.5∓0.8∓2.1) × 10 −4 fm 3 in close agreement with the free-nucleon values.
Total photoabsorption cross sections forH1,H2, andHe3from 200 to 800 MeV
1996
The total photoabsorption cross sections for $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, and $^{3}\mathrm{He}$ have been measured for incident photon energies ranging from 200 to 800 MeV. The $^{3}\mathrm{He}$ data are the first for this nucleus. By using the large acceptance detector DAPHNE in conjunction with the tagged photon beam facility of the MAMI accelerator in Mainz, cross sections of high precision have been obtained. The results show clearly the changes in the nucleon resonances in going from $^{1}\mathrm{H}$ to $^{3}\mathrm{He}$. In particular, for the ${\mathit{D}}_{13}$ region the behavior for $^{3}\mathrm{He}$ is intermediate between that for $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, and h…
Three-nucleon mechanisms in photoreactions
2002
The $^{12}$C$(\gamma,ppn)$ reaction has been measured for E$_{\gamma}$=150-800 MeV in the first study of this reaction in a target heavier than $^3$He. The experimental data are compared to a microscopic many body calculation. The model, which predicts that the largest contribution to the reaction arises from final state interactions following an initial pion production process, overestimates the measured cross sections and there are strong indications that the overestimate arises in this two-step process. The selection of suitable kinematic conditions strongly suppresses this two-step contribution leaving cross sections in which up to half the yield is predicted to arise from the absorptio…
Mirror decay of 75Sr
2003
The β-decay of 75Sr to its mirror nucleus 75Rb was studied at the ISOLDE PSB facility at CERN by means of β-delayed γ and proton spectroscopy. The decay Q-value and β-delayed γ intensity were measured for the first time. These results, 10.60±0.22 MeV and 4.5+1.9 -0.7%, together with accurate measurements of the β-decay half-life and β-delayed proton branching ratio yielded the Gamow-Teller strength 0.35±0.05 for the mirror transition. Implications of the results on studies of deformation effects and on the path of the rapid proton capture process are discussed.
Search for supermassive nuclei in nature
1991
We report on a search for supermassive nuclei in nature with masses up to 107 amu. Such exotic nuclei might consist, for example, of stable strange matter, which comprises a mixture of up, down, and strange quarks, or of relic particles from the early Universe. The experiments are based on Rutherford backscattering of heavy ions, preferably238U, from various target samples. The measured parameters of a detected particle are its time-of-flight, scattering angle, and specific ionization. From this information the mass of the target nucleus can be inferred. Upper limits for the abundance of strange supermassive nuclei with massesA−4·102 to 107 amu relative to the number of nucleons were found …
Absorptive effects inK+Λphotoproduction on nucleons and nuclei
1989
Incorporating final state correlation effects, we have reinvestigated the ..gamma.. /sup 1/H..-->..K/sup +/..lambda.. elementary process. Our model not only resolves the persisting trouble of the small KN..lambda.. coupling constant, but also yields agreement with cross section data at higher energies. Using our amplitudes, we calculate angular distributions for the reaction /sup 16/O(..gamma..,K/sup +/)/sub ..lambda..//sup 16/N . While the forward cross section increases with increasing energy, the total cross section is almost constant from E/sub ..gamma../ = 1.2 GeV through 2 GeV, suggesting that rather low photon energies hold promise for exploration of hypernuclear excitations.
Gamow-Teller Transitions Starting from T[sub z] = +3∕2 Nucleus [sup 47]Ti
2011
Gamow‐Teller (GT) transitions are mediated by the στ operator. Owing to its simplicity and also its spin‐isospin nature, GT transitions play key roles in the studies of nuclear structure as well as astro‐nuclear processes. In violent neutrino‐induced reactions at the core‐collapse stage of type II supernovae, Gamow‐Teller (GT) transitions starting from stable as well as unstable pf‐shell nuclei play important roles. We study GT transitions starting from 47Ti in a high‐resolution (3He,t) charge‐exchange reactions at 0° and at an intermediate incident energy of 140 MeV/nucleon at Research Center for Nuclear Physics (RCNP), Osaka. Individual GT transitions up to high excitations were observed.…
Experimental study ofβ-delayed proton decay ofAl23for nucleosynthesis in novae
2011
The $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ and proton decay of $^{23}\mathrm{Al}$ has been studied with an alternative detector setup at the focal plane of the momentum achromat recoil separator MARS at Texas A University. We could detect protons down to an energy of 200 keV and determine the corresponding branching ratios. Contrary to results of previous $\ensuremath{\beta}$-decay studies, no strong proton intensity from the decay of the isobaric analog state (IAS) of the $^{23}\mathrm{Al}$ ground state at ${E}_{x}=7803$ keV in $^{23}\mathrm{Mg}$ was observed. Instead we assign the observed low-energy group ${E}_{p,\mathrm{c}.\mathrm{m}.}=206$ keV to the decay from a state that…
Gamow-Teller Transitions Studied in ([sup 3]He, t) Reaction and Analogous β decay
2010
Due to the simplicity of the στ operator that causes Gamow‐Teller (GT) transitions, they are the most popular nuclear weak process in the Universe. The GT transitions in pf‐shell nuclei, for example, starting from stable Tz = +1 and proton‐rich Tz = +1 nuclei, where Tz = (N−Z)/2, play important roles in the supernova‐explosion or rp‐process nucleosynthesis. In the β‐decay study of pf‐shell nuclei, half‐lives can be measured rather accurately. On the other hand, in a high‐resolution (3He, t) charge‐exchange reaction at 0°, individual GT transitions up to high excitations can be studied. In order to derive reliable GT transition strengths B(GT), we present a unique analysis that combines the …