Search results for "Isobar"
showing 10 items of 210 documents
Energy-density-functional calculations including the proton-neutron mixing
2013
We present results of calculations based on the Skyrme energy density functional including the arbitrary mixing between protons and neutrons. In this framework, single-particle states are superpositions of proton and neutron components and the energy density functional is fully invariant with respect to three-dimensional rotations in the isospin space. The isospin of the system is controlled by means of the isocranking method, which carries over the standard cranking approach to the isospin space. We show numerical results of the isocranking calculations performed for isobaric analogue states in the A=14 and $A=40-56$ nuclei. We also present such results obtained for high-isospin states in …
Dispersion relation analysis of neutral pion photoproduction and electroproduction at threshold
2002
Neutral pion photoproduction and electroproduction at threshold is analyzed in the framework of dispersion relations. For this purpose, we evaluate the real threshold amplitudes in terms of Born contributions and dispersion integrals determined by the imaginary parts of the multipoles of the unitary isobar model (MAID) and the phenomenological partial-wave analysis (SAID). The results show considerable cancellations between Born terms and resonance contributions. Good agreement with the data is found for photoproduction. While our dispersion analysis suggests considerable discrepancies for electroproduction, the present state of the experimental multipole analysis at finite ${Q}^{2}$ does n…
PHOTOPRODUCTION OF η AND η′ MESONS ON THE NUCLEON
2007
The isobar models η-MAID and η′-MAID have been used to analyze new data on quasi-free η photoproduction on the deuteron from Bonn and recent η′ data on the proton from Jlab. In η photoproduction on the neutron a bump around W = 1700 MeV was observed which could possibly arise from a narrow P11 state that is discussed as a non-strange member of the Θ+ antidecuplett. In η′ photoproduction on the proton resonance contributions are found that can be attributed to missing resonances in the energy region around W = 1900 MeV .
The isospin structure of photoproduction of πη pairs from the nucleon in the threshold region
2015
Abstract Photoproduction of πη-pairs from nucleons has been investigated from threshold up to incident photon energies of ≈ 1.4 GeV. The quasi-free reactions γ p → p π 0 η , γ n → n π 0 η , γ p → n π + η , and γ n → p π − η were for the first time measured from nucleons bound in the deuteron. The corresponding reactions from a free-proton target were also studied to investigate final-state interaction effects (for neutral pions the free-proton results could be compared to previous measurements; the γ p → n π + η reaction was measured for the first time). For the π 0 η final state coherent production via the γ d → d π 0 η reaction was also investigated. The experiments were performed at the …
Photon absorption on a proton-proton pair inHe3
1995
We calculate the total cross sections for different multiple transitions in photon absorption in a {sup 1}{ital S}{sub 0} {ital pp} pair embedded in a {sup 3}He nucleus. Employing two models, one involving only nucleon degrees of freedom, the other in addition the {Delta}(1232) isobar, we show that the {Delta} gives important effects even in transitions where the photon cannot couple directly to the isobar.
Multiparticle emission in the decay ofAr31
2014
A multihit capacity setup was used to study the decay of the dripline nucleus Ar-31, produced at the ISOLDE facility at CERN. A spectroscopic analysis of the beta-delayed three-proton decay of Ar-31 is presented for the first time together with a quantitative analysis of the beta-delayed 2p gamma decay. A new method for determination of the spin of low-lying levels in the beta p daughter 30S using proton-proton angular correlations is presented and used to determine that the spin of the 5.2-MeV level is most likely 3(+) with 4(+) also possible. The half-life of Ar-31 is found to be 15.1(3) ms. An improved analysis of the Fermi beta strength including the beta 3p-decay mode gives a total mea…
Opening of the Z=40 subshell gap and the double-beta decay of 100Mo
2002
Abstract Experimental and theoretical study of the β − decay of 100 Nb to the two-quasiparticle states in 100 Mo suggests the opening of the Z =40 subshell gap in the proton pf-0g 9/2 shell for isobars near 100 Mo. Assuming the opening of the Z =40 subshell gap both for 100 Mo and 100 Ru enables the study of the effects of this subshell gap upon the two-neutrino and neutrinoless double-beta-decay rates of 100 Mo to the ground state and excited states in 100 Ru. It is found that the influence of the opening of the Z =40 gap has very minor effects on the beta-decay and double-beta-decay feeding of the 0 + and 2 + states of 100 Ru.
Spectroscopy of nuclei approaching the proton drip-line using a secondary-fragmentation technique with the RISING detector array
2005
An experiment utilizing a double fragmentation reaction was performed to study isobaric analogue states in A similar to 50 nuclei approaching the proton drip-line. gamma-ray spectroscopy will be used to identify excited states in the neutron-deficient nuclei produced in the second fragmentation reaction. Excited state level schemes will be obtained, through comparison with states in their well-known mirror partners, along with information on Coulomb effects through measurements of the Coulomb energy differences between isobaric analogue excited states. The validity of isospin symmetry for nuclei approaching the proton drip-line can also be investigated and the information gained will aid in…
Polarized structure functions of the nucleon in the resonance region
2000
Abstract We present predictions for the spin structure functions of the proton in the framework of a unitary isobar model for one-pion photo- and electroproduction. Our results are compared with recent experimental data from SLAC. The first moments of the calculated structure functions fullfil the Gerasimov-Drell-Hearn and Burkhardt-Cottingham sum rules within an error of typically 5–10%.
Two-proton decay of the isobaric analogue state of Ar-31
1998
8 pages, 1 table, 4 figures.-- Journal issue title: "Nucleus-Nucleus Collisions".