50 research outputs found
SEARCH FOR NARROW ISOVECTOR DIBARYONS CLOSE TO LOW MASSES THRESHOLD
For masses larger than 2 MN + Mπ, narrow peaks in two proton invariant (missing) masses spectra : Mpp (Mx) are now well established. The existence of such narrow peaks is not so unquestionable below 2 MN + Mπ. Tensor analyzing power T20 of the invariant mass Mpp has been studied using the p ([MATH], pp) reaction. Depending on the assumption done for background substraction -a hole or an oscillation may appear at Mpp = 1941 MeV. Additional data are under analysis and will improve the statistics
Eta-N Final State Interaction in incoherent Photoproduction of Eta-mesons from the Deuteron near Threshold
An analysis of incoherent photoproduction of mesons off the deuteron
for photon energies from threshold to 800 MeV is presented. The dominant
contribution, the N-N amplitude, is described within an isobar
model. Effects of the final state interactions in the as well as the
systems are included employing models derived within the
meson-exchange approach. It is found that their consideration is important.
Specifically, due to an interference effect the influence of the final
state interaction is enhanced in the reaction close to
threshold.Comment: 11 pages (LaTeX), 7 postscript figure
Invariant mass distributions for the pp to p p eta reaction at Q=10 MeV
Proton-proton and proton-eta invariant mass distributions and the total cross
section for the pp to pp eta reaction have been determined near the threshold
at an excess energy of Q=10 MeV. The experiment has been conducted using the
COSY-11 detector setup and the cooler synchrotron COSY. The determined
invariant mass spectra reveal significant enhancements in the region of low
proton-proton relative momenta, similarly as observed previously at higher
excess energies of Q=15.5 MeV and Q= 40MeV.Comment: 6 pages, 3 figures, submitted to Eur.Phys. J.
Evidence for a backward peak in the gamma+d->pi^0+d cross section near the eta threshold
High-quality cross sections for the reaction gamma+d->pi^0+d have been
measured using the CLAS at Jefferson Lab over a wide energy range near and
above the eta-meson photoproduction threshold. At backward c.m. angles for the
outgoing pions, we observe a resonance-like structure near E_gamma=700 MeV. Our
model analysis shows that it can be explained by eta excitation in the
intermediate state. The effect is the result of the contribution of the
N(1535)S_11 resonance to the amplitudes of the subprocesses occurring between
the two nucleons and of a two-step process in which the excitation of an
intermediate eta meson dominates.Comment: slightly modified title, additional paragraph and a table (Table 2)
added on p. 5; to be submitted to EPJA, 6 pages, 3 figure
Isobaric analogue of the lowest 3/2 state of Ca (populated in Ca(p,p) and (p,) reactions)
Résonances isobariques analogues dans les réactions 66Zn(p, p') 66Zn* et 68Zn(p, p')68Zn*
Excitation functions of inelastic scattering for 66Zn(p, p') 66Zn* and 68Zn(p, p')68Zn* reactions were measured from 2.8 to 4.2 MeV incident energy. Four isobaric analogue resonances were found. The ratios of the inelastic partial widths to the elastic partial widths were determined.Les courbes d'excitation des réactions 66Zn(p,p')66Zn* et 68Zn(p, p')68zn* sont mesurées entre 2,8 et 4,2 MeV d'énergie incidente. Des résonances isobariques analogues sont mises en évidence. Les rapports des largeurs partielles inélastiques aux largeurs partielles élastiques sont déterminés