The reaction pd→(pp)npd\to(pp)n at high momentum transfer and short-range NN properties

A recent cross section measurement of the deuteron breakup reaction $pd\to (pp)(0^\circ)+n(180^\circ)$, in the GeV region in a kinematics similar to backward $pd$ elastic scattering, strongly contradicts predictions of a $pd \to dp$ model based on the one-nucleon exchange, single pN scattering and $\Delta$ excitation mechanisms, and on the wave functions of the Reid soft core and Paris $NN$ potentials. We show within the same model that for the CD Bonn $NN$ potential there is qualitative agreement with the data. It is attributed to a reduction of the one-nucleon exchange at energies above 1 GeV and an increase of the $\Delta(1232)$-isobar contribution, both related to the short-range properties of the wave functions generated by this potential.Comment: 14 pages, Latex, 4 modified figure

3^3He Structure and Mechanisms of p3p^3He Backward Elastic Scattering

The mechanism of $p^3$He backward elastic scattering is studied. It is found that the triangle diagrams with the subprocesses $pd\to ^3$He$\pi^0$, $pd^*\to ^3$He$\pi^0$ and $p(pp)\to^3$He$\pi^+$, where $d^*$ and $pp$ denote the singlet deuteron and diproton pair in the $^1S_0$ state, respectively, dominate in the cross section at 0.3-0.8 GeV, and their contribution is comparable with that for a sequential transfer of a $np$ pair at 1-1.5 GeV. The contribution of the $d^*+pp$, estimated on the basis of the spectator mechanism of the $p(NN)\to ^3$He$\pi$ reaction, increases the $p^3$He$\to ^3$He$p$ cross section by one order of magnitude as compared to the contribution of the deuteron alone. Effects of the initial and final states interaction are taken into account.Comment: 17 pages, Latex, 4 postscript figures, expanded version, accepted by Physical Review

Backward Elastic p3He Scattering at Energies 1 - 2 GeV

The two-body transfer amplitude for the rearrangement process i+(jkl) - j+(ikl) is constructed on the basis of technique of 4-dimensional covariant nonrelativistic graphs. The developed formalism is applied to describing backward elastic $p^3He$ scattering in the energy range 0.5 - 1.7 GeV. Numerical calculations performed using the 5- channel wave function of the $^3He$ nucleus show that the transfer of a noninteracting np- pair dominates and explains satisfactorily the energy and angular dependence of the differential cross section at energies 0.9 - 1.7$GeV. A weak sensitivity to high momentum components of the$~^3He$ wave function in spite of large momentum transfer as well as a very important role of rescatterings in the initial and final states are established.Comment: 7 pages, Latex, 3 Postscript figure

Singlet-to-triplet ratio in the deuteron breakup reaction pd→pnppd\to pnp at 585 MeV

Available experimental data on the exclusive $pd\to pnp$ reaction at 585 MeV show a narrow peak in the proton-neutron final-state interaction region. It was supposed previously, on the basis of a phenomenological analysis of the shape of this peak, that the final spin-singlet $pn$ state provided about one third of the observed cross section. By comparing the absolute value of the measured cross section with that of $pd$ elastic scattering using the F\"aldt-Wilkin extrapolation theorem, it is shown here that the $pd\to pnp$ data can be explained mainly by the spin-triplet final state with a singlet admixture of a few percent. The smallness of the singlet contribution is compatible with existing $pN\to pN\pi$ data and the one-pion exchange mechanism of the $pd\to pnp$ reaction.Comment: 10 pages, Latex, 2 Postscript figure

Spin observables of the reaction pd-3He eta and quasi-bound 3He-eta pole

A formalism for spin observables of the reaction $pd\to ~^3He\eta$ is derived in a model independent way. The general case with a full set of six independent spin amplitudes is studied. Furthermore, approximations by five and four spin amplitudes are investigated in the near threshold region. This region is of great interest to search for a quasi-bound $^3He-\eta$ state, in particular, by measurement of energy dependence of relative phases of s- and p-wave amplitudes. Complete polarization experiments, allowing determination of spin amplitudes, are analyzed. It is shown that measurement of only analyzing powers and spin correlation coefficients hardly allows one to separate the s- and p-wave amplitudes, but additional measurement of polarization transfer coefficients simplifies this problem. Specific observables, given by products of one s- and one p-wave amplitudes, are found. Measurement of these observables will provide new independent information on the $^3He-\eta$ pole position.Comment: 16 pages, Latex. Submitted to Nuclear Physics

Resonance behaviour of the reactions pp → {pp}sπ0 and pd → pdππ in the 1-2 GeV region

Resonance peaks observed in the cross sections of the reaction pp → {pp}sπ0, where {pp}s is the 1S0 state of the proton pair, and pd → pdππ in the GeV region are considered in the framework of mechanisms involving known baryon and two-baryon resonances