Abstract
A study of the deuteron breakup reaction pd→(pp)n with forward emission of a fast proton pair with small excitation energy Epp< 3 MeV has been performed using the ANKE spectrometer at COSY-Jülich. An exclusive measurement was carried out at six proton-beam energies Tp= 0.6, 0.7, 0.8, 0.95, 1.35 and 1.9 GeV by reconstructing the momenta of the two protons. The differential cross section of the breakup reaction, averaged up to 8° over the cm polar angle of the total momentum of the pp pairs, has been obtained. Since the kinematics of this process is quite similar to that of backward elastic pd→dp scattering, the results are compared to calculations based on a theoretical model previously applied to the pd→dp process.
Highlights
Backward elastic pd → dp scattering at energies of several hundred MeV is one of the simplest hadron–nucleus processes with high transferred momentum
The data allowed us to deduce the three–fold differential cross sections d3σ/(d cos θpcmp · dφcpmp · dEpp), where θpcmp and φcpmp are the polar and azimuthal cm angles of the total momentum of the pp pair, respectively. (The neutron emission angles correspond to 180◦−θpcmp )
We report here the first measurement of the cross section of the pd →n reaction with a fast singlet pp pair emitted in forward direction at beam energies between 0.6 and 1.9 GeV
Summary
Backward elastic pd → dp scattering at energies of several hundred MeV is one of the simplest hadron–nucleus processes with high transferred momentum. At higher energies, where internal momenta above 0.3 GeV/c are probed in the deuteron, the dynamics becomes more complicated, because of a possible excitation of N∗ and ∆ resonances in the intermediate states. These effects are taken into account to some extent in the one–pion–exchange model, but when adding the ONE amplitude, the problem of double counting arises [2,9,10]. The excitation of the ∆(1232) resonance in the intermediate state (∆ mechanism) is explicitly included in a model [3,5], which takes into account coherently ONE and single pN scattering (SS) in a consistent way (Fig. 1). We have measured the differential cross section at six beam energies in the interval 0.6–1.9 GeV, which covers the region of the dip predicted by the ONE+SS+∆ model, thereby probing a wide range of high internal momenta of the NN system (qNN ∼ 0.3–0.6 GeV/c)
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