New data on T20 in inclusive deuteron breakup at 9 GeV/c on protons and correlation between polarization observables

Abstract

Experiments probing the deuteron structure at short distances with smooth transition to the intermediate and large distances provide a basis for crucial tests of the modern QCD‐motivated theory of strong interactions. Such data are particularly important when the internal momentum is too large to allow separate identities for the nucleons in the deuteron. The very notion of the wave function is not defined in this region at all. Progress has been achieved1,2 especially in the measurement of cross section data and polarization observables for the inclusive deuteron breakup A(d,p)X for beam momenta up to 9 GeV/c (Fig. 1). The main results are as follows: (1) the empirical momentum density (EMD) of the nucleon in the deuteron is almost independent of the deuteron energy, of the target and of the type of the inclusive breakup reaction (see Fig. 1b and refs.1,2). (2) Polarization observables are also largely independent of the target and initial energy up to 9 GeV/c, as follows from comparison of our new data with data of ref.2 (Fig. 1a,c,d). (3) Impulse Approximation (IA) predictions are in agreement with all data sets only for k≤150 MeV/c; a drastic disagreement is seen beyond this region. More complicated models, taking into account various additional contributions to the reaction mechanism, or ‘‘relativization effects,’’ result in a partial success for a given observable, but not for the whole set of observables (Fig. 1,2 and ref.3; see also references therein).