Hard breakup of the deuteron into twoΔisobars

Abstract

We study high-energy photodisintegration of the deuteron into two $\ensuremath{\Delta}$ isobars at large center of mass angles within the QCD hard rescattering model (HRM). According to the HRM, the process develops in three main steps: the photon knocks a quark from one of the nucleons in the deuteron; the struck quark rescatters off a quark from the other nucleon sharing the high energy of the photon; then the energetic quarks recombine into two outgoing baryons which have large transverse momenta. Within the HRM, the cross section is expressed through the amplitude of $\mathit{pn}\ensuremath{\rightarrow}\ensuremath{\Delta}\ensuremath{\Delta}$ scattering which we evaluated based on the quark-interchange model of hard hadronic scattering. Calculations show that the angular distribution and the strength of the photodisintegration is mainly determined by the properties of the $\mathit{pn}\ensuremath{\rightarrow}\ensuremath{\Delta}\ensuremath{\Delta}$ scattering. We predict that the cross section of the deuteron breakup to ${\ensuremath{\Delta}}^{++}{\ensuremath{\Delta}}^{\ensuremath{-}}$ is 4--5 times larger than that of the breakup to the ${\ensuremath{\Delta}}^{+}{\ensuremath{\Delta}}^{0}$ channel. Also, the angular distributions for these two channels are markedly different. These can be compared with the predictions based on the assumption that two hard $\ensuremath{\Delta}$ isobars are the result of the disintegration of the preexisting $\ensuremath{\Delta}\ensuremath{\Delta}$ components of the deuteron wave function. In this case, one expects the angular distributions and cross sections of the breakup in both ${\ensuremath{\Delta}}^{++}{\ensuremath{\Delta}}^{\ensuremath{-}}$ and ${\ensuremath{\Delta}}^{+}{\ensuremath{\Delta}}^{0}$ channels to be similar.