$^3$He Structure and Mechanisms of $p^3$He 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. 
Yu. N. Uzikov (JINR, Dubna, Russia), J. Haidenbauer (Forschungszentrum   J\"ulich, Germany)