Dominance of Tensor Correlations in High-Momentum Nucleon Pairs Studied by $(p,pd)$ Reaction

The isospin character of $p\text{−}n$ pairs at large relative momentum has been observed for the first time in the ${}^{16}\mathrm{O}$ ground state. A strong population of the $J,T=1,0$ state and a very weak population of the $J,T=0,1$ state were observed in the neutron pickup domain of ${}^{16}\mathrm{O}(p,pd)$ at 392 MeV. This strong isospin dependence at large momentum transfer is not reproduced by the distorted-wave impulse approximation calculations with known spectroscopic amplitudes. The results indicate the presence of high-momentum protons and neutrons induced by the tensor interactions in the ground state of ${}^{16}\mathrm{O}$.

Figure 1

Schematic view of neutron pickup reaction with coincidence with a proton assuming (a) a $S,T=1,0$ correlated pair and (b) a $S,T=0,1$ correlated pair at the initial states in the $(p,pd)$ reaction.

Figure 2

The excitation energy spectrum of ${}^{16}\mathrm{O}(p,pd)$ for ${\theta }_d=8.6°/{\theta }_p=138.4°$ with the total and individual fitting results shown by the solid and dashed lines, respectively.

Figure 3

Energy sharing spectra of deuterons around 4 MeV in the ${}^{16}\mathrm{O}(p,pd)$ reaction at four different proton angles (a),(b),(c), and (d). The upper abscissas provide scales for the averaged recoil momentum. The curves represent the DWIA calculations with the three different prescriptions, final energy (red-solid), initial energy (blue-dashed), and momentum-final energy (black-dotted).

Figure 4

Ratio of cross section for 2.31 to 3.95 MeV in the sharing energy spectra of protons in the ${}^{16}\mathrm{O}(p,pd)$ reaction with different magnetic rigidity settings of the spectrometer. The vertical and horizontal bars of the data show the statistical error and detector coverage for each setting, respectively. See the text for details.