Complete set of polarization transfer observables for the ${}^{16}$O${(\vec{p},\vec{n})}^{16}$F reaction at 296 MeV and 0 degrees

We report measurements of the cross section and a complete set of polarization transfer observables for the ${}^{16}\mathrm{O}(\vec{p},\vec{n}){}^{16}\mathrm{F}$ reaction at a bombarding energy of $T_p$ $=$ 296 MeV and a reaction angle of ${\theta }_{\mathit{lab}}$ $=$ $0^{\circ }$. The data are compared with distorted-wave impulse approximation calculations employing the large configuration-space shell-model (SM) wave functions. The well-known Gamow-Teller and spin-dipole (SD) states at excitation energies of $E_x$ $\lesssim$ 8 MeV have been reasonably reproduced by the calculations except for the spin-parity $J^{\pi }$ $=$ $2^{-}$ state at $E_x$ $=$ 5.86 MeV. The SD resonance at $E_x$ $\simeq$ 9.5 MeV appears to have more $J^{\pi }$ $=$ $2^{-}$ strength than $J^{\pi }$ $=$ $1^{-}$ strength, consistent with the calculations. The data show significant strength in the spin-longitudinal polarized cross section $I{D}_L\left(0^{\circ }\right)$ at $E_x$ $\simeq$ 15 MeV, which indicates the existence of the $J^{\pi }$ $=$ $0^{-}$ SD resonance as predicted in the SM calculations.

Figure 1

Double-differential cross section spectrum $I$ (top panel), and a complete set of polarization transfer observables $D_{NN}\left(0^{\circ }\right)$ (middle panel) and $D_{LL}\left(0^{\circ }\right)$ (bottom panel) for the ${}^{16}\mathrm{O}(\vec{p},\vec{n}){}^{16}\mathrm{F}$ reaction at $T_p$ $=$ 296 MeV and ${\theta }_{\mathit{lab}}$ $=$ $0^{\circ }$.

Figure 2

Nonspin $I{D}_0$ (unfilled), spin-longitudinal $I{D}_L$ (cross hatched), and spin-transverse $I{D}_T$ (hatched) polarized cross sections for the ${}^{16}\mathrm{O}(\vec{p},\vec{n}){}^{16}\mathrm{F}$ reaction at $T_p$ $=$ 296 MeV and ${\theta }_{\mathit{lab}}$ $=$ $0^{\circ }$.

Figure 3

Polarization transfer $D_{LL}\left(0^{\circ }\right)$ for the ${}^{12}\mathrm{C}(\vec{p},\vec{n}){}^{12}\mathrm{N}(\mathrm{g}.\mathrm{s}.,1^{+})$ (upper panel) and ${}^{12}\mathrm{C}(\vec{p},\vec{n}){}^{12}\mathrm{N}(4.2\mathit{MeV},2^{-})$ (lower panel) reactions at $T_p$ $=$ 296 MeV and ${\theta }_{\mathit{lab}}$ $=$ $0^{\circ }$ [31]. The data are shown by the filled circles and horizontal dashed lines, and the corresponding uncertainties shown by the vertical error bars and horizontal bands. The curves represent the results of the DWIA calculations as a function of $\beta$ as defined in Eq. (7). See the main text for details.

Figure 4

Optimization of the $\beta$ values [see Eq. (7a)] to reproduce the polarization transfer observables $D_{ii}\left(0^{\circ }\right)$ for the ${}^{12}\mathrm{C}(\vec{p},\vec{n}){}^{12}\mathrm{N}(\mathrm{g}.\mathrm{s}.,1^{+})$ and ${}^{12}\mathrm{C}(\vec{p},\vec{n}){}^{12}\mathrm{N}(4.2\mathit{MeV},2^{-})$ reactions at $T_p=296$ MeV and ${\theta }_{\mathit{lab}}=0^{\circ }$ [31]. The vertical line and band represent the averaged value and its uncertainty, respectively.

Figure 5

Spin-longitudinal $I{D}_L$ (top panel), spin-transverse $I{D}_T$ (middle panel), and nonspin $I{D}_0$ (bottom panel) polarized cross sections for the ${}^{16}\mathrm{O}(\vec{p},\vec{n}){}^{16}\mathrm{F}$ reaction at $T_p$ $=$ 296 MeV and ${\theta }_{\mathit{lab}}$ $=$ $0^{\circ }$. The shaded, cross-hatched, hatched, and unfilled regions represent the results of the DWIA calculations for the $J^{\pi }$ $=$ $1^{+}$, $0^{-}$, $1^{-}$, and $2^{-}$ components, respectively. The dashed curves show the total $I{D}_i$ including contributions of up to $J^{\pi }$ $=$ $4^{-}$. The intrinsic widths for the states at $E_x$ $⩾$ 9.5 MeV have been set to $\Gamma$ $=$ 2 MeV. The DWIA results have been convoluted with a Gaussian function with an experimental energy resolution of 700 keV in FWHM.

Figure 6

Same as Fig. 5 but the intrinsic widths for the GT $1^{+}$ states at $E_x$ $⩾$ 7 MeV have been set to $\Gamma$ $=$ 5 MeV. See text for details.