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Elastic $α$-$^{12}$C scattering at low energies with the sharp resonant $0_3^+$ state of $^{16}$O

An inclusion of sharp resonant $0_3^+$ state of $^{16}$O and first excited $2_1^+$ state of $^{12}$C in a study of $s$-wave elastic $α$-$^{12}$C scattering at low energies is investigated in an effective Lagrangian approach. The elastic scattering amplitude is parted into two; one is for the sharp resonant $0_3^+$ state of $^{16}$O parameterized by Breit-Wigner formula, and the other is for a non-resonant part of the amplitude parameterized by effective range expansion. In the non-resonant part of the amplitude, a contribution from the $2_1^+$ state of $^{12}$C is included. We discuss a large correlation between a coupling for the $2_1^+$ state of $^{12}$C and an effective range parameter $Q_0$ as well as a necessity of inclusion of a vertex correction for the initial and final $α$-$^{12}$C states. After fixing parameters appearing in the amplitudes by using experimental data, we calculate asymptotic normalization coefficients for ground $0_1^+$ state and first excited $0_2^+$ state of $^{16}$O and compare them to previous results found in literature.