Speaker
Dr
Masanori Dozono
(Riken Nishina Center)
Description
The spin-isospin excitation modes in nuclei have been instrumental for
the understanding of nuclear structure for the several decades.
Spin-dipole (SD) $(L=1,S=1,J^{\pi}=0^{-},1^{-},2^{-})$ excitations have
been under extensive theoretical studies.
Isovector $0^{-}$ excitations are of particular interest
since they carry the simplest pion-like quantum number.
The distribution of $0^{-}$ states is expected to reflect pion-like correlations
in nuclei.
Recently, the effects of tensor correlations on the $0^{-}$ excitations
have been investigated by using a self-consistent HF+RPA calculations~\cite{bai2010,bai2011}.
From the calculations, It is found that the tensor correlations produce
a strong hardening (shifting toward higher excitation energy) effect on the collective $0^{-}$ resonance,
and the effect is very sensitive to the magnitude of tensor strength.
Therefore, from the study of $0^{-}$ states,
we are able to pin down the tensor correlation effects.
In spite of its importance, experimental information on $0^{-}$ states is very limited.
We propose a new probe, a parity-transfer reaction $(^{16}{\rm O},^{16}{\rm F})$ for the $0^{-}$ study.
The parity-transfer reaction uses $0^{+} \rightarrow 0^{-}$ transition
as a probe to $0^{-}$ states in nuclei.
This reaction has advantages over other reactions used so far.
In order to confirm its effectiveness, we study the $0^-$ distribution in $^{12}{¥rm B}$
by using the $^{12}{¥rm C}(^{16}{\rm O},^{16}{\rm F})$ reaction at 250MeV/u.
The excitation energy of $^{12}{¥rm B}$ are deduced by means of the missing-mass spectroscopy by using the SHARAQ spectrometer~¥cite{uesaka2008}. The outgoing $^{16}{¥rm F}$ are identified by using the invariant-mass of the decayed $p$ + $^{15}{¥rm O}$ pairs, which are measured at the low-momentum side of the first dipole magnet and the focal plane of the SHARAQ spectrometer.
\bibitem{bai2010} C.~L.~Bai {\it et al.}, Phys. Rev. Lett. {\bf 105}, 072501 (2010).
\bibitem{bai2011} C.~L.~Bai {\it et al.}, Phys. Rev. C {¥bf 83}, 054316 (2011).
\bibitem{uesaka2008} T.~Uesaka {\it et al.}, Nucl. Instrum. Meth. In Phys. Res. {\bf B266}, 4218 (2008).
Primary author
Dr
Masanori Dozono
(Riken Nishina Center)
