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Spectroscopic factors are generally quenched relative to the occupancy numbers predicted by the independent particle model(IPM) due to nucleon-nucleon correlations, which is quantified by the reduction/quenching factor Rs. Rs extracted from knock-out reactions were found to be strongly dependent on the isospin asymmetry (ΔS = Sn- Sp / Sp- Sn for neutron/proton removing reaction) [1]. However, Rs deduced from the transfer reactions induced by stable nuclei were found to be independent of ΔS[2]. How about Rs from the transfer reactions of unstable nuclei with larger absolute values of ΔS?
In order to answer this question, a combined experiment with radioactive beams of 15C and 16N was performed at Radioactive Beam Line in Lanzhou (RIBLL) in 2022[3,4]. The differential cross sections of the single-nucleon transfer reactions 15C(p, d)14C, 15C(d, 3He)14B, 16N(p, d) 15N, and 16N(d, 3He)15C were obtained. By comparing the experimental angular distributions to the DWBA theoretical calculations, the spectroscopic factors and the corresponding Rs with ΔS = -19.12-19.86 MeV were extracted. Weak dependencies of Rs on ΔS were found in the present experiment. Note that the recoil target-like light charged particles were measured in coincidence with the projectile-like heavy particle, which clearly exclude effects of other reaction channels. The most important thing is that these different transfer reaction channels were measured in one experiment using the same target, which can reduce the systematic errors of Rs.
A new resonance at about Ex = 6.0 MeV in 14B which may correspond to the 1_2^- state predicted by shell model was observed from the 15C(d,3He)14B reaction[5]. Together with the spectroscopic factors of 1_1^-, 2_1^-, 2_2^- states extracted from the 15C(d,3He)14B reaction, all the spectroscopic factors were normalized according to the sum rule, and the normalization factor was found to be consistent with stable nuclei [2]. The effect of halo structure in 15C on the quenching factors[6] of 15C(d,3He)14B and 15C(p, d)14C was also carefully discussed[7].
[1] J. A. Tostevin, A. Gade, Phys. Rev. C, 2021, 103, 054610.
[2] B. P. Kay, J. P. Schiffer, S. J. Freeman, et al., Phys. Rev. Lett. 2013, 111: 042502.
[3] Hong-Yu Zhu, Jian-Ling Lou, Yan-Lin Ye, et al., Nucl. Sci. Tech., 34 (2023) 159.
[4] H. Y. Ge, J. L. Lou, Y. L. Ye, et al., Nucl. Sci. Tech., Nucl. Instr. Meth. A, submitted.
[5] H. Y Zhu, J. L. Lou, Y. L. Ye, et al., in preparation.
[6] H. Y Zhu, J. L. Lou, Y. L. Ye, et al., Chinese Science Bulletin, accepted.
[7] H. Y Zhu, J. L. Lou, Y. L. Ye, et al., in preparation.
