Ⅱ-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

Gamow-Teller transitions in magic nuclei calculated based on thecharge-exchange subtracted second random phase approximation†
M. J. Yang,∗1 C. L. Bai,∗1 H. Sagawa,∗2,∗3 and H. Q. Zhang∗4experimental data, except for 90 Zr, in which the calculated peak height is approximately two times larger
than the experimental result. We examined the eﬀectof tensor terms of the SAMi-T EDF and found thatthe terms shift the main peaks downward by approximately 1 MeV in 48 Ca, 132 Sn, and 208 Pb; however,they hardly aﬀect 90 Zr. The quenching factor has increased slightly; however these values with the tensor
interactions are still about a half of the experimental
quenching factors. We explored the possibility whether
the tensor force with diﬀerent strengths further enhances the quenching factor of the GT strength. To
this end, we adopt the T21, T44, and T55 EDFs fromthe TIJ family3) with diﬀerent values of of the tensorterms. We realized that none of these three parameter
90Zrsets well described the strength distributions. How1290
12EXPever, Zrthe T55 EDF produces large quenching factors:
48
12Ca SAMi-T w/o
EXP
EXP 25% for 90 Zr, 27% for 132 Sn, and 19%
30% for 48 Ca,
SAMi-T w/i
SAMi-T w/ow/oSAMi-T w/o
208SAMi-T
SAMi-T w/i
SAMi-TInw/i208 Pb, the quenching factors are smaller,Pb.
for
8SAMi-T w/i
SAMi-T w/o
SAMi-T w/o
8SAMi-T w/i
8 which isSAMi-Tw/i
relatedto the insuﬃcient cutoﬀ energy of 2p2h conﬁgurations.
4
Further we studied the role of tensor interactions(b)4
4in quenching with the parameter
sets, i.e., SGII +(b)
(a)
Te1,
SGII+
Te2,and
SGII+
Te3
keeping the cen00
5
10
15
20
25
25
tral
partunchanged.
Withtheseparametersets, we00
E (MeV)
0
5
10 x
15
20
250 found 5that the10 tensor
15 interactions
2025
signiﬁcantly
aﬀect
Ex(MeV)Ex(MeV)the strength distributions of GT peaks, i.e., strong ef9060
Zr
fect on the spreading of the strength distribution and208
12Pb
6050EXP
shift208ofthe excitation energy. Among the parameters,
50132Pbw/o
Sn SAMi-TEXP
SGII+Te1 best reproduces the GT strength distriSAMi-T w/i
50
SAMi-T w/o40
SAMi-Tw/o
EXP
40
SAMi-T EXPw/ibutions
inthe four nuclei. While the SGII + Te1 and8SAMi-Tw/i
SAMi-T w/o
SAMi-T
SAMi-Tw/ow/o40
SAMi-Tw/i
SAMi-T
SAMi-Tw/iw/i
SGII+Te3EDFs,
in which the strengths of the tripletSAMi-T w/o30
30
SAMi-T w/o
SAMi-T term
w/i
SAMi-T w/ioddtensor
aresigniﬁcantly diﬀerent even in the3020sign,
producelargequenchingfactors similar to those420(b)
20 of T55. In addition, as SGII is optimized excluding(d)
10J2 terms, we performed the calculations
in which the10(d)(c)
10200terms
areexcluded
inHF
andSSRPA
for the SGII
J
2500
1055
10151520 2025 2500 EDF. The calculations indicate that the exclusion of(MeV)
EE(MeV)
0510 x x
15200510152025Ex(MeV)
Ex(MeV)
from the momentum dependent inJ2 terms originatedFig. 1. GT− strength distributions of 48 Ca [panel (a)], andteractions generates larger quenching factors, close to208 60
Pb [panel208(b)]calculated
withSAMi-Tby
RPA(dashexperiments. However, the systematical description ofPblines)
the strength distributions in the four nuclei has not im50 and SSRPA (solid lines) with or without tensor
terms. The red lines EXP
represent SAMi-T without tensor
proved much compared to those with the J2 terms. It isSAMi-T w/o
40 labeled w/o,
SAMi-Tterms
andw/ithe blue lines represent SAMi-T
still a challenge to describe realistic strength distribuSAMi-T w/owith tensor terms
labeledw/i. Experimental data are
SAMi-Tw/itions and large quenching factors with Skyrme EDFs.
30(c)
(a)
20

GT strength(MeV-1)

-1-1

20

GT strength(MeV-1)

EXP
SAMi-T w/o
SAMi-T w/i
SAMi-T w/o
SAMi-T w/i

GT strength(MeV )20-1 -1
GT strength(MeV) )-1
GT strength(MeV(a)GT strength(MeV )EXPSAMi-T w/o
SAMi-T w/i
SAMi-T w/o
SAMi-T w/i

GT strength(MeV) -1)
GT strength(MeVWe studied the Gamow-Teller (GT) transitions infour magic nuclei, i.e., 48 Ca, 90 Zr, 132 Sn, and 208 Pb
based on a self-consistent Hartree-Fock (HF) + subtracted second random phase approximation (SSRPA)
model with diﬀerent Skyrme energy density functionals (EDFs). The SSRPA model describes systematically and quantitatively the GT strength distribution
in the four nuclei better than the RPA model.
The results of SAMi-T1) with and without tensor
terms are shown in Fig. 1. Speciﬁcally, SGII2) andSAMi-T EDFs well reproduce the strength distributions of the main GT peaks in terms of the excitation energy and peak height in comparison with thetaken from Ref. 4) for 48 Ca and Ref. 5) for 208 Pb.

(c)

†∗1
∗220

∗3
∗4References

20

Condensed from the article in Phys. Rev. C 106, 014219(2022)(d)10College of Physics, Sichuan University
RIKEN Nishina Center0Center 0for Mathematics
and510 Physics,15 University
20 of Aizu
25Ex(MeV)
China Institute of Atomic Energy

1) S. H. Shen et al., Phys. Rev. C 99, 034322 (2019).
2) C. L. Bai et al., Phys. Rev. C 83, 054316 (2011).
3) T. Lesinsky et al., Phys. Rev. C 76, 014312 (2008).
4) K. Yako et al., Phys. Rev. Lett. 103, 012503 (2009).
5) T. Wakasa et al., Phys. Rev. C 85, 064606 (2012).

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