II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Production cross-section measurement and new-isotope search forvery-neutron-rich RIs produced from 70 Zn beam at 345 MeV/nucleaon
by BigRIPS separator
H. Suzuki,∗1 M. Yoshimoto,∗2 N. Fukuda,∗1 H. Takeda,∗1 Y. Shimizu,∗1 Y. Yanagisawa,∗1 H. Sato,∗1 andK. Yoshida∗120

Production cross section (mb)

We performed production cross-section measurements
and a new-isotope search in the neutron-rich region
with the atomic numbers Z = 12–19, located southeast of 48 Ca in the nuclear chart. The neutron-rich radioactive isotopes (RIs) were produced by the projectile fragmentation of a 600-particle-nA 70 Zn beam at345 MeV/nucleon impinged on a 10-mm-thick Be target
in the BigRIPS separator. Particle identiﬁcation basedon the TOF-Bρ-∆E method1) was performed in the second stage of BigRIPS. Three BigRIPS settings were usedwith 45 S, 43 Si, and 45 Si as centeral particles. The former
two settings were for the cross-section measurements,
and the last one was for the new-isotope search. Theproduction cross sections were deduced from the measured production rates and their transmission eﬃciencies

(a)

-4

10ArCaZ

1410-10

10-12862.7

Ti

Production cross section (mb)

Sc

10P

Cl

K

40

45

50

V

10-8

10-10

10-12

10-14

2012 data
2014 data

45
S setting43
Si setting45

Si setting

2530

35

Mass number

55

60

65

∗2

3.1

3.2

3.3

3.4

References

701) N. Fukuda et al., Nucl. Instrum. Methods Phys. Res. B
317, 323 (2013).
2) O. B. Tarasov, D. Bazin, lise++ site, http://lise.nscl.edu,MichiganStateUniversity .
3) H. Suzuki et al., Nucl. Instrum. Methods Phys. Res. B
317, 756 (2013).
4) B. Mei, Phys. Rev. C 95, 034608 (2017).
5) K. Sümmerer, B. Blank, Phys. Rev. C 61, 034607 (2000).
6) K. Sümmerer, Phys. Rev. C 86, 014601 (2012).

Fig. 1. Measured production cross sections of RIs producedin the 70 Zn + Be reaction at 345 MeV/nucleon with semiempirical cross-section formulae. (a) Results for even-Zisotopes. (b) Results for odd-Z isotopes.
∗13in BigRIPS, which were simulated with lise++ calculations.2) In the simulation, parameters that control themomentum and angular distribution2,3) are not changed
from the default values in the current preliminary analysis.
Figure 1 shows the production cross sections of RIs
obtained in this work (ﬁlled symbols), together withmeasurements in 2012 and 2014 (open symbols). The
solid, dashed, and dotted lines show the cross sections
predicted by the semi-empirical formula FRACS1.1,4)
EPAX2.15,5) and EPAX3.1a.6) Overall, FRACS1.1 best
reproduces the measured cross sections among these formulae; however, around the very-neutron-rich region,
the discrepancy between the measured and predictedcross sections becomes larger. A new isotope, 45 Si,
was discovered in this work, as shown in Fig. 2. One
event was also observed at the location of 46 Si, althoughmore elaborate analysis, such as background removal, isneeded for conﬁrmation as a new isotope. The detailed
analysis is currently in progress.

Al-6

10

2.9

Cr

EPAX3.1a
EPAX2.15
10-14 FRACS1.1(b)

2.8

A/Q

Mg

-4

12
10-6-8Si

16

1010

45Fig. 2. PID plots obtained in the 45 Si setting. Events of a
new isotope, 45 Si, were clearly observed.

SSi

18

RIKEN Nishina Center
Department of Physics, Gifu University-2-1