II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Study of the 9 C proton breakup reaction
A. I. Chilug,∗1,∗2,∗3 V. Panin,∗4 L. Trache,∗1 D. State,∗1,∗2 I. C. Stefanescu,∗1,∗2 J. Tanaka,∗3 H. Otsu,∗3T. Motobayashi,∗3 A. Spiridon,∗1 and T. Uesaka∗3 for HI-p Collaboration

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The 9 C proton breakup reaction was studied during
the SAMURAI29 experiment at RIKEN. The reaction
was studied by two methods: Coulomb dissociation andnuclear breakup. The physics goal of the experiment
was to evaluate the astrophysical S18 -factor of the inverse process, the 8 B(p, γ)9 C, at energies relevant forastrophysics.
The SAMURAI29 experiment is the first performed
among a series of 4 experiments with proton-richsecondary beams and was carried out with a 160MeV/nucleon 9 C beam produced from an 18 O primarybeam, at the F13 focal plane using the SAMURAI magnetic spectrometer. The whole experimental setup isdetailed in Ref. 1) and in Ref. 2). The detection system was prepared to ensure the inclusive and exclusive
measurements of the 9 C breakup reaction. Therefore,a silicon GLAST-type detector system and a set of two
new drift chambers (PDC1 and PDC2) were used to detect the protons produced in the breakup. Both systems
were used for the first time during the experiment.
The silicon detectors, the signals of which were processed using a combination of HINP16 electronics andthe new Dual-Gain Preamplifiers developed by theRIKEN-ATOMKI collaboration,3) enabled the simultaneous detection of the proton and 8 B from the reaction.
Therefore, they cover a large dynamic energy range, as
shown in Fig. 1. Having these tracking detectors together with other SAMURAI standard detectors enabled

proton40Counts

359C unreacted
beam

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Fig. 1. Energy deposited by the proton and 8 B recorded simultaneously in the first layer of the silicon detector.
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PDC_X [mm]Fig. 2. Protons tracked in the proton drift chambers (PDCs).

the reconstruction of the proton momentum distribution, which provides information on the shell occupiedby the removed proton in 9 C.
A serious complication in the analysis is the background from the interaction of the beam particles withthe experimental detectors, which must be excluded
from the events. One example is the protons producedin the plastic scintillator bars of the HODF, which weredetected in the PDCs. In Fig. 2, the red dots indicate theprotons produced in the target with the condition of coincident proton signals in the silicon detectors, whereas
the events marked with the black box area in the figure
are protons produced in the HODF detector.
The following steps have been achieved so far in thedata analysis.
(1) The one-proton removal channel from 9 C nucleus
is clearly separated in the data.
(2) With the tracked positions in the silicon detectors
placed after the target, it was possible to reconstruct the reaction vertex.
(3) The proton and 8 B momentum distributions weredetermined.
(4) The Coulomb dissociation yield of the 9 C breakup
as a function of the relative energy between theproton and 8 B was obtained.

820500Further analysis of the experimental data is inprogress.
References

1) A. I. Chilug et al., RIKEN Accel. Prog. Rep. 52, 27 (2019).
2) A. I. Chilug et al., AIP. Conf. Proc. 2076, 060001 (2019).
3) V. Panin et al., RIKEN Accel. Prog. Rep. 51, 148 (2018).

Department of Nuclear Physics, IFIN-HH
Doctoral School of Physics, University of Bucharest
RIKEN Nishina Center
GSI Helmholtzzentrum fur Schwerionenforschung GmbH- 11 -1