Nuclear reaction cross-section measurements in mirror nuclei ⁷Li and ⁷Be using Active-Target Time Projection Chamber.

The mirror nuclei ⁷Li and ⁷Be, characterized by α + t and α + ³He cluster structures respectively, provide a compelling system to study the interplay between mean-field and cluster dynamics [1]. Despite structural similarities, they exhibit subtle differences in excitation spectra and reaction behavior, offering insights into the effects of proton-neutron asymmetry and guiding the refinement of nuclear models [2,3].

These nuclei also play a key role in Big Bang Nucleosynthesis, where the overproduction of ⁷Li in models compared to observed abundances — the "lithium problem" — remains unresolved [4,5]. Understanding their internal structure and reaction cross sections is essential for improving astrophysical reaction rate predictions.

This work presents an experiment using the Active-Target Time Projection Chamber (AT-TPC) [6] and HELIOS solenoid with ⁷Li and ⁷Be beams on an active deuterium target at Argonne’s RAISOR facility. Preliminary results on differential cross sections from (d,d), (d,d′), and related channels will be discussed.

[1] I. Lombardo and D. Dell’Aquila, La Rivista del Nuovo Cimento 46 (2023) 521-618.

[2] N. Roshanbakht and M. Shojae, Eur. Phys. J. A 54 (2018) 134.

[3] D. Tao, B. Zhou, S. Wang and Y. Ma, Phys. Rev. C 111 (2025) 014323.

[4] T. Yeh, K. Olive and B. Fields, JCAP 03, (2021) 046.

[5] C.A. Bertulani and T. Kajino, Progress in Particle and Nuclear Physics 89 (2016) 56-100.

[6] J. Bradt et al., Nuclear Inst. and Methods in Physics Research, A 875 (2017) 65-79.