Speaker
Description
The emergence of cluster correlations in finite quantum many-body systems is a fundamental topic in nuclear physics. Previous studies have demonstrated the presence of $ \alpha $-clusters in the nuclear surface of $ \mathrm{Sn} $ isotopes [1]. In the present study, we focus on the hypothesized correlation between the $ \alpha $-cluster formation probability and the $ Q_{\alpha} $ value. In the context of $ \alpha $-decay, the Geiger-Nuttall law describes the relationship between the $ Q_{\alpha} $ values and lifetimes, a phenomenon explained by quantum tunneling [2]. However, the direct connection between $ Q_{\alpha} $ values and $ \alpha$-cluster formation remains poorly understood. To address this gap, we investigate the abnormal isotopic dependence of $ Q_{\alpha} $ values in $ \mathrm{Ca} $ isotopes to evaluate their influence on $ \alpha $-cluster formation.
The $ \alpha $-knockout reaction was employed as a method to quantify $ \alpha $-cluster formation probabilities in $ \mathrm{Ca} $ isotopes. The experiment was performed at the RCNP, Osaka University, using a 392-MeV proton beam incident on the $ ^{40,42,44,48}\mathrm{Ca} $ targets. Recoil protons and knocked-out $ \alpha $-particles were analyzed using the Grand Raiden and Large Acceptance Spectrometers, which were optimized for quasi-free $ p $-$ \alpha $ scattering.
The $ \alpha $-cluster separation energy spectra revealed evidence of $ \alpha $-cluster formation in $ \mathrm{Ca} $ nuclei. Further analyses are underway to investigate the isotopic dependence of reaction cross-sections, which will provide insights into amplitudes of $ \alpha $-cluster formation. This work will clarify the relationship between known $ Q_{\alpha} $ values and $ \alpha $-cluster formation.
We will present the details of the experiment, along with preliminary results and ongoing data analyses.
[1] J. Tanaka, Z.H. Yang, S. Typel et al., Science 371, 260 (2021).
[2] H. Geiger and J.M. Nuttall, Philos. Mag. 22, 613 (1911); ibid. 23, 439 (1912).
