Unexpectedly enhanced $\alpha$-particle preformation in $^{48}$Ti probed by the $(p,p\alpha)$ reaction

TL;DR

This study reveals unexpectedly strong alpha-particle formation in medium-mass nucleus $^{48}$Ti, challenging existing microscopic models and providing new insights into nuclear structure and element synthesis.

Contribution

It provides the first experimental evidence of enhanced alpha preformation in $^{48}$Ti, highlighting the need for improved microscopic descriptions of nucleon correlations.

Findings

Alpha formation in $^{48}$Ti is much stronger than mean-field predictions.

Estimated alpha-residue distance is approximately 4.5 fm.

Results challenge current microscopic nuclear models.

Abstract

The formation of $\alpha$ particle on nuclear surface has been a fundamental problem since the early age of nuclear physics. It strongly affects the $\alpha$ decay lifetime of heavy and superheavy elements, level scheme of light nuclei, and the synthesis of the elements in stars. However, the $\alpha$-particle formation in medium-mass nuclei has been poorly known despite its importance. Here, based on the $^{48}{\rm Ti}(p,p\alpha)^{44}{\rm Ca}$ reaction analysis, we report that the $\alpha$-particle formation in a medium-mass nucleus $^{48}{\rm Ti}$ is much stronger than that expected from a mean-field approximation, and the estimated average distance between $\alpha$ particle and the residue is as large as 4.5 fm. This new result poses a challenge of describing four nucleon correlations by microscopic nuclear models.