<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi></mml:math> knockout reaction as a new probe for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi></mml:math> formation in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi></mml:math> -decay nuclei

The $\alpha$-decay phenomennon has been studied for more than a century but the mechanism of $\alpha$ particle formation and its tunneling process have not yet fully understood. As an alternative to lifetime measurement, we propose proton-induced knockout reaction, ($p$,$p\alpha$), as new probe surface probability nuclei. $^{210,212}$Po($p$,$p\alpha$)$^{206,208}$Pb reaction is described by distorted-wave impulse approximation framework. It shows that $^{212}$Po/$^{210}$Po ratio cross sections agrees with probabilities determined measurements. result implies ($p$,$p\alpha$) section direct probability, which essential quantity lead us complete understanding phenomenon.