Pion emission source in pp collisions using the AMPT model with sub-nucleon structure

Based the on the fitting results, the \rcore values in each \kt interval are extracted for four different scenarios: (\rmnum{1}) before ART without further boost, (\rmnum{2}) before ART with a boost of $\tau\in[1.5,5]$ fm/$\it{c}$, (\rmnum{3}) after ART stage without boost, and (\rmnum{4}) after ART with a boost of $\tau\in[1,3]$ fm/$\it{c}$. In (\rmnum{2}), the upper limit originates from the general assumption that resonances with $\textit{c}\tau_\text{res} > 5$ fm are long-lived, while in (\rmnum{4}), the $\tau$ values are deliberately reduced to roughly match the results of (\rmnum{2}).

Figure ~\ref{fig:FinalmTscaling} shows the \mt-scaling behavior of \rcore. It can be seen that all four cases are in line with the expectation that the source radii decrease as \mt increases, roughly following the power-law relationship~\cite{SourceMaxi}: $R_\text{core} = \it{a} + \it{b}\cdot\langle m_\text{T}\rangle^{\it{c}}$. This can be understood in terms of the collectivity generated since the partonic stage.