Extracted core source size $r_\text{core}$ for primordial p$-\pi^-$ pairs for several $m_{\rm T}$ ranges. The obtained result is compared with the results from p$-$p pairs, $\pi^\pm-\pi^\pm$ and $\text{p--}\text{K}^+$ pairs. The statistical (systematic) uncertainties are shown as lines (boxes). The extrapolated scaling of p--p pairs  is shown as the gray band.