Invariant mass distributions of $\pi^{+}\pi^{-}$ pairs in $|y|$ 0.5 after the like-sign background subtraction in MB pp collisions at $\sqrt{s}=$ 13 TeV. The left (right) plot is obtained using low (high) $p_{\mathrm{T}}$ of $\pi^{+}\pi^{-}$ pairs.