Measurement of $\rm p\overlineΛ\oplus\overline{p}Λ$ and $Λ\overlineΛ$ interactions with femtoscopic correlations in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV and $\sqrt{s_{\rm NN}} = 5.02$ TeV

ALICE Collaboration

Published 2019-03-14Version 1

Femtoscopic correlation functions were measured for $\rm p\overline{p}$, $\rm p\overline{\Lambda}\oplus\overline{p}\Lambda$, and $\Lambda\overline{\Lambda}$ pairs, as a function of collision centrality, in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV and $\sqrt{s_{\rm NN}}=5.02$ TeV recorded by the ALICE experiment at the LHC. A simultaneous fit to all obtained correlation functions was performed, maximising the precision and sensitivity to the strong interaction parameters for the selected baryon pairs. Real and imaginary components of the scattering lengths, as well as the effective ranges, were extracted for combined $\rm p\overline{\Lambda}\oplus\overline{p}\Lambda$ pairs and, for the first time, for $\Lambda\overline{\Lambda}$ pairs. Effective averaged scattering parameters for heavier baryon$-$anti-baryon pairs, not measured directly, are also provided. The results reveal similarly strong interaction between measured baryon$-$anti-baryon pairs, suggesting that they annihilate in the same manner as $\rm p\overline{p}$ at the same pair relative momentum $k^{*}$. Moreover, the reported significant non-zero imaginary part and negative real part of the scattering length open up a possibility for future baryon$-$anti-baryon bound state searches.