Investigating the role of strangeness in baryon$-$antibaryon annihilation at the LHC

Abstract

Annihilation dynamics plays a fundamental role in the baryon$-$antibaryon interaction (B$-\overline{\mathrm{B}}$) at low-energy and its strength and range are crucial in the assessment of possible baryonic bound states. Experimental data on annihilation cross sections are available for the p$-\overline{\mathrm{p}}$ system but not in the low relative momentum region. Data regarding the B$-\overline{\mathrm{B}}$ interaction with strange degrees of freedom are extremely scarce, hence the modeling of the annihilation contributions is mainly based on nucleon$-$antinucleon (N$-\overline{\mathrm{N}}$) results, when available. In this letter we present a measurement of the p$-\overline{\mathrm{p}}$, p$-\overline{\Lambda }\oplus \overline{\mathrm{p}}-\mathrm{\Lambda }$ and $\Lambda -\overline{\Lambda }$ interaction using correlation functions in the relative momentum space in high-multiplicity triggered pp collisions at $\sqrt{s}=13$ TeV recorded by ALICE at the LHC. In the p$-\overline{\mathrm{p}}$ system the couplings to the mesonic channels in different partial waves are extracted by adopting a coupled-channel approach with recent $\chi \mathrm{EFT}$ potentials. The inclusion of these inelastic channels provides good agreement with the data, showing a significant presence of the annihilation term down to zero momentum. Predictions obtained using the Lednický$-$Lyuboshits formula and scattering parameters obtained from heavy-ion collisions, hence mainly sensitive to elastic processes, are compared with the experimental p$-\overline{\Lambda }\oplus \overline{\mathrm{p}}-\mathrm{\Lambda }$ and $\Lambda -\overline{\Lambda }$ correlations. The model describes the $\Lambda -\overline{\Lambda }$ data and underestimates the p$-\overline{\Lambda }\oplus \overline{\mathrm{p}}-\mathrm{\Lambda }$ data in the region of momenta below 200 MeV/$c$. The observed deviation indicates a different contribution of annihilation channels to the two systems containing strange hadrons.

22 pages, 6 captioned figures, authors from page 17, published version, figures at http://alice-publications.web.cern.ch/node/7075 (with ROR in author list xml file for inspire)

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