Study of the Λ–Λ interaction with femtoscopy correlations in and p–Pb collisions at the LHC

This work presents new constraints on the existence and the binding energy of a possible Λ–Λ bound state, the H-dibaryon, derived from Λ–Λ femtoscopic measurements by the ALICE collaboration. The results are obtained from a new measurement using the femtoscopy technique in Image 1 collisions at $\sqrt{s}=13$ TeV and $p\text{–}\mathrm{Pb}$ collisions at $\sqrt{{s}_{\mathrm{NN}}}=5.02$ TeV, combined with previously published results from Image 1 collisions at $\sqrt{s}=7$ TeV. The Λ–Λ scattering parameter space, spanned by the inverse scattering length ${f}_{0}^{-1}$ and the effective range ${d}_{0}$, is constrained by comparing the measured Λ–Λ correlation function with calculations obtained within the Lednický model. The data are compatible with hypernuclei results and lattice computations, both predicting a shallow attractive interaction, and permit to test different theoretical approaches describing the Λ–Λ interaction. The region in the $\left({f}_{0}^{-1},{d}_{0}\right)$ plane which would accommodate a Λ–Λ bound state is substantially restricted compared to previous studies. The binding energy of the possible Λ–Λ bound state is estimated within an effective-range expansion approach and is found to be ${B}_{\Lambda \Lambda }={3.2}_{-2.4}^{+1.6}{\text{(stat)}}_{-1.0}^{+1.8}\text{(syst)}$ MeV.