Study of the $\Lambda$-$\Lambda$ interaction with femtoscopy correlations in pp and p-Pb collisions at the LHC
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The ALICE collaboration

Abstract (data abstract)
This work presents new constraints on the existence and the binding energy of a possible $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ bound state, the H-dibaryon, derived from $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ femtoscopic measurements by the ALICE collaboration. The results are obtained from a new measurement using the femtoscopy technique in p-p collisions at $\sqrt{s}=13$ TeV and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV, combined with previously published results from p-p collisions at $\sqrt{s}=7$ TeV. The $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ scattering parameter space, spanned by the inverse scattering length $f_0^{-1}$ and the effective range $d_0$, is constrained by comparing the measured $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ correlation function with calculations obtained within the Lednick'y 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 $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ interaction. The region in the $(f_0^{-1},d_0)$ plane which would accommodate a $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ bound state is substantially restricted compared to previous studies. The binding energy of the possible $\mathrm{\Lambda}$-$\mathrm{\Lambda}$ bound state is estimated within an effective-range expansion approach and is found to be $B_{\Lambda\Lambda} = 3.2^{+1.6}_{-2.4}\text{(stat)}^{+1.8}_{-1.0}\text{(syst)}$ MeV.

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