Search for weakly decaying $\bar{\Lambda\mathrm{n}}$ and $\Lambda\Lambda $ exotic bound states in central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV

TL;DR

This study searches for hypothetical strange dibaryon bound states, the H-dibaryon and $ar{ ext{Lambda}} ext{n}$, in high-energy Pb-Pb collisions using invariant mass analysis, but finds no evidence for their existence.

Contribution

First experimental search for the H-dibaryon and $ar{ ext{Lambda}} ext{n}$ states in Pb-Pb collisions at 2.76 TeV, setting upper limits on their production.

Findings

No evidence for the bound states was observed.

Upper limits were set at 99% confidence level.

Results align with thermal and coalescence model predictions.

Abstract

We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible $\bar{\Lambda\mathrm{n}}$ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at $ \sqrt{s_{\rm{NN}}} = 2.76$ TeV, by invariant mass analysis in the decay modes $\bar{\Lambda\mathrm{n}} \rightarrow \bar{\mathrm{d}} \pi^{+} $ and H-dibaryon $\rightarrow \Lambda \mathrm{p} \pi^{-}$. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.