Quark-level analogue of nuclear fusion with doubly-heavy baryons

Abstract

The recent discovery by LHCb of the first doubly-charmed baryon $\Xi_{cc}^{++} = ccu$ at $3621.40 \pm 0.78$ MeV implies a large binding energy $\sim 130$ MeV between the two $c$ quarks. This strong binding enables a quark-rearrangement exothermic reaction $\,\Lambda_c \Lambda_c \to \Xi_{cc}^{++}\,n\,$ with $Q=12$ MeV, which is a quark-level analogue of deuterium-tritium nuclear fusion reaction $DT\to {}^4{\rm He}\,n$. Due to much larger binding energy between two $b$ quarks $\sim 280$ MeV, the analogous reaction with $b$ quarks, $\,\Lambda_b \Lambda_b \to \Xi_{bb}\,N\,$ is expected to have a dramatically larger $Q$-value, $138\pm 12$ MeV.