A search for the doubly-charmed-baryon decay ${ \it \Xi}_{ cc}^{ ++}\to{ \it \Xi}_{ c}^{ 0}\pi^{ +}\pi^{ +}$ is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of $13\text{ TeV}$ and corresponding to an integrated luminosity of $5.4\text{ fb}^{ -1}$. A significant structure consistent with the ${ \it \Xi}_{ cc}^{ ++}$ baryon is observed in the ${ \it \Xi}_{ c}^{ 0} \pi^{ +}\pi^{ +}$ invariant-mass spectrum. Using the ${ \it \Xi}_{ cc}^{ ++}\to{ \it \Lambda}_{ c}^{ +}K^{ -}\pi^{ +}\pi^{ +}$ decay as the normalisation channel, the branching fraction ratio, $\frac{ { \cal B}({ \it \Xi}_{ cc}^{ ++} \to { \it \Xi}_{ c}^{ 0}\pi^{ +}\pi^{ +})} { { \cal B}({ \it \Xi}_{ cc}^{ ++}\to{ \it \Lambda}_{ c}^{ +} K^{ -}\pi^{ +}\pi^{ +})}$, is measured to be $1.37\pm 0.18\text{ (stat)} \pm 0.09\text{ (syst)} \pm 0.35\text{ (ext)}$. This measurement provides critical input for testing QCD factorisation methods in the weak decays of doubly-heavy baryons, particularly in quantifying nonperturbative effects such as final-state interactions and resonance contributions to the hadronisation process.
Categories: hep-ex