Observation of the ${{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$ and ${{{{\varXi } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$ decays

Aaij, R.; Abdelmotteleb, A. S. W.; Beteta, C. Abellan; Abudinén, F.; Ackernley, T.; Adefisoye, A. A.; Adeva, B.; Adinolfi, M.; Adlarson, P.; Agapopoulou, C.; Aidala, C. A.; Ajaltouni, Z.; Akar, S.; Akiba, K.; Albicocco, P.; Albrecht, J.; Alessio, F.; Alexander, M.; Aliouche, Z.; Cartelle, P. Alvarez; Amalric, R.; Amato, S.; Amey, J. L.; Amhis, Y.; An, L.; Anderlini, L.; Andersson, M.; Andreianov, A.; Andreola, P.; Andreotti, M.; Andreou, D.; Anelli, A.; Ao, D.; Archilli, F.; Argenton, M.; Cuendis, S. Arguedas; Artamonov, A.; Artuso, M.; Aslanides, E.; Da Silva, R. Ataíde; Atzeni, M.; Audurier, B.; Bacher, D.; Perea, I. Bachiller; Bachmann, S.; Bachmayer, M.; Back, J. J.; Rodriguez, P. Baladron; Balagura, V.; Balboni, A.; Baldini, W.; Balzani, L.; Bao, H.; de Souza Leite, J. Baptista; Pretel, C. Barbero; Barbetti, M.; Barbosa, I. R.; Barlow, R. J.; Barnyakov, M.; Barsuk, S.; Barter, W.; Bartz, J.; Basels, J. M.; Bashir, S.; Bassi, G.; Batsukh, B.; Battista, P. B.; Bay, A.; Beck, A.; Becker, M.; Bedeschi, F.; Bediaga, I. B.; Behling, N. A.; Belin, S.; Belous, K.; Belov, I.; Belyaev, I.; Benane, G.; Bencivenni, G.; Ben-Haim, E.; Berezhnoy, A.; Bernet, R.; Andres, S. Bernet; Bertolin, A.; Betancourt, C.; Betti, F.; Bex, J.; Bezshyiko, Ia.; Bhom, J.; Bieker, M. S.; Biesuz, N. V.; Billoir, P.; Biolchini, A.; Birch, M.; Bishop, F. C. R.; Bitadze, A.; Bizzeti, A.; Blake, T.; Blanc, F.; Blank, J. E.; et al.

doi:10.1140/epjc/s10052-025-14129-6

research article

Observation of the ${{{\varLambda } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$ and ${{{{\varXi } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$ decays

Aaij, R.

•

Abdelmotteleb, A. S. W.

•

Beteta, C. Abellan

July 28, 2025

The European Physical Journal C

The first observation of the ${{{{\varXi } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$ decay and the most precise measurement of the branching fraction of the ${{{\varLambda } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016–2018 at a centre-of-mass energy of 13$\text {,Te\hspace{-1.00006pt}V}$, corresponding to an integrated luminosity of 5.4$\text {,fb} ^{-1}$. Using the ${{{{\varLambda } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {\varLambda } }}$ and ${{{{\varXi } ^-{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} }}$ decays as normalisation channels, the ratios of branching fractions are measured to be $\begin{aligned} {\frac{{{\mathcal {B}}}({{{\varLambda } ^0{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} })}{{{\mathcal {B}}}({{{{\varLambda } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {\varLambda } }})}}&= (1.17 \pm 0.14 \pm 0.08)\times 10^{-2} , ,\ {\frac{{{\mathcal {B}}}({{{{\varXi } ^0_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }})}{{{\mathcal {B}}}({{{{\varXi } ^-_{b}} !\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} }})}}&= (11.9 \pm 1.4 \pm 0.6)\times 10^{-2}, , \end{aligned}$ B ( Λ b 0 → J / ψ Ξ - K + ) B ( Λ b 0 → J / ψ Λ ) = ( 1.17 ± 0.14 ± 0.08 ) × 10 - 2 , B ( Ξ b 0 → J / ψ Ξ - π + ) B ( Ξ b - → J / ψ Ξ - ) = ( 11.9 ± 1.4 ± 0.6 ) × 10 - 2 , where the first uncertainty is statistical and the second systematic.