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1. Measurements of the branching fractions of $$ {\Xi}_c^0\to {\Xi}^0{\pi}^0 $$, $$ {\Xi}_c^0\to {\Xi}^0\eta $$, and $$ {\Xi}_c^0\to {\Xi}^0{\eta}^{\prime } $$ and asymmetry parameter of $$ {\Xi}_c^0\to {\Xi}^0{\pi}^0 $$

   https://doi.org/10.1007/JHEP10(2024)045  

   Adachi, I; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Althubiti, N; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, T; et al (October 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We present a study of$$ {\Xi}_c^0\to {\Xi}^0{\pi}^0 $$ ${\Xi }_c^0\to {\Xi }^0{\pi }^0$ ,$$ {\Xi}_c^0\to {\Xi}^0\eta $$ ${\Xi }_c^0\to {\Xi }^0\eta$ , and$$ {\Xi}_c^0\to {\Xi}^0{\eta}^{\prime } $$ ${\Xi }_c^0\to {\Xi }^0{\eta }^{\prime }$ decays using the Belle and Belle II data samples, which have integrated luminosities of 980 fb⁻¹and 426 fb⁻¹, respectively. We measure the following relative branching fractions$$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^0\to {\Xi}^0{\pi}^0\right)/\mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right)=0.48\pm 0.02\left(\textrm{stat}\right)\pm 0.03\left(\textrm{syst}\right),\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Xi}^0\eta \right)/\mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right)=0.11\pm 0.01\left(\textrm{stat}\right)\pm 0.01\left(\textrm{syst}\right),\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Xi}^0{\eta}^{\prime}\right)/\mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right)=0.08\pm 0.02\left(\textrm{stat}\right)\pm 0.01\left(\textrm{syst}\right)\end{array}} $$ $\begin{array}{c}B\left({\Xi }_c^0\to {\Xi }^0{\pi }^0\right)/B\left({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}\right)=0.48\pm 0.02\left(\text{stat}\right)\pm 0.03\left(\text{syst}\right),\\ B\left({\Xi }_c^0\to {\Xi }^0\eta \right)/B\left({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}\right)=0.11\pm 0.01\left(\text{stat}\right)\pm 0.01\left(\text{syst}\right),\\ B\left({\Xi }_c^0\to {\Xi }^0{\eta }^{\prime }\right)/B\left({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}\right)=0.08\pm 0.02\left(\text{stat}\right)\pm 0.01\left(\text{syst}\right)\end{array}$ for the first time, where the uncertainties are statistical (stat) and systematic (syst). By multiplying by the branching fraction of the normalization mode,$$ \mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right) $$ $B\left({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}\right)$ , we obtain the following absolute branching fraction results$$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^0\to {\Xi}^0{\pi}^0\right)=\left(6.9\pm 0.3\left(\textrm{stat}\right)\pm 0.5\left(\textrm{syst}\right)\pm 1.3\left(\operatorname{norm}\right)\right)\times {10}^{-3},\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Xi}^0\eta \right)=\left(1.6\pm 0.2\left(\textrm{stat}\right)\pm 0.2\left(\textrm{syst}\right)\pm 0.3\left(\operatorname{norm}\right)\right)\times {10}^{-3},\\ {}\mathcal{B}\left({\varXi}_c^0\to {\Xi}^0{\eta}^{\prime}\right)=\left(1.2\pm 0.3\left(\textrm{stat}\right)\pm 0.1\left(\textrm{syst}\right)\pm 0.2\left(\operatorname{norm}\right)\right)\times {10}^{-3},\end{array}} $$ $\begin{array}{c}B\left({\Xi }_c^0\to {\Xi }^0{\pi }^0\right)=\left(6.9\pm 0.3\left(\text{stat}\right)\pm 0.5\left(\text{syst}\right)\pm 1.3\left(norm\right)\right)\times {10}^{-3},\\ B\left({\Xi }_c^0\to {\Xi }^0\eta \right)=\left(1.6\pm 0.2\left(\text{stat}\right)\pm 0.2\left(\text{syst}\right)\pm 0.3\left(norm\right)\right)\times {10}^{-3},\\ B\left({\Xi }_c^0\to {\Xi }^0{\eta }^{\prime }\right)=\left(1.2\pm 0.3\left(\text{stat}\right)\pm 0.1\left(\text{syst}\right)\pm 0.2\left(norm\right)\right)\times {10}^{-3},\end{array}$ where the third uncertainties are from$$ \mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right) $$ $B\left({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}\right)$ . The asymmetry parameter for$$ {\Xi}_c^0\to {\Xi}^0{\pi}^0 $$ ${\Xi }_c^0\to {\Xi }^0{\pi }^0$ is measured to be$$ \alpha \left({\Xi}_c^0\to {\Xi}^0{\pi}^0\right)=-0.90\pm 0.15\left(\textrm{stat}\right)\pm 0.23\left(\textrm{syst}\right) $$ $\alpha \left({\Xi }_c^0\to {\Xi }^0{\pi }^0\right)=-0.90\pm 0.15\left(\text{stat}\right)\pm 0.23\left(\text{syst}\right)$ . 

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2. Measurement of the $$ {\varOmega}_c^0 $$ and $$ {\Xi}_c^0 $$ baryon lifetimes using hadronic b-baryon decays

   https://doi.org/10.1007/JHEP09(2025)157  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (September 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> The lifetimes of the$$ {\varOmega}_c^0 $$ ${\Omega }_c^0$ and$$ {\Xi}_c^0 $$ ${\Xi }_c^0$ baryons are measured using appcollision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb⁻¹. The charm baryons are produced in the fully reconstructed decay chains$$ {\varOmega}_b^{-}\to {\varOmega}_c^0\left(\to p{K}^{-}{K}^{-}{\pi}^{+}\right){\pi}^{-} $$ ${\Omega }_b^{-}\to {\Omega }_c^0\left(\to p{K}^{-}{K}^{-}{\pi }^{+}\right){\pi }^{-}$ and$$ {\Xi}_b^{-}\to {\Xi}_c^0\left(\to p{K}^{-}{K}^{-}{\pi}^{+}\right){\pi}^{-} $$ ${\Xi }_b^{-}\to {\Xi }_c^0\left(\to p{K}^{-}{K}^{-}{\pi }^{+}\right){\pi }^{-}$ . The measurement uses topologically and kinematically similarB⁻→D⁰(→K⁻K⁺π⁻π⁺)π⁻decays for normalisation. The measured lifetimes are$$ {\displaystyle \begin{array}{c}{\tau}_{\varOmega_c^0}=276.3\pm 19.4\left(\textrm{stat}\right)\pm 1.8\left(\textrm{syst}\right)\pm 0.7\left({\tau}_{D^0}\right)\textrm{fs},\\ {}{\tau}_{\Xi_c^0}=149.2\pm 2.5\left(\textrm{stat}\right)\pm 0.9\left(\textrm{syst}\right)\pm 0.4\ \left({\tau}_{D^0}\right)\textrm{fs},\end{array}} $$ $\begin{array}{c}{\tau }_{{\Omega }_c^0}=276.3\pm 19.4\left(\text{stat}\right)\pm 1.8\left(\text{syst}\right)\pm 0.7\left({\tau }_{D^0}\right)\mathrm{fs},\\ {\tau }_{{\Xi }_c^0}=149.2\pm 2.5\left(\text{stat}\right)\pm 0.9\left(\text{syst}\right)\pm 0.4\left({\tau }_{D^0}\right)\mathrm{fs},\end{array}$ where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of theD⁰lifetime. These results are consistent with previous measurements performed by the LHCb experiment. 

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3. Observation of the doubly-charmed-baryon decay $$ {\Xi}_{cc}^{++}\to {\Xi}_c^0{\pi}^{+}{\pi}^{+} $$

   https://doi.org/10.1007/JHEP10(2025)136  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (October 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> A search for the doubly-charmed-baryon decay$$ {\Xi}_{cc}^{++}\to {\Xi}_c^0{\pi}^{+}{\pi}^{+} $$ ${\Xi }_{\mathrm{cc}}^{++}\to {\Xi }_c^0{\pi }^{+}{\pi }^{+}$ is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.4 fb⁻¹. A significant structure consistent with the$$ {\Xi}_{cc}^{++} $$ ${\Xi }_{\mathrm{cc}}^{++}$ baryon is observed in the$$ {\Xi}_c^0{\pi}^{+}{\pi}^{+} $$ ${\Xi }_c^0{\pi }^{+}{\pi }^{+}$ invariant-mass spectrum. Using the$$ {\Xi}_{cc}^{++}\to {\Lambda}_c^{+}{K}^{-}{\pi}^{+}{\pi}^{+} $$ ${\Xi }_{\mathrm{cc}}^{++}\to {\Lambda }_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$ decay as the normalisation channel, the branching fraction ratio,$$ \frac{\mathcal{B}\left({\Xi}_{cc}^{++}\to {\Xi}_c^0{\pi}^{+}{\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_{cc}^{++}\to {\Lambda}_c^{+}{K}^{-}{\pi}^{+}{\pi}^{+}\right)} $$ $\frac{B\left({\Xi }_{\mathrm{cc}}^{++}\to {\Xi }_c^0{\pi }^{+}{\pi }^{+}\right)}{B\left({\Xi }_{\mathrm{cc}}^{++}\to {\Lambda }_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}\right)}$ , is measured to be 1.37±0.18 (stat)±0.09 (syst)±0.35 (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. 

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4. Improved branching-fraction measurements of $$ {B}_{(s)}^0\to {K}_{\mathrm{S}}^0{h}^{+}h{\prime}^{-} $$ decays and first observation of $$ {B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-} $$

   https://doi.org/10.1007/JHEP07(2026)071  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Afsharnia, H; et al (July 2026, Journal of High Energy Physics)

   A<sc>bstract</sc> This paper presents a study of the charmless three-body decays$$ {B}_{(s)}^0\to {K}_{\mathrm{S}}^0{h}^{+}h{\prime}^{-} $$ $B_{\left(s\right)}^0\to K_S^0{h}^{+}h{\prime }^{-}$ (whereh⁽′⁾=π, K), using a sample ofppcollision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of 9 fb⁻¹. The decay$$ {B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-} $$ $B_s^0\to K_S^0{K}^{+}{K}^{-}$ is observed for the first time, and the following ratios of branching fractions are measured:$$ {\displaystyle \begin{array}{l}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ {}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{K}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ {}\begin{array}{l}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{\pi}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}} $$ $\begin{array}{c}\frac{B\left(B^0\to K_S^0{K}^{+}{K}^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ \frac{B\left(B^0\to K_S^0{K}^{\pm }{K}^{\mp }\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ \begin{array}{c}\frac{B\left(B_s^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ \frac{B\left(B_s^0\to K_S^0{K}^{+}{K}^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ \frac{B\left(B_s^0\to K_S^0{K}^{\pm }{\pi }^{\mp }\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}$ where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the$$ {B}_s^0 $$ $B_s^0$ andB⁰mesons, respectively. 

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5. Improved measurement of η/η′ mixing in $$ {B}_{(s)}^0\to J/\psi {\eta}^{\left(\prime \right)} $$ decays

   https://doi.org/10.1007/JHEP10(2025)113  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (October 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> Branching fraction ratios between the decays$$ {B}_{(s)}^0\to J/\psi {\eta}^{\left(\prime \right)} $$ $B_{\left(s\right)}^0\to J/\psi {\eta }^{\left(\prime \right)}$ are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb⁻¹. The measured ratios of these branching fractions are$$ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({B}^0\to J/{\psi \eta}^{\prime}\right)}{\mathcal{B}\left({B}^0\to J/\psi \eta \right)}=0.48\pm 0.06\pm 0.02\pm 0.01,\\ {}\frac{\mathcal{B}\left({B}_s^0\to J/{\psi \eta}^{\prime}\right)}{\mathcal{B}\left({B}_s^0\to J/\psi \eta \right)}=0.80\pm 0.02\pm 0.02\pm 0.01,\end{array}} $$ $\begin{array}{c}\frac{B\left(B^0\to J/{\mathrm{\psi \eta }}^{\prime }\right)}{B\left(B^0\to J/\mathrm{\psi \eta }\right)}=0.48\pm 0.06\pm 0.02\pm 0.01,\\ \frac{B\left(B_s^0\to J/{\mathrm{\psi \eta }}^{\prime }\right)}{B\left(B_s^0\to J/\mathrm{\psi \eta }\right)}=0.80\pm 0.02\pm 0.02\pm 0.01,\end{array}$ where the uncertainties are statistical, systematic and related to the precision of theη^(′)branching fractions, respectively. They are used to constrain theη/η′ mixing angle,ϕ_P, and to probe the presence of a possible glueball component in theη′ meson, described by the gluonic mixing angleϕ_G. The obtained results are $$ {\displaystyle \begin{array}{c}{\phi}_{\textrm{P}}={\left({41.6}_{-1.2}^{+1.0}\right)}^{\circ },\\ {}{\phi}_{\textrm{G}}={\left({28.1}_{-4.0}^{+3.9}\right)}^{\circ },\end{array}} $$ $\begin{array}{c}{\varphi }_P={\left({41.6}_{-1.2}^{+1.0}\right)}^{\circ },\\ {\varphi }_G={\left({28.1}_{-4.0}^{+3.9}\right)}^{\circ },\end{array}$ where the uncertainties are statistically dominated. While the value ofϕ_Pis compatible with existing experimental determinations and theoretical calculations, the angleϕ_Gdiffers from zero by more than four standard deviations, which points to a substantial glueball component in theη′ meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established$$ {B}_s^0\to J/\psi \phi $$ $B_s^0\to J/\mathrm{\psi \varphi }$ decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date. 

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