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1. Searches for $B^0\to K^{+}{\pi }^{-}{\tau }^{+}{\tau }^{-}$ and $B_s^0\to K^{+}{K}^{-}{\tau }^{+}{\tau }^{-}$ Decays

   https://doi.org/10.1103/y968-44v8  

   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 (May 2026, Physical Review Letters)

   The first searches for $B^0\to K^{+}{\pi }^{-}{\tau }^{+}{\tau }^{-}$ and $B_s^0\to K^{+}{K}^{-}{\tau }^{+}{\tau }^{-}$ decays at the LHCb experiment are conducted with $pp$ collision data corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . The tau leptons are reconstructed using the ${\tau }^{+}\to {\mu }^{+}{\overline{\nu }}_{\tau }{\nu }_{\mu }$ decay and the results are presented in bins of $K^{+}{\pi }^{-}$ or $K^{+}{K}^{-}$ mass. No signal is observed and upper limits are set on the branching fractions. The searches result in the first upper limits for $B^0\to K^{+}{\pi }^{-}{\tau }^{+}{\tau }^{-}$ decays outside the $K^{*}(892{)}^0$ region in $K^{+}{\pi }^{-}$ mass and the first limits for $B_s^0\to K^{+}{K}^{-}{\tau }^{+}{\tau }^{-}$ decays. The searches are recast into limits on the decays $B^0\to K^{*}(892{)}^0{\tau }^{+}{\tau }^{-}$ and $B_s^0\to \varphi \left(1020\right){\tau }^{+}{\tau }^{-}$ , yielding $2.8\times {10}^{-4}$ ( $2.5\times {10}^{-4}$ ) and $4.7\times {10}^{-4}$ ( $4.1\times {10}^{-4}$ ) at the 95% (90%) confidence level, respectively. For the decay $B^0\to K^{*}(892{)}^0{\tau }^{+}{\tau }^{-}$ , this result improves on the current best upper limit by an order of magnitude. 

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2. Search for Lepton-Flavor-Violating Decay Modes $B^0\to K_S^0{\tau }^{\pm }{\ell }^{\mp }$ with Hadronic $B$ Tagging at Belle and Belle II

   https://doi.org/10.1103/yzvh-v3hm  

   Adachi, I; Adamczyk, K; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Alhakami, M; Aloisio, A; Althubiti, N; Ky, N Anh; et al (July 2025, Physical Review Letters)

   We present the first search for the lepton-flavor-violating decay modes $B^0\to K_S^0{\tau }^{\pm }{\ell }^{\mp }$ ( $\ell =\mu ,e$ ) using the 711 and $365{\mathrm{fb}}^{-1}$ data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic $B$ -tagging technique to fully reconstruct a $B$ meson and search for signal decays in the system recoiling against the tagged meson, considering $\tau$ decays to either light leptons, one charged hadron, or one charged hadron and a neutral pion. We find no evidence for $B^0\to K_S^0{\tau }^{\pm }{\ell }^{\mp }$ decays and set 90% confidence level upper limits on the branching fractions in the range of $[0.8,3.6]\times {10}^{-5}$ . 

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3. Evidence for $B^{-}\to D^{**0}{\tau }^{-}\overline{{\nu }_{\tau }}$ Decays

   https://doi.org/10.1103/rj9h-n4w1  

   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 (July 2025, Physical Review Letters)

   The first evidence for the decay $B^{-}\to D^{**0}{\tau }^{-}{\overline{\nu }}_{\tau }$ is obtained using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ , at centre-of-mass energies of 7, 8, and 13 TeV. Here, the $D^{**0}$ meson represents any of the three excited charm mesons $D_1(2420{)}^0$ , $D_2^{*}(2460{)}^0$ , and $D_1^{\prime }(2400{)}^0$ . The $B^{-}\to D^{**0}{\tau }^{-}{\overline{\nu }}_{\tau }$ signal is measured with a significance of $3.5\sigma$ , including systematic uncertainties. The combined branching fraction $\mathcal{B}(B^{-}\to D_{1,2}^{**0}{\tau }^{-}{\overline{\nu }}_{\tau })\times \mathcal{B}(D_{1,2}^{**0}\to D^{*+}{\pi }^{-})$ , where $D_{1,2}^{**0}$ denotes both $D_1(2420{)}^0$ and $D_2^{*}(2460{)}^0$ contributions, is measured to be $[0.051\pm 0.013\left(\mathrm{stat}\right)\pm 0.006\left(\mathrm{syst}\right)\pm 0.009(\mathrm{ext}\left)\right]\%$ , where the last uncertainty reflects that of the branching fraction of the normalization channel $B^{-}\to D_{1,2}^{**0}{D_s^{-}}^{(*)}$ . The ratio between the tauonic and muonic semileptonic $B$ decays, with the latter taken from world average values, is also determined and found to be $\mathcal{R}\left(D_{1,2}^{**0}\right)=0.13\pm 0.03\left(\mathrm{stat}\right)\pm 0.01\left(\mathrm{syst}\right)\pm 0.02\left(\mathrm{ext}\right)$ . 

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4. Evidence of $h_b\left(2\mathrm{P}\right)\to \mathrm{\Upsilon }\left(1\mathrm{S}\right)\eta$ Decay and Search for $h_b(1\mathrm{P},2\mathrm{P})\to \mathrm{\Upsilon }\left(1\mathrm{S}\right){\pi }^0$ with the Belle Detector

   https://doi.org/10.1103/PhysRevLett.133.261901  

   Kovalenko, E; Adachi, I; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Babu, V; Banerjee, Sw; Belous, K; Bennett, J; et al (December 2024, Physical Review Letters)

   We report the first evidence for the $h_b\left(2\mathrm{P}\right)\to \mathrm{\Upsilon }\left(1\mathrm{S}\right)\eta$ transition with a significance of 3.5 standard deviations. The decay branching fraction is measured to be $\mathcal{B}\left[h_b\right(2\mathrm{P})\to \mathrm{\Upsilon }(1\mathrm{S}\left)\eta \right]=({7.1}_{-3.2}^{+3.7}\pm 0.8)\times {10}^{-3}$ , which is noticeably smaller than expected. We also set upper limits on ${\pi }^0$ transitions of $\mathcal{B}\left[h_b\right(2\mathrm{P})\to \mathrm{\Upsilon }(1\mathrm{S}\left){\pi }^0\right]<1.8\times {10}^{-3}$ , and $\mathcal{B}\left[h_b\right(1\mathrm{P})\to \mathrm{\Upsilon }(1\mathrm{S}\left){\pi }^0\right]<1.8\times {10}^{-3}$ , at the 90% confidence level. These results are obtained with a $131.4{\mathrm{fb}}^{-1}$ data sample collected near the $\mathrm{\Upsilon }\left(5\mathrm{S}\right)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. Published by the American Physical Society2024 

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5. Observation of the decay $B^0\to J/\psi \omega$ at Belle II

   https://doi.org/10.1103/PhysRevD.111.032012  

   Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Alhakami, M; Aloisio, A; Althubiti, N; Anh_Ky, N; Asner, D M; et al (February 2025, Physical Review D)

   We measure the branching fraction of the decay $B^0\to J/\psi \omega$ using data collected with the Belle II detector at the SuperKEKB collider. The data contain $(387\pm 6)\times {10}^{6}B\overline{B}$ meson pairs produced in energy-asymmetric $e^{+}{e}^{-}$ collisions at the $\mathrm{\Upsilon }\left(4S\right)$ resonance. The measured branching fraction $\mathcal{B}(B^0\to J/\psi \omega )=(2.16\pm 0.30\pm 0.14)\times {10}^{-5}$ , where the first uncertainty is statistical and the second is systematic, is more precise than previous results and constitutes the first observation of the decay with a significance of 6.5 standard deviations. Published by the American Physical Society2025 

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