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1. Observation of time-dependent $CP$ violation and measurement of the branching fraction of $B^0\to J/\psi {\pi }^0$ decays

   https://doi.org/10.1103/PhysRevD.111.012011  

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

   We present a measurement of the branching fraction and time-dependent charge-parity ( $CP$ ) decay-rate asymmetries in $B^0\to J/\psi {\pi }^0$ decays. The data sample was collected with the Belle II detector at the SuperKEKB asymmetric $e^{+}{e}^{-}$ collider in 2019–2022 and contains $(387\pm 6)\times {10}^{6}B\overline{B}$ meson pairs from $\mathrm{\Upsilon }\left(4S\right)$ decays. We reconstruct $392\pm 24$ signal decays and fit the $CP$ parameters from the distribution of the proper-decay-time difference of the two $B$ mesons. We measure the branching fraction to be $\left({\mathcal{B}}^0\to J/\psi {\pi }^0\right)=(2.00\pm 0.12\pm 0.09)\times {10}^{-5}$ and the direct and mixing-induced $CP$ asymmetries to be $C_{CP}=0.13\pm 0.12\pm 0.03$ and $S_{CP}=-0.88\pm 0.17\pm 0.03$ , respectively, where the first uncertainties are statistical and the second are systematic. We observe mixing-induced $CP$ violation with a significance of 5.0 standard deviations for the first time in this mode. Published by the American Physical Society2025 

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2. First Observation of $CP$ Violation and Measurement of Polarization in $B^{+}\to \rho \left(770{)}^0{K}^{*}\right(892{)}^{+}$ Decays

   https://doi.org/10.1103/9zhl-kkwg  

   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 (January 2026, Physical Review Letters)

   An amplitude analysis of the $B^{+}\to \left({\pi }^{+}{\pi }^{-}\right)\left(K_{\mathrm{S}}^0{\pi }^{+}\right)$ decay is performed in the mass regions $0.30<m_{{\pi }^{+}{\pi }^{-}}<1.10\mathrm{GeV}/c^2$ and $0.75<m_{K_{\mathrm{S}}^0{\pi }^{+}}<1.20\mathrm{GeV}/c^2$ , using $pp$ collision data recorded with the LHCb detector corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . The polarization fractions and $CP$ asymmetries for $B^{+}\to \rho \left(770{)}^0{K}^{*}\right(892{)}^{+}$ decays are measured. Violation of the $CP$ symmetry in the decay $B^{+}\to \rho \left(770{)}^0{K}^{*}\right(892{)}^{+}$ is observed for the first time, with a significance exceeding 9 standard deviations. The $CP$ asymmetry is measured to be ${\mathcal{A}}_{CP}=0.507\pm 0.062\left(\mathrm{stat}\right)\pm 0.024\left(\mathrm{syst}\right)$ and the $CP$ -averaged longitudinal polarization fraction of $f_L=0.720\pm 0.028\left(\mathrm{stat}\right)\pm 0.009\left(\mathrm{syst}\right)$ . The measurements help to shed light on the polarization puzzle of $B$ mesons decaying to two vector mesons. 

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3. Measurement of $CP$ Asymmetries in $B^0\to K_S^0{\pi }^0\gamma$ Decays at Belle II

   https://doi.org/10.1103/PhysRevLett.134.011802  

   Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, T; et al (January 2025, Physical Review Letters)

   We report measurements of time-dependent $CP$ asymmetries in $B^0\to K_S^0{\pi }^0\gamma$ decays based on a data sample of $(388\pm 6)\times {10}^{6}B\overline{B}$ events collected at the $\mathrm{\Upsilon }\left(4S\right)$ resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We measure decay-time distributions to determine $CP$ -violating parameters $S$ and $C$ . We determine these parameters for two ranges of $K_S^0{\pi }^0$ invariant mass: $m\left(K_S^0{\pi }^0\right)\in (0.8,1.0)\mathrm{GeV}/c^2$ , which is dominated by $B^0\to K^{*0}(\to K_S^0{\pi }^0)\gamma$ decays, and a complementary region $m\left(K_S^0{\pi }^0\right)\in (0.6,0.8)\cup (1.0,1.8)\mathrm{GeV}/c^2$ . Our results have improved precision as compared to previous measurements and are consistent with theory predictions. Published by the American Physical Society2025 

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4. Observation and investigation of the $T_{c\overline{c}1}(4430{)}^{+}$ structure in $B^{+}\to \psi \left(2S\right)K_{\mathrm{S}}^0{\pi }^{+}$ decays

   https://doi.org/10.1103/rcfs-ynh2  

   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 (April 2026, Physical Review D)

   The first four-dimensional amplitude analysis of the $B^{+}\to \psi \left(2S\right)K_{\mathrm{S}}^0{\pi }^{+}$ decay is performed with proton-proton collision data collected by the LHCb experiment at $\sqrt{s}=13\mathrm{TeV}$ , corresponding to an integrated luminosity of $5.4\mathrm{f}{\mathrm{b}}^{-1}$ . The data cannot be fully explained by $B^{+}\to \psi \left(2S\right)K^{*+}$ contributions alone. A significantly better description of the data is obtained by adding a $T_{c\overline{c}}^{+}$ contribution decaying to $\psi \left(2S\right){\pi }^{+}$ . The properties of the $T_{c\overline{c}}^{+}$ structure are consistent with the exotic state $T_{c\overline{c}1}(4430{)}^{+}$ reported in the isospin-related ${\overline{B}}^0\to \psi \left(2S\right)K^{-}{\pi }^{+}$ decay. Effects of a possible $T_{c\overline{c}1}(4430{)}^{+}\to {\overline{D}}_1^{*}(2600{)}^0{D}^{+}$ decay mode on the $T_{c\overline{c}1}(4430{)}^{+}\to \psi (2S){\pi }^{+}$ mass distribution are investigated through a Flatté parametrization, providing constraints on the relative decay strength. A description of the $T_{c\overline{c}1}(4430{)}^{+}$ structure using the triangle singularity mechanism is studied and also found to be consistent with the data. 

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5. 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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