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1. 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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2. Production cross sections of light and charmed mesons in $e^{+}{e}^{-}$ annihilation near 10.58 GeV

   https://doi.org/10.1103/PhysRevD.111.052003  

   Seidl, R; Adachi, I; Aihara, H; Aushev, T; Ayad, R; Banerjee, Sw; Belous, K; Bennett, J; Bessner, M; Bhuyan, B; et al (March 2025, Physical Review D)

   We report measurements of production cross sections for ${\rho }^{+}$, ${\rho }^0$, $\omega$, $K^{*+}$, $K^{*0}$, $\varphi$, $\eta$, $K_S^0$, $f_0\left(980\right)$, $D^{+}$, $D^0$, $D_s^{+}$, $D^{*+}$, $D^{*0}$, and $D_s^{*+}$in $e^{+}{e}^{-}$collisions at a center-of-mass energy near 10.58 GeV. The data were recorded by the Belle experiment, consisting of $571{\mathrm{fb}}^{-1}$at 10.58 GeV and $74{\mathrm{fb}}^{-1}$at 10.52 GeV. Production cross sections are extracted as a function of the fractional hadron momentum $x_p$. The measurements are compared to Monte Carlo generator predictions with various fragmentation settings, including those that have increased fragmentation into vector mesons over pseudoscalar mesons. The cross sections measured for light hadrons are consistent with no additional increase of vector over pseudoscalar mesons. The charmed-meson cross sections are compared to earlier measurements—when available—including older Belle results, which they supersede. They are in agreement before application of an improved initial-state radiation correction procedure that causes slight changes in their $x_p$shapes. Published by the American Physical Society2025 

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3. Measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ cross section in the energy range 0.62–3.50 GeV at Belle II

   https://doi.org/10.1103/PhysRevD.110.112005  

   Adachi, I; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, V; Aversano, M; et al (December 2024, Physical Review D)

   We report a measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an $e^{+}{e}^{-}$data sample corresponding to $191{\mathrm{fb}}^{-1}$of integrated luminosity, collected at a center-of-mass energy at or near the $\mathrm{\Upsilon }\left(4S\right)$resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0\gamma$events, which involve a ${\pi }^0\to \gamma \gamma$decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the $\omega$and $\varphi$resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62–1.80 GeV energy range yield $a_{\mu }^{3\pi }=[48.91\pm 0.23(\mathrm{stat})\pm 1.07(\mathrm{syst}\left)\right]\times {10}^{-10}$for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by 2.5 standard deviations from the most precise current determination. Published by the American Physical Society2024 

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4. Search for the decay $B^0\to \gamma \gamma$ using Belle and Belle II data

   https://doi.org/10.1103/PhysRevD.110.L031106  

   Adachi, I; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Al_Said, S; Althubiti, N; Anh_Ky, N; Asner, D M; Atmacan, H; et al (August 2024, Physical Review D)

   We report the result of a search for the rare decay $B^0\to \gamma \gamma$using a combined dataset of $753\times {10}^{6}B\overline{B}$pairs collected by the Belle experiment and $387\times {10}^{6}B\overline{B}$pairs collected by the Belle II experiment from decays of the $\mathrm{\Upsilon }\left(4\mathrm{S}\right)$resonance produced in $e^{+}{e}^{-}$collisions. A simultaneous fit to the Belle and Belle II data sets yields ${11.0}_{-5.5}^{+6.5}$signal events, corresponding to a $2.5\sigma$significance. We determine the branching fraction $\mathcal{B}(B^0\to \gamma \gamma )=\left({3.7}_{-1.8}^{+2.2}\right(\text{stat})\pm 0.5(\text{syst}\left)\right)\times {10}^{-8}$and set a 90% credibility level upper limit of $\mathcal{B}(B^0\to \gamma \gamma )<6.4\times {10}^{-8}$. Published by the American Physical Society2024 

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5. Observation of the Open-Charm Tetraquark Candidate $T_{cs0}^{*}(2870{)}^0$ in the $B^{-}\to D^{-}{D}^0{K}_S^0$ Decay

   https://doi.org/10.1103/PhysRevLett.134.101901  

   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 (March 2025, Physical Review Letters)

   An amplitude analysis of $B^{-}\to D^{-}{D}^0{K}_S^0$decays is performed using proton-proton collision data, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$, collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. A resonant structure of spin-parity $0^{+}$is observed in the $D^0{K}_S^0$invariant-mass spectrum with a significance of $5.3\sigma$. The mass and width of the state, modeled with a Breit-Wigner line shape, are determined to be $2883\pm 11\pm 8\mathrm{MeV}/c^2$and ${87}_{-47}^{+22}\pm 17\mathrm{MeV}$, respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark candidate $T_{cs0}^{*}(2870{)}^0$observed previously in the $D^{+}{K}^{-}$final state of the $B^{-}\to D^{-}{D}^{+}{K}^{-}$decay. This result confirms the existence of the $T_{cs0}^{*}(2870{)}^0$state in a new decay mode. The $T_{cs1}^{*}(2900{)}^0$state, reported in the $B^{-}\to D^{-}{D}^{+}{K}^{-}$decay, is also searched for in the $D^0{K}_S^0$invariant-mass spectrum of the $B^{-}\to D^{-}{D}^0{K}_S^0$decay, without finding evidence for it. © 2025 CERN, for the LHCb Collaboration2025CERN 

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