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Using a data sample of $427.9{\mathrm{fb}}^{-1}$ collected by the Belle II detector at or near the $\mathrm{\Upsilon }\left(4S\right)$ and $\mathrm{\Upsilon }\left(10753\right)$ resonances, the cross sections for $e^{+}{e}^{-}\to h^{+}{h}^{-}J/\psi (h=\pi /K/p)$ at center-of-mass energies ranging from 3.8 GeV or the production threshold to $5.5/6.0/7.0\mathrm{GeV}$ have been measured via initial-state radiation. The cross sections for the processes $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}J/\psi$ and $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ are consistent with previously published results. The cross sections for these channels obtained by combining with previous Belle results are also given. The process $e^{+}{e}^{-}\to p\overline{p}J/\psi$ is investigated for the first time. The yields are small and no significant structure is observed in the cross section versus energy. Searches for vector charmoniumlike states in the $h^{+}{h}^{-}J/\psi$ systems, and for associated intermediate states in the $h^{\pm }J/\psi$ systems, are also presented. 

We report the first search for the flavor-changing neutral-current decays $B\to X_s\nu \overline{\nu }$ , where $X_s$ is a hadronic system with strangeness equal to 1, in data collected with the Belle II detector at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The data sample corresponds to an integrated luminosity of $365{\mathrm{fb}}^{-1}$ collected at the $\mathrm{\Upsilon }\left(4S\right)$ resonance and $43{\mathrm{fb}}^{-1}$ collected at a center-of-mass energy 60 MeV below resonance for estimation of $e^{+}{e}^{-}\to q\overline{q}$ continuum background. One of the $B$ mesons from the $\mathrm{\Upsilon }\left(4S\right)\to B\overline{B}$ decay is fully reconstructed in a hadronic decay mode. The $B\to X_s\nu \overline{\nu }$ decay is reconstructed with a sum-of-exclusives approach that uses 30 $X_s$ decay modes. This approach provides high sensitivity to the inclusive decay, despite the presence of two undetected neutrinos. The search is performed in three regions of the $X_s$ mass, $M_{X_s}^{\mathrm{true}}$ , chosen to separate contributions from $K$ , $K^{*}\left(892\right)$ , and heavier strange final states. We do not observe a significant signal and set upper limits at 90% confidence level on the partial branching fractions for the regions $0.0<M_{X_s}^{\mathrm{true}}<0.6\mathrm{GeV}/c^2$ , $0.6<M_{X_s}^{\mathrm{true}}<1.0\mathrm{GeV}/c^2$ , and $1.0\mathrm{GeV}/c^2<M_{X_s}^{\mathrm{true}}$ of $2.2\times {10}^{-5}$ , $9.3\times {10}^{-5}$ , and $30.9\times {10}^{-5}$ , respectively. Combining the three mass regions, we obtain the upper limit on the branching fraction, $B(B\to X_s\nu \overline{\nu })<3.3\times {10}^{-4}$ . 

A<sc>bstract</sc> Using data samples collected by the Belle and Belle II experiments at the Υ(4S) resonance with integrated luminosities of 571 fb⁻¹and 365 fb⁻¹, respectively, we measure the pseudoscalarB-meson mass difference to bem(B⁰) −m(B⁺) = (0.495 ± 0.024 ± 0.005) MeV/c². The results are based on a simultaneous fit to the variable$${\overline{M} }_{bc}$$, which is related to theBmomentum, forB⁰andB⁺candidates; and to the energy dependence of$$\mathcal{R}=\sigma ({e}^{+}{e}^{-}\to {B}^{0}{\overline{B} }^{0}) / \sigma ({e}^{+}{e}^{-}\to {B}^{+}{B}^{-})$$, which is measured using changes in the average center-of-mass energy over the data taking periods. The phase-space hypothesis$$\mathcal{R}={({p}_{{B}^{0}} /{p}_{{B}^{+}})}^{3}$$, upon which previous measurements rely, is strongly disfavored by our fit; the measured mass-difference value for the phase-space hypothesis also differs significantly from our measurement. We constrain$$\mathcal{R}$$in a broader energy range than covered by the direct measurement and extract the energy dependence of$$\mathcal{R}$$in the range from the$$B\overline{B }$$threshold up to 10.59 GeV. We interpret the results using a phenomenological model and constrain the parameters of the$$B\overline{B }$$potential in the isovector channel. 

A<sc>bstract</sc> Using the data samples of 102 million Υ(1S) and 158 million Υ(2S) events collected by the Belle detector, we search for a pentaquark state in thepJ/ψfinal state from Υ(1,2S) inclusive decays. Here, the charge-conjugate$$\overline{p }J/\psi $$is included. We observe clearpJ/ψproduction in Υ(1,2S) decays and measure the branching fractions to be$$\mathcal{B}[\Upsilon (1S)\to pJ/\psi +anything]=[8.1\pm 0.6(stat.)\pm 0.5(syst.)]\times {10}^{-5}$$and$$\mathcal{B}[\Upsilon (2S)\to pJ/\psi +anything]=[4.3\pm 0.5(stat.)\pm 0.4(syst.)]\times {10}^{-5}$$. We also measure the cross section of inclusivepJ/ψproduction ine⁺e⁻annihilation to beσ(e⁺e⁻→pJ/ψ+anything) = [108 ± 11(stat.) ± 6(syst.)] fb at$$\sqrt{s}=10.52$$GeV using an 89.5 fb⁻¹continuum data sample. There is no significantP_c(4312)⁺,P_c(4440)⁺orP_c(4457)⁺signal found in thepJ/ψfinal states in Υ(1,2S) inclusive decays. We determine the upper limits of$$\mathcal{B}\left[\Upsilon \left({1},{2}S\right)\to {P}_{c}^{+}+anything\right]\cdot \mathcal{B}\left({P}_{c}^{+}\to pJ/\psi \right)$$to be at the 10⁻⁶level. 

We measure the time- and phase-space-integrated $CP$ asymmetry ${\mathcal{A}}_{CP}$ in $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays reconstructed in $e^{+}{e}^{-}\to c\overline{c}$ events collected by the Belle II experiment from 2019 to 2022. This sample corresponds to an integrated luminosity of $428{\mathrm{fb}}^{-1}$ . We require $D^0$ mesons to be produced in $D^{*+}\to D^0{\pi }^{+}$ decays to determine their flavor at production. Control samples of $D^0\to K^{-}{\pi }^{+}$ decays are used to correct for reconstruction-induced asymmetries. The result, ${\mathcal{A}}_{CP}\left(D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0\right)=(0.29\pm 0.27\pm 0.13)\%$ , where the first uncertainty is statistical and the second systematic, is the most precise result to date and is consistent with $CP$ conservation. 

We search for the $e^{+}{e}^{-}\to \gamma {\chi }_{bJ}$ ( $J=0$ , 1, 2) processes at center-of-mass energies $\sqrt{s}=10.653$ , 10.701, 10.746, and 10.804 GeV. These data were collected with the Belle II detector at the SuperKEKB collider and correspond to 3.5, 1.6, 9.8, and $4.7{\mathrm{fb}}^{-1}$ of integrated luminosity, respectively. We set upper limits at the 90% confidence level on the Born cross sections for $e^{+}{e}^{-}\to \gamma {\chi }_{bJ}$ at each center-of-mass energy $\sqrt{s}$ near 10.746 GeV. The upper limits at 90% confidence level on the Born cross sections for $e^{+}{e}^{-}\to \gamma {\chi }_{b1}$ are significantly smaller than the corresponding measured values for $e^{+}{e}^{-}\to \omega {\chi }_{b1}$ and $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\mathrm{\Upsilon }\left(2S\right)$ at $\sqrt{s}=10.746\mathrm{GeV}$ . 

We report decay-rate $CP$ asymmetries of the singly-Cabibbo-suppressed decays ${\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^{+}{h}^{+}{h}^{-}$ and ${\mathrm{\Lambda }}_c^{+}\to p{h}^{+}{h}^{-}$ , with $h=K$ , $\pi$ , measured using $428{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collisions collected by the Belle II experiment at the SuperKEKB collider. The results, $A_{CP}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^{+}{K}^{+}{K}^{-})=(3.7\pm 6.6\pm 0.6)\%$ , $A_{CP}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^{+}{\pi }^{-})=(9.5\pm 6.8\pm 0.5)\%$ , $A_{CP}({\mathrm{\Lambda }}_c^{+}\to p{K}^{+}{K}^{-})=(3.9\pm 1.7\pm 0.7)\%$ , $A_{CP}({\mathrm{\Lambda }}_c^{+}\to p{\pi }^{+}{\pi }^{-})=(0.3\pm 1.0\pm 0.2)\%$ , where the first uncertainties are statistical and the second systematic, agree with $CP$ symmetry. From these results we derive the sums $A_{CP}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^{+}{\pi }^{-})+A_{CP}({\mathrm{\Lambda }}_c^{+}\to p{K}^{+}{K}^{-})=(13.4\pm 7.0\pm 0.9)\%$ , $A_{CP}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^{+}{K}^{+}{K}^{-})+A_{CP}({\mathrm{\Lambda }}_c^{+}\to p{\pi }^{+}{\pi }^{-})=(4.0\pm 6.6\pm 0.7)\%$ , which are consistent with the $U$ -spin symmetry prediction of zero. These are the first measurements of $CP$ asymmetries for individual hadronic three-body charmed-baryon decays. 

We present an analysis of the processes $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ , $\eta \mathrm{\Upsilon }\left(2S\right)$ , and $\gamma X_b$ with $X_b\to {\pi }^{+}{\pi }^{-}{\chi }_{bJ},{\chi }_{bJ}\to \gamma \mathrm{\Upsilon }\left(1S\right)$ ( $J=1$ , 2) reconstructed from $\gamma \gamma {\pi }^{+}{\pi }^{-}{\ell }^{+}{\ell }^{-}$ $(\ell =e,\mu )$ final states in $19.6{\mathrm{fb}}^{-1}$ of Belle II data collected at four energy points near the peak of the $\mathrm{\Upsilon }\left(10753\right)$ resonance. Here, $X_b$ is a hypothetical bottomonium-sector partner of the $X\left(3872\right)$ . In the process $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(2S\right)$ , we observe a signal with a significance that exceeds $6.0\sigma$ when all energy points are combined. A signal with a significance of $4.2\sigma$ is observed at a center-of-mass energy of 10.653 GeV, close to the $B^{*}{\overline{B}}^{*}$ threshold. At this energy, we measure $\sigma \left(\eta \mathrm{\Upsilon }\right(2S\left)\right)/\sigma \left({\pi }^{+}{\pi }^{-}\mathrm{\Upsilon }\right(2S\left)\right)>23$ at the 90% confidence level, indicating a strong violation of heavy-quark spin symmetry. No significant signal is observed for $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ or $\gamma X_b$ . Upper limits on the Born cross sections for the processes $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ and $e^{+}{e}^{-}\to \gamma X_b$ with $X_b\to {\pi }^{+}{\pi }^{-}{\chi }_{bJ}$ are determined. 

We perform an angular analysis of the $B\to K^{*}{e}^{+}{e}^{-}$ decay for the dielectron mass squared, $q^2$ , range of $0.0008–1.1200{\mathrm{GeV}}^2/c^4$ using the full Belle dataset in the $K^{*0}\to K^{+}{\pi }^{-}$ and $K^{*+}\to K_S^0{\pi }^{+}$ channels, incorporating new methods of electron identification to improve the statistical power of the dataset. This analysis is sensitive to contributions from right-handed currents from physics beyond the Standard Model by constraining the Wilson coefficients ${\mathcal{C}}_7^{(\prime )}$ . We perform a fit to the $B\to K^{*}{e}^{+}{e}^{-}$ differential decay rate and measure the imaginary component of the transversality amplitude to be $A_T^{\mathrm{Im}}=-1.27\pm 0.52\pm 0.12$ , and the $K^{*}$ transverse asymmetry to be $A_T^{\left(2\right)}=0.52\pm 0.53\pm 0.11$ , with $F_L$ and $A_T^{\mathrm{Re}}$ fixed to the Standard Model values. The resulting constraints on the value of ${\mathcal{C}}_7^{\prime }$ are consistent with the Standard Model within a $2\sigma$ confidence interval. Published by the American Physical Society2024 

We report the results of the first search for Standard Model and baryon-number-violating two-body decays of the neutral $B$ mesons to ${\mathrm{\Lambda }}^0$ and ${\mathrm{\Omega }}_c^{(*)0}$ using $711{\mathrm{fb}}^{-1}$ of data collected at the $\mathrm{\Upsilon }\left(4S\right)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We observe no evidence of signal from any such decays and set 95% confidence-level upper limits on the products of $B^0$ and ${\overline{B}}^0$ branching fractions for these two-body decays with $\mathcal{B}({\mathrm{\Omega }}_c^0\to {\pi }^{+}{\mathrm{\Omega }}^{-})$ in the range between $9.5\times {10}^{-8}$ and $31.2\times {10}^{-8}$ . Published by the American Physical Society2024