We present measurements of B → K*(892)γ decays using 365 fb−1 of data collected from 2019 to 2022 by the Belle II experiment at the SuperKEKB asymmetric-energy e+e− collider. The data sample contains (387 ± 6) × 106 Υ(4S) events. We measure branching fractions ( ℬ ) and CP asymmetries ( 𝒜_CP ) for both B0 → K*0γ and B+ → K*+γ decays. The difference in CP asymmetries ( Δ𝒜_CP ) and the isospin asymmetry (∆0+) between these neutral and charged channels are also measured. We obtain the following branching fractions and CP asymmetries: ℬ(B^0→K^*0γ)=(4.14± 0.10± 0.11)×10^-5 , ℬ(B^+→K^*+γ)=(4.04±0.13_-0.15^+0.13)×10^-5 , 𝒜_CP(B^0→K^*0γ)=(-3.3± 2.3± 0.4)% , and Δ𝒜_CP(B^+→K^*+γ)=(-0.7± 2.9± 0.5)% . The measured difference in CP asymmetries is Δ𝒜_CP=(+2.6±3.8± 0.6)% , and the measured isospin asymmetry is ∆0+ = (+4.8 ± 2.0 ± 1.8)

We present measurements of B+ -> rho(+) gamma and B-0 -> rho(0) gamma. decays using a combined data sample of 772 x 10(6) B (B) over bar pairs collected by the Belle experiment and 387 x 10(6) B (B) over bar pairs collected by the Belle II experiment in e(+) e(-) collisions at the Upsilon(4S) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II datasets yields 114 +/- 12 B+ -> rho(+) gamma. and 99 +/- 12 B-0 -> rho(0) gamma decays. The measured branching fractions are (13.1(-1.9-1.2)(+2.0+1.3)) x 10(-7) and (7.6 +/- 1.3(-0.8)(+1.0)) x 10(-7) for B+ -> rho(+) gamma. and B-0 -> rho(0) gamma. decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A(I)(B -> rho gamma) = (10.9(-11.7-7.3)(+11.2+7.8))% and the direct CP asymmetry A(CP)(B+ -> rho(+) gamma) = (-8.2 +/- 15.2(-1.3)(+2.0))%.

Abstract We report measurements of the absolute branching fractions $$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)$$ , $$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)$$ , and $$\mathcal{B}\left({B}_{s}^{0}\to {D}^{\pm }X\right)$$ , where the latter is measured for the first time. The results are based on a 121.4 fb −1 data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energy e + e − collider. We reconstruct one $${B}_{s}^{0}$$ meson in $${e}^{+}{e}^{-}\to \Upsilon\left(10860\right)\to {B}_{s}^{*}{\overline{B} }_{s}^{*}$$ events and measure yields of $${D}_{s}^{+}$$ , D 0, and D + mesons in the rest of the event. We obtain $$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)=\left(68.6\pm 7.2\pm 4.0\right)\%$$ , $$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)=\left(21.5\pm 6.1\pm 1.8\right)\%$$ , and $$\mathcal{B}\left({B}_{s}^{0}\to {D}^{\pm }X\right)=\left(12.6\pm 4.6\pm 1.3\right)\%$$ , where the first uncertainty is statistical and the second is systematic. Averaging with previous Belle measurements gives $$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)=\left(63.4\pm 4.5\pm 2.2\right)\%$$ and $$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)=\left(23.9\pm 4.1\pm 1.8\right)\%$$ . For the $${B}_{s}^{0}$$ production fraction at the Υ(10860), we find $${f}_{s}=\left({21.4}_{-1.7}^{+1.5}\right)\%$$ .

We present a measurement of the branching fraction and time-dependent charge-parity (CP) decay-rate asymmetries in B0→J/ψπ0 decays. The data sample was collected with the Belle II detector at the SuperKEKB asymmetric e+e− collider in 2019–2022 and contains (387±6)×106 BB¯ meson pairs from ϒ(4S) decays. We reconstruct 392±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 (B0→J/ψπ0)=(2.00±0.12±0.09)×10−5 and the direct and mixing-induced CP asymmetries to be CCP=0.13±0.12±0.03 and SCP=−0.88±0.17±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 Society 2025

We report measurements of time-dependent CP asymmetries in B^{0}→K_{S}^{0}π^{0}γ decays based on a data sample of (388±6)×10^{6}  BB[over ¯] events collected at the ϒ(4S) 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}π^{0} invariant mass: m(K_{S}^{0}π^{0})∈(0.8,1.0)  GeV/c^{2}, which is dominated by B^{0}→K^{*0}(→K_{S}^{0}π^{0})γ decays, and a complementary region m(K_{S}^{0}π^{0})∈(0.6,0.8)∪(1.0,1.8)  GeV/c^{2}. Our results have improved precision as compared to previous measurements and are consistent with theory predictions.

We measure the tau-to-light-lepton ratio of inclusive B-meson branching fractions R ( X tau= l ) equivalent to B ( B-* X tau nu ) = B ( B-* X l nu ) , where l indicates an electron or muon, and thereby test the universality of charged-current weak interactions. We select events that have one fully reconstructed B meson and a charged lepton candidate from 189 fb-1 - 1 of electron-positron collision data collected with the Belle II detector. We find R ( X tau= l ) = 0.228 + 0.016(stat) ( stat ) + 0.036(syst), ( syst ) , in agreement with standard-model expectations. This is the first direct measurement of R ( X tau= l ) .

Abstract We report results from a study of B±→ DK± decays followed by D decaying to the CP-even final state K+K− and CP-odd final state $$ {K}_S^0{\pi}^0 $$ K S 0 π 0 , where D is an admixture of D0 and $$ {\overline{D}}^0 $$ D ¯ 0 states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ3. The results are based on a combined analysis of the final data set of 772 × 106$$ B\overline{B} $$ B B ¯ pairs collected by the Belle experiment and a data set of 198 × 106$$ B\overline{B} $$ B B ¯ pairs collected by the Belle II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be $$ \mathcal{A} $$ A CP+ = (+12.5 ± 5.8 ± 1.4)% and $$ \mathcal{A} $$ A CP− = (−16.7 ± 5.7 ± 0.6)%, and the ratios of branching fractions to be $$ \mathcal{R} $$ R CP+ = 1.164 ± 0.081 ± 0.036 and $$ \mathcal{R} $$ R CP− = 1.151 ± 0.074 ± 0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries $$ \mathcal{A} $$ A CP+ and $$ \mathcal{A} $$ A CP− have similar magnitudes and opposite signs; their difference corresponds to 3.5 standard deviations. From these values we calculate 68.3% confidence intervals of (8.5° < ϕ3 < 16.5°) or (84.5° < ϕ3 < 95.5°) or (163.3° < ϕ3 < 171.5°) and 0.321 < rB < 0.465.

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral $B$ mesons produced in $\Upsilon(4S)$ decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using $B$ decays to flavor-specific hadronic final states reconstructed in a 362 $\text{fb}^{-1}$ sample of electron-positron collisions collected at the $\Upsilon(4S)$ resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of $(37.40 \pm 0.43 \pm 0.36) \%$, where the first uncertainty is statistical and the second systematic, which is $18\%$ better than the previous Belle II algorithm. Demonstrating the algorithm, we use $B^{0}\to J/\psi K^0_\text{S}$ decays to measure the mixing-induced and direct $CP$ violation parameters, $S = (0.724 \pm 0.035 \pm 0.009)$ and $C = (-0.035 \pm 0.026 \pm 0.029)$.

We report measurements of the e+e− → BB , BB^∗ , and B^∗B^∗ cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle II experiment. We reconstruct one B meson in a large number of hadronic final states and use its momentum to identify the production process. In the first 2 – 5 MeV above B^∗B^∗ threshold, the e+e− → B^∗B^∗ cross section increases rapidly. This may indicate the presence of a pole close to the threshold.

The description of the procedures of the direct statistical Monte Carlo simulation of weakly ionized flows arising during the flow of returning spacecraft is presented. For ionization and recombination reactions, expressions are given for the model dependence of the probability of reactions on the velocities and energies of the reagents. The dissociative recombination algorithm is presented, the computational efficiency of which is achieved by bypassing the simulation of the interaction of electrons and heavy particles. An approach to the construction of a weight scheme for elastic collisions and chemical reactions is described, which significantly increases the computational efficiency of calculations. An example of using the described numerical models and procedures to study the weakly ionized flow near the return capsule in typical entry conditions of orbiting spacecraft is presented. The calculation results are compared with the data of measurements of plasma parameters in the flight experiment.

We report a measurement of decay-time-dependent charge-parity (CP) asymmetries in B0→KS0KS0KS0 decays. We use 387×106 BB¯ pairs collected at the ϒ(4S) resonance with the Belle II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the CP-violating parameters S and C from a fit to the distribution of the decay-time difference between the two B mesons. The resulting confidence region is consistent with previous measurements in B0→KS0KS0KS0 and B0→(cc¯)K0 decays and with predictions based on the standard model. Published by the American Physical Society 2024

We report a determination of the CKM angle ϕ3, also known as γ, from a combination of measurements using samples of up to 711 fb−1 from the Belle experiment and up to 362 fb−1 from the Belle II experiment. We combine results from analyses of B+ → DK+, B+ → Dπ+, and B+ → D*K+ decays, where D is an admixture of D0 and D^0 mesons, in a likelihood fit to obtain ϕ3 = (75.2 ± 7.6)°. We also briefly discuss the interpretation of this result.

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral B mesons produced in Upsilon(4S) decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using B decays to flavor-specific hadronic final states reconstructed in a 362 fb(-1) sample of electron-positron collisions collected at the Upsilon(4S) resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of (37.40 +/- 0.43 +/- 0.36%), where the first uncertainty is statistical and the second systematic, which is 18% better than the previous Belle II algorithm. Demonstrating the algorithm, we use B-0 -> J/psi K-S(0) decays to measure the mixing-induced and direct CP violation parameters, S = (0.724 +/- 0.035 +/- 0.009) and C = (-0.035 +/- 0.026 +/- 0.029).

We perform a model-independent measurement of the D^0-D^0 mixing parameters using samples of e^+e^--collision data collected by the Belle and Belle II experiments that have integrated luminosities of 951fb^-1 and 408 fb^-1, respectively. Approximately 2.05×10^6 neutral D mesons are reconstructed in the D^0→ K^0_Sπ^+π^- channel, with the neutral D flavor tagged by the charge of the pion in the D^*+→ D^0π^+ decay. Assuming charge-parity symmetry, the mixing parameters are measured to be x = (4.0±1.7±0.4)× 10^-3 and y = (2.9±1.4±0.3)× 10^-3, where the first uncertainties are statistical and the second systematic. The results are consistent with previous determinations.

We describe a measurement of charge-parity (CP) violation asymmetries in B^0→η'K^0_S decays using Belle II data. We consider η'→η(→γγ)π^+π^- and η'→ρ(→π^+π^-)γ decays. The data were collected at the SuperKEKB asymmetric-energy e^+e^- collider between the years 2019 and 2022, and contain (387± 6) × 10^6 bottom-antibottom meson pairs. We reconstruct 829±35 signal decays and extract the CP violating parameters from a fit to the distribution of the proper-decay-time difference between the two B mesons. The measured direct and mixing-induced CP asymmetries are C_η'K^0_S = -0.19 ± 0.08 ± 0.03 and S_η'K^0_S = +0.67 ± 0.10 ± 0.04, respectively, where the first uncertainties are statistical and the second are systematic. These results are in agreement with current world averages and standard model predictions.

The effects of final-state interaction of hadrons, produced in e(+)e(-) annihilation near the threshold, are discussed. If there is a loosely bound state or a virtual state in a system of produced hadrons, then the energy dependence of hadroproduction cross section is very strong. Our approach is based on the use of the effective potentials accounting for the interaction between hadrons in the final state. The cases of a few channels with nonzero transition amplitudes between them are considered. It is shown that these transitions drastically change the energy dependence of the cross sections. In particular, a narrow resonance below the threshold in one channel leads to a broad peak in another channel. We explained the non-trivial energy dependence of the production cross sections of B (B) over bar, B* (B) over bar, B (B) over bar*, B* (B) over bar* near the thresholds in e(+)e(-) annihilation and obtained good agreement between our predictions and the experimental data available.

The cross section of the process e+e- -> x-+x-- has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on a full dataset collected below 1 GeV during three data taking seasons, corresponding to an integrated luminosity of about 62 pb-1. In the dominant p-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around 0-resonance the x-+x-- production cross section was measured for the first time with high beam energy resolution. The forward-backward charge asymmetry in the x-+x-- production has also been measured. It shows a strong deviation from the theoretical prediction based on the conventional scalar quantum electrodynamics framework, and it is in good agreement with the generalized vector-meson-dominance and dispersive-based predictions. The impact of the presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed.

We search for the e+e−→ηb(1S)ω and e+e−→χb0(1P)ω processes at a center-of-mass energy of 10.745 GeV, which is close to the peak of the ϒ(10753) state. We use data collected by the Belle II experiment during a special run, corresponding to an integrated luminosity of 9.8 fb−1. We reconstruct ω→π+π−π0 decays and use the ω meson's recoil mass to search for the signals. We do not find evidence for either process, and set upper limits on the corresponding Born-level cross sections of 2.5 pb and 7.8 pb, respectively, at the 90% confidence level. The χb0(1P)ω limit is the result of a combination of this analysis and a previous search using full reconstruction.Received 21 December 2023Accepted 7 March 2024DOI:https://doi.org/10.1103/PhysRevD.109.072013Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMultiquark bound statesQuark modelParticles & Fields

We report a measurement of decay-time dependent charge-parity (CP) asymmetries in B^0 → K^0_S K^0_S K^0_S decays. We use 387 × 10^6 BB̅ pairs collected at the Υ(4S) resonance with the Belle II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the CP-violating parameters S and C from a fit to the distribution of the decay-time difference between the two B mesons. The resulting confidence region is consistent with previous measurements in B^0 → K^0_S K^0_S K^0_S and B^0 → (cc̅)K^0 decays, and with predictions based on the standard model.

The ratio of branching fractions R(D*) = B((B) over bar -> D* tau(-) (nu) over bar (tau))/B((B) over bar -> D* l(-)(nu) over bar (l)), where l is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of 189 fb(-1) at the SuperKEKB asymmetric-energy e(+)e(-) collider. Data is collected at the Upsilon(4S) resonance, and one B meson in the Upsilon(4S) -> B (B) over bar decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as (B) over bar -> D* tau(-) (nu) over bar (tau)using leptonic t decays. The normalization decay, (B) over bar -> D* l(-)(nu) over bar (l,) produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields R(D*) = 0.262(-0.039)(+0.041) (stat)(-0.032)(+0.035) (syst). This result is consistent with the current world average and with Standard Model predictions.