arXiv subjects

B. G. Fulsom

Publications and source records attributed to B. G. Fulsom.

At least 19 recordsLinked to original sources

arXiv2026

First measurements of the branching fractions for the decay modes $Ξ_c^{0} \to Λη$ and $Ξ_c^0 \to Λη'$ and search for the decay $Ξ_c^{0} \to Λπ^0$ using Belle and Belle II data

Using data samples of 988.4 fb$^{-1}$ and 427.9 fb$^{-1}$ collected with the Belle and Belle II detectors, we present a study of the singly Cabibbo-suppressed decays $Ξ_c^{0} \to Λη$, $Λη'$, and $Λπ^0$. We observe the decay $Ξ_c^0 \to Λη$ and find evidence for the decay $Ξ_c^0 \to Λη'$, with corresponding branching ratios determined to be ${\mathcal{B}(Ξ_c^0 \to Λη)}/{\mathcal{B}(Ξ_c^0 \to Ξ^- π^+)}= (4.16 \pm 0.91 \pm {0.23})\%$ and ${\mathcal{B}(Ξ_c^0 \to Λη')}/{\mathcal{B}(Ξ_c^0 \to Ξ^- π^+)}= (2.48 \pm 0.82 \pm {0.12})\%$, respectively. We find no significant signal in the $Ξ_c^0 \to Λπ^0$ decay mode and set an upper limit at the 90% credibility level of ${\mathcal{B}(Ξ_c^0 \to Λπ^0)}/{\mathcal{B}(Ξ_c^0 \to Ξ^- π^+)}< {3.5\%}$. Multiplying these ratios by the world-average branching fraction of the normalization channel, $\mathcal{B}(Ξ_c^0 \to Ξ^- π^+)=(1.43 \pm 0.27)\%$, we obtain the absolute branching fractions of $\mathcal{B}(Ξ_c^0 \to Λη)= (5.95 \pm 1.30 \pm {0.32} \pm 1.13) \times 10^{-4}$, $\mathcal{B}(Ξ_c^0 \to Λη')= (3.55 \pm 1.17 \pm {0.17} \pm 0.68) \times 10^{-4}$, and an upper limit at the 90% credibility level on the absolute branching fraction of $\mathcal{B}(Ξ_c^0 \to Λπ^0)< {5.2} \times 10^{-4}$. The quoted first and second uncertainties are statistical and systematic, respectively, while the third uncertainties arise from the branching fraction of the normalization mode. These results are consistent with most theoretical predictions and further the understanding of the underlying decay mechanisms.

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arXiv2026

Measurement of time-dependent $CP$ asymmetries in $B^0 \to K_{\rm S}^0 \: π^{+} π^{-} γ$ decays at Belle and Belle II

We present a measurement of the time-dependent $CP$ asymmetry in $B^0 \to K_{\rm S}^0 \: π^{+} π^{-} γ$ decays using a data set of 365 fb$^{-1}$ recorded by the Belle II experiment and the final data set of 711 fb$^{-1}$ recorded by the Belle experiment at the ${\rm Υ(4S)}$ resonance. The direct and mixing-induced time-dependent $CP$ violation parameters $C$ and $S$ are determined along with two additional quantities, $S^{+}$ and $S^{-}$, defined in the two halves of the $m^2(K_{\rm S}^0 π^{+})-m^2(K_{\rm S}^0 π^{-})$ plane. The measured values are $C = -0.17 \pm 0.09 \pm 0.04$, $S = -0.29 \pm 0.11 \pm 0.05$, $S^{+} = -0.57 \pm 0.23 \pm 0.10$ and $S^{-} = 0.31 \pm 0.24 \pm 0.05$, where the first uncertainty is statistical and the second systematic.

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arXiv2025

Model-agnostic likelihood for the reinterpretation of the $B^+\to K^+ν\barν$ measurement at Belle II

We recently measured the branching fraction of the $B^{+}\rightarrow K^{+}ν\barν$ decay using 362fb$^{-1}$ of on-resonance $e^+e^-$ collision data under the assumption of Standard Model kinematics, providing the first evidence for this decay. To facilitate future reinterpretations and maximize the scientific impact of this measurement, we publicly release the full analysis likelihood along with all necessary material required for reinterpretation under arbitrary theoretical models sensitive to this measurement. In this work, we demonstrate how the measurement can be reinterpreted within the framework of the Weak Effective Theory. Using a kinematic reweighting technique in combination with the published likelihood, we derive marginal posterior distributions for the Wilson coefficients, construct credible intervals, and assess the goodness of fit to the Belle II data. For the Weak Effective Theory Wilson coefficients, the posterior mode of the magnitudes $|C_\mathrm{VL}+C_\mathrm{VR}|$, $|C_\mathrm{SL}+C_\mathrm{SR}|$, and $|C_\mathrm{TL}|$ corresponds to the point ${(11.3, 0.0, 8.2)}$. The respective 95\% credible intervals are $[1.9, 16.2]$, $[0.0, 15.4]$, and $[0.0, 11.2]$.

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arXiv2025

Observation of the radiative decay $D_s (2317)^+ \to D_s^* \gamma$

We observe the radiative decay $D^{*}_{s0}(2317)^{+} \to D_{s}^{*+} \gamma$ for the first time, with a significance exceeding $10$ standard deviations. The signal is found in the continuum $e^+ e^- \to c\bar{c}$ process with the combined data samples of 980.4~$\rm fb^{-1}$ and 427.9~$\rm fb^{-1}$ collected by the Belle and Belle~II detectors operating at the KEKB and SuperKEKB asymmetric-energy $e^+e^-$ colliders, respectively. The branching fraction ratio ${\cal B}(D^{*}_{s0}(2317)^{+} \to D_{s}^{*+} \gamma)/{\cal B}(D^{*}_{s0}(2317)^{+} \to D_{s}^{+} \pi^{0})$ is measured to be $[7.13 \pm 0.70({\rm stat.}) \pm 0.23({\rm syst.})]\%$. This result provides significant new experimental input for the determination of the quark structure of the $D^{*}_{s0}(2317)^{+}$, which remains unknown.

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arXiv2025

Measurement of the time-integrated $CP$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays using opposite-side flavor tagging at Belle and Belle II

We measure the time-integrated $CP$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays reconstructed in $e^+e^-\to c{\overline c}$ events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb${}^{-1}$, respectively. To infer the flavor of the $D^0$ meson, we exploit the correlation between the flavor of the reconstructed decay and the electric charges of particles reconstructed in the rest of the $e^+e^-\to c{\overline c}$ event. This results in a sample which is independent from any other previously used at Belle or Belle II. The result, $A_{CP}(D^0 \to K^0_{\rm S} K^0_{\rm S}) = (1.3 \pm 2.0 \pm 0.2)\%$, where the first uncertainty is statistical and the second systematic, is consistent with previous determinations and with $CP$ symmetry.

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arXiv2025

Search for lepton flavor-violating decay modes $B^0 \to K^{\ast 0}τ^\pm\ell^\mp$ ($\ell = e,μ$) with hadronic B-tagging at Belle and Belle II

We present the results of a search for the charged-lepton-flavor violating decays $B^0 \rightarrow K^{*0}τ^\pm \ell^{\mp}$, where $\ell^{\mp}$ is either an electron or a muon. The results are based on 365 fb$^{-1}$ and 711 fb$^{-1}$ datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic $B$-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed $B$ meson. We find no evidence for $B^0 \rightarrow K^{*0}τ^\pm \ell^{\mp}$ decays and set upper limits on the branching fractions in the range of $(2.9-6.4)\times10^{-5}$ at 90% confidence level.

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arXiv2025

Measurement of $C\!P$ violation in $B^{0}\rightarrow K_{S}^{0}π^{0}$ decays at Belle II

We report a measurement of the $C\!P$-violating parameters $A$ and $S$ in $B^{0}\to K_{S}^{0} π^{0}$ decays at Belle II using a sample of $387\times 10^{6}$ $B\bar{B}$ events recorded in $e^{+}e^{-}$ collisions at a center-of-mass energy corresponding to the $Υ(4S)$ resonance. These parameters are determined by fitting the proper decay-time distribution of a sample of 415 signal events. We obtain $A = 0.04^{+0.15}_{-0.14}\pm 0.05$ and $S = 0.75^{+0.20}_{-0.23}\pm 0.04$, where the first uncertainties are statistical and the second are systematic.

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arXiv2025

Search for $CP$ violation in $\Xi_c^+\to\Sigma^+h^+h^-$ and $\Lambda_c^+\to ph^+h^-$ at Belle II

We report decay-rate $CP$ asymmetries of the singly-Cabibbo-suppressed decays $\Xi_c^+\to\Sigma^+h^+h^-$ and $\Lambda_c^+\to ph^+h^-$, with $h=K,\pi$, measured using 428 fb$^{-1}$ of $e^+e^-$ collisions collected by the Belle II experiment at the SuperKEKB collider. The results, \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+K^+K^-) = (3.7\pm6.6\pm0.6)\%, \end{equation} \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+\pi^+\pi^-) = (9.5\pm6.8\pm0.5)\%, \end{equation} \begin{equation} A_{CP}(\Lambda_c^+\to pK^+K^-) = (3.9\pm1.7\pm0.7)\%, \end{equation} \begin{equation} A_{CP}(\Lambda_c^+\to p\pi^+\pi^-) = (0.3\pm1.0\pm0.2)\%, \end{equation} where the first uncertainties are statistical and the second systematic, agree with $CP$ symmetry. From these results we derive the sums \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+\pi^+\pi^-) \, + \, A_{CP}(\Lambda_c^+\to pK^+K^-) = (13.4 \pm 7.0\pm 0.9)\%, \end{equation} \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+K^+K^-) \, + \, A_{CP}(\Lambda_c^+\to p\pi^+\pi^-) = (\phantom{0}4.0 \pm 6.6\pm 0.7)\%, \end{equation} 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.

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arXiv2025

Measurement of the time-integrated CP asymmetry in $D^{0}\rightarrow K^{0}_{S}K^{0}_{S}$ decays using Belle and Belle II data

We measure the time-integrated CP asymmetry in $D^{0} \rightarrow K^{0}_{S}K^{0}_{S}$ decays reconstructed in $e^{+}e^{-} \rightarrow c\overline{c}$ events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 fb$^{-1}$ and 428 fb$^{-1}$, respectively. The $D^{0}$ decays are required to originate from the $D^{*+} \rightarrow D^{0}π^{+}$ decay, which determines the charm flavor at production time. A control sample of $D^{0} \rightarrow K^{+}K^{-}$ decays is used to correct for production and detection asymmetries. The result, $(-1.4\pm1.3{\rm(stat)}\pm0.1{\rm (syst)})\%$, is consistent with previous determinations and with CP symmetry.

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arXiv2025

Measurement of the time-integrated $CP$ asymmetry in $D^0\toπ^0π^0$ decays at Belle II

We measure the time-integrated $CP$ asymmetry, $A_{CP}$, in $D^0\toπ^0π^0$ decays reconstructed in $e^+e^-\to c\bar{c}$ events collected by Belle II during 2019--2022. The data corresponds to an integrated luminosity of 428$\mathrm{fb}^{-1}$. The $D^0$ decays are required to originate from the flavor-conserving $D^{*+} \to D^0 π^+$ decay to determine the charm flavor at production time. Control samples of $D^0\to K^- π^+$ decays, with or without an associated pion from a $D^{*+}$ decay, are used to correct for detection asymmetries. The result, $A_{CP}(D^0\toπ^0π^0) = (0.30\pm 0.72\pm 0.20)\%$, where the first uncertainty is statistical and the second systematic, is consistent with $CP$ symmetry.

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arXiv2025

Search for a pentaquark state decaying into $pJ/ψ$ in $Υ(1,2S)$ inclusive decays at Belle

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 the $pJ/ψ$ final state from $Υ(1,2S)$ inclusive decays. Here, the charge-conjugate $\bar{p}J/ψ$ is included. We observe clear $pJ/ψ$ production in $Υ(1,2S)$ decays and measure the branching fractions to be $B[Υ(1S) \to pJ/ψ+ anything] = [8.1 \pm 0.6(stat.) \pm 0.5(syst.)] \times 10^{-5}$ and $B[Υ(2S) \to pJ/ψ+ anything] = [4.3 \pm 0.5(stat.) \pm 0.4(syst.)] \times 10^{-5}$. We also measure the cross section of inclusive $pJ/ψ$ production in $e^+e^-$ annihilation to be $σ(e^+e^- \to pJ/ψ+ anything) = [108 \pm 11 (stat.) \pm 6(syst.)]$~fb at $\sqrt{s} = 10.52~\hbox{GeV}$ using an 89.5~fb$^{-1}$ continuum data sample. There is no significant $P_c(4312)^+$, $P_c(4440)^+$ or $P_c(4457)^+$ signal found in the $pJ/ψ$ final states in $Υ(1,2S)$ inclusive decays. We determine the upper limits of $B[Υ(1,2S)\to P_c^{+} + anything] \cdot B(P_c^{+}\to pJ/ψ)$ to be at the $10^{-6}$ level.

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arXiv2025

Measurements of the branching fractions of $Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}$, $Ξ_{c}^{+}\to Ξ^{0}π^{+}$, and $Ξ_{c}^{+}\to Ξ^{0}K^{+}$ at Belle and Belle II

Using 983.0 $\rm{fb}^{-1}$ and 427.9 $\rm{fb}^{-1}$ data samples collected with the Belle and Belle II detectors at the KEKB and SuperKEKB asymmetric energy $e^+e^-$ colliders, respectively, we present studies of the Cabibbo-favored $Ξ_c^+$ decays ${Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}}$ and $Ξ_{c}^{+}\to Ξ^{0}π^{+}$, and the singly Cabibbo-suppressed decay $Ξ_{c}^{+}\to Ξ^{0}K^{+}$. The ratios of branching fractions of ${Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}}$ and $Ξ_{c}^{+}\to Ξ^{0}K^{+}$ relative to that of $Ξ_{c}^{+}\toΞ^{-}π^{+}π^{+}$ are measured for the first time, while the ratio ${\cal B}(Ξ_{c}^{+}\toΞ^{0}π^{+})/{\cal B}(Ξ_{c}^{+}\toΞ^{-}π^{+}π^{+}) $ is also determined and improved by an order of magnitude in precision. The measured branching fraction ratios are $\frac{\cal{B}(Ξ_{c}^{+} \to Σ^{+}K_{S}^{0})}{\cal{B}(Ξ_{c}^{+}\to Ξ^{-}π^{+}π^+)}= 0.067 \pm 0.007 \pm 0.003$, $\frac{\cal{B}(Ξ_c^{+} \to Ξ^{0}π^{+})}{\cal{B}(Ξ_{c}^{+}\to Ξ^{-}π^{+}π^+)} = 0.251 \pm 0.005 \pm 0.010$, $\frac{\cal{B}(Ξ_c^{+} \to Ξ^{0}K^{+})}{\cal{B}(Ξ_{c}^{+}\to Ξ^{-}π^{+}π^+)} = 0.017 \pm 0.003 \pm 0.001$. Additionally, the ratio ${\cal B}(Ξ_{c}^{+}\toΞ^{0}K^{+})/{\cal B}(Ξ_{c}^{+}\toΞ^{0}π^{+})$ is measured to be $ 0.068 \pm 0.010 \pm 0.004$. Here, the first and second uncertainties are statistical and systematic, respectively. Multiplying the ratios by the branching fraction of the normalization mode, ${\mathcal B}(Ξ_{c}^{+}\toΞ^{-}π^{+}π^+)= (2.9\pm 1.3)\%$, we obtain the following absolute branching fractions ${\cal B}(Ξ_{c}^{+}\toΣ^{+}K^{0}_{S}) = (0.194 \pm 0.021 \pm 0.009 \pm 0.087 )%$, ${\cal B}(Ξ_{c}^{+}\toΞ^{0}π^{+}) = (0.728 \pm 0.014 \pm 0.027 \pm 0.326 )%$, ${\cal B}(Ξ_{c}^{+}\toΞ^{0}K^{+}) = (0.049 \pm 0.007 \pm 0.003 \pm 0.022 )%$.

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arXiv2025

Study of $χ_{bJ}(2P)\toωΥ(1S)$ at Belle

We report a study of the hadronic transitions $χ_{bJ}(2P)\toωΥ(1S)$, with $ω\toπ^{+}π^{-}π^{0}$, using $28.2\times10^6~Υ(3S)$ mesons recorded by the Belle detector. We present the first evidence for the near--threshold transition $χ_{b0}(2P)\toωΥ(1S)$, the analog of the near-threshold charm sector decay $χ_{c1}(3872)\toωJ/ψ$, with a branching fraction of $\cal{B}\big(χ_{b0}(2P)\toωΥ(1S)\big) = \big(0.55\pm0.19\pm0.07\big)\%$. We also obtain branching fractions of $\cal{B}\big(χ_{b1}(2P)\toωΥ(1S)\big) = \big(2.39{}^{+0.20}_{-0.19}\pm0.24\big)\%$ and $\cal{B}\big(χ_{b2}(2P)\toωΥ(1S)\big) = \big(0.47{}^{+0.13}_{-0.12}\pm0.06\big)\%$, confirming the measurement of the $ω$ transitions of the $J=1,2~P$--wave states. The ratio for the $J=2$ to $J=1$ transitions is also measured and found to differ by 3.3 standard deviations from the expected value in the QCD multipole expansion.

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arXiv2025

Search for Pcs(4459) and Pcs(4338) in Upsilon(1S,2S) inclusive decays at Belle

Using data samples of 102 million Upsilon(1S) events and 158 million Upsilon(2S) events collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we search for [udsccbar] pentaquark states decaying to Jpsi Lambda. Using the first observations of Upsilon(1S, 2S) inclusive decays to Jpsi Lambda, we find evidence of the P_ccbars(4459)0 state with a local significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the Pccbars(4459)0 to be (4471.7 +- 4.8 +- 0.6) MeV/c2 and (21.9 +- 13.1 +- 2.7) MeV, respectively. The branching fractions for P_ccbars(4459)0 production are measured to be B[Upsilon(1S) -> P_ccbars(4459)0/ Pbar_ccbars(4459)0 + anything] = (3.5 +- 2.0 +- 0.2)*10-6 and B[Upsilin(2S) -> P_ccbars(4459)0/ Pbar_ccbars(4459)0 +anything] = (2.9 +- 1.7 +- 0.4)*10-6. The inclusive branching fractions of Upsilon(1S, 2S) -> Jpsi Lambda/Lambdabar are measured to be B[Upsilin(1S) -> Jpsi Lambda/Lambdabar + anything] = (36.9 +- 5.3 +- 2.4)*10-6 and B[Upsilon(2S) -> Jpsi Lambda/Lambdabar + anything] = (22.3 +- 5.7 +- 3.1)*10-6. We measure the visible cross section $σ(e^+e^- \to J/psi Λ/\barΛ$ + anything) = (90 +- 14 +- 6) fb for the continuum production at $\sqrt{s} = 10.52$ GeV. In all cases, the first uncertainties are statistical and the second are systematic.

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arXiv2025

Search for lepton-flavor-violating tau decays to $\ellα$ at Belle

We report a search for the lepton-flavor-violating decays $τ^{\pm}\to\ell^{\pm}α$~($\ell=e,μ$), where $α$ is an undetected spin-0 particle, such as an axion-like particle using $736\times10^{6}$ tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at 95\% confidence level: $\mathcal{B}(τ^{\pm}\rightarrow e^{\pm}α)$ $<$ $(0.4$--$6.4)\times10^{-4}$ and $\mathcal{B}(τ^{\pm}\rightarrow μ^{\pm}α)$ $<$ $(0.2$--$3.5)\times10^{-4}$ at 95\% confidence level for an $α$ mass in the range $0.0\leq m_α\leq 1.6$~GeV/$c^{2}$.

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arXiv2025

Measurement of the Ratio of Partial Branching Fractions of Inclusive $\overline{B} \to X_u \ell \overlineν$ to $\overline{B} \to X_{c} \ell \overlineν$ and the Ratio of their Spectra with Hadronic Tagging

We present a measurement of the ratio of partial branching fractions of the semi-leptonic inclusive decays, $\overline{B} \to X_{u} \ell \overlineν$ to $\overline{B} \to X_{c} \ell \overlineν$, where $\ell = (e, μ)$, using the full Belle sample of $772 \times 10^{6}$ $B \kern 0.18em\overline{\kern -0.18em B}$ pairs collected at the $Υ(4S)$ resonance. The ratio is measured via a two-dimensional fit to the squared four-momentum transfer to the lepton pair, and the charged lepton energy in the $B$ meson rest frame, where the latter must be larger than $1$ Ge\kern -0.1em V, covering approximately $86\%$ and $78\%$ of the $\overline{B} \to X_{u} \ell \overlineν$ and $\overline{B} \to X_{c} \ell \overlineν$ phase space, respectively. We find $Δ\mathcal{B}(\overline{B} \to X_{u} \ell \overlineν)/ Δ\mathcal{B}(\overline{B} \to X_{c} \ell \overlineν) = (1.99 \pm 0.17_{\rm stat} \pm 0.16_{\rm syst}) \times 10^{-2}$ where the uncertainties are statistical and systematic, respectively. In addition, we report the partial branching fractions separately for charged and neutral $B$ meson decays, and for electron and muon decay channels. We place a limit on isospin breaking in $\overline{B} \to X_{u} \ell \overlineν$ decays, and find no indication of lepton flavor universality violation in either the charmed or charmless mode. Furthermore, we unfold the $\overline{B} \to X_{u} \ell \overlineν$ and $\overline{B} \to X_{c} \ell \overlineν$ yields and report the differential ratio in lepton energy and four-momentum transfer squared.

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arXiv2025

Model-independent measurement of $D^0$-$\overline{D}{}^0$ mixing parameters in $D^0\rightarrow K^0_{S}π^+π^-$ decays at Belle and Belle II

We perform a model-independent measurement of the $D^0$-$\overline{D}{}^0$ mixing parameters using samples of $e^+e^-$-collision data collected by the Belle and Belle II experiments that have integrated luminosities of $951\ \text{fb}^{-1}$ and $408\ \text{fb}^{-1}$, respectively. Approximately $2.05\times10^6$ neutral $D$ mesons are reconstructed in the $D^0\rightarrow K^0_{S}π^+π^-$ channel, with the neutral $D$ flavor tagged by the charge of the pion in the $D^{*+}\rightarrow D^0π^+$ decay. Assuming charge-parity symmetry, the mixing parameters are measured to be $ x = (4.0\pm1.7\pm0.4)\times 10^{-3} $ and $ y = (2.9\pm1.4\pm0.3)\times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results are consistent with previous determinations.

hep-ex↗

arXiv2025

Measurement of the branching fraction, polarization, and time-dependent $CP$ asymmetry in $B^0 \to ρ^+ρ^-$ decays and constraint on the CKM angle $ϕ_2$

We present a measurement of the branching fraction and fraction of longitudinal polarization of $B^0 \to ρ^+ ρ^-$ decays, which have two $π^0$'s in the final state. We also measure time-dependent {\it CP} violation parameters for decays into longitudinally polarized $ρ^+ ρ^-$ pairs. This analysis is based on a data sample containing $(387\pm6) \times 10^6$ $Υ(4S)$ mesons collected with the Belle~II detector at the SuperKEKB asymmetric-energy $e^+e^-$ collider in 2019-2022. We obtain $\mathcal{B}(B^0\toρ^+ρ^-) = (2.89 ^{+0.23}_{-0.22} {}^{+0.29}_{-0.27}) \times 10^{-5}, f_{L} = 0.921 ^{+0.024}_{-0.025} {}^{+0.017}_{-0.015}$, \mbox{$S = -0.26\pm0.19\pm0.08$}, and $C = -0.02\pm0.12^{+0.06}_{-0.05}$, where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the CKM angle $ϕ_2$ and obtain two solutions; the result consistent with other Standard Model constraints is $ϕ_2 = (92.6^{+4.5}_{-4.7})^\circ$.

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