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Ferber, T. (ORCID:0000000268490427)

Publications and source records attributed to Ferber, T. (ORCID:0000000268490427).

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Search for an axion-like particle in B β†’ K (*) a(β†’ Ξ³Ξ³) decays at Belle

We report a search for an axion-like particle a in B β†’ K (*) a decays using data collected with the Belle detector at the KEKB asymmetric-energy electron-positron collider. The search is based on a 711 fb βˆ’1 data sample collected at the Ξ₯(4S) resonance energy, corresponding to a sample of 772 Γ— 10 6 Ξ₯(4S) events. In this study, we search for the decay of the axion-like particle into a pair of photons, a β†’ Ξ³Ξ³. We scan the two-photon invariant mass in the range 0.16 GeV–4.50 GeV for the K modes and 0.16 GeV–4.20 GeV for the K * modes. No significant signal is observed in any of the modes, and 90% confidence level upper limits are established on the coupling to the W boson, g aW , as a function of a mass. The limits range from 3 Γ— 10 βˆ’6 GeV βˆ’1 to 3 Γ— 10 βˆ’5 GeV βˆ’1 , improving the current constraints on g aW by a factor of two over the most stringent previous experimental results.

B physics↗
DOE OSTI2025

Model-agnostic likelihood for the reinterpretation of the 𝐡 + β†’ 𝐾 + ⁒$𝑣\bar{𝑣}$ measurement at Belle II

We recently measured the branching fraction of the 𝐡 + β†’ 𝐾 + ⁒$𝑣\bar{𝑣}$ decay using 362 fb βˆ’1 of on-resonance 𝑒 + ⁒𝑒 βˆ’ 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 |𝐢 VL +𝐢 VR |, |𝐢 SL +𝐢 SR |, and |𝐢 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].

bottom quark↗
DOE OSTI2025

Charged-hadron identification at Belle II

The Belle II experiment’s ability to identify particles critically affects the sensitivity of its measurements. We describe Belle II’s algorithms for identifying charged particles and evaluate their performance in separating pions, kaons, and protons using $426\,\text {fb}^{-1}$ of data collected at the energy-asymmetric $e^{+}e^{-}$ collider SuperKEKB in 2019–2022 at center-of-mass energies at and near the mass of the $\Upsilon$ (4S).

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2025

Measurement of 𝐡 + β†’πœ + ⁒𝜈 𝜏 branching fraction with a hadronic tagging method at Belle II

We present a measurement of the branching fraction of 𝐡 + β†’πœ + ⁒𝜈 𝜏 decays using 387Β±6Γ—10 6 ϒ⁑(4⁒𝑆) collected between 2019 and 2022 with the Belle II detector at the SuperKEKB 𝑒 + ⁒𝑒 βˆ’ collider. We reconstruct the accompanying 𝐡 βˆ’ meson using the hadronic tagging method, while 𝐡 + β†’πœ + ⁒𝜈 𝜏 candidates are identified in the recoil. We find evidence for 𝐡 + β†’πœ + ⁒𝜈 𝜏 decays at 3.0 standard deviations, including systematic uncertainties. The measured branching fraction is ℬ⁑(𝐡 + β†’πœ + ⁒𝜈 𝜏 )=[1.24Β±0.41⁒(stat)Β±0.19⁒(syst)]Γ—10 βˆ’4 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Observation of the decays 𝐡 + β†’ Ξ£ 𝑐 ⁒(2455) ++ $\bar{Ξ}^-_c$ and 𝐡 0 β†’ Ξ£ 𝑐 ⁒(2455) 0⁒ $\bar{Ξ}^0_𝑐$

We report the first observation of the two-body baryonic decays 𝐡 + β†’ Ξ£ 𝑐 ⁒(2455) ++ $\bar{Ξ}^-_c$ and 𝐡 0 β†’ Ξ£ 𝑐 ⁒(2455) 0⁒ $\bar{Ξ}^0_𝑐$ with significances of 7.3⁒𝜎 and 6.2⁒𝜎, respectively, including statistical and systematic uncertainties. The branching fractions are measured to be ℬ⁑(𝐡 + β†’ Ξ£ 𝑐 ⁒(2455) ++ $\bar{Ξ}^-_c$) = (5.74 Β± 1.11 Β± 0.4⁒2$^{+2.47}_{βˆ’1.53}$) Γ—10 βˆ’4 and ℬ⁑(𝐡 0 β†’ Ξ£ 𝑐 ⁒(2455) 0⁒ $\bar{Ξ}^0_𝑐$) = (4.83 Β± 1.12 Β± 0.3⁒7$^{+0.72}_{βˆ’0.60}$) Γ—10 βˆ’4 . The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the absolute branching fractions of $\bar{Ξ}^-_c$ or $\bar{Ξ}^0_𝑐$ decays. The data samples used for this analysis have integrated luminosities of 711 fb βˆ’1 and 365 fb βˆ’1 , and were collected at the ϒ⁑(4⁒𝑆) resonance by the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy 𝑒 + ⁒𝑒 βˆ’ colliders, respectively.

branching fraction↗
DOE OSTI2025

Measurements of the branching fractions of ${\Xi }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}$, ${\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+}$, and ${\Xi }_{c}^{+}\to {\Xi }^{0}{K}+$ at Belle and Belle II

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

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for lepton flavor-violating decay modes B 0 β†’ K* 0 Ο„ Β± β„“ βˆ“ (β„“ = e, ΞΌ) 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 β†’ K *0 Ο„ Β± β„“ βˆ“ , where β„“ βˆ“ is either an electron or a muon. The results are based on 365 fb βˆ’1 and 711 fb βˆ’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 β†’ K* 0 Ο„ Β± β„“ βˆ“ decays and set upper limits on the branching fractions in the range of (2.9–6.4)Γ—10 βˆ’5 at 90% confidence level.

B physics↗
DOE OSTI2025

Search for lepton-flavor-violating tau decays to β„“Ξ± at Belle

We report a search for the lepton-flavor-violating decays Ο„ Β± β†’ β„“ Β± Ξ± (β„“ = e, ΞΌ), where Ξ± is an undetected spin-0 particle, such as an axion-like particle using 736 Γ— 10 6 tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energy e + e βˆ’ collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at 95% confidence level: $\mathcal{B}$ (Ο„ Β± β†’ e Β± Ξ±) < (0.4–6.4) Γ— 10 βˆ’4 and $\mathcal{B}$ (Ο„ Β± β†’ ΞΌ Β± Ξ±) < (0.2–3.5) Γ— 10 βˆ’4 at 95% confidence level for an Ξ± mass in the range 0.0 ≀ m Ξ± ≀ 1.6 GeV/c 2 .

tau physics↗
DOE OSTI2025

Search for lepton-flavor-violating ${\tau }^{-}\to {{\ell}}^{-}{K}_{s}^{0}$ decays at Belle and Belle II

We present the results of a search for charged-lepton-flavor violating decays ${\tau }^{-}\to {{\ell}}^{-}{K}_{s}^{0}$, where β„“ βˆ’ is either an electron or a muon. We combine e + e βˆ’ data samples recorded by the Belle II experiment at the SuperKEKB collider (428 fb βˆ’1 ) with samples recorded by the Belle experiment at the KEKB collider (980 fb βˆ’1 ) to obtain a sample of 1.3 billion e + e βˆ’ β†’ Ο„ + Ο„ βˆ’ events. We observe 0 and 1 events and set 90% confidence level upper limits of 0.8 Γ— 10 βˆ’8 and 1.2 Γ— 10 βˆ’8 on the branching fractions of the decay modes ${\tau }^{-}\to {e}^{-}{K}_{S}^{0}$ and ${\tau }^{-}\to {\mu }^{-}{K}_{S}^{0}$, respectively. These are the most stringent upper limits to date.

beyond Standard Model↗
DOE OSTI2025

Measurement of the 𝐢⁒𝑃 asymmetry in 𝐷 + β†’ πœ‹ + β’πœ‹ 0 decays at Belle II

We measure the 𝐢⁒𝑃 asymmetry in 𝐷 + β†’ πœ‹ + β’πœ‹ 0 decays reconstructed in 𝑒 + ⁒𝑒 βˆ’ collisions at the Belle II experiment using a dataset corresponding to an integrated luminosity of 428 fb βˆ’1 . A control sample of 𝐷 + β†’ πœ‹ + ⁒𝐾$^0_𝑆$ decays is used to correct for detection and production asymmetries. The result 𝐴 𝐢⁒𝑃 ⁑(𝐷 + β†’ πœ‹ + β’πœ‹ 0 ) = (βˆ’1.8 Β± 0.9 Β± 0.1)%, where the first uncertainty is statistical and the second systematic, is the most precise determination to date. It agrees with the prediction of 𝐢⁒𝑃 symmetry from the standard model and with results of previous measurements.

CP violation↗
DOE OSTI2025

Search for Lepton-Flavor-Violating Decay Modes 𝐡 0 →𝐾$^0_𝑆$⁒𝜏 Β± ⁒ℓ βˆ“ with Hadronic 𝐡 Tagging at Belle and Belle II

We present the first search for the lepton-flavor-violating decay modes 𝐡 0 →𝐾$^0_𝑆$⁒𝜏 Β± ⁒ℓ βˆ“ (β„“=πœ‡,𝑒) using the 711 and 365 fb βˆ’1 data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic 𝐡-tagging technique to fully reconstruct a 𝐡 meson and search for signal decays in the system recoiling against the tagged meson, considering 𝜏 decays to either light leptons, one charged hadron, or one charged hadron and a neutral pion. We find no evidence for 𝐡 0 →𝐾$^0_𝑆$⁒𝜏 Β± ⁒ℓ βˆ“ decays and set 90% confidence level upper limits on the branching fractions in the range of [0.8,3.6] Γ—10 βˆ’5 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the time-integrated 𝐢⁒𝑃 asymmetry in 𝐷 0 β†’ 𝐾$^{0}_{S}$𝐾$^{0}_{S}$ decays using opposite-side flavor tagging at Belle and Belle II

We measure the time-integrated 𝐢⁒𝑃 asymmetry in 𝐷 0 β†’ 𝐾$^{0}_{S}$𝐾$^{0}_{S}$ decays reconstructed in 𝑒 + ⁒𝑒 βˆ’ β†’ $c\bar{c}$ events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb βˆ’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 βˆ’ β†’ $c\bar{c}$ event. This results in a sample which is independent from any other previously used at Belle or Belle II. The result, 𝐴 𝐢⁒𝑃 ⁑(𝐷 0 β†’ 𝐾$^{0}_{S}$𝐾$^{0}_{S}$)=(1.3Β±2.0Β±0.2)%, where the first uncertainty is statistical and the second systematic, is consistent with previous determinations and with 𝐢⁒𝑃 symmetry.

CP violation↗
DOE OSTI2025

Search for 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 and 𝑃 𝑐$\overline{𝑐}$𝑠 (4338) 0 in Ο’(1𝑆,2𝑆) Inclusive Decays at Belle

Using data samples of 102 million ϒ⁑(1⁒𝑆) events and 158 million ϒ⁑(2⁒𝑆) events collected by the Belle detector at the KEKB asymmetric-energy 𝑒+β’π‘’βˆ’ collider, we search for [𝑒⁒𝑑⁒𝑠⁒𝑐$\overline{𝑐}$ ] pentaquark states decaying to 𝐽/πœ“β’Ξ›. Using the first observations of ϒ⁑(1⁒𝑆,2⁒𝑆) inclusive decays to 𝐽/πœ“β’Ξ›, we find evidence of the 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(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 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 to be (4471.7Β±4.8Β±0.6) MeV/𝑐 2 and (22 Β±13 Β±3) MeV, respectively. The branching fractions for 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 production are measured to be ℬ⁑[ϒ⁑(1⁒𝑆)→𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459)0/ $\overline{𝑃}$ 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 +anything]=(3.5Β±2.0Β±0.2)Γ—10 βˆ’6 and ℬ⁑[ϒ⁑(2⁒𝑆)→𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 /$\overline{𝑃}$ 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 +anything]=(2.9Β±1.7Β±0.4)Γ—10 βˆ’6 . The inclusive branching fractions of ϒ⁑(1⁒𝑆,2⁒𝑆) →𝐽/πœ“β’Ξ›/$\overline{Ξ›}$ are measured to be ℬ⁑[ϒ⁑(1⁒𝑆) →𝐽/πœ“β’Ξ›/$\overline{Ξ›}$ +anything] =(36.9 Β±5.3 Β±2.4) Γ—10 βˆ’6 and ℬ⁑[ϒ⁑(2⁒𝑆) →𝐽/πœ“β’Ξ›/$\overline{Ξ›}$ +anything] =(22.3 Β±5.7 Β±3.1) Γ—10 βˆ’6 . We measure the visible cross section 𝜎⁑(𝑒+β’π‘’βˆ’β†’π½/πœ“β’Ξ›/ $\overline{Ξ›}$ +anything)=(90Β±14Β±6) fb for the continuum production at βˆšπ‘  =10.52 GeV. In all cases, the first uncertainties are statistical and the second are systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the branching fraction of Ξ› + 𝑐 →𝑝⁒𝐾 0 𝑆⁒ πœ‹ 0 at Belle

We report a precise measurement of the ratio of branching fractions ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾$^0_𝑆$β’πœ‹ 0 )/ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ) using 980 fb βˆ’1 of 𝑒 + ⁒𝑒 βˆ’ data from the Belle experiment. We obtain a value of ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾$^0_𝑆$β’πœ‹ 0 )/ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ) =0.339 Β±0.002 Β±0.009, where the first and second uncertainties are statistical and systematic, respectively. This Belle result is consistent with the previous measurement from the CLEO experiment but has a fivefold improvement in precision. By combining our result with the world average ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ), we obtain the absolute branching fraction ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾$^0_𝑆$β’πœ‹ 0 ) =(2.12 Β± 0.01 Β±0.05 Β±0.10)%, where the uncertainties are statistical, systematic, and the uncertainty in the absolute branching fraction scale ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ), respectively. This measurement can shed light on hadronic decay mechanisms in charmed baryon decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the time-integrated 𝐢⁒𝑃 asymmetry in 𝐷 0 β†’ πœ‹ 0 β’πœ‹ 0 decays at Belle II

We measure the time-integrated 𝐢⁒𝑃 asymmetry, 𝐴 𝐢⁒𝑃 , in 𝐷 0 β†’ πœ‹ 0 β’πœ‹ 0 decays reconstructed in 𝑒 + ⁒𝑒 βˆ’ β†’ $𝑐⁒\bar{𝑐}$ events collected by Belle II during 2019–2022. The data corresponds to an integrated luminosity of 428 fb βˆ’1 . The 𝐷 0 decays are required to originate from the flavor-conserving 𝐷 *+ β†’ 𝐷 0 β’πœ‹ + decay to determine the charm flavor at production time. Control samples of 𝐷 0 β†’ 𝐾 βˆ’ β’πœ‹ + decays, with or without an associated pion from a 𝐷 *+ decay, are used to correct for detection asymmetries. The result, 𝐴 𝐢⁒𝑃 ⁑(𝐷 0 β†’ πœ‹ 0 β’πœ‹ 0 ) = (0.30 Β± 0.72 Β± 0.20)%, where the first uncertainty is statistical and the second systematic, is consistent with 𝐢⁒𝑃 symmetry.

CP violation↗
DOE OSTI2025

Model-independent measurement of 𝐷 0 βˆ’$\overline{D}$ 0 mixing parameters in 𝐷 0 β†’ 𝐾$^{0}_{𝑆}$β’πœ‹ + β’πœ‹ βˆ’ decays at Belle and Belle II

We perform a model-independent measurement of the 𝐷 0 βˆ’$\overline{D}$ 0 mixing parameters using samples of 𝑒 + ⁒𝑒 βˆ’ -collision data collected by the Belle and Belle II experiments that have integrated luminosities of 951 fb βˆ’1 and 408 fb βˆ’1 , respectively. Approximately 2.05 Γ— 10 6 neutral 𝐷 mesons are reconstructed in the 𝐷 0 β†’ 𝐾$^{0}_{S}$β’πœ‹ + β’πœ‹ βˆ’ channel, with the neutral 𝐷 flavor tagged by the charge of the pion in the 𝐷* + β†’ 𝐷 0⁒ πœ‹ + decay. Assuming charge-parity symmetry, the mixing parameters are measured to be π‘₯ = (4.0 Β±1.7 Β±0.4) Γ— 10 βˆ’3 and 𝑦 = (2.9 Β±1.4 Β±0.3) Γ— 10 βˆ’3 , where the first uncertainties are statistical and the second systematic. The results are consistent with previous determinations.

Charmed mesons↗
DOE OSTI2025

Measurement of the branching fraction, polarization, and time-dependent C P asymmetry in B 0 β†’ ρ + ρ βˆ’ decays and constraint on the CKM angle Ο• 2

We present a measurement of the branching fraction and fraction of longitudinal polarization of B 0 β†’ ρ + ρ βˆ’ decays, which have two Ο€ 0 ’s in the final state. We also measure time-dependent C P violation parameters for decays into longitudinally polarized ρ + ρ βˆ’ pairs. This analysis is based on a data sample containing ( 387 Β± 6 ) Γ— 10 6 Ο’ ( 4 S ) mesons collected with the Belle II detector at the SuperKEKB asymmetric-energy e + e βˆ’ collider in 2019–2022. We obtain B ( B 0 β†’ ρ + ρ βˆ’ ) = ( 2.8 9 βˆ’ 0.22 + 0.23 βˆ’ 0.27 + 0.29 ) Γ— 10 βˆ’ 5 , f L = 0.92 1 βˆ’ 0.025 + 0.024 βˆ’ 0.015 + 0.017 , S = βˆ’ 0.26 Β± 0.19 Β± 0.08 , and C = βˆ’ 0.02 Β± 0.1 2 βˆ’ 0.05 + 0.06 , where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the Cabibbo-Kobayashi-Maskawa angle Ο• 2 and obtain two solutions; the result consistent with other Standard Model constraints is Ο• 2 = ( 92.6 βˆ’ 4.7 + 4.5 ) Β° . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2025

Measurement of branching fractions, C P asymmetry, and isospin asymmetry for B β†’ ρ Ξ³ decays using Belle and Belle II data

We present measurements of B + β†’ ρ + Ξ³ and B 0 β†’ ρ 0 Ξ³ decays using a combined data sample of 772 Γ— 10 6 B B Β― pairs collected by the Belle experiment and 387 Γ— 10 6 B B Β― pairs collected by the Belle II experiment in e + e βˆ’ collisions at the Ο’ ( 4 S ) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II datasets yields 114 Β± 12 B + β†’ ρ + Ξ³ and 99 Β± 12 B 0 β†’ ρ 0 Ξ³ decays. The measured branching fractions are ( 13.1 βˆ’ 1.9 βˆ’ 1.2 + 2.0 + 1.3 ) Γ— 10 βˆ’ 7 and ( 7.6 Β± 1.3 βˆ’ 0.8 + 1.0 ) Γ— 10 βˆ’ 7 for B + β†’ ρ + Ξ³ and B 0 β†’ ρ 0 Ξ³ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A I ( B β†’ ρ Ξ³ ) = ( 10.9 βˆ’ 11.7 βˆ’ 7.3 + 11.2 + 7.8 ) % and the direct C P asymmetry A C P ( B + β†’ ρ + Ξ³ ) = ( βˆ’ 8.2 Β± 15.2 βˆ’ 1.3 + 2.0 ) % . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)β†—