Update on Z(4430) and X(3872) at Belle

Monte Carlo Event Generator更新：针对Belle II能量下的tau对事件

Monte Carlo Event Generator updates, for tau pair events at Belle II energies

本文介绍了为适应Belle II实验精确数据需求，对由KKMC、tauola和photos组成的轻子对产生与tau衰变Monte Carlo系统的更新，包括扩展相空间模块以支持额外轻子对衰变和辐射修正，并在tauola中增加奇异衰变通道以支持新物理探索。

Study of the Suppressed Decays $B^\pm \to [K^\mp π^\pm]_D K^\pm$ and $B^\pm \to [K^\mp π^\pm]_D π^\pm$ at Belle

We report an updated study of the suppressed decays $B^- \to [K^+π^-]_D K^-$ and $B^- \to [K^+π^-]_D π^-$ where $[K^+π^-]_D$ indicates that the $K^+π^-$ pair originates from a neutral $D$ meson. A data sample containing 386 million $B\bar{B}$ pairs recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric $e^{+}e^{-}$ storage ring is used. This decay mode is sensitive to the CKM angle $ϕ_{3}$. We do not see a significant signal for $B^- \to [K^+π^-]_{D} K^-$, and we set a limit on the ratio of B decay amplitudes $r_B < 0.18$ at the 90% confidence level. We measure the CP…

HFLAV 对 2026 年欧洲粒子物理战略更新的意见书

HFLAV input to the 2026 update of the European Strategy for Particle Physics

本文代表 HFLAV 呼吁欧洲战略支持 LHCb Upgrade II 和 Belle II 升级，并规划在 $e^+e^-$ 对撞机上运行 $Z$ 工厂以整合味物理，从而深化标准模型检验与新物理搜寻。

Belle II 实验中的时间依赖 $CP$ 破坏测量结果

Time-dependent $CP$ violation results at Belle II

Belle II 实验利用 2019-2022 年数据测量时间依赖 CP 破坏可观测量，给出 $b\to q\overline{q}s$ 跃迁中 $\sin2ϕ_1$ 有效值的新结果，对非标准模型物理敏感。

Direct CP Violation in Charmless B Decays

We report the updated results of direct CP violation measurements from Belle and BaBar for the following modes: B -> h+h-/h+-pi^0, B -> eta(') h+- and B -> K+-pi+-pi-+, where h stands for a charged kaon or pion. The data used in these studies are up to 386 million BBbar pairs for Belle and 232 million BBbar pairs for BaBar. The current significant measurements include: Acp(B -> K+ pi-)=-0.108+/-0.016, Acp(B -> rho0(770) K+)=0.31+0.11-0.10, and Acp(B -> eta K+)=-0.33+/-0.12.

Charmless B Decays

We report several new and updated results from Belle and BABAR for rare hadronic B decays. These include many new results for B decays to eta'X and omegaX and new measurements of the longitudinal polarisation in the decays B -> rho K*.

Updated Cross Section Measurement of $e^+ e^- \to K^+ K^- J/ψ$ and $K_S^0K_S^0J/ψ$ via Initial State Radiation at Belle

The cross sections of the processes $e^+ e^- \to K^+ K^- J/ψ$ and $K_S^0K_S^0J/ψ$ are measured via initial state radiation at center-of-mass energies between the threshold and 6.0~GeV using a data sample of 980~fb$^{-1}$ collected with the Belle detector on or near the $Υ(nS)$ resonances, where $n=$1, 2, ..., 5. The cross sections for $e^+ e^- \to K^+ K^- J/ψ$ are at a few pb level and the average cross section for $e^+ e^- \to K_S^0K_S^0J/ψ$ is $1.8\pm 0.6 (\rm stat.)\pm 0.3 (\rm syst.)$~pb between 4.4 and 5.2~GeV. All of them are consistent with previously published results with improved pre…

Diversity and inclusion activities in Belle II

These proceedings accompany the Belle II talk in the Science in Society parallel session delivered during Lepton Photon 2021. In this talk we present updated membership statistics using 10 years of data with a diversity and inclusion lens, and we present Belle II's most recent activities to aid and improve diversity and inclusion. This report has the intention to bring light to the social working environment and population representation within our collaboration and, by extension, within high energy physics. Belle II is a particle physics collaboration that has over 1000 people from institutio…

Addendum to "Impact of polarization observables and $B_c\to τν$ on new physics explanations of the $b\to c τν$ anomaly"

In this addendum to arXiv:1811.09603 we update our results including the recent measurement of ${\cal R}(D)$ and ${\cal R}(D^*)$ by the Belle collaboration: ${\cal R}(D)_{\rm Belle} = 0.307\pm0.037\pm0.016$ and ${\cal R}(D^*)_{\rm Belle}=0.283\pm0.018\pm0.014$, resulting in the new HFLAV fit result ${\cal R}(D) = {0.340\pm0.027 \pm 0.013}$, ${\cal R}(D^*) = {0.295\pm0.011 \pm 0.008 }$, exhibiting a $3.1\,σ$ tension with the Standard Model. We present the new fit results and update all figures, including the relevant new collider constraints. The updated prediction for ${\cal R}(Λ_c)$ from our …

Recent studies of CP violation in bottom meson decays at Belle

We present a summary of recent studies on $CP$ violation with the Belle experiment using the final data sample of $772 \times 10^{6}$ B\bar{B} pairs produced at the Ypsilon(4S) resonance at the KEK asymmetric e^+ e^- collider. We discuss preliminary measurements of the branching fraction, the polarization and the $CP$ asymmetries of the decay $B^0 \rightarrow ρ^{+} ρ^{-}$ and an updated constraint on the CKM angle $ϕ_2$ from the $B\toρρ$ system. Being also related to $ϕ_2$, we present a preliminary measurement of the branching fraction of $B^0\rightarrow π^0π^0$ decays. Last, a preliminary mod…

Updated Measurement of phi_3 with a Dalitz Plot Analysis of B->D(*)K Decay

We present an updated measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the K^0_S pi+ pi- decay of the neutral D meson produced in B+- ->D(*)K+- decays. The method exploits the interference between D^0 and Dbar^0 to extract the angle phi_3, strong phase delta and the ratio r of suppressed and allowed amplitudes. We apply this method to a 605 fb-1 data sample collected by the Belle experiment. The analysis uses two modes: B+- -> DK+-, and B+- -> D*K+- with D* -> D pi0, as well as the corresponding charge-conjugate modes. From a combined maximum likelihood fit to …

Belle II 处的暗扇区和 τ 物理

Dark sectors and τ physics at Belle II

Belle II 实验探索暗扇区与标准模型的弱耦合，通过多种搜索（如稀有 B 衰变、双 τ 共振、不可见 Z′ 玻色子、轻子味破坏及 τ 质量精确测量）来寻找新物理信号，并给出世界最精确的 τ 质量测量。

The $V_{cb}$ puzzle: an update

We discuss the impact of the recent untagged analysis of ${B}^0\rightarrow D^{*}l\barν_l$ decays by the Belle Collaboration on the extraction of the CKM element $|V_{cb}|$ and provide updated SM predictions for the $b\to cτν$ observables $R(D^*)$, $P_τ$, and $F_L^{D^*}$. The value of $|V_{cb}|$ that we find is about $2σ$ from the one from inclusive semileptonic $B$ decays, and is very sensitive to the slope of the form factor at zero recoil which should soon become available from lattice calculations.

Update of inclusive cross sections of single and pairs of identified light charged hadrons

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-sta…

Tetraquark Interpretation and Production Mechanism of the Belle $Y_b (10750)$-Resonance

Recently, the Belle Collaboration has updated the analysis of the cross sections for the processes $e^+ e^- \to Υ(nS)\, π^+ π^-$ ($n = 1,\, 2,\, 3$) in the $e^+ e^-$ center-of-mass energy range from 10.52 to 11.02~GeV. A new structure, called $Y_b (10750)$, with the mass $M (Y_b) = (10752.7 \pm 5.9^{+0.7}_{-1.1})$~MeV and the Breit-Wigner width $Γ(Y_b) = (35.5^{+17.6 +3.9}_{-11.3 -3.3})$~MeV was observed. We interpret $Y_b (10750)$ as a compact $J^{PC} = 1^{--}$ state with a dominant tetraquark component. The mass eigenstate $Y_b (10750)$ is treated as a linear combination of the diquark-antid…

Study of the pi+pi-J/psi Mass Spectrum via Initial-State Radiation at BABAR

We present an update of the study of the Y(4260) resonance, produced in the process $e^+e^-\toγ_{ISR} π^+π^-J/ψ$ using initial-state radiation events at the PEP-II $e^+e^-$ storage rings. This study is based on 454fb$^{-1}$ of data recorded with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at a center-of-mass energy in the $Υ(4S)$ resonance region. From a fit with a single non-relativistic Breit-Wigner shape we obtain updated parameters for the Y(4260) resonance which are $m_Y = 4252 \pm6 ^{+2}_{-3}$MeV/c$^2$ and $Γ_Y = 105 \pm 18^{+4}_{-6}$…

Observation of $Ξ_{c}(2930)^0$ and updated measurement of $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ at Belle

We report the first observation of the $Ξ_{c}(2930)^0$ charmed-strange baryon with a significance greater than 5$σ$. The $Ξ_{c}(2930)^0$ is found in its decay to $K^- Λ_{c}^+$ in $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ decays. The measured mass and width are $[2928.9 \pm 3.0(\rm stat.)^{+0.9}_{-12.0}(\rm syst.)]$ MeV/$c^{2}$ and $[19.5 \pm 8.4(\rm stat.) ^{+5.9}_{-7.9}(\rm syst.)]$ MeV, respectively, and the product branching fraction is ${\cal B}(B^{-} \to Ξ_{c}(2930)^0 \barΛ_{c}^{-}) {\cal B}(Ξ_{c}(2930)^0 \to K^- Λ_{c}^{+})=[1.73 \pm 0.45(\rm stat.) \pm 0.21(\rm syst.)]\times 10^{-4}$. We…

Evidence of a structure in $\bar{K}^{0} Λ_{c}^{+}$ consistent with a charged $Ξ_c(2930)^{+}$, and updated measurement of $\bar{B}^{0} \to \bar{K}^{0} Λ_{c}^{+} \barΛ_{c}^{-}$ at Belle

We report evidence for the charged charmed-strange baryon $Ξ_{c}(2930)^+$ with a signal significance of 3.9$σ$ with systematic errors included. The charged $Ξ_{c}(2930)^+$ is found in its decay to $K_{S}^{0} Λ_{c}^+$ in the substructure of $\bar{B}^{0} \to K^{0}_{S} Λ_{c}^{+} \barΛ_{c}^{-}$ decays. The measured mass and width are $[2942.3 \pm 4.4 (\rm stat.) \pm 1.5(\rm syst.)]$~MeV/$c^{2}$ and $[14.8 \pm 8.8(\rm stat.) \pm 2.5(\rm syst.)]$~MeV, respectively, and the product branching fraction is $\cal{B}(\bar{B}^{0} \to Ξ_c(2930)^{+} \barΛ_{c}^{-}) \cal{B}(Ξ_c(2930)^{+}\to \bar{K}^{0} Λ_{c}^{…

Constructing $J/ψ$ family with updated data of charmoniumlike $Y$ states

Based on the updated data of charmoniumlike state $Y(4220)$ reported in the hidden-charm %and open-charm channels of the $e^+e^-$ annihilation, we propose a $4S$-$3D$ mixing scheme to categorize $Y(4220)$ into the $J/ψ$ family. We find that the present experimental data can support this charmonium assignment to $Y(4220)$. Thus, $Y(4220)$ plays a role of a scaling point in constructing higher charmonia above 4 GeV. To further test this scenario, we provide more abundant information on the decay properties of $Y(4220)$, and predict its charmonium partner $ψ(4380)$, whose evidence is found by ana…

关于 $\vert V_{cb} \vert$、$R(D^{*})$ 和 $\vert V_{ub} \vert/\vert V_{cb} \vert$ 测定的更新

Updates on the determination of $\vert V_{cb} \vert$, $R(D^{*})$ and $\vert V_{ub} \vert/\vert V_{cb} \vert$

基于Belle实验新数据和格点QCD形状因子理论进展，采用色散矩阵和BGL方法更新测定了 $\vert V_{cb} \vert$、$R(D^*)$ 和 $\vert V_{ub} \vert/\vert V_{cb} \vert$ 的值，结果与实验及包容性测定兼容。

Interpretation of $Y_b (10750)$ as a tetraquark and its production mechanism

Recently, the Belle Collaboration has updated the analysis of the cross sections for the processes $e^+ e^- \to Υ(nS)\, π^+ π^-$ ($n = 1,\, 2,\, 3$) in the $e^+ e^-$ center-of-mass energy range from 10.52 to 11.02 GeV. A new structure, called here $Y_b (10750)$, with the mass $M (Y_b) = (10752.7 \pm 5.9^{+0.7}_{-1.1})$ MeV and the Breit-Wigner width $Γ(Y_b) = (35.5^{+17.6 +3.9}_{-11.3 -3.3})$ MeV was observed \cite{Abdesselam:2019gth}. We interpret $Y_b (10750)$ as a compact $J^{PC} = 1^{--}$ state with a dominant tetraquark component. The mass eigenstate $Y_b (10750)$ is treated as a linear c…