$CP$ violation and branching fraction measurements in $D$ decays are interesting topics as any difference with respect to the Standard Model prediction would be an indication of new physics. With the large data sample collected by the Belle detector, which sits at the interaction point of KEKB asymmetric $e^{+} e^{-}$ collider in Japan, we present the results of searches for $CP$ violation in $D^{0}\rightarrow Vγ~(V = ϕ, \overline{K}^{*0}, ρ^{0})$ decay and the rare $D$ decay $D^{0}\rightarrow γγ$.
Belle II合作在SuperKEKB能量非对称e+ e对撞机上运行一个大幅升级的Belle探测器。Belle II将于2018年开始记录在Upperdance(4S)能量下的碰撞,目标是到2025年收集50 ab^{-1}的数据,是Belle实验的50倍。我们报告了测量与电荷宇称破坏相关的量的前景,特别强调了Cabibbo-Kobayashi-Maskawa角phi_3(γ)和与夸克混合矩阵元Vub相关的半轻子B介子衰变中的可观测量。
Evidence from the \babar, Belle and CDF experiments for the phenomenon of \dzdzb\ oscillations is reviewed. A summary is made of the current understanding of the parameters defining the mixing of mass eigenstates that give rise to the oscillations. Results of searches for CP violation induced by mixing, are given, and estimates for the precision of measurements that can be expected in future experiments are made.
Measurements of Charmed Meson Lifetimes and Search for $D^0$-$\overline{D}^0$ Mixing with the Belle Experiment
用11.1 fb $^{-1} of data collected with the Belle detector at KEKB. Each candidate is fully reconstructed to identify the flavor of the charmed meson. The lifetimes are measured to be $ τ(D^0)=(414.5 \pm 1.7)$ fs, $ τ(D^+)=(1029 \pm 12)$ fs and $ τ(D^+)=(488.4^{+7.8}-7.7})$ fs, where the error is statistical only. The mixing parameter $ y_{CP} $ is also measured to be $ y_{CP} =(1.16^{+1.67}-1.65}(stat.))%测量了粲介子的寿命$ through the lifetime difference of $ D^0$介子衰变到CP混合态和CP本征态。
We report a measurement of the branching fraction of inclusive semileptonic $B$ meson decays $B\to X_c\ellν\ell$ in $Υ(4S)\to B\bar B$~data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy $e^+e^-$ collider and corresponding to 62.8 fb$^{-1}$ of integrated luminosity. Only a charged lepton (electon or muon) is reconstructed and the signal yield is determined from a fit to the lepton momentum distribution in the center-of-mass frame of the colliding beams. Averaging the result in the electron and muon channels, we find ${\cal B}(B\to X_c\ellν_\ell) = (9.75\pm 0.03(\text{st…
We measure the branching fraction for the Singly Cabibbo-suppressed decay $D^0\rightarrow K^0_S\,K^0_S\,π^+π^-$, and we search for $CP$ violation via a measurement of the $CP$ asymmetry $A^{}_{CP}$ and also the $T$-odd triple-product asymmetry $a_{CP}^{T}$. The later two measurements are complementary. We use 922~fb$^{-1}$ of data recorded by the Belle experiment, which ran at the KEKB asymmetric-energy $e^+ e^-$ collider. The branching fraction is measured relative to the Cabibbo-favored normalization channel $D^0\rightarrow K^0_S\,π^+π^-$. Singly Cabibbo-suppressed charm decays are expected …
我们报道了三体无粲衰变B+=>K+pi+pi-,B_0 => K_0 pi +pi-和B+=>K+K+K-的Dalitz分析结果,包括在B+=>K+pi+pi-模式中寻找直接的CP破坏.报道了一些准二体中间态的分支分数。我们还观察到在B+-=>rho(770)0 K +-通道中存在大的直接CP破坏的3.9 σ显著性证据。这是荷电介子衰变中CP破坏的第一个证据。使用Dalitz分析技术获得的结果与大数据样本的BBbar对收集的Belle探测器在KEKB非对称能量e+e-对撞机。
Observation of two narrow mesons in the D+_s pi^0 and D+_s pi^0 gamma final states. Results from BaBar, Belle and CLEO
BaBar实验在质心能量接近10.6 GeV的包含$e^{+}e^{-}$相互作用中发现了一个窄态,记为D*_{sJ}(2317)+,其质量分布在D+s pi ^0不变质量分布中接近2.32 GeV/c^2。同样的实验也暗示了在D+ s π ^0伽马能谱中,在2.46 GeV/c^2附近存在第二个新态。这些发现触发了CLEO和Belle实验寻找与D+_s介子耦合的新态。他们证实了D*_{sJ}(2317)^+态的存在,并为D*_{sJ}(2458)^+态的存在提供了证据。Belle不仅在连续e+e-湮灭中,而且在B衰变中报告了这两种状态的证据。这两个新的窄共振的特点是质量显着低于预测的潜在的模型,足以关闭最自然的衰变模式,从而迫使违反同位旋过渡。他们的发现令人惊讶,因为它与显然已建立的理论的预期相矛盾。这种情况也导致了理论方面的巨大努力。
本文研究了稀有衰变B -> h(*)nu nubar,其中h(*)代表轻介子.使用KEKB e+e对撞机Belle探测器收集的5.35亿个BBbar对的数据样本。信号候选者需要有一个伴随的B介子完全重建在强子模式和信号侧粒子符合一个单一的h(*)介子。未观察到显著信号,我们将分支分数的上限设定为90%置信水平。对B 0-> K*0 nu nubar和B+ -> K+ nu nubar衰变的限制比以前的限制更严格,而对B 0-> K 0 nu nubar,pi 0 nu nubar,rho 0 nu nubar,phi nu nubar和B+ -> K*+ nu nubar,rho+ nu nubar的首次搜索也被报道。
Searches for lepton flavor violation in tau decays are unambiguous signatures of new physics. The branching ratios of tau leptons at the level of 10^-10 - 10^-9 can be probed with 50 ab^-1 of electron-positron annihilation data being collected by the Belle II experiment at the world's highest luminosity accelerator, the SuperKEKB, located at the High Energy Accelerator Research Organization, KEK, in Tsukuba, Japan. Searches with such expected sensitivity will either discover new physics or strongly constrain several new physics models.
Semileptonic decays of $B$ mesons that proceed via $b\rightarrow u$ and $b\rightarrow c$ transitions, as well as rare leptonic $B$ decays, are fertile grounds for probing new physics beyond the Standard Model. The Belle II experiment presents as an excellent opportunity to study such decays, and since beginning operation in 2019, Belle II has already recorded half of the data collected by its predecessor and reached an instantaneous luminosity greater than $4\times 10^{34}$ cm$^{-2}$s$^{-1}$. Belle II expects to explore flavour physics with $B$ and charmed mesons with unprecedented precision, …