High precision measurements in the quark flavor sector are essential for searching for new physics beyond the Standard model. SuperKEKB collider and Belle II detector are designed to perform such measurements. The status and prospects of the SuperKEKB and Belle II are presented in this article.
This report presents the results of studies that investigate the physics reach at a Super $B$ factory, an asymmetric-energy $e^+e^-$ collider with a design luminosity of $8 times 10^{35}$ cm$^{-2}$s$^{-1}$, which is around 50 times as large as the pe
ak luminosity achieved by the KEKB collider. The studies focus on flavor physics and CP violation measurements that could be carried out in the LHC era. The physics motivation, key observables, measurement methods and expected precisions are presented.
We present a study of $Bto X(3872)K$ with X(3872) decaying to $D^{*0}bar D^0$ using a sample of 657 million $Bbar B$ pairs recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Both $D^{*0}to
D^0gamma$ and $D^{*0}to D^0pi^0$ decay modes are used. We find a peak of $50.1^{+14.8}_{-11.1}$ events with a mass of $(3872.9^{+0.6 +0.4}_{-0.4 -0.5}){rm MeV}/c^2$, a width of $(3.9^{+2.8 +0.2}_{-1.4 -1.1}){rm MeV}/c^2$ and a product branching fraction ${cal B}(Bto X(3872)K)times{cal B}(X(3872)to D^{*0}bar D^0)=(0.80pm0.20pm0.10)times10^{-4}$, where the first errors are statistical and the second ones are systematic. The significance of the signal is $6.4sigma$. The difference between the fitted mass and the $D^{*0}bar D^0$ threshold is calculated to be $(1.1^{+0.6 +0.1}_{-0.4 -0.3}){rm MeV}/c^2$. We also obtain an upper limit on the product of branching fractions ${cal B}(Bto Y(3940)K)times{cal B}(Y(3940)to D^{*0}bar D^0)$ of $0.67times10^{-4}$ at 90% CL.
In this report we summarize the most recent results of measurements of the angle $gamma/phi_3$ of the Unitarity Triangle.
