No Arabic abstract
Quarkonium is the bound state of a heavy quark and its anti-quark counterpart. The study of this system has experienced a renaissance thanks to results from e+e- collider experiments, including discoveries of long-predicted conventional quarkonia, and unusual states consisting of four quarks. The Belle Experiment operated at KEK in Japan from 1999-2010. Analysis of the collected data continues to produce new findings. The Belle II experiment is a substantial upgrade of both the Belle detector and the KEKB accelerator, aiming to collect 50 times more data beginning in 2018. This talk presented recent Belle results related to hadronic and radiative decays in the bottomonium system. It described the capabilities of Belle II to explore these topics, with a particular focus on the physics reach of the first data, where unique opportunities exist to make an immediate impact in this area.
The search for multi-quark states beyond the constituent quark model (CQM) has resulted in the discovery of many new exotic states, starting with the observation of the X(3872), discovered by Belle in 2003. Also in the sector of charm-strange physics the CQM does not seem to describe properly all spectrum, despite of theoretical expectations. These new forms of quark bounds clearly show that mesons and baryons are not the only possibilities to be considered. We shortly report in this paper selected recent results on searching for such states at Belle, with the perspectives in the hadron physics program at the Belle II experiment.
Search for exotics has increased importance since the observation of the X(3872), 13 years ago, announced by the Belle Collaboration. The observation of pentaquark states by LHCb, and the Z-charged states observed at Belle and BES III have raised even more the attention to the field. Presently several states are observed that do not fit potential models, and looking for them in different production mechanisms and search for their decay modes it is important, as well as to do precise measurement of their mass, width, lineshape. We shortly report in this note about the plan in searching for exotics at Belle II at KEK (Tsukuba, Japan), that just ended the Phase-II running period, and show the first re-discovery results using 5 pb$^{-1}$ integrated luminosity.
Recent results on quarkonium and quarkonuim-like states at Belle are presented.
In 2018 the Belle II experiment, aimed at detailed studies of B-mesons, started operation at the electron-positron collider SuperKEKB at KEK (Japan). This was preceded by a long and quite successful work of the B-factories of previous generations, including the Belle experiment for which Belle II is a successor. This experiment is unique and has no analogues or competitors in the world. The spectrum of problems it is aimed at is quite broad: from studies of hadronic states containing heavy quarks to precision measurements and searches for New Physics beyond the Standard Model. This review describes specific features of the Belle II experiment, its ambitious goals and specific tasks, expected results of its work and the hopes related to its successful accomplishment.
We present a summary of recent studies on $CP$ violation with the Belle experiment using the final data sample of $772 times 10^{6}$ Bbar{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 $B^0 rightarrow rho^{+} rho^{-}$ and an updated constraint on the CKM angle $phi_2$ from the $Btorhorho$ system. Being also related to $phi_2$, we present a preliminary measurement of the branching fraction of $B^0rightarrow pi^0pi^0$ decays. Last, a preliminary model independent dalitz plot analysis of the decay $B^0 rightarrow D^0[K_S^0pi^+pi^-]K^{*0}$ is presented and its sensitivity to the CKM angle $phi_3$ is discussed.