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At present very large data samples in the energy region of 2.0-4.6 GeV were accumulated by the BESIII detector, which is operated in the upgraded Beijing electron positron collider (BEPCII). These data samples provide an unprecedented opportunity in the study of light hadron spectra and charmonium(-like) decays. We review some experimental analyses related to isospin violations at BESIII in this proceeding, which can be classify into three categories: isospin violating processes with a $f_0(980)$ or $a^0_0(980)$ production, isospin violating processes with baryon final states, and isospin violating hadronic transitions in the charmonium system.
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The BESIII experiment in Beijing takes data in $tau$-charm domain since 2009. For the moment the world largest samples of $J/psi$, $psi(3686)$, $psi(3770)$ and $psi(4040)$ data have been collected. Hadron spectroscopy is a unique way to access QCD, which is one of the most important physics goals of BESIII. Experimental search of new forms of hadrons and subsequent investigation of their properties would provide validation of and valuable input to the quantitative understanding of QCD. The key to success lies in high levels of precision during the measurement and high statistics in the recorded data set complemented with sophisticated analysis methods. Partial wave analysis (PWA) is a powerful tool to study the hadron spectroscopy, that allows one to extract the resonances spin-parity, mass, width and decay properties with high sensitivity and accuracy. In this poster, we present the working PWA framework of BESIII -- GPUPWA and the recent results of PWA of $J/psitogammaetaeta$. GPUPWA is a PWA framework for high statistics partial wave analyses harnessing the GPU parallel computing.
Based on $psi(3686)$ decays of 106 million, the 1.31 billion J/psi events and a data sample of $psi(3770)$ with $2.9~fb^{-1}$ integrated luminosity, many analyses are performed. Exclusively baryonic decays of the $psi(3770)$, the radiative transition $psi(3770)togammaeta_c(2S)$, the $psi(3770)$ transition to $chi_{cJ}$, isospin violation decay $chi_{c0,2}topi^0eta_c$, the $C-$parity violation decays $J/psitogammagamma,gammaphi$ are searched for, but no significant signals are observed, and upper limits are set for these decays. The decays of $psi(3770)togammachi_{c1}$ and $J/psitopi^0phi$ signals are observed. These measurements provide more information on the charmonium structure, and the isospin and $C$-parity violation in the charmonium decays.
Since few years, a new family of exotic states has been appearing above the open-heavy meson thresholds: the so-called $XYZ$ states. BESIII at the BEPCII $e^+e^-$ collider plays a unique role in the study of those particles in the charmonium sector. Changing the beam energy, BESIII can collect large data samples by means of scans of the resonant region, accessing directly to all vector states. As part of a larger upgrade program, BESIII has planned to increase the center of mass energy to reach $4.7$ GeV: this will allow BESIII to investigate the nature of the $Y(4660)$, that was at first observed by Belle and BaBar after Initial State Radiation only in $pipi psi(2s)$ and $Lambda_c$ $bar{Lambda}_c$ final states. The relative branching ratio seems to point toward a baryonium interpretation of the resonance, as expected in Rossi-Veneziano model. BESIII can directly measure the cross sections around the expected peak position and verify this prediction. In this presentation, the status of the $XYZ$ searches at BESIII will be presented, with a focus also on the plans for the newest data taking and for the $Y(4660)$ studies.
The standard model of particle physics is a well-tested theoretical framework, but there are still a number of issues that deserve further experimental and theoretical investigation. For quark physics, such questions include: the nature of quark confinement, the mechanism that connects the quarks and gluons of the standard model theory to the strongly interacting particles; and the weak decays of quarks, which may provide insights into new physics mechanisms responsible for the matter-antimatter asymmetry of the Universe. These issues are addressed by the Beijing Spectrometer III (BESIII) experiment at the Beijing Electron-Positron Collider II (BEPCII) storage ring, which for the past decade has been studying particles produced in electron-positron collisions in the tau-charm energy-threshold region, and has by now accumulated the worlds largest datasets that enables searches for nonstandard hadrons, weak decays of the charmed particles, and new physics phenomena beyond the standard model. Here, we review the contributions of BESIII to such studies and discuss future prospects for BESIII and other experiments.
There has recently been a dramatic renewal of interest in the subjects of hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like $XYZ$ states at BESIII and $B$ factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related $X(1835)$ meson state at BESIII, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESIII over the remaining lifetime of BEPCII operation. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCII to higher luminosity.
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