The BESIII physics programme

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 issues 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 world's largest dataset that enables searches for non-standard 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. Electron-positron annihilations at centre-of-mass energies between 2.0 GeV and 4.6GeV at BESIII enabled precision measurements of fundamental constants of the standard model of particle physics, discovered non-standard, multi-quark hadrons and observed a number of unusual properties of standard mesons and baryons. Key pointsPrecision measurements of the tau-lepton mass, || and || Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, low-energy electron-positron (+-) annihilation cross-sections and complex phases in meson decays test the standard model and provide important input for experiments at other energies.VcdVcseeD-Measurements of the purely leptonic and semileptonic decay rates of and mesons provide sensitive tests of lattice quantum chromodynamics calculations of charmed-meson decay constants and form factors.DDsStudies of directly produced (4260) mesons led to discoveries of the (3900) and (4020) non-standard, four-quark hadrons and a new production mode for the (3872).YZcZcXHuge samples of radiative / decays have provided a deeper understanding of scalar, pseudoscalar and tensor glueballs, and the intriguing but poorly understood resonant structures at the proton-antiproton mass threshold.JThe discovery of substantial polarization of strange baryons produced in / decays provides new and unique opportunities for high-sensitivity searches for non-standard-model sources of charge conjugation-parity (CP) symmetry violation.p id=Par J psi Investigations of time-like electromagnetic form factors of Lambda 0 and baryons revealed unexpected threshold behaviours and motivated measurements for other stable baryons.