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Lianjin Wu
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BESIII experiment has collected about 20 fb$^{-1}$ luminosity data between $sqrt{s}=3.8$ and 4.7 GeV via $e^{+}e^{-}$ collision. In this talk, we present the recent $XYZ$ results at BESIII, including mass and width measurements of $Y(4220)$, search for $Y$ states with rare decay modes, isospin parity determination of $Z_{c}^{0}(3900)$ as well as the mass and width determination, and search for new decay modes of $X(3872)$.
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With the ability to run above 4~GeV, the BESIII experiment located in the Beijing Electron Positron Collider (BEPCII), has becoming a pioneer in searching and studying charmoniumlike states ($XYZ$ particles). In 2013, BESIII Collaboration discovered a charged charmoniumlike state $Z_c(3900)$, which is confirmed immediately experimentally, and provides the best candidate for a four quark state by now. Continuous studies by BESIII Collaboration show new decay behavior of $Z_c(3900)$, and there are possible partner particle $Z_c(4020)/Z_c(4025)$ existing. By scanning above 4~GeV, BESIII also reveals the potential connection between $Y(4260)$ and $X(3872)$ for the first time, which may help us understand $XYZ$ particles in a new sight.
Using 58 million $J/psi$ and 14 million $psi(2S)$ events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays $J/psi$ and $psi(2S) to Lambda bar{Lambda} pi^0$ and $Lambda bar{Lambda} eta$ are measured, and the decays of $J/psi$ and $psi(2S)$ to $n K^0_S bar{Lambda}+c.c.$ are observed and measured for the first time. Finally, $R$ measurement data taken with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV are fitted to determine resonance parameters of the high mass charmonium states, $psi(3770)$, $psi(4040)$, $psi(4160)$, and $psi(4415)$. The Beijing Electron Collider is being upgraded to a two-ring collider (BEPCII) with a design luminosity of $1 times 10^{33}$cm$^{-2}$ s$^{-1}$ at 3.89 GeV and will operate between 2 and 4.2 GeV in the center of mass. With this luminosity, the new BESIII detector will beable to collect, for example, 10 billion $J/psi$ events in one year of running. BEPCII and BESIII are currently nearing completion, and commissioning of both is expected to begin in mid-2008.
Hadron spectroscopy is one of the most important physics goals of BESIII. BESIII brings great opportunities to study the XYZ states of charmonium by directly producing the Y states up to 4.6 GeV. High statistics of charmonium decays collected at BESIII provide an excellent place for hunting gluonic excitations and studying the excited baryons. Recent results of light hadron spectroscopy and charmonium spectroscopy from BESIII will be reported.
In 2009, the BESIII experiment has collected about 225M $jpsi$ and 106M $psip$ samples, both of which are the world largest on-peak charmonium production. Based on these dataset, BESIII has made great effort on the study of the charmonium decays, some important of which have been reviewed in this proceeding. In addition, a searching for new physics through the $CP/P$ violation process is reported.
One of the basic motivations of the KLOE and KLOE-2 collaborations is the test of fundamental symmetries and the search for phenomena beyond the Standard Model via the hadronic and leptonic decays of ground-state mesons and via their production in the fusion of virtual gamma quanta exchanged between colliding electrons and positrons. This contribution includes brief description of results of recent analysis of the KLOE data aimed at (i) the search for the dark matter boson, (ii) determination of the hadronic and light-by-light contributions to the g-2 muon anomaly and (iii) tests of QCD anomalies.
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