We study the process e + e − → π + π − J/ψ at a center-of-mass energy of 4.260 GeV using a 525 pb −1 data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9 ± 1.9 ± 3.7) pb, consistent with the production of the Y (4260). We observe a structure at around 3.9 GeV/c 2 in the π ± J/ψ mass spectrum, which we refer to as the Zc(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the π ± J/ψ invariant mass spectrum, neglecting interference, results in a mass of (3899.0 ± 3.6 ± 4.9) MeV/c 2 and a width 3 of (46 ± 10 ± 20) MeV. Its production ratio is measured to be R = σ(e + e − →π ± Zc(3900) ∓ →π + π − J/ψ)) σ(e + e − →π + π − J/ψ) = (21.5 ± 3.3 ± 7.5)%. In all measurements the first errors are statistical and the second are systematic. PACS numbers: 14.40.Rt, 14.40.Pq, 13.66.Bc Since its discovery in the initial-state-radiation (ISR) process e + e − → γ ISR π + π − J/ψ [1], and despite its subsequent observations [2][3][4][5], the nature of the Y (4260) state has remained a mystery. Unlike other charmonium states with the same quantum numbers and in the same mass region, such as the ψ (4040) A similar situation has recently become apparent in the bottomonium system above the BB threshold, where there are indications of anomalously large couplings between the Υ(5S) state (or perhaps an unconventional bottomonium state with similar mass, the Y b (10890)) and the π + π − Υ(1S, 2S, 3S) and π + π − h b (1P, 2P ) final states [14,15]. More surprisingly, substructure in these π + π − Υ(1S, 2S, 3S) and π + π − h b (1P, 2P ) decays indicates the possible existence of charged bottomoniumlike states [16], which must have at least four constituent quarks to have a non-zero electric charge, rather than the two in a conventional meson. By analogy, this suggests there may exist interesting substructure in the Y (4260) → π + π − J/ψ process in the charmonium region.In this Letter, we present a study of the process e + e − → π + π − J/ψ at a center-of-mass (CM) energy of √ s = (4.260± 0.001) GeV, which corresponds to the peak of the Y (4260) cross section. We observe a charged structure in the π ± J/ψ invariant mass spectrum, which we refer to as the Z c (3900). The analysis is performed with a 525 pb −1 data sample collected with the BESIII detector, which is described in detail in Ref. [17]. In the studies presented here, we rely only on charged particle tracking in the main drift chamber (MDC) and energy deposition in the electromagnetic calorimeter (EMC).The GEANT4-based Monte Carlo (MC) simulation software, which includes the geometric description of the BE-SIII detector and the detector response, is used to optimize the event selection criteria, determine the detection efficiency, and estimate backgrounds. For the signal process, we use a sample of e + e − → π + π − J/ψ MC events generated assuming the π + π − J/ψ is produced via Y (4260) decays, and using the...

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We report on a study of the process e+ e- → π± (DD*)∓ at sqrt[s] = 4.26  GeV using a 525 pb(-1) data sample collected with the BESIII detector at the BEPCII storage ring. A distinct charged structure is observed in the (DD*)∓ invariant mass distribution. When fitted to a mass-dependent-width Breit-Wigner line shape, the pole mass and width are determined to be Mpole = (3883.9±1.5(stat)±4.2(syst))  MeV/c2 and Γpole = (24.8±3.3(stat)±11.0(syst))  MeV. The mass and width of the structure, which we refer to as Zc(3885), are 2σ and 1σ, respectively, below those of the Zc(3900) → π± J/ψ peak observed by BESIII and Belle in π+ π- J/ψ final states produced at the same center-of-mass energy. The angular distribution of the πZc(3885) system favors a JP = 1+ quantum number assignment for the structure and disfavors 1- or 0-. The Born cross section times the DD* branching fraction of the Zc(3885) is measured to be σ(e+ e- → π± Zc(3885)∓)×B(Zc(3885)∓ → (DD*)∓) = (83.5±6.6(stat)±22.0(syst))   pb. Assuming the Zc(3885) → DD* signal reported here and the Zc(3900) → πJ/ψ signal are from the same source, the partial width ratio (Γ(Zc(3885) → DD*)/Γ(Zc(3900) → πJ/ψ)) = 6.2±1.1(stat)±2.7(syst) is determined.

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The first observation of the Z boson decaying to four leptons in proton-proton collisions is presented. The analyzed data set corresponds to an integrated luminosity of 5.02 fb −1 at √ s = 7 TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 σ, is observed in the distribution of the invariant mass of four leptons (electrons and/or muons) with mass and width consistent with expectations for Z boson decays. The branching fraction and cross section reported here are defined by phase space restrictions on the leptons, namely, 80 < m 4 < 100 GeV, where m 4 is the invariant mass of the four leptons, and m > 4 GeV for all pairs of leptons, where m is the two-lepton invariant mass. The measured branching fraction is B(Z → 4 ) = 4.2

Abstract:Data sets were collected with the BESIII detector at the BEPCII collider at the center-of-mass energy of Author's Copy scattering events, the integrated luminosities of the two data sets are measured to be (44.49 ± 0.02 ± 0.44) pb −1 and (2916.94 ± 0.18 ± 29.17) pb −1 , respectively, where the first error is statistical and the second error is systematic.

The decays of J/psi --> etaphif(0)(980)[eta --> gammagamma, phi --> K(+) K(-), f(0)(980) --> pi(+)pi(-)] are analyzed using a sample of 5.8 x 10(7) J/psi events collected with the BESII detector at the Beijing Electron-Positron Collider. A structure at around 2.18 GeV/c(2) with about 5 sigma significance is observed in the phif(0)(980) invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of m = 2.186+/-0.010(stat)+/-0.006(syst) GeV/c(2) and Gamma = 0.065+/-0.023(stat)+/-0.017(syst) GeV/c(2), respectively, which are consistent with those of Y(2175), observed by the BABAR Collaboration in the initial-state radiation process e(+)e(-) --> gamma(ISR) phif(0)(980). The production branching ratio is determined to be Br(J/psi --> etaY(2175))Br(Y(2175)- -> phif(0)(980))Br(f(0)(980) --> pi(+)pi(-)) = [3.23+/-0.75(stat)+/-0.73(syst)] x 10(-4), assuming that the Y(2175) is a 1(--) state.

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