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2016-12-26T15:11:00

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...

The decay J/ψ → ωpp has been studied, using 225.3 × 10 6 J/ψ events accumulated at BESIII. No significant enhancement near the pp invariant-mass threshold (denoted as X(pp)) is observed. The upper limit of the branching fraction B(J/ψ → ωX(pp) → ωpp) is determined to be 3.9 × 10 −6 at the 95% confidence level. The branching fraction of J/ψ → ωpp is measured to be B(J/ψ → ωpp) = (9.0 ± 0.2 (stat.) ± 0.9 (syst.)) × 10 −4 . 124The investigation of the near-threshold pp invariant 125 mass spectrum in other J/ψ decay modes will be helpful 126 in understanding the nature of the observed structure. 127The decay J/ψ → ωpp restricts the isospin of the pp 128 system, and it is helpful to clarify the role of the pp in the return iron yoke of the superconducting magnet. 174The position resolution is about 2 cm. 175The optimization of the event selection and the es- 247The branching fraction of J/ψ → ωpp is calculated 248 according to :(1) where N obs is the number of signal events determined Breit-Wigner function :Here, q is the momentum of the proton in the pp rest where N obs is the number of signal events, and L is the Author's Copy where σ sys. is the total systematic uncertainty which will 299 be described in the next section. The upper limit on the 300 product of branching fractions is B(J/ψ → ωX(pp) → 301 ωpp) < 3.9 × 10 −6 at the 95% C.L.. 302An alternative fit with a Breit-Wigner function includ-for X(pp) is performed. Here, f FSI is the Jülich FSI cor- between data and MC simulation is 2% per charged track. 323The systematic uncertainty from PID is 2% per proton 324(anti-proton). 325The photon detection systematic uncertainty is studied efficiency difference is about 1% for each photon [32, 33]. 329Author's Copy Near-threshold pp invariant-mass spectrum. The signal J/ψ → ωX(pp) → ωpp is described by an acceptanceweighted Breit-Wigner function, and and signal yield is consistent with zero. The dotted line is the shape of the signal which is normalized to five times the estimated upper limit. The dashed line is the non-resonant contribution described by the function f (δ) and the dashed-dotted line is the non ωpp contribution which is estimated from ω sidebands. The solid line is the total contribution of the two components. The hatched area is from the sideband region.Here, 3% is taken as the systematic error for the efficien- ciency between data and MC is 3%, and is taken as the 338 systematic uncertainty caused by the kinematic fit. 339As described above, the yield of J/ψ → ωpp is de- The signal J/ψ → ωX(pp) → ωpp is described by an acceptanceweighted Breit-Wigner function, and and signal yield is consistent with zero. The dashed line is the non-resonant contribution fixed to a phase space MC simulation of J/ψ → ωpp and the dashed-dotted line is the non ωpp contribution which is estimated from ω sidebands. The solid line is the total contribution of the two components. The hatched area is from a phase space MC simulation of J/ψ → ωpp.sented by Figure.

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We study e+e-→π+π-hc at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e+e-→π+π-J/ψ but with a different line shape. In the π±hc mass spectrum, a distinct structure, referred to as Zc(4020), is observed at 4.02  GeV/c2. The Zc(4020) carries an electric charge and couples to charmonium. A fit to the π±hc invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9±0.8±2.7)  MeV/c2 and a width of (7.9±2.7±2.6)  MeV for the Zc(4020), where the first errors are statistical and the second systematic. The difference between the parameters of this structure and the Zc(4025) observed in the D*D[over ¯]* final state is within 1.5σ, but whether they are the same state needs further investigation. No significant Zc(3900) signal is observed, and upper limits on the Zc(3900) production cross sections in π±hc at center-of-mass energies of 4.23 and 4.26 GeV are set.

We report the first measurements of inclusive W and Z boson cross sections times the corresponding leptonic branching ratios for pp collisions at √ s = 1.96 TeV based on the decays of the W and Z bosons into electrons and muons. The data were recorded with the CDF II detector at the Fermilab 4Tevatron and correspond to an integrated luminosity of 72.0 ± 4.3 pb −1 . We test e-µ lepton universality in W decays by measuring the ratio of the W → µν to W → eν cross sections and determine a value of 0.991 ± 0.004(stat.) ± 0.011(syst.) for the ratio of W −ℓ−ν couplings (gµ/ge). Since there is no sign of non-universality, we combine our cross section measurements in the different lepton decay modes and obtain σW ×Br(pp → W → ℓν) = 2.749 ± 0.010(stat.) ± 0.053(syst.) ± 0.165(lum.) nb and σ γ * /Z × Br(pp → γ * /Z → ℓℓ) = 254.9 ± 3.3(stat.) ± 4.6(syst.) ± 15.2(lum.) pb for dilepton pairs in the mass range between 66 GeV/c 2 and 116 GeV/c 2 . We compute the ratio R of the W → ℓν to Z → ℓℓ cross sections taking all correlations among channels into account and obtain R = 10.84 ± 0.15(stat.) ± 0.14(syst.) including a correction for the virtual photon exchange component in our measured γ * /Z → ℓℓ cross section. Based on the measured value of R, we extract values for the W leptonic branching ratio, Br(W → ℓν) = 0.1082 ± 0.0022; the total width of the W boson, Γ(W ) = 2092 ± 42 MeV; and the ratio of W and Z boson total widths, Γ(W )/Γ(Z) = 0.838 ± 0.017. In addition, we use our extracted value of Γ(W ) whose value depends on various electroweak parameters and certain CKM matrix elements to constrain the Vcs CKM matrix element, |Vcs| = 0.976± 0.030.

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