arXiv subjects

X. R. Chen

Publications and source records attributed to X. R. Chen.

760 records · Page 43Linked to original sources

arXiv2013

Observation of a charged charmoniumlike structure Z_c(4020) and search for the Z_c(3900) in e+e- to pi+pi-h_c

We study e+e- --> pi+pi-h_c at center-of-mass energies from 3.90 GeV to 4.42 GeV 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- --> pi+pi-J/psi but with a different line shape. In the π^\pm h_c mass spectrum, a distinct structure, referred to as Z_c(4020), is observed at 4.02 GeV/c^2. The Z_c(4020) carries an electric charge and couples to charmonium. A fit to the π^\pm h_c invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9\pm 0.8\pm 2.7) MeV/c^2 and a width of (7.9\pm 2.7\pm 2.6) MeV for the Z_c(4020), where the first errors are statistical and the second systematic. No significant Z_c(3900) signal is observed, and upper limits on the Z_c(3900) production cross sections in π^\pm h_c at center-of-mass energies of 4.23 and 4.26 GeV are set.

hep-ex↗

arXiv2013

Observation of a structure at 1.84 GeV/c$^2$ in the $3(π^+π^-)$ mass spectrum in $J/ψ\rightarrow γ3(π^+π^-)$ decays

With a sample of 225.3 million $J/ψ$ events taken with the BESIII detector, the decay $J/ψ\rightarrow γ3(π^+π^-)$ is analyzed. A structure at 1.84 GeV/c$^2$ is observed in the $3(π^+π^-)$ invariant mass spectrum with a statistical significance of 7.6$σ$ . The mass and width are measured to be $M=1842.2\pm 4.2^{+7.1}_{-2.6}$ MeV/c$^2$ and $Γ=83\pm 14 \pm 11$ MeV. The product branching fraction is determined to be $B(J/ψ\rightarrowγX(1840))\times B(X(1840)\rightarrow 3(π^+π^-))=(2.44\pm0.36^{+0.60}_{-0.74})\times 10^{-5}$. No $η^\prime$ signals are observed in the $3(π^+π^-)$ invariant mass spectrum, and the upper limit of the branching fraction for the decay $η^\prime\rightarrow 3(π^+π^-)$ is set to be $3.1\times10^{-5}$ at a 90% confidence level.

hep-ex↗

arXiv2013

Observation of the decay $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{\pm}π^{\mp}+c.c.$

Using a sample of $1.06\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector, we present the first observation of the decays of $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{+}π^{-}+c.c.$ and $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{-}π^{+}+c.c.$. The branching fractions are measured to be $\mathcal{B}(ψ(3686) \rightarrow Λ\barΣ^{+}π^{-} + c.c.)=(1.40\pm 0.03 \pm 0.13)\times10^{-4}$ and $\mathcal{B}(ψ(3686) \rightarrow Λ\barΣ^{-}π^{+}+c.c.)=(1.54\pm 0.04 \pm 0.13)\times10^{-4}$, where the first errors are statistical and the second ones systematic.

hep-ex↗

arXiv2013

Precision Measurements of ${\cal B}[ψ(3686) \to π^+π^- J/ψ]$ and ${\cal B}[J/ψ\to l^+l^-]$

Based on $(106.41 \pm 0.86)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, the branching fractions of $ψ(3686) \to π^+π^- J/ψ$, $J/ψ\to e^+e^- $, and $J/ψ\to μ^+μ^-$ are measured. We obtain ${\cal B}[ψ(3686) \to π^+π^-J/ψ]=(34.98\pm 0.02\pm 0.45)%$, ${\cal B}[J/ψ\to e^+e^-] = (5.983 \pm 0.007 \pm 0.037)%$ and ${\cal B}[J/ψ\to μ^+μ^-] = (5.973 \pm 0.007 \pm 0.038)%$. The measurement of ${\cal B}[ψ(3686) \to π^{+}π^{-}J/ψ]$ confirms the CLEO-c measurement, and is apparently larger than the others. The measured $J/ψ$ leptonic decay branching fractions agree with previous experiments within one standard deviation. These results lead to ${\cal B}[J/ψ\to l^+l^-] = (5.978 \pm 0.005 \pm 0.040)%$ by averaging over the $e^{+}e^{-}$ and $μ^{+}μ^{-}$ channels and a ratio of ${\cal B}[J/ψ\to e^+e^-] / {\cal B}[J/ψ\to μ^+μ^-] = 1.0017 \pm 0.0017 \pm 0.0033$, which tests $e$-$μ$ universality at the four tenths of a percent level. All the measurements presented in this paper are the most precise in the world to date.

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