Publications (90)121.58 Total impact

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ABSTRACT: We report the first observation of the Dalitz decay $\eta' \to \gamma e^+e^$, based on a data sample of 1.31 billion $J/\psi$ events collected with the BESIII detector. The $\eta'$ mesons are produced via the $J/\psi \to \gamma \eta'$ decay process. The ratio $\Gamma(\eta' \to \gamma e^+ e^)/\Gamma(\eta'\to\gamma\gamma)$ is measured to be $(2.13\pm0.09(\text{stat.})\pm0.07(\text{sys.}))\times10^{2}$. This corresponds to a branching fraction ${\cal B}(\eta' \to \gamma e^+e^)= (4.69 \pm0.20(\text{stat.})\pm0.23(\text{sys.}))\times10^{4}$. The transition form factor is extracted and different expressions are compared to the measured dependence on the $e^+e^$ invariant mass. The results are consistent with the prediction of the Vector Meson Dominance model. 
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ABSTRACT: As the main tracking detector of BESIII, the drift chamber works for accurate measurements of the tracking and the momentum of the charged particles decayed from the reaction of BEPCII e+ and e. After operation six years, the drift chamber is suffering from aging problems due to huge beam related background. The gains of the cells in the first ten layers experience an obvious decrease, reaching a maximum of about 29% for the first layer cells. Two calculation methods for the gains change (Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells) get almost the same results. For the Malter effect encountered by the inner drift chamber in Jan., 2012, about 0.2% water vapor was added to MDC gas mixture to solve this cathode aging problem. These results provide an important reference for MDC operation high voltage setting and the upgrade of the inner drift chamber. 
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ABSTRACT: Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of $e^{+}e^{}\rightarrow p\bar{p}$ at 12 centerofmass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal $(G_{E}= G_{M})$. In addition, the ratio of electric to magnetic form factors, $G_{E}/G_{M}$, and $G_{M}$ are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at $\sqrt{s}=$ 2232.4 and 2400.0 MeV and a combined sample at $\sqrt{s}$ = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BaBar, improving the overall uncertainty by about 30\%. The $G_{E}/G_{M}$ ratios are close to unity and consistent with BaBar results in the same $q^{2}$ region, which indicates the data are consistent with the assumption that $G_{E}=G_{M}$ within uncertainties. 
Article: Observation of the electromagnetic doubly OZIsuppressed decay $J/\psi \rightarrow \phi \pi^{0}$
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ABSTRACT: Using a sample of $1.31$ billion $J/\psi$ events accumulated with the BESIII detector at the BEPCII collider, we report the observation of the decay $J/\psi \rightarrow \phi\pi^{0}$, which is the first evidence for a doubly OkuboZweigIizuka suppressed electromagnetic $J/\psi$ decay. A clear structure is observed in the $K^{+} K^{}$ mass spectrum around 1.02 GeV/$c^2$, which can be attributed to interference between $J/\psi \rightarrow \phi\pi^{0}$ and $J/\psi \rightarrow K^{+}K^{}\pi^{0}$ decays. Due to this interference, two possible solutions are found. The corresponding measured values of the branching fraction of $J/\psi \to \phi\pi^{0}$ are $[2.94 \pm 0.16\text{(stat.)} \pm 0.16\text{(syst.)}] \times 10^{6}$ and $[1.24 \pm 0.33\text{(stat.)} \pm 0.30\text{(syst.)}] \times 10^{7}$. 
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ABSTRACT: Using a sample of $1.06\times10^8\ \psip$ events produced in $e^+e^$ collisions at $\sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $\klx+c.c.$ and $\gklx+c.c.$. We observe two hyperons, $\Xi(1690)^$ and $\Xi(1820)^$, in the $K^\Lambda$ invariant mass distribution in the decay $\klx+c.c.$ with significances of $4.9 \sigma$ and $6.2 \sigma$, respectively. The branching fractions of $\klx+c.c.$, $\ksx+c.c.$, $\psip\to\gamma \chi_{cJ}\to \gamma K^ \Lambda \bar{\Xi}^+ +c.c.$ $(J=0,\ 1,\ 2)$, and $\psip\to \Xi(1690/1820)^{} \bar{\Xi}^++c.c$ with subsequent decay $\Xi(1690/1820)^\to K^\Lambda$ are measured for the first time. 
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ABSTRACT: We report the observation of the $X(3823)$ in the process $e^+e^\to \pi^+\pi^X(3823) \to \pi^+\pi^\gamma\chi_{c1}$ with a statistical significance of $6.2\sigma$, in data samples at centerofmass energies $\sqrt{s}=$4.230, 4.260, 4.360, 4.420 and 4.600~GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the $X(3823)$ is $(3821.7\pm 1.3\pm 0.7)$~MeV/$c^2$, where the first error is statistical and the second systematic, and the width is less than $16$~MeV at the 90\% confidence level. The products of the Born cross sections for $e^+e^\to \pi^+\pi^X(3823)$ and the branching ratio $\mathcal{B}[X(3823)\to \gamma\chi_{c1,c2}]$ are also measured. These measurements are in good agreement with the assignment of the $X(3823)$ as the $\psi(1^3D_2)$ charmonium state. 
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ABSTRACT: Using data samples collected with the BESIII detector operating at the BEPCII collider at centerofmass energies from 3.810 to 4.600 GeV, we perform a study of $e^{+}e^{} \to \eta J/\psi$ and $\pi^0 J/\psi$. Statistically significant signals of $e^{+}e^{} \to \eta J/\psi$ are observed at $\sqrt{s}$ = 4.190, 4.210, 4.220, 4.230, 4.245, 4.260, 4.360 and 4.420 GeV, while no signals of $e^{+}e^{} \to \pi^{0} J/\psi$ are observed. The measured energydependent Born cross section for $e^{+}e^{} \to \eta J/\psi$ shows an enhancement around 4.2~GeV. The measurement is compatible with an earlier measurement by Belle, but with a significantly improved precision. 
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ABSTRACT: Using a data sample of 106 million $\psi(3686)$ events collected with the BESIII detector operated at the BEPCII storage ring, we study for the first time the decay $\chi_{cJ}\to\phi K^{0}_S K^{\pm}\pi^{\mp}$ and $\chi_{cJ}\to\phi K^{+} K^{}\pi^{0}$ in the E1 radiative transition $\psi(3686)\to\gamma\chi_{cJ}$. The decays are dominated by the threebody decay $\chi_{cJ}\to \phi K^*(892)\bar{K}$. We measure branching fractions for this reaction via the neutral and charged $K^*(892)$ and find them consistent with each other within the expectation of isospin symmetry. In the $K\bar{K}\pi$ invariant mass distribution a structure near the $K^*(892)\bar{K}$ mass threshold is observed, and the corresponding mass and width are measured to be $1412\pm4(\mathrm{stat.})\pm8(\mathrm{sys.}) \mathrm{MeV}/c^2$ and $\Gamma$ = $84\pm12(\mathrm{stat.})\pm40(\mathrm{sys.}) \mathrm{MeV}$, respectively. The observed state favors an assignment to the $h_1(1380)$, considering its possible $J^{PC}$ and comparing its mass, width and decay mode to those reported in the Particle Data Group. 
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ABSTRACT: From December 2011 to May 2014, about 5 $\rm fb^{1}$ of data were taken with the BESIII detector at centerofmass energies between 3.810 GeV and 4.600 GeV to study the charmoniumlike states and higher excited charmonium states. The time integrated luminosity of the collected data sample is measured to a precision of 1% by analyzing events produced by the largeangle Bhabha scattering process. 
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ABSTRACT: Based on data samples collected with the BESIII detector at the BEPCII collider at nine center of mass energies from 4.21 to 4.42 GeV, we search for the production of e^{+}e^{}→ωχ_{cJ} (J=0, 1, 2). The process e^{+}e^{}→ωχ_{c0} is observed for the first time, and the Born cross sections at sqrt[s]=4.23 and 4.26 GeV are measured to be (55.4±6.0±5.9) and (23.7±5.3±3.5) pb, respectively, where the first uncertainties are statistical and the second are systematic. The ωχ_{c0} signals at the other seven energies and the e^{+}e^{}→ωχ_{c1} and ωχ_{c2} signals are not significant, and the upper limits on the cross sections are determined. By examining the ωχ_{c0} cross section as a function of center of mass energy, we find that it is inconsistent with the line shape of the Y(4260) observed in e^{+}e^{}→π^{+}π^{}J/ψ. Assuming the ωχ_{c0} signals come from a single resonance, we extract the mass and width of the resonance to be (4230±8±6) MeV/c^{2} and (38±12±2) MeV, respectively, and the statistical significance is more than 9σ.Physical Review Letters 03/2015; 114(9):092003. · 7.73 Impact Factor 
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ABSTRACT: We present the first upperlimit measurement of the branching fractions of the isospinviolating transitions $\chi_{c0,2} \rightarrow \pi^{0} \eta_{c}$. The measurements are performed using $106\times 10^{6}$ $\psi(3686)$ events accumulated with the BESIII detector at the BEPCII $e^{+}e^{}$ collider at a centerofmass energy corresponding to the $\psi(3686)$ mass. We obtained upper limits on the branching fractions at a 90\% confidence level of $B(\chi_{c0} \rightarrow \pi^{0} \eta_{c}) < 1.6 \times 10^{3}$ and $B(\chi_{c2} \rightarrow \pi^{0} \eta_{c}) < 3.2 \times 10^{3}$. 
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ABSTRACT: We report a measurement of the parameter $y_{CP}$ in $\ensuremath{D^0}\xspace\ensuremath{\overline{D}^{0}}\xspace$ oscillations performed by taking advantage of quantum coherence between pairs of $\ensuremath{D^0}\xspace \ensuremath{\overline{D}^{0}}\xspace$ mesons produced in $e^+e^$ annihilations near threshold. In this work, doublytagged $\ensuremath{D^0}\xspace \ensuremath{\overline{D}^{0}}\xspace$ events, where one $D$ decays to a $CP$ eigenstate and the other $D$ decays in a semileptonic mode, are reconstructed using a data sample of 2.92\,fb$^{1}$ collected with the BESIII detector at the centerofmass energy of $\sqrt{s}$ = 3.773\,GeV. We obtain $y_{CP} = (2.0\pm1.3\pm0.7)\%$, where the first uncertainty is statistical and the second is systematic. This result is compatible with the current world average. 
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ABSTRACT: Based on a sample of $2.25\times 10^{8} J/\psi$ events taken with the BESIII detector at the BEPCII collider, we present the results of a study of the decay $J/\psi\to \eta \phi\pi^{+}\pi^{}$. The $Y(2175)$ resonance is observed in the invariant mass spectrum of $\phi f_{0}(980)$ with a statistical significance of greater than $10\sigma$. The corresponding mass and width are determined to be $M=2200\pm 6 \mathrm{(stat.)} \pm 5\mathrm{(syst.)} \mathrm{MeV}/c^{2}$ and $\Gamma=104\pm 15\mathrm{(stat.)}\pm 15\mathrm{(syst.)}$ MeV, respectively, and the product branching fraction is measured to be $\mathcal{B}(J/\psi\to\eta Y(2175)$, $Y(2175)\to \phi f_{0}(980)$, $f_{0}(980)\to \pi^{+}\pi^{})= (1.20\pm 0.14\mathrm{(stat.)}\pm 0.37 \mathrm{(syst.)})\times 10^{4}$. The results are consistent within errors with those of previous experiments. We also measure the branching fraction of $J/\psi\to \phi f_1(1285)$ with $f_1(1285)\to \eta\pi^{+}\pi^{}$ and set upper limits on the branching fractions for $J/\psi\to \phi\eta(1405)$/$\phi X(1835)$/$\phi X(1870)$ with $\eta(1405)$/$X(1835)$/$X(1870)\to \eta\pi^{+}\pi^{}$ at the 90\% confidence level. 
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ABSTRACT: Using 482 pb$^{1}$ of data taken at $\sqrt{s}=4.009$ GeV, we measure the branching fractions of the decays of $D^{*0}$ into $D^0\pi^0$ and $D^0\gamma$ to be $\BR(D^{*0} \to D^0\pi^0)=(65.5\pm 0.8\pm 0.5)%$ and $\BR(D^{*0} \to D^0\gamma)=(34.5\pm 0.8\pm 0.5)%$ respectively, by assuming that the $D^{*0}$ decays only into these two modes. The ratio of the two branching fractions is $\BR(D^{*0} \to D^0\pi^0)/\BR(D^{*0} \to D^0\gamma) =1.90\pm 0.07\pm 0.05$, which is independent of the assumption made above. The first uncertainties are statistical and the second ones systematic. The precision is improved by a factor of three compared to the present world average values. 
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ABSTRACT: Using data samples collected at centerofmass energies $\sqrt{s} = 4.23$, 4.26, and 4.36~GeV with the BESIII detector operating at the BEPCII storage ring, we search for the production of the charmoniumlike state $Y(4140)$ through a radiative transition followed by its decay to $\phi J/\psi$. No significant signal is observed and upper limits on $\sigma[e^{+} e^{} \rightarrow \gamma Y(4140)] \cdot \mathcal{B}(Y(4140)\rightarrow \phi J/\psi)$ at the $90\%$ confidence level are estimated as 0.35, 0.28, and 0.33~pb at $\sqrt{s} = 4.23$, 4.26, and 4.36~GeV, respectively. 
Article: Evidence for $e^+e^\to\gamma\chi_{c1, 2}$ at centerofmass energies from 4.009 to 4.360 GeV
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ABSTRACT: Using data samples collected at centerofmass energies of $\sqrt{s}$ = 4.009, 4.230, 4.260, and 4.360 GeV with the BESIII detector operating at the BEPCII collider, we perform a search for the process $e^+e^\to\gamma\chi_{cJ}$ $(J = 0, 1, 2)$ and find evidence for $e^+e^\to\gamma\chi_{c1}$ and $e^+e^\to\gamma\chi_{c2}$ with statistical significances of 3.0$\sigma$ and 3.4$\sigma$, respectively. The Born cross sections $\sigma^{B}(e^+e^\to\gamma\chi_{cJ})$, as well as their upper limits at the 90% confidence level are determined at each centerofmass energy. 
Article: Observation of e^{+}e^{}→π^{0}π^{0}h_{c} and a Neutral Charmoniumlike Structure Z_{c}(4020)^{0}
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ABSTRACT: Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at centerofmass energies of sqrt[s]=4.23, 4.26, and 4.36 GeV, we observe e^{+}e^{}→π^{0}π^{0}h_{c} for the first time. The Born cross sections are measured and found to be about half of those of e^{+}e^{}→π^{+}π^{}h_{c} within less than 2σ. In the π^{0}h_{c} mass spectrum, a structure at 4.02 GeV/c^{2} is found. It is most likely to be the neutral isospin partner of the Z_{c}(4020)^{±} observed in the process of e^{+}e^{}→π^{+}π^{}h_{c} being found. A fit to the π^{0}h_{c} invariant mass spectrum, with the width of the Z_{c}(4020)^{0} fixed to that of its charged isospin partner and possible interferences with nonZ_{c}(4020)^{0} amplitudes neglected, gives a mass of (4023.9±2.2±3.8) MeV/c^{2} for the Z_{c}(4020)^{0}, where the first error is statistical and the second systematic.Physical Review Letters 11/2014; 113(21):212002. · 7.73 Impact Factor 
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ABSTRACT: Using a sample of $2.25\times 10^8$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider, we search for the $J/\psi$ semileptonic weak decay $J/\psi \to D^{}_{s} e^{+}\nu_{e}+c.c.$ with a much higher sensitivity than previous searches. We also perform the first search for $J/\psi \to D^{*}_{s} e^{+}\nu_{e}+c.c.$ No significant excess of a signal above background is observed in either channel. At the $90\%$ confidence level, the upper limits are determined to be $\mathcal{B}(J/\psi \to D^{}_{s}e^{+}\nu_{e}+c.c.)<1.3\times10^{6}$ and $\mathcal{B}(J/\psi \to {D^{*}_{s}}^{}e^{+}\nu_{e}+c.c.)<1.8\times10^{6}$, respectively. Both are consistent with Standard Model predictions. 
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ABSTRACT: Based on data samples collected with the BESIII detector at the BEPCII collider at 9 centerofmass energies from 4.21 to 4.42 GeV, we search for the production of $e^+e^\to \omega\chi_{cJ}$ ($J$=0, 1, 2). The process $e^+e^\to \omega\chi_{c0}$ is observed for the first time, and the Born cross sections at $\sqrt{s}$=4.23 and 4.26 GeV are measured to be $(55.4\pm 6.0\pm 5.9)$ and $(23.7\pm 5.3\pm 3.5)$ pb, respectively, where the first uncertainties are statistical and the second are systematic. The $\omega\chi_{c0}$ signals at the other 7 energies and $e^+e^\to \omega\chi_{c1}$ and $\omega\chi_{c2}$ signals are not significant, and the upper limits on the cross sections are determined. By examining the $\omega\chi_{c0}$ cross section as a function of centerofmass energy, we find that it is inconsistent with the line shape of the $Y(4260)$ observed in $e^+ e^\to\pi^+\pi^J/\psi$. 
Article: Observation of $e^+e^\to \pi^0\pi^0 h_c$ and a neutral charmoniumlike structure $Z_c(4020)^0$
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ABSTRACT: Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at centerofmass energies of $\sqrt{s}$=4.23, 4.26, and 4.36 GeV, we observe $e^+e^\to \pi^0\pi^0 h_c$ for the first time. The Born cross sections are measured and found to be about half of those of $e^+e^ \to \pi^+\pi^h_c$ within less than 2$\sigma$. In the $\pi^0h_c$ mass spectrum, a structure at 4.02~GeV/$c^2$ that is most likely the neutral isospin partner of the $Z_c(4020)^{\pm}$ observed in the process of $e^+e^ \to \pi^+\pi^h_c$ is found. A fit to the $\pi^0 h_c$ invariant mass spectrum with the width of the $Z_c(4020)^0$ fixed to that of its charged isospin partner and possible interferences with non$Z_c(4020)^0$ amplitudes neglected, gives a mass of ($4023.9\pm 2.2 \pm 3.8$)~MeV/$c^2$ for the $Z_c(4020)^0$, where the first error is statistical and the second systematic.
Publication Stats
178  Citations  
121.58  Total Impact Points  
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Institutions

2014–2015

Università degli Studi di Torino
Torino, Piedmont, Italy 
Chinese Academy of Sciences
Peping, Beijing, China


2012

Institute of physics china
Peping, Beijing, China
