J M Bian

Publications (58)78.28 Total impact

• Article: Observation of a structure at 1.84 GeV/c$^2$ in the $3(\pi^+\pi^-)$ mass spectrum in $J/\psi\rightarrow \gamma 3(\pi^+\pi^-)$ decays

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: With a sample of 225.3 million $J/\psi$ events taken with the BESIII detector, the decay $J/\psi\rightarrow \gamma 3(\pi^+\pi^-)$ is analyzed. A structure at 1.84 GeV/c$^2$ is observed in the $3(\pi^+\pi^-)$ invariant mass spectrum with a statistical significance of 7.6$\sigma$ . The mass and width are measured to be $M=1842.2\pm 4.2^{+7.1}_{-2.6}$ MeV/c$^2$ and $\Gamma=83\pm 14 \pm 11$ MeV. The product branching fraction is determined to be $B(J/\psi\rightarrow\gamma X(1840))\times B(X(1840)\rightarrow 3(\pi^+\pi^-))=(2.44\pm0.36^{+0.60}_{-0.74})\times 10^{-5}$. No $\eta^\prime$ signals are observed in the $3(\pi^+\pi^-)$ invariant mass spectrum, and the upper limit of the branching fraction for the decay $\eta^\prime\rightarrow 3(\pi^+\pi^-)$ is set to be $3.1\times10^{-5}$ at a 90% confidence level.
  05/2013;
• Article: Search for Baryonic Decays of \psi(3770) and \psi(4040)

  BESIII Collaboration, M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482 pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the BEPCII storage ring, we search for \psi(3770) and \psi(4040) decay to baryonic final states, including \Lambda\bar\Lambda\pi^+\pi^-, \Lambda \bar\Lambda\pi^0, \Lambda\bar\Lambda\eta, \Sigma^+ \bar\Sigma^-, \Sigma^0 \bar\Sigma^0, \Xi^-\bar\Xi^+ and \Xi^0\bar\Xi^0 decays. None are observed, and upper limits are set at the 90% confidence level.
  05/2013;
• Article: Partial wave analysis of $\psi(2S) \to p \bar{p}\eta$

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Using a sample of $1.06 \times 10^{8}$ $\psi(2S)$ events collected with the BESIII detector at BEPCII, the decay $\psi(2S) \to p \bar{p}\eta$ is studied. A partial wave analysis determines that the intermediate state N(1535) with a mass of $1524\pm5^{+10}_{-4}$ MeV/$c^2$ and a width of $130^{+27+57}_{-24-10}$ MeV/$c^2$ is dominant in the decay; the product branching fraction is determined to be $B(\psi(2S) \to N(1535)\bar{p})\times B(N(1535)\to p\eta)+c.c. = (5.2\pm0.3^{+3.2}_{-1.2})\times 10^{-5}$. Furthermore, the branching fraction of $\psi(2S) \to \eta p \bar{p}$ is measured to be $(6.4\pm0.2\pm0.6)\times 10^{-5}$.
  04/2013;
• Article: Measurement of $\eta^\prime\rightarrow \pi^+\pi^- e^+e^-$ and $\eta^\prime\rightarrow \pi^+\pi^-\mu^+\mu^-$

  BESIII Collaboration, M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Based on a sample of 225.3 million J/\psi events accumulated with the BESIII detector at the BEPCII, the decays of \eta' to pi+pi-l+l- are studied via J/\psi to \gamma\eta'. A clear \eta' signal is observed in the pi+pi-e+e- mass spectrum, and the branching fraction is measured to be \BR(\eta' to pi+pi-e+e-) = (2.11\pm0.12 (stat.)\pm0.15 (syst.))\times10^{-3}, which is in good agreement with theoretical predictions and the previous measurement, but is determined with much higher precision. No \eta' signal is found in the pi+ pi- mu+ mu- mass spectrum, and the upper limit is determined to be \BR(\eta' to pi+ pi- mu+ mu-)<2.9\times10^{-5} at the 90% confidence level.
  03/2013;
• Article: Observation of a charged charmoniumlike structure in e+e- to pi+pi-J/psi at \sqrt{s}=4.26 GeV

  BESIII Collaboration, M. Ablikim, M. N. Achasov, X. C. Ai, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: We study the process e+e- to pi+pi-J/psi 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\pm 1.9\pm 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c^2 in the \pi^\pm J/psi mass spectrum, which we refer to as the Z_c(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 \pi^\pm J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0\pm 3.6\pm 4.9) MeV/c^2 and a width of (46\pm 10\pm 20) MeV. Its production ratio is measured to be R=\frac{\sigma(e+e- to \pi^\pm Z_c(3900)^\mp to pi+pi-J/psi))} {\sigma(e+e- to pi+pi-J/psi)}=(21.5\pm 3.3\pm 7.5)%. In all measurements the first errors are statistical and the second are systematic.
  03/2013;
• Article: Study of $J/\psi \rightarrow \omega p \bar{p}$ at BESIII

  The BESIII Collaboration, M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: The decay $J/\psi \rightarrow \omega p \bar{p}$ has been studied, using $225.3\times 10^{6}$ $J/\psi$ events accumulated at BESIII. No significant enhancement near the $p\bar{p}$ invariant-mass threshold (denoted as $X(p\bar{p})$) is observed. The upper limit of the branching fraction $\mathcal{B}(J/\psi \rightarrow \omega X(p\bar{p}) \rightarrow \omega p \bar{p})$ is determined to be $3.9\times10^{-6}$ at the 95% confidence level. The branching fraction of $J/\psi \rightarrow \omega p \bar{p}$ is measured to be $\mathcal{B}(J/\psi \rightarrow \omega p \bar{p}) =(9.0 \pm 0.2\ (\text{stat.})\pm 0.9\ (\text{syst.})) \times 10^{-4}$.
  03/2013;
• Article: Observation of Two New N^{*} Resonances in the Decay ψ(3686)→pp[over ¯]π^{0}.

  M Ablikim, M N Achasov, D J Ambrose, F F An, Q An, Z H An, J Z Bai, Y Ban, J Becker, N Berger, [......], S H Zhu, X L Zhu, X W Zhu, Y M Zhu, Y S Zhu, Z A Zhu, J Zhuang, B S Zou, J H Zou, J X Zuo
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  ABSTRACT: Based on 106×10^{6}ψ(3686) events collected with the BESIII detector at the BEPCII facility, a partial wave analysis of ψ(3686)→pp[over ¯]π^{0} is performed. The branching fraction of this channel has been determined to be B(ψ(3686)→pp[over ¯]π^{0})=(1.65±0.03±0.15)×10^{-4}. In this decay, 7 N^{*} intermediate resonances are observed. Among these, two new resonances, N(2300) and N(2570) are significant, one 1/2^{+} resonance with a mass of 2300_{-30-0}^{+40+109} MeV/c^{2} and width of 340_{-30-58}^{+30+110} MeV/c^{2}, and one 5/2^{-} resonance with a mass of 2570_{-10-10}^{+19+34} MeV/c^{2} and width of 250_{-24-21}^{+14+69} MeV/c^{2}. For the remaining 5 N^{*} intermediate resonances [N(1440), N(1520), N(1535), N(1650) and N(1720)], the analysis yields mass and width values that are consistent with those from established resonances.
  Physical Review Letters 01/2013; 110(2):022001. · 7.37 Impact Factor
• Article: Evidence for \eta_{c}(2S) in \psi(3686) \to \gamma K_{S}^{0}K^{\pm}\pi^{\mp}\pi^{+}\pi^{-}

  The BESIII Collaboration, M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: We search for the M1 radiative transition \psi(3686) \to \gamma\eta_{c}(2S) by reconstructing the exclusive \eta_{c}(2S) \to K_{S}^{0}K^{\pm}\pi^{\mp}\pi^{+}\pi^{-} decay using 1.06 \times 10^8 \psi(3686) events collected with the BESIII detector. The signal is observed with a statistical significance of greater than 4 standard deviations. The measured mass of the \eta_{c}(2S) is 3646.9 \pm 1.6(stat) \pm 3.6(syst) MeV/c^2, and the width is 9.9 \pm 4.8(stat) \pm 2.9(syst) MeV/c^2. The product branching fraction is measured to be B(\psi(3686) \to \gamma\eta_{c}(2S)) \times B(\eta_{c}(2S) \to K_{S}^{0}K^{\pm}\pi^{\mp}\pi^{+}\pi^{-}) = (7.03 \pm 2.10(stat) \pm 0.70(syst)) \times 10^{-6}. This measurement complements a previous BESIII measurement of \psi(3686) \to \gamma\eta_{c}(2S) with \eta_{c}(2S) \to K_{S}^{0} K^{\pm}\pi^{\mp} and K^{+}K^{-}\pi^{0}.
  01/2013;
• Article: Partial wave analysis of $J/\psi \to \gamma \eta \eta$

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Based on a sample of $2.25\times 10^{8}$ $J/\psi$ events collected with the BESIII detector at BEPCII, a full partial wave analysis on $J/\psi\to\gamma\eta\eta$ was performed using the relativistic covariant tensor amplitude method. The results show that the dominant $0^{++}$ and $2^{++}$ components are from the $f_0(1710)$, $f_0(2100)$, $f_0(1500)$, $f_2'(1525)$, $f_2(1810)$ and $f_2(2340)$. The resonance parameters and branching fractions are also presented.
  12/2012;
• Article: Study of the near-threshold $\omega\phi$ mass enhancement in doubly OZI suppressed $J/\psi \to \gamma\omega\phi$ decays

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, J. V. Bennett, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: A 2.25$\times10^8$ $\jpsi$ event sample accumulated with the BESIII detector is used to study the doubly OZI suppressed decay modes $\jpsi\to\gamma\of$, $\omega\to\ppp$, $\phi\to\kk$. A strong deviation ($>$ 30$\sigma$) from three-body $\jpsi\to\gamma\omega\phi$ phase space is observed near the $\omega\phi$ mass threshold that is consistent with a previous observation reported by the BESII experiment. A partial wave analysis with a tensor covariant amplitude that assumes that the enhancement is due to the presence of a resonance, the X(1810), is performed, and confirms that the spin-parity of the X(1810) is $0^{++}$. The mass and width of the X(1810) are determined to be $M=1795\pm7$(stat)$^{+13}_{-5}$(syst)$\pm$19(mod) MeV/$c^2$ and $\Gamma=95\pm10$(stat)$^{+21}_{-34}$(syst)$\pm$75(mod) MeV/$c^2$, respectively, and the product branching fraction is measured to be ${\cal B}(\jpsi\to\gamma X(1810))\times{\cal B}(X(1810)\to\of)=(2.00\pm0.08$(stat)$^{+0.45}_{-1.00}$(syst)$\pm$1.30(mod))$\times10^{-4}$. %where the first error is the statistical error and the second the systematical error. These results are consistent within errors with those of the BESII experiment.
  11/2012;
• Article: Search for $\eta$ and $\eta^\prime\to \pi^+ e^- \bar{\nu}_e +c.c.$ decays in $\jpsi \to \phi \eta$ and $\phi \eta^\prime$

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Using a sample of 225.3 million $\jpsi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider in 2009, searches for the decays of $\eta$ and $\eta^\prime\to\pi^+ e^- \bar{\nu}_e +c.c.$ in $\jpsi \to \phi \eta$ and $\phi\eta^\prime$ are performed. The $\phi$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag $\eta$ and $\eta^\prime$ semileptonic decays. No signals are observed for either $\eta$ or $\eta^\prime$, and upper limits at the 90% confidence level are determined to be $7.3\times 10^{-4}$ and $5.0\times 10^{-4}$ for the ratios $\frac{{\mathcal B}(\eta\to \pi^+ e^- \bar{\nu}_e +c.c.)}{{\mathcal B}(\eta \to \pip\pim\piz)}$ and $\frac{{\mathcal B}(\eta^\prime\to \pi^+ e^-\bar{\nu}_e +c.c.)}{{\mathcal B}(\eta^\prime \to \pip\pim\eta)}$, respectively. These are the first upper limit values determined for $\eta$ and $\eta^\prime$ semileptonic weak decays.
  11/2012;
• Article: Measurements of Baryon Pair Decays of $\chi_{cJ}$ Mesons

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, J. V. Bennett, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Using 106 $\times 10^{6}$ $\psi^{\prime}$ decays collected with the BESIII detector at the BEPCII, three decays of $\chi_{cJ}$ ($J=0,1,2$) with baryon pairs ($\llb$, $\ssb$, $\SSB$) in the final state have been studied. The branching fractions are measured to be $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Lambda\bar\Lambda) =(33.3 \pm 2.0 \pm 2.6)\times 10^{-5}$, $(12.2 \pm 1.1 \pm 1.1)\times 10^{-5}$, $(20.8 \pm 1.6 \pm 2.3)\times 10^{-5}$; $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{0}\bar\Sigma^{0})$ = $(47.8 \pm 3.4 \pm 3.9)\times 10^{-5}$, $(3.8 \pm 1.0 \pm 0.5)\times 10^{-5}$, $(4.0 \pm 1.1 \pm 0.5) \times 10^{-5}$; and $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{+}\bar\Sigma^{-})$ = $(45.4 \pm 4.2 \pm 3.0)\times 10^{-5}$, $(5.4 \pm 1.5 \pm 0.5)\times 10^{-5}$, $(4.9 \pm 1.9 \pm 0.7)\times 10^{-5}$, where the first error is statistical and the second is systematic. Upper limits on the branching fractions for the decays of $\chi_{c1,2}\rightarrow\Sigma^{0}\bar\Sigma^{0}$, $\Sigma^{+}\bar\Sigma^{-}$, are estimated to be $\cal{B}$$(\chi_{c1}\rightarrow\Sigma^{0}\bar\Sigma^{0}) < 6.2\times 10^{-5}$, $\cal{B}$$(\chi_{c2}\rightarrow\Sigma^{0}\bar\Sigma^{0}) < 6.5\times 10^{-5}$, $\cal{B}$$(\chi_{c1}\rightarrow\Sigma^{+}\bar\Sigma^{-}) < 8.7\times 10^{-5}$ and $\cal{B}$$(\chi_{c2}\rightarrow\Sigma^{+}\bar\Sigma^{-}) < 8.8\times 10^{-5}$ at the 90% confidence level.
  11/2012;
• Article: Evidence for the Direct Two-Photon Transition from ψ(3686) to J/ψ

  M Ablikim, M N Achasov, D J Ambrose, F F An, Q An, Z H An, J Z Bai, R B Ferroli, Y Ban, J Becker, [......], S H Zhu, X L Zhu, X W Zhu, Y M Zhu, Y S Zhu, Z A Zhu, J Zhuang, B S Zou, J H Zou, J X Zuo
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  ABSTRACT: The two-photon transition ψ(3686)→γγJ/ψ is studied in a sample of 1.06×10^{8} ψ(3686) decays collected by the BESIII detector. The branching fraction is measured to be (3.1±0.6(stat)_{-1.0}^{+0.8}(syst))×10^{-4} using J/ψ→e^{+}e^{-} and J/ψ→μ^{+}μ^{-} decays, and its upper limit is estimated to be 4.5×10^{-4} at the 90% confidence level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the ψ(3686) decay plane and the J/ψ polarization in this decay are also studied. In addition, the product branching fractions of sequential E1 transitions ψ(3686)→γχ_{cJ} and χ_{cJ}→γJ/ψ(J=0,1,2) are reported.
  Physical Review Letters 10/2012; 109(17):172002. · 7.37 Impact Factor
• Article: Precision measurements of branching fractions for $ \psi'\to\pi^0 J\psi$ and $\eta J\psi$

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, J. V. Bennett, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: We present a precision study of the $\psip\to\pi^0 J/\psi$ and $\eta J/\psi$ decay modes. The measurements are obtained using $106\times10^6$ $\psi'$ events accumulated with the BESIII detector at the BEPCII $\ee$ collider operating at a center-of-mass energy corresponding to the $\psip$ mass. We obtain $\mathcal{B}(\psip\to\pi^0 J/\psi)=(1.26\pm0.02{\rm (stat.)}\pm0.03{\rm (syst.)})\times 10^{-3}$ and $\mathcal{B}(\psip\to\eta J/\psi)=(33.75\pm0.17{\rm (stat.)}\pm0.86{\rm (syst.)})\times 10^{-3}$. The branching fraction ratio $R=\frac{\mathcal{B}(\psip\to\pi^0 J/\psi)}{\mathcal{B}(\psip\to\eta J/\psi)}$ is determined to be $(3.74\pm0.06 {\rm(stat.)}\pm0.04 {\rm(syst.)})\times 10^{-2}$. The precision of these measurements of $\mathcal{B}(\psip\to\pi^{0} J/\psi)$ and $R$ represent a significant improvement over previously published values.
  10/2012;
• Article: Observation of $\eta_{c}$ decay into $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$ final states

  The BESIII Collaboration, M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Using a data sample of $2.25\times10^{8}$ $J/\psi$ events collected with the BESIII detector, we present the first observation of the decays of $\eta_{c}$ mesons to $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$. The branching fractions are measured to be $(2.11\pm0.28_{\rm stat.}\pm0.18_{\rm syst.}\pm0.50_{\rm PDG})\times10^{-3}$ and $(0.89\pm0.16_{\rm stat.}\pm0.08_{\rm syst.}\pm0.21_{\rm PDG})\times10^{-3}$ for $\eta_{c} \to \Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$, respectively. These branching fractions provide important information on the helicity selection rule in charmonium-decay processes.
  10/2012;
• Article: Study of $\psi(3686)\to\pi^0 h_c, h_c\to\gamma\eta_c$ via $\eta_c$ exclusive decays

  The BESIII Collaboration, M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: The process $\psi(3686) \to \pi^0 h_c, h_c \to \gamma \eta_c$ has been studied with a data sample of $106 \pm 4$ million $\psi(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The mass and width of the $P$-wave charmonium spin-singlet state $h_c(^1P_1)$ are determined by simultaneously fitting distributions of the $\pi^0$ recoil mass for 16 exclusive $\eta_c$ decay modes. The results, $M(\hc) = 3525.31 \pm 0.11 {\rm (stat.)} \pm 0.14 {\rm (syst.)}$\,MeV/$c^2$ and $\Gamma(\hc) = 0.70 \pm 0.28 \pm 0.22$\,MeV, are consistent with and more precise than previous measurements. We also determine the branching ratios for the 16 exclusive $\eta_c$ decay modes, five of which have not been measured previously. New measurements of the $\eta_c$ line-shape parameters in the $E1$ transition $h_c\to\gamma\eta_c$ are made by selecting candidates in the $h_c$ signal sample and simultaneously fitting the hadronic mass spectra for the 16 $\eta_c$ decay channels. The resulting $\eta_c$ mass and width values are $M(\eta_c) = 2984.49 \pm 1.16 \pm 0.52$\,MeV/$c^2$ and $\Gamma(\eta_c) = 36.4 \pm 3.2 \pm 1.7$\,MeV.
  09/2012;
• Article: Observation of χcJ decays to ΛΛ̅ π+π-

  M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, Y. Ban, J. Becker, J. V. Bennett, [......], S. H. Zhu, X. L. Zhu, X. W. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Decays of the χcJ states (J=0, 1, 2) to ΛΛ̅ π+π-, including processes with intermediate Σ(1385), are studied through the E1 transition ψ′→γχcJ using 106×106 ψ′ events collected with the BESIII detector at BEPCII. This is the first observation of χcJ decays to the final state ΛΛ̅ π+π-. The branching ratio of the intermediate process χcJ→Σ(1385)±Σ̅ (1385)∓ is also measured for the first time, and the results agree with the theoretical predictions based on the color-octet effect.
  Phys. Rev. D. 09/2012; 86(5).
• Article: Search for $\eta$ and $\eta'$ Invisible Decays in $J/\psi\to\phi\eta$ and $\phi\eta'$

  M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, Y. Ban, J. Becker, J. V. Bennett, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Using a sample of $(225.3\pm 2.8)\times 10^{6}$ $J/\psi$ decays collected with the BESIII detector at BEPCII, searches for invisible decays of $\eta$ and $\eta^\prime$ in $J/\psi\to\phi\eta$ and $\phi\eta^\prime$ are performed. Decays of $\phi \to K^{+}K^{-}$ are used to tag the $\eta$ and $\eta^\prime$ decays. No signals above background are found for the invisible decays, and upper limits at the 90% confidence level are determined to be $2.58\times10^{-4}$ for the ratio $\frac{\mathcal{B}(\eta\to\rm{invisible})}{\mathcal{B}(\eta\to\gamma\gamma)}$ and $2.39\times10^{-2}$ for $\frac{\mathcal{B}(\eta^\prime\to\rm{invisible})}{\mathcal{B}(\eta^\prime \to\gamma\gamma)}$.
  09/2012;
• Article: Study of J/ψ→pp̅ and J/ψ→nn̅

  M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, Y. Ban, J. Becker, N. Berger, [......], S. H. Zhu, X. L. Zhu, X. W. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou, J. X. Zuo
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  ABSTRACT: The decays J/ψ→pp̅ and J/ψ→nn̅ have been investigated with a sample of 225.2×106 J/ψ events collected with the BESIII detector at the BEPCII e+e- collider. The branching fractions are determined to be B(J/ψ→pp̅ )=(2.112±0.004±0.031)×10-3 and B(J/ψ→nn̅ )=(2.07±0.01±0.17)×10-3. Distributions of the angle θ between the proton or antineutron and the beam direction are well described by the form 1+αcos⁡2θ, and we find α=0.595±0.012±0.015 for J/ψ→pp̅ and α=0.50±0.04±0.21 for J/ψ→nn̅ . Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the J/ψ→NN̅ decay.
  Phys. Rev. D. 08/2012; 86(3).
• Article: Search for hadronic transition $\chi_{cJ}\to\eta_{c}\pi^{+}\pi^{-}$ and observation of $\chi_{cJ}\to K\bar{K}\pi\pi\pi$

  The BESIII Collaboration, M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, Y. Ban, J. Becker, [......], S. H. Zhu, X. L. Zhu, X. W. Zhu, Y. C. Zhu, Y. M. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou
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  ABSTRACT: Hadronic transitions of $\chi_{cJ}\to \eta_{c}\pi^{+}\pi^{-}$ (J=0, 1, 2) are searched for using a sample of $1.06\times 10^{8}$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The $\etac$ is reconstructed with $K_{S}^{0}K^{+}\pi^{-}+c.c.$ and $K^{+}K^{-}\pi^{0}$ final states. No signals are observed in any of the three $\chi_{cJ}$ states in either $\etac$ decay mode. At the 90% confidence level, the upper limits are determined to be $\BR(\chi_{c0}\to \eta_{c}\pi^{+}\pi^{-})<0.07%$, $\BR(\chi_{c1}\to \eta_{c}\pi^{+}\pi^{-})<0.32%$, and $\BR(\chi_{c2}\to \eta_{c}\pi^{+}\pi^{-})<0.54%$. The upper limit of $\BR(\chi_{c1}\to \eta_{c}\pi^{+}\pi^{-}$ is lower than the existing theoretical prediction by almost an order of magnitude. The branching fractions of $\chi_{cJ}\to K_{S}^{0}K^{+}\pi^{-}\pi^{+}\pi^{-}+c.c.$, $K^{+}K^{-}\pi^{+}\pi^{-}\pi^{0}$, $\omega K^{+}K^{-}$ and $\phi\pi^{+}\pi^{-}\pi^{0}$ (J=0, 1, 2) are measured for the first time.
  08/2012;