X W Zhu

Publications (48)77.65 Total impact

• 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 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: 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: 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;
• Article: Experimental study of psi' decays to K+K- pi^0 and K+K- eta

  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, [......], 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, J. X. Zuo
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  ABSTRACT: Using $(106\pm4)\times 10^6$ $\psip$ events accumulated with the BESIII detector at the BEPCII $e^+e^-$ collider, we present measurements of the branching fractions for psi' decays to $K^{+}K^{-}\pi^{0}$ and $K^{+}K^{-}\eta$. In these final states, the decay $\psi'\to K_2^{*}(1430)^+K^-+c.c.$ is observed for the first time, and its branching fraction is measured to be $(7.12\pm{0.62}{\rm (stat.)}^{+1.13}_{-0.61}{\rm (syst.)})\times 10^{-5}$, which indicates a violation of the helicity selection rule in $\psip$ decays. The branching fractions of $\psi'\to K^*(892)^+K^-+c.c., \phi\eta, \phi\pi^0$ are also measured. The measurements are used to test the QCD predictions on charmonium decays.
  08/2012;
• Article: Observation of $e^{+}e^{-} \to \eta J/\psi$ at center-of-mass energy $sqrt{s}=4.009$ GeV

  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: Using a 478 pb$^{-1}$ data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of $\sqrt{s}=4.009$ GeV, the production of $e^{+}e^{-}\to \eta J\psi$ is observed for the first time with a statistical significance of greater than $10\sigma$. The Born cross section is measured to be $(32.1\pm 2.8 \pm 1.3)$ pb, where the first error is statistical and the second systematic. Assuming the $\eta J\psi$ signal is from a hadronic transition of the $\psi(4040)$, the fractional transition rate is determined to be ${\cal B}(\psi(4040)\to \eta J\psi)=(5.2\pm 0.5\pm 0.2\pm 0.5)\times 10^{-3}$, where the first, second, and third errors are statistical, systematic, and the uncertainty from the $\psi(4040)$ resonant parameters, respectively. The production of $e^{+}e^{-} \to \pi^0 J\psi$ is searched for, but no significant signal is observed, and ${\cal B}(\psi(4040)\to \pi^0 J\psi) < 2.8 \times 10^{-4}$ is obtained at the 90% confidence level.
  08/2012;
• Article: Evidence for $\eta_{c} \rightarrow \gamma\gamma$ and Measurement of $J/\psi\rightarrow 3\gamma$

  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: The decay of $J/\psi$ to three photons is studied using $\psi(3686)\to\pi^+\pi^-J/\psi$ in a sample of $1.0641\times10^8$ $\psi(3686)$ events collected with the BESIII detector. Evidence of the direct decay of $\eta_c$ to two photons, $\eta_c\to\gamma\gamma$, is reported, and the product branching fraction is determined to be $\mathcal{B}(J/\psi\to\gamma\eta_c,\eta_c\to \gamma\gamma)=(4.5\pm1.2\pm0.6)\times10^{-6}$, where the first error is statistical and the second is systematic. The branching fraction for $J/\psi\to3\gamma$ is measured to be $(11.3\pm1.8\pm2.0)\times 10^{-6}$ with improved precision.
  08/2012;
• Article: Observation of chi_{cJ} Decays to \Lambda \Lambda bar\pi^{+}\pi^{-}

  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: Decays of the chi_{cJ} states (J=0,\ 1,\ 2) to \Lambda \Lambda bar\ pi^{+} \pi^{-}, including processes with intermediate \Sigma(1385), are studied through the E1 transition psi'-->\gamma chi_{cJ} using 106 million psi' events collected with the BESIII detector at BEPCII. This is the first observation of chi_{cJ} decays to the final state \Lambda\Lambda bar \pi^{+}\pi^{-}. The branching ratio of the intermediate process chi_{cJ}-->\Sigma(1385)^{+/-} \bar{\Sigma}(1385)^{-/+} is also measured for the first time, and the results agree with the theoretical predictions based on the color-octet effect.
  07/2012;
• Article: First observation of the isospin violating decay $J/\psi\rightarrow \Lambda\bar{\Sigma}^{0}+c.c.$

  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, [......], 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, J. X. Zuo
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  ABSTRACT: Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the BESIII detector, we present results of a study of $J/\psi\rightarrow \gamma\Lambda\bar{\Lambda}$ and report the first observation of the isospin violating decay $J/\psi\rightarrow\Lambda\bar{\Sigma}^{0}+c.c.$, in which $\bar{\Sigma}^{0}$ decays to $\gamma \bar{\Lambda}$. The measured branching fractions are $\mathcal{B}(J/\psi\rightarrow\bar{\Lambda}\Sigma^{0}$) = $(1.46\pm0.11\pm0.12) \times10^{-5}$ and $\mathcal{B}(J/\psi\rightarrow\Lambda\bar{\Sigma^{0}}$) = $(1.37\pm0.12\pm0.11) \times10^{-5}$. We search for $\Lambda(1520) \rightarrow \gamma \Lambda$ decay, and find no evident signal, and an upper limit for the product branching fraction $\mathcal{B}(J/\psi\rightarrow\Lambda\bar{\Lambda}(1520)+c.c.)\times \mathcal{B}(\Lambda(1520)\rightarrow\gamma\Lambda)<4.1 \times10^{-6}$ is set at the 90% confidence level. We also report the observation of $\eta_{c}\rightarrow\Lambda\bar{\Lambda}$ in $J/\psi \rightarrow \gamma \eta_{c}$, $\eta_{c}\rightarrow\Lambda\bar{\Lambda}$ and measure the branching fraction $\mathcal{B}(\eta_{c}\rightarrow\Lambda\bar{\Lambda}) =(1.16\pm0.12 (stat)\pm0.19(syst)\pm0.28(PDG))\times10^{-3}$.
  07/2012;
• Article: Two-photon widths of the χc0,2 states and helicity analysis for χc2→γγ

  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 a data sample of 106×106 ψ′ events collected with the BESIII detector, the decays ψ′→γχc0,2, χc0,2→γγ are studied to determine the two-photon widths of the χc0,2 states. The two-photon decay branching fractions are determined to be B(χc0→γγ)=(2.24±0.19±0.12±0.08)×10-4 and B(χc2→γγ)=(3.21±0.18±0.17±0.13)×10-4. From these, the two-photon widths are determined to be Γγγ(χc0)=(2.33±0.20±0.13±0.17) keV, Γγγ(χc2)=(0.63±0.04±0.04±0.04) keV, and R=Γγγ(χc2)/Γγγ(χc0)=0.271±0.029±0.013±0.027, where the uncertainties are statistical, systematic, and those from the PDG B(ψ′→γχc0,2) and Γ(χc0,2) errors, respectively. The ratio of the two-photon widths for helicity λ=0 and helicity λ=2 components in the decay χc2→γγ is measured for the first time to be f0/2=Γγγλ=0(χc2)/Γγγλ=2(χc2)=0.00±0.02±0.02.
  Phys. Rev. D. 06/2012; 85(11).
• Article: First observation of the M1 transition $\psi(3686)\to \gamma\eta_c(2S)$

  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: Using a sample of 106 million \psi(3686) events collected with the BESIII detector at the BEPCII storage ring, we have made the first measurement of the M1 transition between the radially excited charmonium S-wave spin-triplet and the radially excited S-wave spin-singlet states: \psi(3686)\to\gamma\eta_c(2S). Analyses of the processes \psi(2S)\to \gamma\eta_c(2S) with \eta_c(2S)\to \K_S^0 K\pi and K^+K^-\pi^0 gave an \eta_c(2S) signal with a statistical significance of greater than 10 standard deviations under a wide range of assumptions about the signal and background properties. The data are used to obtain measurements of the \eta_c(2S) mass (M(\eta_c(2S))=3637.6\pm 2.9_\mathrm{stat}\pm 1.6_\mathrm{sys} MeV/c^2), width (\Gamma(\eta_c(2S))=16.9\pm 6.4_\mathrm{stat}\pm 4.8_\mathrm{sys} MeV), and the product branching fraction (\BR(\psi(3686)\to \gamma\eta_c(2S))\times \BR(\eta_c(2S)\to K\bar K\pi) = (1.30\pm 0.20_\mathrm{stat}\pm 0.30_\mathrm{sys})\times 10^{-5}). Combining our result with a BaBar measurement of \BR(\eta_c(2S)\to K\bar K \pi), we find the branching fraction of the M1 transition to be \BR(\psi(3686)\to\gamma\eta_c(2S)) = (6.8\pm 1.1_\mathrm{stat}\pm 4.5_\mathrm{sys})\times 10^{-4}.
  05/2012;
• Article: Two-photon widths of the $\chi_{c0, 2}$ states and helicity analysis for $\chi_{c2}\ar\gamma\gamma$}

  BESIII Collaboration, M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. Ferroli, Y. Ban, [......], 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 a data sample of 106 M $\psi^{\prime}$ events collected with the BESIII detector, the decays $\psi^{\prime}\ar\gamma\chi_{c0, 2}$,$\chi_{c0, 2}\ar\gamma\gamma$ are studied to determine the two-photon widths of the $\chi_{c0, 2}$ states. The two-photon decay branching fractions are determined to be ${\cal B}(\chi_{c0}\ar\gamma\gamma) = (2.24\pm 0.19\pm 0.12\pm 0.08)\times 10^{-4}$ and ${\cal B}(\chi_{c2}\ar\gamma\gamma) = (3.21\pm 0.18\pm 0.17\pm 0.13)\times 10^{-4}$. From these, the two-photon widths are determined to be $\Gamma_{\gamma \gamma}(\chi_{c0}) = (2.33\pm0.20\pm0.13\pm0.17)$ keV, $\Gamma_{\gamma \gamma}(\chi_{c2}) = (0.63\pm0.04\pm0.04\pm0.04)$ keV, and $\cal R$ $=\Gamma_{\gamma \gamma}(\chi_{c2})/\Gamma_{\gamma \gamma}(\chi_{c0})=0.271\pm 0.029\pm 0.013\pm 0.027$, where the uncertainties are statistical, systematic, and those from the PDG ${\cal B}(\psi^{\prime}\ar\gamma\chi_{c0,2})$ and $\Gamma(\chi_{c0,2})$ errors, respectively. The ratio of the two-photon widths for helicity $\lambda=0$ and helicity $\lambda=2$ components in the decay $\chi_{c2}\ar\gamma\gamma$ is measured for the first time to be $f_{0/2} =\Gamma^{\lambda=0}_{\gamma\gamma}(\chi_{c2})/\Gamma^{\lambda=2}_{\gamma\gamma}(\chi_{c2}) = 0.00\pm0.02\pm0.02$.
  05/2012;
• Article: Search for a light exotic particle in J/ψ radiative decays

  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: Using a data sample containing 1.06×108 ψ′ events collected with the BESIII detector at the BEPCII electron-positron collider, we search for a light exotic particle X in the process ψ′→π+π-J/ψ, J/ψ→γX, X→μ+μ-. This light particle X could be a Higgs-like boson A0, a spin-1 U boson, or a pseudoscalar sgoldstino particle. In this analysis, we find no evidence for any μ+μ- mass peak between the mass threshold and 3.0 GeV/c2. We set 90%-confidence-level upper limits on the product-branching fractions for J/ψ→γA0, A0→μ+μ- which range from 4×10-7 to 2.1×10-5, depending on the mass of A0, for M(A0)<3.0 GeV/c2. Only one event is seen in the mass region below 255 MeV/c2, and this has a μ+μ- mass of 213.3 MeV/c2 and the product-branching-fraction upper limit 5×10-7.
  Phys. Rev. D. 05/2012; 85(9).
• Article: Study of $J/\psi\to p\bar{p}$ and $J/\psi\to n\bar{n}$

  BESIII Collaboration, M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. Ferroli, Y. Ban, [......], 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 $J/\psi\to p\bar{p}$ and $J/\psi\to n\bar{n}$ have been investigated with a sample of 225.2 million $J/\psi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are determined to be $\mathcal{B}(J/\psi\to p\bar{p})=(2.112\pm0.004\pm0.031)\times10^{-3}$ and $\mathcal{B}(J/\psi\to n\bar{n})=(2.07\pm0.01\pm0.17)\times10^{-3}$. Distributions of the angle $\theta$ between the proton or anti-neutron and the beam direction are well described by the form $1+\alpha\cos^2\theta$, and we find $\alpha=0.595\pm0.012\pm0.015$ for $J/\psi\to p\bar{p}$ and $\alpha=0.50\pm0.04\pm0.21$ for $J/\psi\to n\bar{n}$. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the $J/\psi\to N\bar{N}$ decay.
  05/2012;
• Article: First observation of η(1405) decays into f(0)(980)π0.

  M Ablikim, M N Achasov, D Alberto, D J Ambrose, F F An, Q An, Z H An, J Z Bai, R B F Baldini Ferroli, Y Ban, [......], K J Zhu, S H Zhu, X L Zhu, X W 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 → γ π+ π- π0 and J/ψ → γ π0 π0 π0 are analyzed using a sample of 225×10(6) J/ψ events collected with the BESIII detector. The decay of η(1405) → f(0)(980)π0 with a large isospin violation is observed for the first time. The width of the f(0)(980) observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the η' are also measured precisely.
  Physical Review Letters 05/2012; 108(18):182001. · 7.37 Impact Factor
• Article: Evidence for the Direct Two-Photon Transition from $\psi(3686)$ to $J/\psi$

  BESIII Collaboration, M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. Ferroli, Y. Ban, [......], 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 $\psi(3686)\to\gamma\gamma J/\psi$ is studied in a sample of 106 million $\psi(3686)$ decays collected by the BESIII detector. The branching fraction is measured to be $(3.1\pm0.6(\unit{stat})^{+0.8}_{-1.0}(\unit{syst})) \times10^{-4}$ using $J/\psi\to e^+e^-$ and $J/\psi\to\mu^+\mu^-$ decays, and its upper limit is estimated to be $4.5\times10^{-4}$ at the 90% conference level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the $\psi(3686)$ decay plane and the $J/\psi$ polarization in this decay are also studied. In addition, the product branching fractions of sequential $E1$ transitions $\psi(3686)\to\gamma\chi_{cJ}, \chi_{cJ}\to\gamma J/\psi (J=0,1,2)$ are reported.
  04/2012;
• Article: Spin-parity analysis of pp¯ mass threshold structure in J/ψ and ψ(3686) radiative decays.

  M Ablikim, M N Achasov, D Alberto, D J Ambrose, F F An, Q An, Z H An, J Z Bai, R B F Baldini Ferroli, Y Ban, [......], K J Zhu, S H Zhu, X L Zhu, X W Zhu, Y S Zhu, Z A Zhu, J Zhuang, B S Zou, J H Zou, J X Zuo
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  ABSTRACT: A partial wave analysis of the pp¯ mass-threshold enhancement in the reaction J/ψ→γpp¯ is used to determine its J(PC) quantum numbers to be 0(-+), its peak mass to be below threshold at M=1832(-5)(+19)(stat)(-17)(+18)(syst)±19(model) MeV/c(2), and its total width to be Γ<76 MeV/c(2) at the 90% C.L. The product of branching ratios is measured to be BR[J/ψ→γX(pp¯)]BR[X(pp¯)→pp¯]=[9.0(-1.1)(+0.4)(stat)(-5.0)(+1.5)(syst)±2.3(model)]×10(-5). A similar analysis performed on ψ(3686)→γpp¯ decays shows, for the first time, the presence of a corresponding enhancement with a production rate relative to that for J/ψ decays of R=[5.08(-0.45)(+0.71)(stat)(-3.58)(+0.67)(syst)±0.12(model)]%.
  Physical Review Letters 03/2012; 108(11):112003. · 7.37 Impact Factor
• Source

  Available from: Niklaus Berger

  Article: Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0

  BESIII Collaboration, M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. F. Baldini Ferroli, Y. Ban, [......], 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: We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data samples at both resonances collected with the BES III detector in 2009. We measure the corresponding branching fractions with unprecedented precision and provide mass spectra and Dalitz plots. The branching fraction for J/psi -> pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4. The J/psi decay is found to be dominated by an intermediate rho(770) state, whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2, leading to strikingly different Dalitz distributions.
  02/2012;
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  Available from: Niklaus Berger

  Article: First observation of $\eta(1405)$ decays into $f_{0}(980)\pi^0$

  BESIII Collaboration, M. Ablikim, M. N. Achasov, D. Alberto, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. F. Baldini Ferroli, [......], K. J. Zhu, S. H. Zhu, X. L. Zhu, X. W. 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 $J/\psi \rightarrow \gamma \pi^+\pi^-\pi^0$ and $J/\psi \rightarrow \gamma \pi^0\pi^0\pi^0$ are analyzed using a sample of 225 million $\jpsi$ events collected with the BESIII detector. The decay of $\eta(1405)\ar f_{0}(980)\pi^0$ with a large isospin violation is observed for the first time. The width of the $f_{0}(980)$ observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the $\eta'$ are also measured precisely.
  01/2012;