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BES Collaboration

Publications and source records attributed to BES Collaboration.

At least 19 recordsLinked to original sources
arXiv2010

Observation of charged kappa in J/psi -> K*(892)-+Kspi+-, K*(892)-+ -> Kspi-+ at BESII

Using 58 million J/psi decays obtained by BESII, a charged kappa particle is observed in the analysis of the Kspi+- system recoiling against K*(892)-+ selected in J/psi -> KsKspi+pi-. The mass and width values of the charged kappa are obtained to be (826+-49_{-34}^{+49}) MeV/c^2 and (449+-156_{-81}^{+144}) MeV/c^2 for the Breit-Wigner parameters, and the pole position is determined to be (764+-63_{-54}^{+71})-i(306+-149_{-85}^{+143}) MeV/c^2. They are in good agreement with those of the neutral kappa observed by the BES collaboration.

hep-ex↗
arXiv2009

Partial wave analysis of J/psi to p pbar pi0

Using a sample of 58 million $J/\psi$ events collected with the BESII detector at the BEPC, more than 100,000 $J/\psi \to p\bar p \pi^0$ events are selected, and a detailed partial wave analysis is performed. The branching fraction is determined to be $Br(J/\psi \to p \bar p \pi^0)=(1.33 \pm 0.02 \pm 0.11) \times 10^{-3}$. A long-sought `missing' $N^*$, first observed in $J/\psi \to p \bar n \pi^-$, is observed in this decay too, with mass and width of $2040_{-4}^{+3}\pm 25$ MeV/c$^2$ and $230_{-8}^{+8}\pm 52$ MeV/c$^2$, respectively. Its spin-parity favors ${3/2}^+$. The masses, widths, and spin-parities of other $N^*$ states are obtained as well.

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arXiv2008

Measurements of the observed cross sections for e+e -> exclusive light hadrons containing K^S_0 meson at \sqrt{s} = 3.773 and 3.650 GeV

By analyzing the data sets of 17.3 pb$^{-1}$ taken at $\sqrt s= 3.773$ GeV and of 6.5 pb$^{-1}$ taken at $\sqrt s= 3.650$ GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for the exclusive light hadron final states of $K_S^0K^-\pi^+$, $K_S^0K^-\pi^+\pi^0$, $K_S^0K^-\pi^+\pi^+\pi^-$, $K_S^0K^-\pi^+\pi^+\pi^-\pi^0$, $K_S^0K^-\pi^+\pi^+\pi^+\pi^-\pi^-$ and $K_S^0K^-\pi^+\pi^0\pi^0$ produced in $e^+ e^-$ annihilation at the two energy points. We set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay to these final states at 90% C.L..

hep-ex↗
arXiv2008

Measurements of the observed cross sections for $e^+e^-\to$ exclusive light hadrons containing $\pi^0\pi^0$ at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV

By analyzing the data sets of 17.3, 6.5 and 1.0 pb$^{-1}$ taken, respectively, at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$, $K^+K^-\pi^0\pi^0$, $2(\pi^+\pi^-\pi^0)$, $K^+K^-\pi^+\pi^-\pi^0\pi^0$ and $3(\pi^+\pi^-)\pi^0\pi^0$ at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay into these final states at 90% C.L..

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arXiv2008

First measurements of J/Psi decays into $\Sigma^+ \bar{\Sigma}^-$ and $\Xi^0 \bar{\Xi}^0$

Based on 58 million J/Psi events collected with the BESII detector at the BEPC, the baryon pair processes J/Psi to $\Sigma^+ \bar{\Sigma}^-$ and J/Psi to $\Xi^0 \bar{\Xi}^0$ are observed for the first time. The branching fractions are measured to be ${\cal B}(J/Psi to \Sigma^+ \bar{\Sigma}^-)=(1.50\pm 0.10\pm 0.22)\times 10^{-3}$ and ${\cal B}(J/Psi to \Xi^0 \bar{\Xi}^0)=(1.20\pm 0.12\pm 0.21)\times 10^{-3}$, where the first errors are statistical and the second ones are systematic.

hep-ex↗
arXiv2008

Anomalous Line-Shape of Cross Sections for $e^+e^- \to {\rm Hadrons}$ in the Center-of-Mass Energy Region between 3.650 and 3.872 GeV

We observe an obvious anomalous line-shape of the $e^+e^- \to {\rm hadrons}$ total cross sections in the energy region between 3.700 and 3.872 GeV from the data samples taken with the BES-II detector at the BEPC Collider. Re-analysis of the data shows that it is inconsistent with the explanation for only one simple $\psi(3770)$ resonance with a statistical significance of $7\sigma$. The anomalous line-shape may be explained by two possible enhancements of the inclusive hadron production near the center-of-mass energies of 3.764 GeV and 3.779 GeV, indicating that either there is likely a new structure in addition to the $\psi(3770)$ resonance around 3.773 GeV, or there are some physics effects reflecting the $D\bar D$ production dynamics.

hep-ex↗
arXiv2008

Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays

By analyzing about 33 $\rm pb^{-1}$ data sample collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we directly measure the branching fractions for the neutral and charged $D$ inclusive semimuonic decays to be $BF(D^0 \to μ^+ X) =(6.8\pm 1.5\pm 0.7)%$ and $BF(D^+ \to μ^+ X) =(17.6 \pm 2.7 \pm 1.8)%$, and determine the ratio of the two branching fractions to be $\frac{BF(D^+ \to μ^+ X)}{BF(D^0 \to μ^+ X)}=2.59\pm 0.70 \pm 0.25$.

hep-ex↗
arXiv2008

psi(2S) Radiative Decay Measurements

Using a sample of 14 million $\psip$ events collected with the BESII detector, branching fractions or upper limits on the branching fractions of $\psip$ decays into $γ\ppb$, $γ2(\pip\pim)$, $γ\kskp$, $γ\kap\kam\pip\pim$, $γ\kstarz\kam\pip+c.c.$, $γ\kstarz \kstarzb$, $γ\pip\pim\ppb$, $\gamma2(\kap\kam)$, $\gamma3(\pip\pim)$ and $\gamma2(\pip\pim)\kap\kam$ with hadron invariant mass less than 2.9$\gev/c^2$ are reported. We also report branching fractions of $\psip$ decays into $γ\ppb\piz$, $\ppb\piz\piz$, $2(\pip\pim)\piz$, $ω\pp$, $ωf_2(1270)$, $b_1^\pmπ^\mp$, $\piz\kskp$, $K^\pmρ^\mp\ks$, $\piz2(\pip\pim)\kap\kam$ and $γ\piz2(\pip\pim)\kap\kam$.

hep-ex↗
arXiv2008

Observation of Y(2175) in $J/ψ\to ηϕf_0(980)$

The decays of $J/ψ\to ηϕf_0(980) (η\to γγ, ϕ\to K^+K^-, f_0(980)\toπ^+π^-)$ are analyzed using a sample of $5.8 \times 10^{7}$ $J/ψ$ events collected with the BESII detector at the Beijing Electron-Positron Collider (BEPC). A structure at around $2.18 $GeV/$c^2$ with about $5σ$ significance is observed in the $ϕf_0(980)$ invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of $m=2.186\pm 0.010 (stat)\pm 0.006 (syst) $GeV/$c^2$ and $Γ=0.065\pm 0.023 (stat)\pm 0.017 (syst) $GeV/$c^2$, respectively, that are consistent with those of Y(2175), observed by the BABAR collaboration in the initial-state radiation (ISR) process $e^+e^-\toγ_{ISR}ϕf_0(980)$. The production branching ratio is determined to be $Br(J/ψ\toηY(2175))\cdot Br(Y(2175)\toϕf_0(980))\cdot Br(f_0(980)\toπ^+π^-)=(3.23\pm 0.75 (stat)\pm0.73 (syst))\times 10^{-4}$, assuming that the Y(2175) is a $1^{--}$ state.

hep-ex↗
arXiv2008

Partial wave analysis of J/\psi \to \gamma \phi \phi

Using $5.8 \times 10^7 J/\psi$ events collected in the BESII detector, the radiative decay $J/\psi \to \gamma \phi \phi \to \gamma K^+ K^- K^0_S K^0_L$ is studied. The $\phi\phi$ invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/$c^{2}$. A partial wave analysis shows that the structure is dominated by a $0^{-+}$ state ($\eta(2225)$) with a mass of $2.24^{+0.03}_{-0.02}{}^{+0.03}_{-0.02}$ GeV/$c^{2}$ and a width of $0.19 \pm 0.03^{+0.06}_{-0.04}$ GeV/$c^{2}$. The product branching fraction is: $Br(J/\psi \to \gamma \eta(2225))\cdot Br(\eta(2225)\to \phi\phi) = (4.4 \pm 0.4 \pm 0.8)\times 10^{-4}$.

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arXiv2007

Direct Measurements of the Branching Fractions for Inclusive $K^\pm$ and Inclusive Semileptonic Decays of $D^+$ and $D^0$ Mesons

With singly-tagged $\bar D$ samples selected from the data collected at and around 3.773 GeV with the BESII detector at the BEPC collider, we have measured the branching fractions for the inclusive $K^\pm$ decays of $D^+$ and $D^0$ mesons, which are $BF(D^+\to K^-X) = (24.7 \pm 1.3 \pm 1.2)%$, $BF(D^+\to K^+X) = (6.1 \pm 0.9 \pm 0.4) %$, $BF(D^0\to K^-X) = (57.8 \pm 1.6 \pm 3.2) %$ and $BF(D^0\to K^+X) = (3.5 \pm 0.7 \pm 0.3) %$, respectively. We have also measured the branching fractions for the inclusive semileptonic decays of $D^+$ and $D^0$ mesons to be $BF(D^+ \to e^+ X)=(15.2 \pm 0.9 \pm 0.8)%$ and $BF(D^0 \to e^+ X) =(6.3 \pm 0.7 \pm 0.4) %$. These yield the ratio of their partial widths to be $\Gamma(D^+ \to e^+X)/\Gamma(D^0 \to e^+X)=0.95 \pm 0.12 \pm 0.07$.

hep-ex↗
arXiv2007

Measurements of J/\psi decays into \omega K \bar{K} \pi and \phi K \bar{K} \pi

The decays of $J/\psi \to \omega K\bar{K}\pi$ and $J/\psi \to \phi K\bar{K}\pi$ are studied using $5.8 \times 10^{7}$ $J/\psi$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider (BEPC). The $K^{0}_{S}K^{\pm}\pi^{\mp}$ and $K^{+}K^{-}\pi^{0}$ systems, produced in $J/\psi \to \omega K\bar{K}\pi$, have enhancements in the invariant mass distributions at around 1.44 GeV/$c^{2}$. However, there is no evidence for mass enhancements in the $K\bar{K}\pi$ system in $J/\psi \to \phi K\bar{K}\pi$. The branching fractions of $J/\psi \to \omega K^{0}_{S}K^{\pm}\pi^{\mp}$, $\phi K^{0}_{S}K^{\pm}\pi^{\mp}$, $\omega K^{*}\bar{K}+c.c.$, and $\phi K^{*}\bar{K}+c.c.$ are obtained, and the $J/\psi \to \eta K^{0}_{S}K^{\pm}\pi^{\mp}$ branching fraction is measured for the first time.

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arXiv2007

Study of J\psi decaying into \omega p \bar p

The decay $J/\psi \to \omega p \bar p$ is studied using a $5.8 \times 10^7$ $J/\psi$ event sample accumulated with the BES II detector at the Beijing electron-positron collider. The decay branching fraction is measured to be $B(J/\psi \to \omega p \bar p)=(9.8\pm 0.3\pm 1.4)\times 10^{-4}$. No significant enhancement near the $p\bar p$ mass threshold is observed, and an upper limit of $B(J/\psi \to \omega X(1860))B(X(1860)\to p\bar p)$$ $$< 1.5 \times 10^{-5}$ is determined at the 95% confidence level, where X(1860) designates the near-threshold enhancement seen in the $p\bar p$ mass spectrum in $J/\psi \to \gamma p \bar p$ decays.

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arXiv2007

First observation of J/\psi and \psi(2S) decaying to n K^0_S\bar\Lambda +c.c

The decays of $\jpsi$ and $\psip$ to ${n}{K^0_S}\bar{\Lambda}+c.c.$ are observed and measured for the first time, and the perturbative QCD ``12%'' rule is tested, based on $5.8 \times 10^7$ $\jpsi$ and $1.4 \times 10^7$ $\psip$ events collected with BESII detector at the Beijing Electron-Positron Collider. No obvious enhancement near $n\bar{\Lambda}$ threshold in $\jpsi \to {n}{K^0_S}\bar{\Lambda}+c.c.$ is observed, and the upper limit on the branching ratio of $\jpsi \to {K^0_S} X, X \to n \bar \Lambda$ is determined.

hep-ex↗
arXiv2007

Search for the decays $J/\psi\to\gamma \rho \phi$ and $J/\psi\to\gamma \rho \omega$

Using 58 million $J/\psi$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider, the decays $J/\psi\to \gamma\phi\rho$ and $J/\psi\to \gamma\omega\rho$ are searched for, and upper limits on their branching fractions are reported at the 90% C. L. No clear structures are observed in the $\gamma \rho$, $\gamma \phi$, or $\rho \phi $ mass spectra for $J/\psi\to \gamma\phi\rho$ nor in the $\gamma \rho$, $\gamma \omega$, or $\rho \omega$ mass spectra for $J/\psi\to \gamma\omega\rho$.

hep-ex↗
arXiv2007

Measurements of $J/ψ$ and $ψ(2S)$ decays into $Λ\barΛπ^0$ and $Λ\barΛη$

Using 58 million $J/ψ$ and 14 million $ψ(2S)$ events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays $J/ψ$ and $ψ(2S) \to Λ\barΛπ^0$ and $Λ\barΛη$ are measured. For the isospin violating decays, the upper limits are determined to be ${\cal B}(J/ψ\to Λ\barΛπ^0)<6.4\times 10^{-5}$ and ${\cal B}(ψ(2S) \to Λ\barΛπ^0)<4.9\times 10^{-5}$ at the 90% confidence level. The isospin conserving process $J/ψ\to Λ\barΛη$ is observed for the first time, and its branching fraction is measured to be ${\cal B}(J/ψ\to Λ\barΛη)=(2.62\pm 0.60\pm 0.44)\times 10^{-4}$, where the first error is statistical and the second one is systematic. No $Λ\barΛη$ signal is observed in $ψ(2S)$ decays, and ${\cal B}(ψ(2S) \to Λ\barΛη)<1.2\times 10^{-4}$ is set at the 90% confidence level. Branching fractions of $J/ψ$ decays into $Σ^+ π^- barΛ$ and $\barΣ^- π^+ Λ$ are also reported, and the sum of these branching fractions is determined to be ${\cal B}(J/ψ\to Σ^+π^- \barΛ + c.c.)=(1.52\pm 0.08\pm 0.16)\times 10^{-3}$.

hep-ex↗
arXiv2006

Production of $\sigma$ in $\psi(2S)\to \pi^{+}\pi^{-}J/\psi$

Using 14M $\psi(2S)$ events accumulated by BESII at the BEPC, a Covariant Helicity Amplitude Analysis is performed for $\psi(2S)\to\pi^+\pi^-J/\psi, J/\psi\to \mu^+\mu^-$. The $\pi^+\pi^-$ mass spectrum, distinctly different from phase space, suggests $\sigma$ production in this process. Two different theoretical schemes are used in the global fit to the data. The results are consistent with the existence of the $\sigma$. The $\sigma$ pole position is determined to be $(552^{+84}_{-106})-i(232^{+81}_{-72})$ MeV/$c^2$.

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