Search for psi(3770)\ra\rho\pi at the BESII detector at the Beijing Electron-Positron Collider

Non-$D\bar{D}$ decay \psppto \rhopi is searched for using a data sample of $(17.3\pm 0.5) pb^{-1}$ taken at the center-of-mass energy of 3.773 GeV by the BESII detector at the BEPC. No \rhopi signal is observed, and the upper limit of the cross section is measured to be \sigma(\EETO \rhopi)<6.0 pb at 90% C. L. Considering the interference between the continuum amplitude and the \pspp resonance amplitude, the branching fraction of \pspp decays to $\rho\pi$ is determined to be \BR(\pspp\ra\rho\pi)\in(6.0\times10^{-6}, 2.4\times10^{-3}) at 90% C. L. This is in agreement with the prediction of the $S$- and $D$-wave mixing scheme of the charmonium states for solving the ``\rhopi puzzle'' between \jpsi and \psp decays.Comment: 15 pages, 5 figure

Measurements of the continuum RudsR_{\rm uds} and RR values in e+e−e^+e^- annihilation in the energy region between 3.650 and 3.872 GeV

We report measurents of the continuum $R_{\rm uds}$ near the center-of-mass energy of 3.70 GeV, the $R_{{\rm uds(c)}+\psi(3770)}(s)$ and the $R_{\rm had}(s)$ values in $e^+e^-$ annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collodier. We obtain the $R_{\rm uds}$ for the continuum light hadron (containing u, d and s quarks) production near the $D\bar D$ threshold to be $R_{\rm uds}=2.141 \pm 0.025 \pm 0.085$.Comment: 5 pages, 3 figure

Partial Wave Analysis of χc0→π+π−K+K−\chi_{c0}\to\pi^+\pi^-K^+K^-

A partial wave analysis of $\chi_{c0}\to\pi^+\pi^-K^+K^-$ in $\psi(2S)\to\gamma\chi_{c0}$ decay is presented using a sample of 14 million $\psi(2S)$ events accumulated by the BES II detector. The data are fitted to the sum of relativistic covariant tensor amplitudes for intermediate resonant decay modes. From the fit, significant contributions to $\chi_{c0}$ decays from the channels $f_0(980)f_0(980)$, $f_0(980)f_0(2200)$, $f_0(1370)f_0(1710)$, $K^*(892)^0\bar K^*(892)^0$, $K^*_0(1430)\bar K^*_0(1430)$, $K^*_0(1430)\bar K^*_2(1430) + c.c.$, and $K_1(1270)K$ are found. Flavor-SU(3)-violating $K_1(1270)-K_1(1400)$ asymmetry is observed. Values obtained for the masses and widths of the resonances $f_0(1710)$, $f_0(2200)$, $f_0(1370)$, and $K^*_0(1430)$ are presented.Comment: 16 pages, 9 figures, and 4 table

Experimental study of ψ(2S)\psi(2S) decays to \K^+ K^- \pi^+ \pi^- \pi^0 final states

$K^+K^-\pi^+\pi^-\pi^0$ final states are studied using a sample of $14\times10^6$ $\psi(2S)$ decays collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Position Collider. The branching fractions of $\psi(2S)$ decays to $K^+K^-\pi^+\pi^-\pi^0$, $\omega K^+ K^-$, $\omega f_0(1710)$, $K^{\ast}(892)^0 K^- \pi^+\pi^0+c.c.$, $K^{\ast}(892)^{+} K^- \pi^+\pi^- +c.c.$, $K^{\ast}(892)^{+} K^- \rho^0+c.c.$ and $K^{\ast}(892)^0 K^-\rho^+ + c.c.$ are determined. The first two agree with previous measurements, and the last five are first measurements.Comment: 19 pages, 9 figure

First observation of ψ(2S)→pnˉπ−+c.c.\psi(2S) \to p \bar{n} \pi^- +c.c.

Using 14 million $\psi(2S)$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider, the branching fractions of $\psi(2S)$ decays to $p \bar{n} \pi^-$ and $\bar{p} n \pi^+$ and the branching fractions of the main background channels $\psi(2S) \to p \bar{n} \pi^-\pi^0$, $\psi(2S) \to \gamma\chi_{c0} \to \gamma p \bar{n} \pi^-$, $\psi(2S) \to \gamma\chi_{c2} \to \gamma p \bar{n} \pi^-$, and $\psi(2S) \to \gamma \chi_{cJ} \to \gamma p \bar{n} \pi^- \pi^0$ are determined. The contributions of the $N^{\ast}$ resonances in $\psi(2S) \to p \bar{n} \pi^- +c.c.$ are also discussed.Comment: 19 pages, 8 figures, add vertex requirement systematic erro

Measurement of the cross section for e^+e^- -> ppbar at center-of-mass energies from 2.0 to 3.07 GeV

Cross sections for e^+e^- -> ppbar have been measured at 10 center-of-mass energies from 2.0 to 3.07 GeV by the BESII experiment at the BEPC, and proton electromagnetic form factors in the time-like region have been determined.Comment: 6 pages, 3 figure

Measurements of the braching fractions for psi(3770)--> D0D0-bar,D+D-,DD-bar$ and the resonance parameters of psi(3770) and psi(2S)

We report measurements of the branching fractions for $\psi(3770)\to D^0 \bar D^0, D^+D^-, D\bar D$ and resonance parameters of $\psi(3770)$ and $\psi(2S)$. By analyzing the line-shapes of the cross sections for inclusive hadron, $D^0 \bar D^0$ and $D^+D^-$ event production in the range from 3.660 GeV to 3.872 GeV covering both $\psi(2S)$ and $\psi(3770)$ resonances, we extract the branching fractions for $\psi(3770)$ decay into $D^0\bar D^0 {\rm and} D^+D^-$ respectively to be $B(\psi(3770)\to D^0 \bar D^0)=(46.7 \pm 4.7 \pm 2.3)$ and $B(\psi(3770)\to D^+ D^-)=(36.9 \pm 3.7 \pm 2.8)$, which give $B(\psi(3770)\to D \bar D)=(83.6 \pm 7.3 \pm 4.2)$ and non-$D\bar D$ branching fraction of $\psi(3770)$ to be $B(\psi(3770)\to non-D \bar D)=(16.4 \pm 7.3 \pm 4.2)$. We meanwhile obtain the resonance parameters of $\psi(3770)$ and $\psi(2S)$ to be $M_{\psi(3770)}=3772.2 \pm 0.7 \pm 0.3$ MeV, $\Gamma^{\rm tot}_{\psi(3770)}=26.9 \pm 2.4 \pm 0.3$ MeV and $\Gamma^{ee}_{\psi(3770)}=251 \pm 26 \pm 11$ eV; $M_{\psi(2S)}=3685.5 \pm 0.0 \pm 0.3$ MeV, $\Gamma^{\rm tot}_{\psi(2S)}=331 \pm 58 \pm 2$ keV and $\Gamma^{ee}_{\psi(2S)}=2.330 \pm 0.036 \pm 0.110$ keV; as well as the $R$ value for the light hadron production directly through one photon annihilation to be $R_{uds}=2.262\pm 0.054\pm 0.109$ in this energy region.Comment: 7 pages, 4 figure

Observation of a near-threshold enhancement in the \omega\phi mass spectrum from the doubly OZI suppressed decay J/\psi \to \gamma \omega \phi

An enhancement near threshold is observed in the \omega \phi invariant mass spectrum from the doubly OZI suppressed decays of J/\psi \to \gamma \omega \phi, based on a sample of 5.8 X 10^7 J/\psi events collected with the BESII detector. A partial wave analysis shows that this enhancement favors J^P = 0^+, and its mass and width are M = 1812^{+19}_{-26} (stat) +- 18 (syst) MeV/c^2 and \Gamma = 105+-20 (stat) +- 28$(syst) MeV/c^2. The product branching fraction is determined to be B(J/\psi\to \gamma X) B(X\to\omega\phi) = (2.61 +- 0.27 (stat) +- 0.65$ (syst)) X 10^{-4}.Comment: Accepted by PRL, the version to be appeared in PR

The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite

The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available.Comment: Accepted by RA

Observation of a resonance X(1835) in J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime}

The decay channel J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime} is analyzed using a sample of 5.8\times 10^7 J\psi events collected with the BESII detector. A resonance, the X(1835), is observed in the \pi^+ \pi^- \eta^{\prime} invariant mass spectrum with a statistical significance of 7.7 \sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 \pm 6.1(stat) \pm 2.7(syst) MeV/c^2, a width \Gamma = 67.7 \pm 20.3(stat) \pm 7.7(syst) MeV/c^2 and a product branching fraction B(J/\psi --> \gamma X) B(X --> \pi^+ \pi^- \eta^{\prime}) = (2.2 \pm 0.4(stat) \pm 0.4(syst)) \times 10^{-4}. The mass and width of the X(1835) are not compatible with any known meson resonance. Its properties are consistent with expectations for the state that produces the strong p\bar{p} mass threshold enhancement observed in the J\psi -->\gamma p \bar{p} process at BESII.Comment: 5 pages, 3 figures, RevTex4, Submitted to Phys. Rev. Let