Dependence of quantum correlations of twin beams on pump finesse of optical parametric oscillator

The dependence of quantum correlation of twin beams on the pump finesse of an optical parametric oscillator is studied with a semi-classical analysis. It is found that the phase-sum correlation of the output signal and idler beams from an optical parametric oscillator operating above threshold depends on the finesse of the pump field when the spurious pump phase noise generated inside the optical cavity and the excess noise of the input pump field are involved in the Langevin equations. The theoretical calculations can explain the previously experimental results, quantitatively.Comment: 27 pages, 8 figure

Measurement of the chi_{c2} Polarization in psi(2S) to gamma chi_{c2}

The polarization of the chi_{c2} produced in psi(2S) decays into gamma chi_{c2} is measured using a sample of 14*10^6 psi(2S) events collected by BESII at the BEPC. A fit to the chi_{c2} production and decay angular distributions in psi(2S) to gamma chi_{c2}, chi_{c2} to pi pi and KK yields values x=A_1/A_0=2.08+/-0.44 and y=A_2/A_0=3.03 +/-0.66, with a correlation rho=0.92 between them, where A_{0,1,2} are the chi_{c2} helicity amplitudes. The measurement agrees with a pure E1 transition, and M2 and E3 contributions do not differ significantly from zero.Comment: 6 pages, 4 figures, 1 tabl

\psi(2S) Decays into \J plus Two Photons

Using \gamma \gamma J/\psi, J/\psi \ra e^+ e^- and $\mu^+ \mu^-$ events from a sample of $14.0\times 10^6$ \psip decays collected with the BESII detector, the branching fractions for \psip\ra \pi^0\J, \eta\J, and \psi(2S)\ar\gamma\chi_{c1},\gamma\chi_{c2}\ar\gamma\gamma\jpsi are measured to be B(\psip\ra \pi^0\J) = (1.43\pm0.14\pm0.13)\times 10^{-3}, B(\psip\ra \eta\J) = (2.98\pm0.09\pm0.23)%, B(\psi(2S)\ar\gamma\chi_{c1}\ar\gamma\gamma\jpsi) = (2.81\pm0.05\pm 0.23)%, and B(\psi(2S)\ar\gamma\chi_{c2}\ar\gamma\gamma\jpsi) = (1.62\pm0.04\pm 0.12)%.Comment: 7 pages, 6 figures. submitted to Phys. Rev.

Measurements of ψ(2S)\psi(2S) decays into Vector- Tensor final states

Decays of the $\psi(2S)$ into vector plus tensor meson final states have been studied with 14 million $\psi(2S)$ events collected with the BESII detector. Branching fractions of \psi(2S) \rt \omega f_{2}(1270), $\rho a_2(1320)$, $K^*(892)^0\bar{K}^*_2(1430)^0+c.c.$ and $\phi f_2^{\prime}(1525)$ are determined. They improve upon previous BESI results and confirm the violation of the "12%" rule for $\psi(2S)$ decays to VT channels with higher precision.Comment: 7 pages, 7 figures and 2 table

Measurements of ψ(2S)\psi(2S) decays into ϕπ0\phi \pi^0, ϕη\phi \eta, ϕη′\phi \eta^{'}, ωη\omega \eta, and ωη′\omega \eta^{'}

Decays of the $\psi(2S)$ into Vector plus Pseudoscalar meson final states have been studied with 14 million $\psi(2S)$ events collected with the BESII detector. Branching fractions of \psi(2S) \rar\phi\eta, \phi\etap, and \omega\etap, and upper limits of \psi(2S) \rar \phi\piz and $\omega\eta$ are obtained: B(\psi(2S) \rar\phi\eta) = (3.3\pm 1.1 \pm 0.5) \times 10^{-5}, B(\psi(2S) \rar\phi\etap) = (3.1\pm 1.4 \pm 0.7)\times 10^{-5}, and B(\psi(2S) \rar\omega\etap) = (3.2^{+2.4}_{-2.0} \pm 0.7) \times 10^{-5}; and B(\psi(2S) \rar\phi\piz) < 0.40 \times 10^{-5}, and B(\psi(2S) \rar\omega\eta) < 3.1 \times 10^{-5} at the 90 % C.L.. These results are used to test the pQCD ``12% rule''.Comment: 7 pages, 7 figures, 2 table

Observation of a threshold enhancement in the p \bar{Lambda} invariant mass spectrum

An enhancement near the m_p + M_{\Lambda} mass threshold is observed in the combined p \bar{\Lambda} and \bar{p}\Lambda invariant mass spectrum from J/\psi --> p K^- \bar{Lambda} + c.c. decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m = 2075 +- 12 (stat) +- 5 (syst) MeV and a width of \Gamma = 90 +- 35 (stat) +- 9 (syst) MeV; it can also be fit with a P-wave Breit-Wigner resonance. Evidence for a similar enhancement is also observed in \psi' --> p K^- \bar{\Lambda} + c.c. decays. The analysis is based on samples of 5.8 X 10^7 J/\psi and 1.4 X 10^7 \psi' decays accumulated in the BES II detector at the Beijing Electron-Positron Collider.Comment: 5 pages, 3 figures, RevTex4, Submitted to Phys. Rev. Let

Observation of K∗(892)0Kˉ∗(892)0K^*(892)^0\bar K^*(892)^0 in χcJ\chi_{cJ} Decays

$K^*(892)^0\bar K^*(892)^0$ signals from $\chi_{cJ} (J=0,1,2)$ decays are observed for the first time using a data sample of 14 million $\psi(2S)$ events accumulated at the BES II detector. The branching fractions ${\cal B}(\chi_{cJ}\to K^*(892)^0\bar K^*(892)^0)$ $(J = 0,1,2)$ are determined to be $(1.55 \pm 0.35 \pm 0.30)\times 10^{-3}$, $(1.58 \pm 0.32 \pm 0.29)\times 10^{-3}$, and $(4.67 \pm 0.55 \pm 0.85)\times 10^{-3}$ for the $\chi_{c0}$, $\chi_{c1}$ and $\chi_{c2}$ decays, respectively, where the first errors are statistical and the second are systematic. The significances of these signals are about 4.2$\sigma$, 4.3$\sigma$, and 7.5$\sigma$, respectively.Comment: 8 pages, 6 figure

Improved measurement of the branching ratio of J/psi-->K_S K_L

The branching ratio of J/psi-->K_S K_L is measured with improved precision to be B(J/psi-->K_S K_L) = (1.82\pm 0.04\pm 0.13)\times 10^{-4}. using J/psi data collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider. This result is used to test the perturbative QCD ``12%'' rule between psi(2S) and J/psi decays and to investigate the relative phase between the three-gluon and one-photon annihilation amplitudes in J/psi decays.Comment: 10 pages, 14 figures, 2 tables, submitted to Phys. Rev.

Experimental study of \etac decays into vector-vector final states

Using 58 million J/\psi events accumulated with the BES II detector, branching fractions for the \eta_{c} ->VV decays, \eta_{c} -> \rho \rho, \eta_{c} -> K^{*}{\bar K}^{*}, \eta_{c} -> \omega \omega, and \eta_{c} -> \phi \phi, are measured. The branching fractions are Br(\eta_{c} -> \rho \rho) = (1.25 \pm 0.37 \pm 0.51) \times 10^{-2}, Br(\eta_{c} -> \K^{*}{\bar K}^{*}) = (10.4 \pm 2.6\pm 4.3) \times 10^{-3}, Br(\eta_{c} -> \omega\omega) < 6.3 \times 10^{-3} (90 % CL), and Br(\eta_{c} -> \phi \phi) = (2.5 \pm 0.5 \pm 0.9) \times 10^{-3}. The process \eta_{c} -> \omega\phi is also searched for, and the 90% CL upper limit Br(eta_{c} -> \omega\phi) < 1.3 \times 10^{-3} is obtained for this process.Comment: 12pages,11figures,to be submitted to PR

A New Look at the Scalar Meson f0(500)f_0(500) via D+→π+π−ℓ+νℓD^+\to \pi^+\pi^-\ell^+\nu_\ell Decays

Using $2.93~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the semileptonic decays $D^+\to \pi^+\pi^- \ell^+\nu_\ell$ ($\ell=e$ and $\mu$). The $D^+\to f_0(500)\mu^+\nu_\mu$ decay is observed for the first time. By analyzing simultaneously the differential decay rates of $D^+\to f_0(500) \mu^+\nu_\mu$ and $D^+\to f_0(500) e^+\nu_e$ in different $\ell^+\nu_\ell$ four-momentum transfer intervals, the product of the relevant hadronic form factor $f^{f_0}_{+}(0)$ and the magnitude of the $c\to d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ is determined to be $f_{+}^{f_0} (0)|V_{cd}|=0.0787\pm0.0060_{\rm stat}\pm0.0033_{\rm syst}$ for the first time. With the input of $|V_{cd}|$ from the global fit in the standard model, we determine $f_{+}^{f_0} (0)=0.350\pm0.027_{\rm stat}\pm0.015_{\rm syst}$. The absolute branching fractions of $D^+\to f_0(500)_{(\pi^+\pi^-)}\mu^+\nu_\mu$ and $D^+\to \rho^0_{(\pi^+\pi^-)} \mu^+\nu_\mu$ are determined as $(0.72\pm0.13_{\rm stat}\pm0.10_{\rm syst})\times10^{-3}$ and $(1.64\pm0.13_{\rm stat}\pm0.11_{\rm syst})\times 10^{-3}$. Combining these results with those of previous BESIII measurements on their semielectronic counterparts from the same data sample, we test lepton flavor universality by measuring the branching fraction ratios ${\mathcal B}_{D^+\to \rho^0 \mu^+\nu_\mu}/{\mathcal B}_{D^+\to \rho^0 e^+\nu_e}=0.88\pm0.10$ and ${\mathcal B}_{D^+\to f_0(500) \mu^+\nu_\mu}/{\mathcal B}_{D^+\to f_0(500) e^+\nu_e}=1.14\pm0.28$, which are compatible with the standard model expectation.Comment: Supplemental Materials added in this versio