4,338 research outputs found

    A Unified Approach to the Classical Statistical Analysis of Small Signals

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    We give a classical confidence belt construction which unifies the treatment of upper confidence limits for null results and two-sided confidence intervals for non-null results. The unified treatment solves a problem (apparently not previously recognized) that the choice of upper limit or two-sided intervals leads to intervals which are not confidence intervals if the choice is based on the data. We apply the construction to two related problems which have recently been a battle-ground between classical and Bayesian statistics: Poisson processes with background, and Gaussian errors with a bounded physical region. In contrast with the usual classical construction for upper limits, our construction avoids unphysical confidence intervals. In contrast with some popular Bayesian intervals, our intervals eliminate conservatism (frequentist coverage greater than the stated confidence) in the Gaussian case and reduce it to a level dictated by discreteness in the Poisson case. We generalize the method in order to apply it to analysis of experiments searching for neutrino oscillations. We show that this technique both gives correct coverage and is powerful, while other classical techniques that have been used by neutrino oscillation search experiments fail one or both of these criteria.Comment: 40 pages, 15 figures. Changes 15-Dec-99 to agree more closely with published version. A few small changes, plus the two substantive changes we made in proof back in 1998: 1) The definition of "sensitivity" in Sec. V(C). It was inconsistent with our actual definition in Sec. VI. 2) "Note added in proof" at end of the Conclusio

    Observation of Y(2175) in J/ψηϕf0(980)J/\psi\to \eta\phi f_0(980)

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    The decays of J/ψηϕf0(980)(ηγγ,ϕK+K,f0(980)π+π)J/\psi\to \eta\phi f_0(980) (\eta\to \gamma\gamma, \phi \to K^+K^-, f_0(980)\to\pi^+\pi^-) are analyzed using a sample of 5.8×1075.8 \times 10^{7} J/ψJ/\psi events collected with the BESII detector at the Beijing Electron-Positron Collider (BEPC). A structure at around 2.182.18 GeV/c2c^2 with about 5σ5\sigma significance is observed in the ϕf0(980)\phi f_0(980) invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of m=2.186±0.010(stat)±0.006(syst)m=2.186\pm 0.010 (stat)\pm 0.006 (syst) GeV/c2c^2 and Γ=0.065±0.023(stat)±0.017(syst)\Gamma=0.065\pm 0.023 (stat)\pm 0.017 (syst) GeV/c2c^2, respectively, that are consistent with those of Y(2175), observed by the BABAR collaboration in the initial-state radiation (ISR) process e+eγISRϕf0(980)e^+e^-\to\gamma_{ISR}\phi f_0(980). The production branching ratio is determined to be Br(J/ψηY(2175))Br(Y(2175)ϕf0(980))Br(f0(980)π+π)=(3.23±0.75(stat)±0.73(syst))×104Br(J/\psi\to\eta Y(2175))\cdot Br(Y(2175)\to\phi f_0(980))\cdot Br(f_0(980)\to\pi^+\pi^-)=(3.23\pm 0.75 (stat)\pm0.73 (syst))\times 10^{-4}, assuming that the Y(2175) is a 11^{--} state.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let

    Partial wave analysis of J/psi to p pbar pi0

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    Using a sample of 58 million J/ψJ/\psi events collected with the BESII detector at the BEPC, more than 100,000 J/ψppˉπ0J/\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/ψppˉπ0)=(1.33±0.02±0.11)×103Br(J/\psi \to p \bar p \pi^0)=(1.33 \pm 0.02 \pm 0.11) \times 10^{-3}. A long-sought `missing' NN^*, first observed in J/ψpnˉπJ/\psi \to p \bar n \pi^-, is observed in this decay too, with mass and width of 20404+3±252040_{-4}^{+3}\pm 25 MeV/c2^2 and 2308+8±52230_{-8}^{+8}\pm 52 MeV/c2^2, respectively. Its spin-parity favors 3/2+{3/2}^+. The masses, widths, and spin-parities of other NN^* states are obtained as well.Comment: Add one author nam

    Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)

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    Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi -> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be 0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.

    Measurement of \psip Radiative Decays

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    Using 14 million psi(2S) events accumulated at the BESII detector, we report first measurements of branching fractions or upper limits for psi(2S) decays into gamma ppbar, gamma 2(pi^+pi^-), gamma K_s K^-pi^++c.c., gamma K^+ K^- pi^+pi^-, gamma K^{*0} K^- pi^+ +c.c., gamma K^{*0}\bar K^{*0}, gamma pi^+pi^- p pbar, gamma 2(K^+K^-), gamma 3(pi^+pi^-), and gamma 2(pi^+pi^-)K^+K^- with the invariant mass of hadrons below 2.9GeV/c^2. We also report branching fractions of psi(2S) decays into 2(pi^+pi^-) pi^0, omega pi^+pi^-, omega f_2(1270), b_1^\pm pi^\mp, and pi^0 2(pi^+pi^-) K^+K^-.Comment: 5 pages, 4 figure

    Measurements of J/ψJ/\psi and ψ(2S)\psi(2S) decays into ΛΛˉπ0\Lambda \bar{\Lambda}\pi^0 and ΛΛˉη\Lambda \bar{\Lambda}\eta

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    Using 58 million J/ψJ/\psi and 14 million ψ(2S)\psi(2S) events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays J/ψJ/\psi and ψ(2S)ΛΛˉπ0\psi(2S) \to \Lambda \bar{\Lambda}\pi^0 and ΛΛˉη\Lambda \bar{\Lambda}\eta are measured. For the isospin violating decays, the upper limits are determined to be B(J/ψΛΛˉπ0)<6.4×105{\cal B}(J/\psi \to \Lambda \bar{\Lambda}\pi^0)<6.4\times 10^{-5} and B(ψ(2S)ΛΛˉπ0)<4.9×105{\cal B}(\psi(2S) \to \Lambda \bar{\Lambda}\pi^0)<4.9\times 10^{-5} at the 90% confidence level. The isospin conserving process J/ψΛΛˉηJ/\psi \to \Lambda \bar{\Lambda}\eta is observed for the first time, and its branching fraction is measured to be B(J/ψΛΛˉη)=(2.62±0.60±0.44)×104{\cal B}(J/\psi \to \Lambda \bar{\Lambda}\eta)=(2.62\pm 0.60\pm 0.44)\times 10^{-4}, where the first error is statistical and the second one is systematic. No ΛΛˉη\Lambda \bar{\Lambda}\eta signal is observed in ψ(2S)\psi(2S) decays, and B(ψ(2S)ΛΛˉη)<1.2×104{\cal B}(\psi(2S) \to \Lambda \bar{\Lambda}\eta)<1.2\times 10^{-4} is set at the 90% confidence level. Branching fractions of J/ψJ/\psi decays into Σ+πbarΛ\Sigma^+ \pi^- bar{\Lambda} and Σˉπ+Λ\bar{\Sigma}^- \pi^+ \Lambda are also reported, and the sum of these branching fractions is determined to be B(J/ψΣ+πΛˉ+c.c.)=(1.52±0.08±0.16)×103{\cal B}(J/\psi \to \Sigma^+\pi^- \bar{\Lambda} + c.c.)=(1.52\pm 0.08\pm 0.16)\times 10^{-3}.Comment: 7 pages, 10 figures. Phys.Rev.D comments considere

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

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    K+Kπ+ππ0K^+K^-\pi^+\pi^-\pi^0 final states are studied using a sample of 14×10614\times10^6 ψ(2S)\psi(2S) decays collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Position Collider. The branching fractions of ψ(2S)\psi(2S) decays to K+Kπ+ππ0 K^+K^-\pi^+\pi^-\pi^0, ωK+K\omega K^+ K^-, ωf0(1710)\omega f_0(1710), K(892)0Kπ+π0+c.c. K^{\ast}(892)^0 K^- \pi^+\pi^0+c.c., K(892)+Kπ+π+c.c.K^{\ast}(892)^{+} K^- \pi^+\pi^- +c.c., K(892)+Kρ0+c.c.K^{\ast}(892)^{+} K^- \rho^0+c.c. and K(892)0Kρ++c.c.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

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

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    Non-DDˉD\bar{D} decay \psppto \rhopi is searched for using a data sample of (17.3±0.5)pb1(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 ρπ\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 SS- and DD-wave mixing scheme of the charmonium states for solving the ``\rhopi puzzle'' between \jpsi and \psp decays.Comment: 15 pages, 5 figure
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