438 research outputs found

    Possible S-wave Dibaryons in SU(3) Chiral Quark Model

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    In the framework of the SU(3) chiral quark model, the S−S-wave baryon-baryon bound states are investigated. It is found that according to the symmetry character of the system and the contributions from chiral fields, there are three types of bound states. The states of the first type, such as [ΩΩ](0,0)[\Omega\Omega]_{(0,0)} and [Ξ∗Ω](0,1/2)[\Xi^{*}\Omega]_{(0,1/2)} are deeply bound dibaryon with narrow widths. The second type states, [Σ∗Δ](0,5/2)[\Sigma^{*} \Delta]_{(0,5/2)},[Σ∗Δ](3,1/2)[\Sigma^{*} \Delta]_{(3,1/2)}, [ΔΔ](0,3)[\Delta\Delta]_{(0,3)} and [ΔΔ](3,0)[\Delta\Delta]_{(3,0)} are also bound states, but with broad widths. [ΞΩ−Ξ∗Ω](1,1/2)[\Xi\Omega - \Xi^{*}\Omega]_{(1,1/2)}, [ΞΞ](0,1)[\Xi\Xi]_{(0,1)}, and [NΩ](2,1/2)[N \Omega]_{(2,1/2)} are third type states. They, like {\em d}, are weakly bound only if the chiral fields can provide attraction between baryons.Comment: Latex files, 1 figur

    Deltaron Dibaryon Structure in Chiral SU(3) Quark Model

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    We discuss the structure of Deltaron dibaryon in the chiral SU(3) quark model. The energy of Deltaron is obtained by considering the coupling of the ΔΔ\Delta\Delta and CCCC (hidden color) channels. The effects of various parameters on the Deltaron mass are also studied. It is shown that the mass of Deltaron is lower than the mass of ΔΔ\Delta\Delta but higher than the mass of ΔNπ\Delta N \pi.Comment: 15 pages, Late

    SU(2)-in-SU(1,1) Nested Interferometer for Highly Sensitive, Loss-Tolerant Quantum Metrology

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    We present experimental and theoretical results on a new interferometer topology that nests a SU(2) interferometer, e.g., a Mach-Zehnder or Michelson interferometer, inside a SU(1,1) interferometer, i.e., a Mach-Zehnder interferometer with parametric amplifiers in place of beam splitters. This SU(2)-in-SU(1,1) nested interferometer (SISNI) simultaneously achieves high signal-to-noise ratio (SNR), sensitivity beyond the standard quantum limit (SQL) and tolerance to photon losses external to the interferometer, e.g., in detectors. We implement a SISNI using parametric amplification by four-wave mixing (FWM) in Rb vapor and a laser-fed Mach-Zehnder SU(2) interferometer. We observe path-length sensitivity with SNR 2.2 dB beyond the SQL at power levels (and thus SNR) 2 orders of magnitude beyond those of previous loss-tolerant interferometers. We find experimentally the optimal FWM gains and find agreement with a minimal quantum noise model for the FWM process. The results suggest ways to boost the in-practice sensitivity of high-power interferometers, e.g., gravitational wave interferometers, and may enable high-sensitivity, quantum-enhanced interferometry at wavelengths for which efficient detectors are not available.Comment: 6 pages + 4 of supplemental material, 5 figure

    Coalescence dynamics of size-selected gold clusters studied by time-resolved transmission electron microscopy

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    Coalescence dynamics of size-selected gold (Au) clusters (each with nominal 923 atoms), on amorphous Si3N4 substrate at room temperature, has been studied via time-resolved transmission electron microscopy (TEM). We found that the clusters approached each other in two stages. In the first stage, the drift velocity was independent of the particle separation and could be attributed to beam-induced random motion. In the second stage, the clusters were found to jump into contact with a much higher final averaged speed. This is independent of beam dose rates and is attributed to the van der Waal attraction

    Possible Dibaryons with Strangeness s=-5

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    In the framework of RGMRGM, the binding energy of the six quark system with strangeness s=-5 is systematically investigated under the SU(3) chiral constituent quark model. The single Ξ∗Ω\Xi^*\Omega channel calculation with spins S=0 and 3 and the coupled ΞΩ\Xi\Omega and Ξ∗Ω\Xi^*\Omega channel calculation with spins S=1 and 2 are considered, respectively. The results show following observations: In the spin=0 case, Ξ∗Ω\Xi^* \Omega is a bound dibaryon with the binding energy being 80.0∼92.4MeV80.0 \sim 92.4 MeV. In the S=1 case, ΞΩ\Xi\Omega is also a bound dibaryon. Its binding energy is ranged from 26.2MeV26.2 MeV to 32.9MeV32.9 MeV. In the S=2 and S=3 cases, no evidence of bound dibaryons are found. The phase shifts and scattering lengths in the S=0 and S=1 cases are also given.Comment: 10 pages, late

    Determining the upper limit of Gamma_{ee} for the Y(4260)

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    By fitting the R values between 3.7 and 5.0 GeV measured by the BES collaboration, the upper limit of the electron width of the newly discovered resonance Y(4260) is determined to be 580 eV at 90% C.L. Together with the BABAR measurement on the product of Gamma_{ee} and BR(Y(4260) --> pi+pi- J/psi), this implies a large decay width of Y(4260) --> pi+pi- J/psi final states.Comment: 8 pages, 4 figure

    Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

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    We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure

    Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar

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    The branching ratios and Angular distributions for J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure

    Direct Measurements of the Branching Fractions for D0→K−e+νeD^0 \to K^-e^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

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    The absolute branching fractions for the decays D0→K−e+νeD^0 \to K^-e ^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e are determined using 7584±198±3417584\pm 198 \pm 341 singly tagged Dˉ0\bar D^0 sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged Dˉ0\bar D^0 meson, 104.0±10.9104.0\pm 10.9 events for D0→K−e+νeD^0 \to K^-e ^+\nu_e and 9.0±3.69.0 \pm 3.6 events for D0→π−e+νeD^0 \to \pi^-e^+\nu_e decays are observed. Those yield the absolute branching fractions to be BF(D0→K−e+νe)=(3.82±0.40±0.27)BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)% and BF(D0→π−e+νe)=(0.33±0.13±0.03)BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)%. The vector form factors are determined to be ∣f+K(0)∣=0.78±0.04±0.03|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03 and ∣f+π(0)∣=0.73±0.14±0.06|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06. The ratio of the two form factors is measured to be ∣f+π(0)/f+K(0)∣=0.93±0.19±0.07|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07.Comment: 6 pages, 5 figure

    Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

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    Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
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