785 research outputs found

    Vortices, circumfluence, symmetry groups and Darboux transformations of the (2+1)-dimensional Euler equation

    Full text link
    The Euler equation (EE) is one of the basic equations in many physical fields such as fluids, plasmas, condensed matter, astrophysics, oceanic and atmospheric dynamics. A symmetry group theorem of the (2+1)-dimensional EE is obtained via a simple direct method which is thus utilized to find \em exact analytical \rm vortex and circumfluence solutions. A weak Darboux transformation theorem of the (2+1)-dimensional EE can be obtained for \em arbitrary spectral parameter \rm from the general symmetry group theorem. \rm Possible applications of the vortex and circumfluence solutions to tropical cyclones, especially Hurricane Katrina 2005, are demonstrated.Comment: 25 pages, 9 figure

    Coupled KdV equations derived from atmospherical dynamics

    Full text link
    Some types of coupled Korteweg de-Vries (KdV) equations are derived from an atmospheric dynamical system. In the derivation procedure, an unreasonable yy-average trick (which is usually adopted in literature) is removed. The derived models are classified via Painlev\'e test. Three types of τ\tau-function solutions and multiple soliton solutions of the models are explicitly given by means of the exact solutions of the usual KdV equation. It is also interesting that for a non-Painlev\'e integrable coupled KdV system there may be multiple soliton solutions.Comment: 19 pages, 2 figure

    Measurement of Inclusive Monmentum Spectra and Multiplicity Distributions of Charged Particles at s25\sqrt{s}\sim 2-5 GeV

    Full text link
    Inclusive momentum spectra and multiplicity distributions of charged particles measured with BESII detector at center of mass energies of 2.2,2.6,3.0,3.2,4.6 and 4.8 GeV are presented. Values of the second binomial moment, R2R_2, obtained from the multiplicity distributions are reported. These results are compared with both experimental data from high energy e+ee^+e^-, epep and ppˉp\bar{p} experiments and QCD calculations.Comment: 9 pages, 7 figures, 3 tables, it will be submitted to PR

    Observation of J/ψJ/\psi decays to e+ee+ee^{+}e^{-}e^{+}e^{-} and e+eμ+μe^{+}e^{-}\mu^{+}\mu^{-}

    Full text link
    Using a data sample of 4.481×1084.481\times 10^8 ψ(3686)\psi(3686) events collected with the BESIII detector, we report the first observation of the four-lepton-decays J/ψe+ee+eJ/\psi\to e^+e^-e^+e^- and J/ψe+eμ+μJ/\psi\to e^+e^-\mu^+\mu^- utilizing the process ψ(3686)π+πJ/ψ\psi(3686)\to \pi^+\pi^- J/\psi. The branching fractions are determined to be [4.32±0.26 (stat)±0.19 (syst)]×105[4.32\pm0.26~(\rm stat)\pm0.19~(\rm syst)]\times 10^{-5} and [2.45 ±0.21 (stat)±0.10 (syst)]×105[2.45~\pm0.21~(\rm stat)\pm0.10~(\rm syst)]\times 10^{-5}, respectively. The results deviate from theoretical predictions, by 2.8 and 5.2 σ\sigma, respectively. No significant signal is observed for J/ψμ+μμ+μJ/\psi\to \mu^+\mu^-\mu^+\mu^-, and an upper limit on the branching fraction is set at 1.6×1061.6\times 10^{-6} at the 90%\% confidence level. A CP asymmetry observable is constructed for the first two channels, which is measured to be (0.019±0.067±0.025)(-0.019\pm0.067\pm0.025) and (0.016±0.081±0.003)(-0.016\pm0.081\pm0.003), respectively. No evidence for CP violation is observed in this process.Comment: 9 pages, 1 figur

    Search for an invisible muon philic scalar X0X_{0} or vector X1X_{1} via J/ψμ+μ+invisibleJ/\psi\to\mu^+\mu^-+\rm{invisible} decay at BESIII

    Full text link
    A light scalar X0X_{0} or vector X1X_{1} particles have been introduced as a possible explanation for the (g2)μ(g-2)_{\mu} anomaly and dark matter phenomena. Using (8.998±0.039)×109(8.998\pm 0.039)\times10^9 \jpsi events collected by the BESIII detector, we search for a light muon philic scalar X0X_{0} or vector X1X_{1} in the processes J/ψμ+μX0,1J/\psi\to\mu^+\mu^- X_{0,1} with X0,1X_{0,1} invisible decays. No obvious signal is found, and the upper limits on the coupling g0,1g_{0,1}' between the muon and the X0,1X_{0,1} particles are set to be between 1.1×1031.1\times10^{-3} and 1.0×1021.0\times10^{-2} for the X0,1X_{0,1} mass in the range of 1<M(X0,1)<10001<M(X_{0,1})<1000~MeV/c2/c^2 at 90%\% confidence level.Comment: 9 pages 7 figure

    Search for an axion-like particle in J/ψJ/\psi radiative decays

    Full text link
    We search for an axion-like particle (ALP) aa through the process ψ(3686)π+πJ/ψ\psi(3686)\rightarrow\pi^+\pi^-J/\psi, J/ψγaJ/\psi\rightarrow\gamma a, aγγa\rightarrow\gamma\gamma in a data sample with (2708.1±14.5)×106(2708.1\pm14.5)\times10^6 ψ(3686)\psi(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/ψγaJ/\psi\rightarrow\gamma a and the ALP-photon coupling constant gaγγg_{a\gamma\gamma} are set at the 95\% confidence level in the mass range of 0.165\leq m_a\leq2.84\,\mbox{GeV}/c^2. The limits on B(J/ψγa)\mathcal{B}(J/\psi\rightarrow\gamma a) range from 8.3×1088.3\times10^{-8} to 1.8×1061.8\times10^{-6} over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165\leq m_a\leq1.468\,\mbox{GeV}/c^2.Comment: 10 pages, 5 figure

    Measurements of the branching fractions of the inclusive decays D0(D+)→π+π+π−X

    Get PDF
    Using eþe− annihilation data corresponding to an integrated luminosity of 2.93 fb−1 taken at a center-of mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the branching fractions of the inclusive decays D0 → πþπþπ−X and Dþ → πþπþπ−X, where pions from K0 S decays have been excluded from the πþπþπ− system and X denotes any possible particle combination. The branching fractions of D0ðDþÞ → πþπþπ−X are determined to be BðD0 → πþπþπ−XÞ¼ð17.60 0.11 0.22Þ% and BðDþ → πþπþπ−XÞ¼ð15.25 0.09 0.18Þ%, where the first uncertainties are statistical and the second systematic

    Updated measurements of the M1 transition ψ(3686)γηc(2S)\psi(3686) \to \gamma \eta_{c}(2S) with ηc(2S)KKˉπ\eta_{c}(2S) \to K \bar{K} \pi

    Full text link
    Based on a data sample of (27.08±0.14)×108 ψ(3686)(27.08 \pm 0.14 ) \times 10^8~\psi(3686) events collected with the BESIII detector at the BEPCII collider, the M1 transition ψ(3686)γηc(2S)\psi(3686) \to \gamma \eta_{c}(2S) with ηc(2S)KKˉπ\eta_{c}(2S) \to K\bar{K}\pi is studied, where KKˉπK\bar{K}\pi is K+Kπ0K^{+} K^{-} \pi^{0} or KS0K±πK_{S}^{0}K^{\pm}\pi^{\mp}. The mass and width of the ηc(2S)\eta_{c}(2S) are measured to be (3637.8±0.8(stat)±0.2(syst))(3637.8 \pm 0.8 (\rm {stat}) \pm 0.2 (\rm {syst})) MeV/c2c^{2} and (10.5±1.7(stat)±3.5(syst))(10.5 \pm 1.7 (\rm {stat}) \pm 3.5 (\rm {syst})) MeV, respectively. The product branching fraction B(ψ(3686)γηc(2S))×B(ηc(2S)KKˉπ)\mathcal{B}\left(\psi(3686) \rightarrow \gamma \eta_{c}(2 S)\right) \times \mathcal{B}(\eta_{c}(2 S) \rightarrow K \bar{K} \pi) is determined to be (0.97±0.06(stat)±0.09(syst))×105(0.97 \pm 0.06 (\rm {stat}) \pm 0.09 (\rm {syst})) \times 10^{-5}. Using BR(ηc(2S)KKˉπ)=(1.860.49+0.68)%\mathcal{BR}(\eta_{c}(2S)\to K\bar{K}\pi)=(1.86^{+0.68}_{-0.49})\%, we obtain the branching fraction of the radiative transition to be BR(ψ(3686)γηc(2S))=(5.2±0.3(stat)±0.5(syst)1.4+1.9(extr))×104\mathcal{BR}(\psi(3686) \to \gamma \eta_{c}(2S)) = (5.2 \pm 0.3 (\rm {stat}) \pm 0.5 (\rm {syst}) ^{+1.9}_{-1.4} (extr)) \times 10^{-4}, where the third uncertainty is due to the quoted BR(ηc(2S)KKˉπ)\mathcal{BR}(\eta_{c}(2S) \to K\bar{K}\pi)

    Measurements of the electric and magnetic form factors of the neutron for time-like momentum transfer