243 Search Results

Abstract A systematic numerical investigation is carried out to understand magnetohydrodynamic stability of the ideal infernal-kink instability in tokamak plasmas with both negative triangularity (neg-D) shaping and negative central shear for the equilibrium safety factor profile. The latter is motivated by the desire to form the internal transport barrier in the neg-D configuration, which is known to have difficulty in forming the edge transport barrier. The infernal-kink mode is generally found to be more unstable in neg-D plasmas as compared to their positive D-shaped (pos-D) counterpart. This is mainly due to less favorable (or even unfavorable) average magnetic curvature near the radial location of the minimum safety factor ( $q_{\text{min}}$ ) as compared to the pos-D configuration. The larger Shafranov shift associated with the neg-D shape helps the mode stabilization but is not sufficient to overcome the destabilizing effect due to bad curvature. Strong poloidal mode coupling due to plasma shaping (toroidicity, elongation, triangularity, etc.) helps explain the slight shift with respect to that predicted by the analytic theory of the peak location of the computed mode growth versus $q_{\text{min}}$ .

Based on $(10.09\pm 0.04)\times {10}^{9}J/\psi$ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay $J/\psi \to \varphi {\pi }^0\eta$ is performed. We observe for the first time two new structures on the $\varphi \eta$ invariant mass distribution, with significances exceeding $27\sigma$ and $13\sigma$ ; the first with $J^{\mathrm{PC}}=1^{+-}$ , mass $\mathrm{M}=(1908\pm 6(\mathrm{stat}\left){}_{-4}^{+8}\right(\mathrm{sys}\left)\right)\mathrm{MeV}/c^2$ , and width $\mathrm{\Gamma }=(175\pm 13(\mathrm{stat}\left){}_{-16}^{+7}\right(\mathrm{sys}\left)\right)\mathrm{MeV}$ , the second with $J^{\mathrm{PC}}=1^{--}$ , mass $\mathrm{M}=(1992\pm 12(\mathrm{stat}\left){}_{-6}^{+15}\right(\mathrm{sys}\left)\right)\mathrm{MeV}/c^2$ , and width $\mathrm{\Gamma }=(132\pm 22(\mathrm{stat}\left){}_{-4}^{+17}\right(\mathrm{sys}\left)\right)\mathrm{MeV}$ . These measurements provide important input for the strangeonium spectrum. In addition, the $f_0\left(980\right)-a_0(980{)}^0$ mixing signal in $J/\psi \to \varphi f_0\left(980\right)\to \varphi a_0(980{)}^0$ and the corresponding electromagnetic decay $J/\psi \to \varphi a_0(980{)}^0$ are measured with improved precision, providing crucial information to understand the nature of $a_0(980{)}^0$ and $f_0\left(980\right)$ . Published by the American Physical Society 2024

We report the precise measurements of the cross section of $e^{+}{e}^{-}\to \text{hadrons}$ at center-of-mass energies from 3.645 to 3.871 GeV. We thereby perform the most precise study of the cross sections and find a complex system composed of three resonances of $\mathcal{R}\left(3760\right)$ , $\mathcal{R}\left(3780\right)$ , and $\mathcal{R}\left(3810\right)$ . For the first time, we measure the $\mathcal{R}\left(3810\right)$ electronic width to be $(19.4\pm 7.4\pm 12.1)\mathrm{eV}$ . For the $\mathcal{R}\left(3760\right)$ resonance, we measure the mass to be $(3751.9\pm 3.8\pm 2.8)\mathrm{MeV}/c^2$ , the total width to be $(32.8\pm 5.8\pm 8.7)\mathrm{MeV}$ , and the electronic width to be $(184\pm 75\pm 86)\mathrm{eV}$ . For the $\mathcal{R}\left(3780\right)$ resonance, we measure its mass to be $(3778.7\pm 0.5\pm 0.3)\mathrm{MeV}/c^2$ , total width to be $(20.3\pm 0.8\pm 1.7)\mathrm{MeV}$ , and electronic width to be $(265\pm 67\pm 83)\mathrm{eV}$ . Forty-seven years ago, the $\psi \left(3770\right)$ resonance was discovered, and was subsequently interpreted as the $1{}^3{D}_1$ -wave dominant state of charmonium. However, our analysis of the total-hadron cross sections indicates that the $\psi \left(3770\right)$ is not a single state, but a complex system composed of the $\mathcal{R}\left(3760\right)$ , $\mathcal{R}\left(3780\right)$ , and $\mathcal{R}\left(3810\right)$ resonances. Among these, we interpret the $\mathcal{R}\left(3780\right)$ is a resonance dominated by the $1{}^3{D}_1$ charmonium state. Published by the American Physical Society 2024

Using a sample of about 10 billion $J/\psi$ events with the BESIII detector, we search for the weak decays of $J/\psi \to {\overline{D}}^0{\pi }^0+\mathrm{c}.\mathrm{c}.$ , $J/\psi \to {\overline{D}}^0\eta +\mathrm{c}.\mathrm{c}.$ , $J/\psi \to {\overline{D}}^0{\rho }^0+\mathrm{c}.\mathrm{c}.$ , $J/\psi \to D^{-}{\pi }^{+}+\mathrm{c}.\mathrm{c}.$ , and $J/\psi \to D^{-}{\rho }^{+}+\mathrm{c}.\mathrm{c}.$ . Since no significant signal is observed, we set the upper limits of the branching fractions of these decays to be $\mathcal{B}(J/\psi \to {\overline{D}}^0{\pi }^0+\mathrm{c}.\mathrm{c}.)<4.7\times {10}^{-7}$ , $\mathcal{B}(J/\psi \to {\overline{D}}^0\eta +\mathrm{c}.\mathrm{c}.)<6.8\times {10}^{-7}$ , $\mathcal{B}(J/\psi \to {\overline{D}}^0{\rho }^0+\mathrm{c}.\mathrm{c}.)<5.2\times {10}^{-7}$ , $\mathcal{B}(J/\psi \to D^{-}{\pi }^{+}+\mathrm{c}.\mathrm{c}.)<7.0\times {10}^{-8}$ , and $\mathcal{B}(J/\psi \to D^{-}{\rho }^{+}+\mathrm{c}.\mathrm{c}.)<6.0\times {10}^{-7}$ at the 90% confidence level. Published by the American Physical Society 2024

Using data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 3.80 to 4.95 GeV, corresponding to an integrated luminosity of $20{\mathrm{fb}}^{-1}$ , a measurement of Born cross sections for the $e^{+}{e}^{-}\to D^0{\overline{D}}^0$ and $D^{+}{D}^{-}$ processes is presented with unprecedented precision. Many clear peaks in the line shape of $e^{+}{e}^{-}\to D^0{\overline{D}}^0$ and $D^{+}{D}^{-}$ around the mass range of $G\left(3900\right)$ , $\psi \left(4040\right)$ , $\psi \left(4160\right)$ , $Y\left(4260\right)$ , and $\psi \left(4415\right)$ , etc., are foreseen. These results offer crucial experimental insights into the nature of hadron production in the open-charm region. Published by the American Physical Society 2024

Using a sample of $448.1\times {10}^6$ $\psi \left(2S\right)$ events collected with the BESIII detector, we perform a study of the decay $J/\psi \to K^{+}{K}^{-}$ via $\psi \left(2S\right)\to {\pi }^{+}{\pi }^{-}J/\psi$ . The branching fraction of $J/\psi \to K^{+}{K}^{-}$ is determined to be ${\mathcal{B}}_{K^{+}{K}^{-}}=(3.072\pm 0.023(\mathrm{stat})\pm 0.050(\mathrm{syst}\left)\right)\times {10}^{-4}$ , which is consistent with previous measurements but with significantly improved precision. Published by the American Physical Society 2024

We search for the diphoton decay of a light pseudoscalar axionlike particle, $a$ , in radiative $J/\psi$ decays, using ${10}^{10}J/\psi$ events collected with the BESIII detector. We find no evidence of a signal and set upper limits at the 95% confidence level on the product branching fraction $\mathcal{B}(J/\psi \to \gamma a)\times \mathcal{B}(a\to \gamma \gamma )$ and the axionlike particle photon coupling constant $g_{a\gamma \gamma }$ in the ranges of $\left(3.7–48.5\right)\times {10}^{-8}$ and $\left(2.2–101.8\right)\times {10}^{-4}{\mathrm{GeV}}^{-1}$ , respectively, for $0.18\le m_a\le 2.85\mathrm{GeV}/c^2$ . These are the most stringent limits to date in this mass region. Published by the American Physical Society 2024

With the data samples taken at center-of-mass energies from 2.00 to 3.08 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis on the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ process is performed. The Born cross sections for $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ and its intermediate processes $e^{+}{e}^{-}\to \rho \pi$ and $\rho \left(1450\right)\pi$ are measured as functions of $\sqrt{s}$ . The results for $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ are consistent with previous results measured with the initial state radiation method within one standard deviation, and improve the uncertainty by a factor of ten. By fitting the line shapes of the Born cross sections for the $e^{+}{e}^{-}\to \rho \pi$ and $e^{+}{e}^{-}\to \rho \left(1450\right)\pi$ , a structure with mass $M=2119\pm 11\pm 15\mathrm{MeV}/c^2$ and width $\mathrm{\Gamma }=69\pm 30\pm 5\mathrm{MeV}$ is observed with a significance of $5.9\sigma$ , where the first uncertainties are statistical and the second ones are systematic. This structure can be interpreted as an excited $\omega$ state. Published by the American Physical Society 2024

We present the first search for the leptonic decays $D^{*+}\to e^{+}{\nu }_e$ and $D^{*+}\to {\mu }^{+}{\nu }_{\mu }$ by analyzing a data sample of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, corresponding to an integrated luminosity of $6.32{\mathrm{fb}}^{-1}$ . No significant signal is observed. The upper limits on the branching fractions for $D^{*+}\to e^{+}{\nu }_e$ and $D^{*+}\to {\mu }^{+}{\nu }_{\mu }$ are set to be $1.1\times {10}^{-5}$ and $4.3\times {10}^{-6}$ at 90% confidence level, respectively. Published by the American Physical Society 2024

The absolute branching fraction of the decay ${\mathrm{\Lambda }}_c(2625{)}^{+}\to {\mathrm{\Lambda }}_c^{+}{\pi }^{+}{\pi }^{-}$ is measured for the first time to be $(50.2\pm {5.7}_{\mathrm{stat}}\pm {3.5}_{\mathrm{syst}})\%$ with $368.48{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII detector at the center-of-mass energies of $\sqrt{s}=4.918$ and 4.950 GeV. Although the central value of the result is lower than the theoretical prediction of 67%, obtained from isospin symmetry, they are consistent taking the uncertainties into account. This is the first absolute branching fraction measurement for ${\mathrm{\Lambda }}_c(2625{)}^{+}$ since it was found. This measurement is necessary to obtain the coupling constants for the transitions between $s$ -wave and $p$ -wave charmed baryons in heavy hadron chiral perturbation theory. In addition, we search for the decay ${\mathrm{\Lambda }}_c(2595{)}^{+}\to {\mathrm{\Lambda }}_c^{+}{\pi }^{+}{\pi }^{-}$ . No significant signal is observed, and the upper limit on its branching fraction is determined to be 85.0% at the 90% confidence level. Published by the American Physical Society 2024