864 Search Results

Using a sample of ( 2712.4 ± 14.3 ) × 10 6     ψ ( 3686 ) events collected with the BESIII detector, we perform a search for the isospin-violating decays χ c J → Λ Σ ¯   0 + c . c . ( J = 0 , 1 , 2 ) and η c → Λ Σ ¯   0 + c . c . No significant signal for χ c J or η c is observed in the Λ Σ ¯   0 invariant mass distribution. The upper limits on the branching fractions at the 90% confidencemore » level are set to be B ( χ c 0 → Λ Σ ¯   0 + c . c . ) < 1.5 × 10 − 6 , B ( χ c 1 → Λ Σ ¯   0 + c . c . ) < 1.6 × 10 − 6 , B ( χ c 2 → Λ Σ ¯   0 + c . c . ) < 1.7 × 10 − 6 , and B ( η c → Λ Σ ¯   0 + c . c . ) < 6.2 × 10 − 5 for the first time.« less

The quantum size effect (QSE) and strain effect are two key factors influencing the surface morphology of thin films, which can increase film surface roughness through QSE-induced thickness oscillation and strain-induced island formation, respectively. Surface roughness usually manifests in the early stages of film growth and diminishes beyond a critical thickness. In this work, we employ molecular beam epitaxy (MBE) to grow β-Sn(100) islands with varying thickness N on bilayer graphene-terminated 6H-SiC(0001) substrates. Scanning tunneling microscopy and spectroscopy measurements reveal an inverse surface roughness effect that highlights the interplay of QSE and misfit strain in shaping the surface morphology ofmore » β-Sn(100) islands. For N ≤ 10, the islands exhibit flat surfaces, while for N ≥ 26, the island surfaces become corrugated and patterned. For the intermediate range, i.e., 12 ≤ N ≤ 24, both flat and patterned surfaces coexist, with the percentage coverage of the patterned surface oscillating as a function of N. By performing density functional theory calculations, we demonstrate that the unusual surface pattern evolution in our MBE-grown β-Sn(100) islands is a result of the interplay between QSE-induced surface roughing and tensile strain-induced smoothening effect.« less

Conjugated polymer thin films offer a unique combination of tunable optoelectronic properties and mechanical flexibility, making them as promising materials for intrinsically stretchable optoelectronic devices. However, achieving both mechanical robustness and high device performance remains a key challenge. Addressing this requires a fundamental understanding of how molecular and mesoscale structures evolve under mechanical strain. Here, we employ a comprehensive suite of X-ray spectroscopy and scattering techniques to investigate the multiscale structural evolution of conjugated polymer thin films during uniaxial deformation. We uncover a two-stage morphological response: an initial stage characterized by polymer chain alignment and rapid crystallite disruption, followed bymore » continued chain orientation accompanied by intrachain torsion at higher strains. These correlative structural adaptations govern key material properties, including stress dissipation, optical absorption, and photovoltaic performance. Our findings establish a mechanistic framework for understanding deformation in semiconducting polymers and provide design principles for developing mechanically robust, high-performance stretchable electronics.« less

Based on 12.0 fb⁻¹ of 𝑒⁺⁢𝑒⁻ collision data samples collected by the BESIII detector at center-of-mass energies from 4.1271 to 4.3583 GeV, a partial wave analysis is performed for the process 𝑒⁺⁢𝑒⁻ → 𝜋⁺⁢𝜋⁻⁢𝐽/𝜓. The cross sections for the subprocesses 𝑒⁺⁢𝑒⁻ → 𝜋⁺⁢𝑍_𝑐⁢(3900)⁻ + c.c. → 𝜋⁺⁢𝜋⁻⁢𝐽/𝜓, 𝑓₀⁡(980)⁢(→ 𝜋⁺⁢𝜋⁻)⁢𝐽/𝜓, and (𝜋⁺⁢𝜋⁻)_S−wave⁢𝐽/𝜓 are measured for the first time. The mass and width of the 𝑍_𝑐⁢(3900)^± are determined to be 3884.6 ± 0.7 ± 3.3 MeV/𝑐² and 37.2 ± 1.3 ± 6.6 MeV, respectively. The first errors are statistical and the second systematic. The final state (𝜋⁺⁢𝜋⁻)_S−wave⁢𝐽/𝜓 dominates the process 𝑒⁺⁢𝑒⁻ →more » 𝜋⁺⁢𝜋⁻⁢𝐽/𝜓. By analyzing the cross sections of 𝜋^±⁢𝑍_𝑐⁢(3900)^∓ and 𝑓₀⁡(980)⁢𝐽/𝜓, 𝑌⁡(4220) has been observed. Its mass and width are determined to be 4225.7 ± 4.1 ± 3.4 MeV/𝑐² and 57.5 ± 9.4 ± 12.1 MeV, respectively.« less

The first direct measurement of the relative phase between the strong and electromagnetic amplitudes for a J/ψ decaying into a vector-pseudoscalar final state is performed using 26 energy points of e⁺e⁻ annihilation data between 3.00 GeV and 3.12 GeV. The data sets were collected by the BESIII detector with a total integrated luminosity of 452 pb⁻¹. By investigating the interference pattern in the cross section lineshape of e⁺e⁻ → ϕη, the relative phase between the strong and electromagnetic amplitudes of J/ψ decay is determined to be within [133°, 228°] at 68% confidence level.

Using (2712 ± 14) × 106ψ(3686) events collected with the BESIII detector, we perform the first amplitude analysis of the radiative decay ψ3686→γKS0KS0$$$$ \psi (3686)\to \gamma {K}_S^0{K}_S^0 $$$$ within the mass region MKS0KS0<2.8$$$$ {M}_{K_S^0{K}_S^0}<2.8 $$$$ GeV/c2. Employing a one-channel K-matrix approach for the description of the dynamics of the KS0KS0$$$$ {K}_S^0{K}_S^0 $$$$ system, the data sample is well described with four poles for the f0-wave and three poles for the f2-wave. The determined pole positions are consistent with those of well-established resonance states. The observed f0 and f2 states are found to be in agreement with those produced in radiativemore » J/ψ decays. The production behaviors of f0 and f2 poles in ψ3686→γKS0KS0$$$$ \psi (3686)\to \gamma {K}_S^0{K}_S^0 $$$$ are qualified with their residues and the converted branching fractions. By comparing with J/ψ→γKS0KS0$$$$ J/\psi \to \gamma {K}_S^0{K}_S^0 $$$$ decay, the ratios Bψ3686→γf0,2BJ/ψ→γf0,2$$$$ \frac{\mathcal{B}\left(\psi (3686)\to \gamma {f}_{0,2}\right)}{\mathcal{B}\left(J/\psi \to \gamma {f}_{0,2}\right)} $$$$ are determined, which provides crucial experimental inputs on the internal structure of the f0,2 states, especially their potential mixing with glueball components.« less

We present the first amplitude analysis and branching fraction measurement of the decay $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$ , using $e^{+}{e}^{-}$ collision data collected with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV corresponding to an integrated luminosity of $7.33{\mathrm{fb}}^{-1}$ , and report the first observation of the pure $W$ -annihilation decay $more »$ D s + → ω ρ + with a branching fraction of $(0.99\pm 0.08_{\mathrm{stat}}{{}_{-0.07}^{+0.05}}_{\mathrm{syst}})\%$ . In comparison to the low significance of the $\mathcal{D}$ wave in the decay $D_s^{+}\to \varphi {\rho }^{+}$ , the dominance of the $\mathcal{D}$ wave over the $\mathcal{S}$ and $\mathcal{P}$ waves, with a fraction of $(51.85\pm 7.28_{\mathrm{stat}}{{}_{-7.90}^{+4.83}}_{\mathrm{syst}})\%$ observed in the decay $D_s^{+}\to \omega {\rho }^{+}$ , provides crucial information for the “polarization puzzle,” as well as for the understanding of charm meson decays. The branching fraction of $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$ is measured to be $(4.41\pm 0.15_{\mathrm{stat}}\pm 0.13_{\mathrm{syst}})\%$ . Moreover, the branching fraction of $D_s^{+}\to \varphi {\rho }^{+}$ is measured to be $(3.98\pm 0.33_{\mathrm{stat}}{{}_{-0.19}^{+0.21}}_{\mathrm{syst}})\%$ , and the $R_{\varphi }=\mathcal{B}(\varphi \to {\pi }^{+}{\pi }^{-}{\pi }^0)/\mathcal{B}(\varphi \to K^{+}{K}^{-})$ is determined to be ( $0.222\pm 0.019_{\mathrm{stat}}{{}_{-0.016}^{+0.016}}_{\mathrm{syst}}$ ), which is consistent with the previous measurement based on charm meson decays, but deviates from the results from $e^{+}{e}^{-}$ annihilation and $K-N$ scattering experiments by more than $3\sigma$ . Published by the American Physical Society 2025« less

Using $(2712.4\pm 14.3)\times {10}^6$ $\psi \left(3686\right)$ events collected with the BESIII detector at BEPCII, a partial wave analysis of the decay $\psi \left(3686\right)\to \varphi \eta {\eta }^{\prime }$ is performed with the covariant tensor approach. In addition to the established states $h_1(1900$ ) and $\varphi \left(2170\right)$ , an axial-vector state with a mass near $more »$ 2.3     GeV / c 2 is observed for the first time. Its mass and width are measured to be $2316\pm 9_{\mathrm{stat}}\pm 30_{\mathrm{syst}}\mathrm{MeV}/c^2$ and $89\pm 15_{\mathrm{stat}}\pm 26_{\mathrm{syst}}\mathrm{MeV}$ , respectively. The product branching fractions of $\mathcal{B}\left[\psi \right(3686)\to X(2300\left){\eta }^{\prime }\right]\mathcal{B}\left[X\right(2300)\to \varphi \eta ]$ and $\mathcal{B}\left[\psi \right(3686)\to X(2300\left)\eta \right]\mathcal{B}\left[X\right(2300)\to \varphi {\eta }^{\prime }]$ are determined to be $(4.8\pm {1.3}_{\mathrm{stat}}\pm {0.7}_{\mathrm{syst}})\times {10}^{-6}$ and $(2.2\pm {0.7}_{\mathrm{stat}}\pm {0.7}_{\mathrm{syst}})\times {10}^{-6}$ , respectively. The branching fraction $\mathcal{B}\left[\psi \right(3686)\to \varphi \eta {\eta }^{\prime }]$ is measured for the first time to be ( $3.14\pm 0.17_{\mathrm{stat}}\pm 0.24_{\mathrm{syst}})\times {10}^{-5}$ . The first uncertainties are statistical and the second are systematic. Published by the American Physical Society 2025« less

Using $20.3{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector operating at the BEPCII collider, the branching fractions of three hadronic charm meson decays, $D^{+}\to \varphi {\pi }^{+}{\pi }^{+}{\pi }^{-}$ , $D^{+}\to K_S^0{K}^{+more »}$ π + π − π 0 , and $D^{+}\to K_S^0{K}^{+}\omega$ , are measured for the first time to be $(0.54\pm 0.19\pm 0.02)\times {10}^{-4}$ , $(2.51\pm 0.34\pm 0.14)\times {10}^{-4}$ , and $(2.02\pm 0.35\pm 0.10)\times {10}^{-4}$ , respectively. Futhermore, the branching fractions of $D^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D^{+}\to K_S^0{K}^{+}\eta$ are measured with improved precision, yielding values of $(0.66\pm 0.11\pm 0.03)\times {10}^{-4}$ and $(2.27\pm 0.22\pm 0.05)\times {10}^{-4}$ , respectively. Published by the American Physical Society 2025« less

Using a dataset of $(27.12\pm 0.14)\times {10}^8\psi \left(3686\right)$ events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of the decay $\psi \left(3686\right)\to {\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0\omega$ with a statistical significance of $8.9\sigma$ . The measured branching fraction is $(1.24\pm 0.16_{\mathrm{stat}}\pm 0.11_{\mathrm{sys}})\times {10}^{more »}$ − 5 , where the first uncertainty is statistical and the second is systematic. Additionally, we investigate potential intermediate states in the invariant mass distributions of ${\mathrm{\Sigma }}^0\omega$ , ${\overline{\mathrm{\Sigma }}}^0\omega$ and ${\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0$ . A hint of a resonance is observed in the invariant mass distribution of $M_{{\mathrm{\Sigma }}^0\left({\overline{\mathrm{\Sigma }}}^0\right)\omega }$ , located around $2.06\mathrm{GeV}/c^2$ , with a significance of $2.5\sigma$ . Published by the American Physical Society 2025« less