3,275 Search Results

Using $\left(2712\pm 14\right)\times {10}^6$ $\psi \left(2S\right)$ events collected with the BESIII detector at the BEPCII collider, we search for the decays ${\eta }_c\left(2S\right)\to \omega \omega$ and ${\eta }_c\left(2S\right)\to \omega \varphi$ via the process $\psi \left(2S\right)\to \gamma {\eta }_c\left(2S\right)$ . No statistically significant signals are observed. Themore » upper limits of their product branching fractions at the 90% confidence level are determined to be $\mathcal{B}\left(\psi \right(2S)\to \gamma {\eta }_c(2S),{\eta }_c(2S)\to \omega \omega )<1.04\times {10}^{-6}$ and $\mathcal{B}\left(\psi \right(2S)\to \gamma {\eta }_c(2S),{\eta }_c(2S)\to \omega \varphi )<1.85\times {10}^{-7}$ , respectively. We also update the branching fractions of ${\chi }_{cJ}\to \omega \omega$ and ${\chi }_{cJ}\to \omega \varphi$ via the $\psi \left(2S\right)\to \gamma {\chi }_{cJ}$ transition. Their branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to \omega \omega )=(10.66\pm 0.11\pm 0.57)\times {10}^{-4}$ , $\mathcal{B}({\chi }_{c1}\to \omega \omega )=(6.43\pm 0.07\pm 0.31)\times {10}^{-4}$ , $\mathcal{B}({\chi }_{c2}\to \omega \omega )=(8.75\pm 0.08\pm 0.42)\times {10}^{-4}$ , $\mathcal{B}({\chi }_{c0}\to \omega \varphi )=(1.18\pm 0.03\pm 0.07)\times {10}^{-4}$ , $\mathcal{B}({\chi }_{c1}\to \omega \varphi )=(2.04\pm 0.15\pm 0.11)\times {10}^{-5}$ , and $\mathcal{B}({\chi }_{c2}\to \omega \varphi )=(9.58\pm 1.07\pm 0.76)\times {10}^{-6}$ , where the first uncertainties are statistical and the second are systematic. Published by the American Physical Society 2025« less

Utilizing a dataset of $6.7{\mathrm{fb}}^{-1}$ from electron-positron collisions recorded by the BESIII detector at the BEPCII storage ring, a search is conducted for the processes $e^{+}{e}^{-}\to \varphi {\chi }_{c0}$ and $\varphi {\eta }_{c2}\left(1D\right)$ across center-of-mass energies from 4.47 to 4.95 GeV. In the absence of any significant signals,more » upper limits are set. These include limits on the dressed cross sections for $e^{+}{e}^{-}\to \varphi {\chi }_{c0}$ , as well as the product of the dressed cross section for $e^{+}{e}^{-}\to \varphi {\eta }_{c2}\left(1D\right)$ and a sum of five branching fractions. Furthermore, the product of the electronic width of $Y\left(4660\right)$ and the branching fraction of the $Y\left(4660\right)\to \varphi {\chi }_{c0}$ , denoted as ${\mathrm{\Gamma }}_{e^{+}{e}^{-}}^{Y\left(4660\right)}{\mathcal{B}}_{Y\left(4660\right)\to \varphi {\chi }_{c0}}$ , is determined to be $<0.35\mathrm{eV}$ at the 90% confidence level. Published by the American Physical Society 2025« less

Studies are performed of the Cabibbo-favored decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{K}^{+}$ and the singly Cabibbo-suppressed decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ , based on a sample of $e^{+}{more »}^{}$ e − collision data, corresponding to an integrated luminosity of $4.5{\mathrm{fb}}^{-1}$ , accumulated at center-of-mass energies between 4599.53 MeV and 4698.82 MeV with the BESIII detector. The decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ is observed for the first time. The branching fractions of ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{K}^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ are measured to be $(3.04\pm 0.30\pm 0.16)\times {10}^{-3}$ and $(1.73\pm 0.27\pm 0.10)\times {10}^{-3}$ , respectively, where the first uncertainties are statistical and the second are systematic. These results correspond to the most precise measurement of these quantities for both decays. Evidence of a $K^{*+}$ contribution in the ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ decay is found with a statistical significance of $4.71\sigma$ . The branching fraction of ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}^{*+}$ is calculated under three possible interference scenarios, with the significance increasing to $5.03\sigma$ when interference is taken into account. Published by the American Physical Society 2025« less

Using $7.9\mathrm{f}{\mathrm{b}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at $\sqrt{s}=3.773\mathrm{GeV}$ with the BESIII detector at the BEPCII collider, we search for the massless dark photon with the flavor-changing neutral current processes $D^0\to \omega {\gamma }^{\prime }$ and $D^0\to \gamma {\gamma }^{\prime }$ for the first time. No significant signals are observed, and the upper limitsmore » at the 90% confidence level on the massless dark photon branching fraction are set to be $1.1\times {10}^{-5}$ and $2.0\times {10}^{-6}$ for $D^0\to \omega {\gamma }^{\prime }$ and $D^0\to \gamma {\gamma }^{\prime }$ , respectively. These results provide the most stringent constraint on the new physics energy scale associated with $cu{\gamma }^{\prime }$ coupling in the world, with the new physics energy scale related parameter $|\mathbb{C}{|}^2+|{\mathbb{C}}_5{|}^2<8.2\times {10}^{-17}{\mathrm{GeV}}^{-2}$ at the 90% confidence level. Published by the American Physical Society 2025« less

Using $(27.12\pm 0.14)\times {10}^8$ $\psi \left(2S\right)$ events collected by the BESIII detector operating at BEPCII, we search for the decay ${\eta }_c\left(2S\right)\to p\overline{p}$ via the process $\psi \left(2S\right)\to \gamma {\eta }_c\left(2S\right)$ and only find a signal with a significance of $1.7\sigma$ . The upper limit of the product branching fractionmore » at the 90% confidence level is determined to be $\mathcal{B}\left(\psi \right(2S)\to \gamma {\eta }_c(2S\left)\right)\times \mathcal{B}\left({\eta }_c\right(2S)\to p\overline{p})<2.4\times {10}^{-7}$ . The branching fractions of ${\chi }_{cJ}\to p\overline{p}(J=0,1,2)$ are also measured to be $\mathcal{B}({\chi }_{c0}\to p\overline{p})=(2.51\pm 0.02\pm 0.08)\times {10}^{-4}$ , $\mathcal{B}({\chi }_{c1}\to p\overline{p})=(8.16\pm 0.09\pm 0.25)\times {10}^{-4}$ , and $\mathcal{B}({\chi }_{c2}\to p\overline{p})=(8.33\pm 0.09\pm 0.22)\times {10}^{-4}$ , where the first uncertainty is statistical and the second systematic. Published by the American Physical Society 2025« less

We report the properties of precision time structures of cosmic nuclei He, Li, Be, B, C, N, and O fluxes over an 11-year solar cycle from May 2011 to November 2022 in the rigidity range from 1.92 to 60.3 GV. The nuclei fluxes show similar but not identical time variations with amplitudes decreasing with increasing rigidity. In particular, below 3.64 GV the Li, Be, and B fluxes, and below 2.15 GV the C, N, and O fluxes, are significantly less affected by solar modulation than the He flux. We observe that these differences in solar modulation are linearly correlated with the differences inmore » the spectral indices of the cosmic nuclei fluxes. This shows, in a model-independent way, that solar modulation of galactic cosmic nuclei depends on their spectral shape. In addition, solar modulation differences due to nuclei velocity dependence on the mass-to-charge ratio ( $A/Z$ ) are not observed. Published by the American Physical Society 2025« less

We present results over an 11-year Solar cycle of cosmic antiprotons based on $1.1\times {10}^6$ events in the rigidity range from 1.00 to 41.9 GV. The $\overline{p}$ fluxes exhibit distinct properties. The magnitude of the $\overline{p}$ flux temporal variation is significantly smaller than those of $p$ , $e^{-}$ , and $e^{+}$ . A hysteresis between the $\overline{p}$ fluxes and the $p$ fluxes is observed, whereas themore » $\overline{p}$ and $e^{-}$ fluxes show a linear correlation. With a model-independent analysis, we found a universal relation between the shape of the rigidity spectrum and the magnitude of flux temporal variation over an 11-year Solar cycle for both positively and negatively charged particles. The simultaneous results on $\overline{p}$ and $p$ , $e^{-}$ , and $e^{+}$ provide unique information for understanding particle transport in the Solar System as a function of mass, charge, and spectral shape. Published by the American Physical Society 2025« less

We perform the first amplitude analysis of $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0$ decays based on data samples of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of $7.33{\mathrm{fb}}^{-1}$ . We report the observation of $more »$ D s + → f 0 ( 980 ) ρ ( 770 ) + with a statistical significance greater than $10\sigma$ and determine the branching fractions $\mathcal{B}(D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0{|}_{\mathrm{non}-\eta })=(2.04\pm 0.08_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}})\%$ and $\mathcal{B}(D_s^{+}\to \eta {\pi }^{+})=(1.56\pm 0.09_{\mathrm{stat}}\pm 0.04_{\mathrm{syst}})\%$ . Moreover, we measure the relative branching fraction between $\varphi \to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\varphi \to K^{+}{K}^{-}$ to be $\left[\mathcal{B}\right(\varphi \left(1020\right)\to {\pi }^{+}{\pi }^{-}{\pi }^0)/\mathcal{B}(\varphi \left(1020\right)\to K^{+}{K}^{-}\left)\right]=0.230\pm 0.014_{\mathrm{stat}}\pm 0.010_{\mathrm{syst}}$ ., which deviates from the world average value by more than $4\sigma$ . Published by the American Physical Society 2025« less

The Forward Silicon Tracker (FST) is a pivotal component of the forward upgrade of the Solenoidal Tracker at RHIC (STAR), designed to discern hadron charge signs with a momentum resolution better than 30% for 0.2 < p_T < 2 GeV/c in the 2.5 < η < 4 pseudorapidity range. Its compact design features three disks along the beam direction, minimized material budget, and scattering effects. The FST uses Hamamatsu’s p-in-n silicon strip sensors with a double metal layer that enables efficient signal routing to the readout electronics, enhancing overall detector performance. The flexible hybrid boards, essential for the readout system,more » are constructed with Kapton and copper layers to optimize signal handling and power distribution. These boards connect silicon strips to analogue pipeline ASIC APV25-S1 chips, which read up to 128 channels each. A cooling system with nonconducting, volatile NOVEC 7200 coolant at 22.2°C mitigates ASIC-generated heat. In conclusion, the FST enhances forward tracking performance at STAR as an integral part of the forward upgrade.« less

We present a study of the semileptonic decay $D^0\to {\pi }^{-}{\pi }^0{e}^{+}{\nu }_e$ using an $e^{+}{e}^{-}$ annihilation data sample of $7.93{\mathrm{fb}}^{-1}$ collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The branching fraction of $D^0\to \rho (770{)}^{-}{e}^{+}{\nu }_e$ is measured to bemore » $(1.439\pm 0.033(\mathrm{stat})\pm 0.027(\mathrm{syst}\left)\right)\times {10}^{-3}$ , which is a factor 1.6 more precise than previous measurements. By performing an amplitude analysis, we measure the hadronic form-factor ratios of $D^0\to \rho (770{)}^{-}{e}^{+}{\nu }_e$ at $q^2=0$ assuming the single-pole-dominance parametrization: $r_V=V\left(0\right)/A_1\left(0\right)=1.548\pm 0.079\left(\mathrm{stat}\right)\pm 0.041\left(\mathrm{syst}\right)$ and $r_2=A_2\left(0\right)/A_1\left(0\right)=0.823\pm 0.056\left(\mathrm{stat}\right)\pm 0.026\left(\mathrm{syst}\right)$ . Published by the American Physical Society 2024« less