2,225 Search Results

Superconducting microwave resonators are critical to quantum computing and sensing technologies. Additionally, they are common proxies for superconducting qubits when determining the effects of performance-limiting loss mechanisms such as from two-level systems (TLS). The extraction of these loss mechanisms is often performed by measuring the internal quality factor $$Q_i$$ as a function of power or temperature. In this work, we investigate large temporal fluctuations of $$Q_i$$ at low powers over periods of 12 to 16 hours (relative standard deviation $$\sigma_{Qi}/Q_i = 13\%$$). These fluctuations are ubiquitous across multiple resonators, chips and cooldowns. We are able to attribute these fluctuations to variations in the TLS loss tangent due to two main indicators. First, measured fluctuations decrease as power and temperature increase. Second, for interleaved measurements, we observe correlations between low- and medium-power $$Q_i$$ fluctuations and an absence of correlations with high-power fluctuations. Agreement with the TLS loss tangent mean is obtained by performing measurements over a time span of a few hours. We hypothesize that, in addition to decoherence due to coupling to individual near-resonant TLS, superconducting qubits are affected by these observed TLS loss tangent fluctuations.

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 the $\overline{p}$ 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

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 in 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

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. The 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

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, 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

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 $e^{+}{e}^{-}$ 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

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 limits 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

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 fraction 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

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 $D_s^{+}\to f_0\left(980\right)\rho (770{)}^{+}$ 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

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 be $(1.439\pm 0.033(\mathrm{stat})\pm 0.027(\mathrm{syst}\left)\right)\times {10}^{-3}$ , 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