arXiv subjects

S. Gu

Publications and source records attributed to S. Gu.

134 records · Page 8Linked to original sources

arXiv2017

Study of $J/ψ$ and $ψ(3686)$ decays to $π^+π^-η^\prime$

Using the data samples of $1.31\times 10^9$ $J/ψ$ events and $4.48\times 10^8$ $ψ(3686)$ events collected with the BESIII detector, partial wave analyses on the decays $J/ψ$ and $ψ(3686) \to π^+π^-η^\prime$ are performed with a relativistic covariant tensor amplitude approach. The dominant contribution is found to be $J/ψ$ and $ψ(3686)$ decays to $ρη^\prime$. In the $J/ψ$ decay, the branching fraction ${\cal B}(J/ψ\to ρη^\prime)$ is determined to be $(7.90\pm0.19(\mathrm{stat})\pm0.49(\mathrm{sys}))\times 10^{-5}$. Two solutions are found in the $ψ(3686)$ decay, and the corresponding branching fraction ${\cal B}(ψ(3686)\to ρη^\prime)$ is $(1.02\pm0.11(\mathrm{stat})\pm0.24(\mathrm{sys}))\times 10^{-5}$ for the case of constructive interference, and $(5.69\pm1.28(\mathrm{stat})\pm2.36(\mathrm{sys}))\times 10^{-6}$ for destructive interference. As a consequence, the ratios of branching fractions between $ψ(3686)$ and $J/ψ$ decays to $ρη^\prime$ are calculated to be $(12.9\pm1.4(\mathrm{stat})\pm3.1(\mathrm{sys}))$\% and $(7.2\pm1.6(\mathrm{stat})\pm3.0(\mathrm{sys}))$\%, respectively. We also determine the inclusive branching fractions of $J/ψ$ and $ψ(3686)$ decays to $π^+π^-η^\prime$ to be $(1.36\pm0.02(\mathrm{stat})\pm0.08(\mathrm{sys}))\times 10^{-4}$ and $(1.51\pm0.14(\mathrm{stat})\pm 0.23(\mathrm{sys}))\times 10^{-5}$, respectively.

hep-ex↗

arXiv2017

Measurements of the branching fractions for the semi-leptonic decays $D^+_s\toϕe^{+}ν_{e}$, $ϕμ^{+}ν_μ$, $ημ^{+}ν_μ$ and $η'μ^{+}ν_μ$

By analyzing 482 pb$^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy $\sqrt s=4.009$ GeV with the BESIII detector, we measure the %absolute branching fractions for the semi-leptonic decays $D_{s}^{+}\to ϕe^{+}ν_{e}$, $ϕμ^{+}ν_μ$, $ημ^{+}ν_μ$ and $η'μ^{+}ν_μ$ to be ${\mathcal B}(D_{s}^{+}\toϕe^{+}ν_{e})=(2.26\pm0.45\pm0.09)$\%, ${\mathcal B}(D_{s}^{+}\toϕμ^{+}ν_μ)=(1.94\pm0.53\pm0.09)$\%, ${\mathcal B}(D_{s}^{+}\toημ^{+}ν_μ)=(2.42\pm0.46\pm0.11)$\% and ${\mathcal B}(D_{s}^{+}\toη'μ^{+} ν_μ) = (1.06\pm0.54\pm0.07)$\%, where the first and second uncertainties are statistical and systematic, respectively. The branching fractions for the three semi-muonic decays $D_s^+\toϕμ^+ν_μ, ημ^+ν_μ$ and $η' μ^+ν_μ$ are determined for the first time and that of $D^+_s\to ϕe^+ν_e$ is consistent with the world average value within uncertainties.

hep-ex↗

arXiv2017

Branching fraction measurements of $ψ(3686) \to γχ_{cJ}$

Using a sample of 106 million $ψ(3686)$ decays, the branching fractions of $ψ(3686) \to γχ_{c0}, ψ(3686) \to γχ_{c1}$, and $ψ(3686) \to γχ_{c2}$ are measured with improved precision to be $(9.389 \pm 0.014 \pm 0.332)\,\%$, $(9.905 \pm 0.011 \pm 0.353)\,\% $, and $(9.621 \pm 0.013 \pm 0.272)\,\% $, respectively, where the first uncertainties are statistical and the second ones are systematic. The product branching fractions of $ψ(3686) \to γχ_{c1}, χ_{c1} \to γJ/ψ$ and $ψ(3686) \to γχ_{c2}, χ_{c2} \to γJ/ψ$ and the branching fractions of $χ_{c1} \to γJ/ψ$ and $χ_{c2} \to γJ/ψ$ are also presented.

hep-ex↗

arXiv2017

Evidence for $e^{+}e^{-} \to γη_c(1S)$ at center-of-mass energies between 4.01 and 4.60 GeV

We present first evidence for the process $e^+e^-\to γη_c(1S)$ at six center-of-mass energies between 4.01 and 4.60~GeV using data collected by the BESIII experiment operating at BEPCII. These data sets correspond to a total integrated luminosity of 4.6~fb$^{-1}$. We measure the Born cross section at each energy using a combination of twelve $η_c(1S)$ decay channels. Because the significance of the signal is marginal at each energy ($\le3.0σ$), we also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the $Y(4260)$, we measure a peak Born cross section $σ_{\mathrm{ peak}}(e^+e^-\toγη_c(1S)) = 2.11 \pm 0.49 (\mathrm{stat.}) \pm 0.36 (\mathrm{syst.})$~pb with a statistical significance of 4.2$σ$.

hep-ex↗

arXiv2016

MiNDSTEp differential photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756: Microlensing and a new time delay

We present V and R photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012. Differential photometry has been carried out using the image subtraction method as implemented in the HOTPAnTS package, additionally using GALFIT for quasar photometry. The quasar WFI2033-4723 showed brightness variations of order 0.5 mag in V and R during the campaign. The two lensed components of quasar HE0047-1756 varied by 0.2-0.3 mag within five years. We provide, for the first time, an estimate of the time delay of component B with respect to A of $Δt= 7.6\pm1.8$ days for this object. We also find evidence for a secular evolution of the magnitude difference between components A and B in both filters, which we explain as due to a long-duration microlensing event. Finally we find that both quasars WFI2033-4723 and HE0047-1756 become bluer when brighter, which is consistent with previous studies.

astro-ph.GA↗

arXiv2016

Combination of two Gas Electron Multipliers and a Micromegas as gain elements for a time projection chamber

We measured the properties of a novel combination of two Gas Electron Multipliers with a Micromegas for use as amplification devices in high-rate gaseous time projection chambers. The goal of this design is to minimize the buildup of space charge in the drift volume of such detectors in order to eliminate the standard gating grid and its resultant dead time, while preserving good tracking and particle identification performance. We measured the positive ion back-flow and energy resolution at various element gains and electric fields, using a variety of gases, and additionally studied crosstalk effects and discharge rates. At a gain of 2000, this configuration achieves an ion back-flow below 0.4% and an energy resolution better than $σ/\text{E}=12\%$ for $^{55}$Fe X-rays.

physics.ins-det↗

arXiv2015

Electric-field Controlled Magnetization Switching in Co/Pt thin-Film Ferromagnets

A study of dynamic and reversible voltage controlled magnetization switching in ferromagnetic Co/Pt thin film with perpendicular magnetic anisotropy at room temperature is presented. The change in the magnetic properties of the system is observed in a relatively thick film of 15 nm. A surface charge is induced by the formation of electrochemical double layer between the metallic thin film and non-aqueous lithium LiClO4 electrolyte to manipulate the magnetism. The change in the magnetic properties occurred by the application of an external electric field. As the negative voltage was increased, the coercivity and the switching magnetic field decreased thus activating magnetization switching. The results are envisaged to lead to faster and ultra-low power magnetization switching as compared to spin-transfer torque (STT) switching in spintronic devices.

cond-mat.mtrl-sci↗

arXiv2005

Scalar interaction limits from the beta-neutrino correlation of trapped radioactive atoms

We have set limits on contributions of scalar interactions to nuclear beta decay. A magneto-optical trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the measurement of the beta-neutrino correlation, in a more direct fashion than previously possible. The beta-neutrino correlation parameter of the 0+ to 0+ pure Fermi decay of 38mK is $\tilde{a}$=0.9981+-0.0030+-0.0037, consistent with the standard model prediction a=1.

nucl-ex↗