arXiv subjects

J. L. Fu

Publications and source records attributed to J. L. Fu.

At least 235 records · Page 13Linked to original sources

arXiv2023

Determination of the $C\!P$-even fraction of $D^0\rightarrow K_S^0π^+π^-π^0$

Quantum-correlated $D\bar{D}$ pairs collected by the BESIII experiment at the $ψ(3770)$ resonance, corresponding to an integrated luminosity of 2.93 fb$^{-1}$, are used to study the $D^0 \rightarrow K^{0}_Sπ^{+} π^{-} π^{0}$ decay mode. The $C\!P$-even fraction of $D^0 \rightarrow K^{0}_Sπ^{+} π^{-} π^{0}$ decays is determined to be $0.235\pm 0.010\pm 0.002$, where the first uncertainty is statistical and the second is systematic.

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arXiv2023

Test of $C\!P$ Symmetry in Hyperon to Neutron Decays

The quantum entangled $J/ψ\to Σ^{+}\barΣ^{-}$ pairs from $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events taken by the BESIII detector are used to study the non-leptonic two-body weak decays $Σ^{+} \to n π^{+}$ and $\barΣ^{-} \to \bar{n} π^{-}$. The $C\!P$-odd weak decay parameters of the decays $Σ^{+} \to n π^{+}$ ($α_{+}$) and $\barΣ^{-} \to \bar{n} π^{-}$ ($\barα_{-}$) are determined to be $-0.0565\pm0.0047_{\rm stat}\pm0.0022_{\rm syst}$ and $0.0481\pm0.0031_{\rm stat}\pm0.0019_{\rm syst}$, respectively. The decay parameter $\barα_{-}$ is measured for the first time, and the accuracy of $α_{+}$ is improved by a factor of four compared to the previous results. The simultaneously determined decay parameters allow the first precision $C\!P$ symmetry test for any hyperon decay with a neutron in the final state with the measurement of $A_{C\!P}=(α_{+}+\barα_{-})/(α_{+}-\barα_{-})=-0.080\pm0.052_{\rm stat}\pm0.028_{\rm syst}$. Assuming $C\!P$ conservation, the average decay parameter is determined as $\left< α_{+}\right>=(α_{+}- \barα_{-})/2 = -0.0506\pm0.0026_{\rm stat}\pm0.0019_{\rm syst}$, while the ratios $α_{+}/α_{0}$ and $\barα_{-}/\barα_{0}$ are $-0.0490\pm0.0032_{\rm stat}\pm0.0021_{\rm syst}$ and $-0.0571\pm0.0053_{\rm stat}\pm0.0032_{\rm syst}$, where $α_{0}$ and $\barα_{0}$ are the decay parameters of the decays $Σ^{+} \to p π^{0}$ and $\barΣ^{-} \to \bar{p} π^{0}$, respectively.

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arXiv2023

First Experimental Study of the Purely Leptonic Decay $D_s^{*+}\to e^+ν_e$

Using $7.33~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data taken with the BESIII detector at the BEPCII collider, we report the first experimental study of the purely leptonic decay $D_s^{*+}\to e^+ν_e$. A signal for the decay $D_s^{*+}\to e^+ν_e$ is observed with a statistical significance of $2.9σ$. The branching fraction of ${D_s^{*+}\to e^+ν_e}$ is measured to be $(2.1{^{+1.2}_{-0.9}}_{\rm stat.}\pm0.2_{\rm syst.})\times 10^{-5}$, corresponding to an upper limit of $4.0\times10^{-5}$ at the 90\% confidence level. Taking the total width of the $D_s^{*+}$~(($0.070\pm0.028$) keV) predicted by lattice quantum chromodynamics as input, the decay constant of the $D^{*+}_s$ is determined to be $f_{D_s^{*+}}=(213.6{^{+61.0}_{-45.8}}_{\rm stat.}\pm43.9_{\rm syst.})$ MeV, corresponding to an upper limit of 353.8 MeV at the 90\% confidence level.

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arXiv2023

Cross section measurements of $e^+e^- \to ΦK^+ K^-$ and $e^+ e^- \to ΦK_S^0 K_S^0$ at center-of-mass energies between 3.7730 GeV and 4.7008 GeV

Based on 22.7 fb$^{-1}$ of $e^+e^-$ annihilation data collected at 33 different center-of-mass energies between 3.7730 GeV and 4.7008 GeV with the BESIII detector at the BEPCII collider, Born cross sections of the two processes $e^+e^-\to ϕK^+ K^-$ and $e^+ e^- \to ϕK_{S}^{0} K_{S}^{0}$ are measured for the first time. No indication of resonant production through an intermediate vector state $V$ is observed, and the upper limits on the product of the electronic width $Γ_{e^+e^-}$ and the branching fraction $Br(V\rightarrow ϕK \bar{K})$ of the processes $e^+e^- \to V \to ϕK^+ K^-$ and $e^+e^- \to V \to ϕK_S^0K_S^0$ at the $90\%$ confidence level are obtained for a large parameter space in resonance masses and widths. For the current world average mass and width of the $ψ(4230)$ of $m=4.2187$ GeV$/c^2$ and $Γ=44$ MeV, we set upper limits on the $ϕK^+ K^-$ and $ϕK_S^0K_S^0$ final states of 1.75 eV and 0.47 eV at the $90\%$ confidence level, respectively.

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arXiv2023

Measurement of the $e^{+}e^{-}\rightarrowΛ\barΛ$ cross section from threshold to 3.00 GeV using events with initial-state radiation

Using initial-state radiation events from a total integrated luminosity of 11.957 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at BEPCII, the cross section for the process $e^{+}e^{-}\rightarrowΛ\barΛ$ is measured in 16 $Λ\barΛ$ invariant mass intervals from the production threshold up to 3.00 GeV$/c^{2}$. The results are consistent with previous results from BaBar and BESIII, but with better precision and with narrower $Λ\barΛ$ invariant mass intervals than BaBar.

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arXiv2022

Determination of U-spin breaking parameters with an amplitude analysis of the decay $D^0 \to K_{\rm L}^0π^+π^-$

We present a study of the resonant structure of the decay $D^0 \to K_{\rm L}^0π^+π^-$, using quantum-correlated $D^0\bar{D}^0$ data produced at $\sqrt{s}=3.773$ GeV. The data sample was collected by the BESIII experiment and corresponds to an integrated luminosity of $2.93$ fb$^{-1}$. This study is the first amplitude analysis of a decay mode involving a $K_{\rm L}^0$, which also results in the first measurement of the complex $\textit{U-spin breaking parameters}$ ($\hatρ$) related to various $\mathit{CP}$-eigenstate resonant modes through which the three-body decay proceeds. The moduli of the $\hatρ$ parameters have central values in a wide range from $0.4$ to $12.1$, which indicates substantial U-spin symmetry breaking. We present the fractional resonant contributions and average strong-phase parameters over regions of phase space for both $K_{\rm S}^0π^+π^-$ and $K_{\rm L}^0π^+π^-$ modes. We also report the ratio of the branching fractions between $K_{\rm L}^0π^+π^-$ and $K_{\rm S}^0π^+π^-$ decay modes and the $\mathit{CP}$-even fraction of the $K_{\rm L}^0π^+π^-$ state calculated using the U-spin breaking parameters.

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arXiv2015

Study of $ψ(3686)\toπ^0 h_c, h_c\toγη_c$ via $η_c$ exclusive decays

The process $ψ(3686) \to π^0 h_c, h_c \to γη_c$ has been studied with a data sample of $106 \pm 4$ million $ψ(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The mass and width of the $P$-wave charmonium spin-singlet state $h_c(^1P_1)$ are determined by simultaneously fitting distributions of the $π^0$ recoil mass for 16 exclusive $η_c$ decay modes. The results, $M(\hc) = 3525.31 \pm 0.11 {\rm (stat.)} \pm 0.14 {\rm (syst.)}$\,MeV/$c^2$ and $Γ(\hc) = 0.70 \pm 0.28 \pm 0.22$\,MeV, are consistent with and more precise than previous measurements. We also determine the branching ratios for the 16 exclusive $η_c$ decay modes, five of which have not been measured previously. New measurements of the $η_c$ line-shape parameters in the $E1$ transition $h_c\toγη_c$ are made by selecting candidates in the $h_c$ signal sample and simultaneously fitting the hadronic mass spectra for the 16 $η_c$ decay channels. The resulting $η_c$ mass and width values are $M(η_c) = 2984.49 \pm 1.16 \pm 0.52$\,MeV/$c^2$ and $Γ(η_c) = 36.4 \pm 3.2 \pm 1.7$\,MeV.

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arXiv2015

Search for the $η_c(2S)/h_c\to p\bar{p}$ decays and measurements of the $χ_{cJ}\to p\bar{p}$ branching fractions

Using a sample of $1.06\times10^{8}~ψ(3686)$ events collected with the BESIII detector at BEPCII, the decays $η_{c}(2S)\to p\bar{p}$ and $h_{c}\to p\bar{p}$ are searched for, where $η_c(2S)$ and $h_c$ are reconstructed in the decay chains $ψ(3686)\toγη_{c}(2S)$, $η_{c}(2S)\to p\bar{p}$ and $ψ(3686)\toπ^{0}h_{c}$, $h_{c}\to p\bar{p}$, respectively. No significant signals are observed. The upper limits of the product branching fractions are determined to be $\mathcal{B}(ψ(3686)\toγη_c(2S))\times\mathcal{B}(η_{c}(2S)\to p\bar{p})<1.4\times10^{-6}$ and $\mathcal{B}(ψ(3686)\toπ^0h_c)\times\mathcal{B}(h_{c}\to p\bar{p})<1.3\times10^{-7}$ at the 90% C.L.. The branching fractions for $χ_{cJ}\to p\bar{p}$ $(J=0,~1,~2)$ are also measured to be $(24.5\pm0.8\pm1.3,~8.6\pm0.5\pm0.5,~8.4\pm0.5\pm0.5)\times10^{-5}$, which are the world's most precise measurements.

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arXiv2014

Observation of $χ_{c1}$ decays into vector meson pairs $ϕϕ$, $ωω$, and $ωϕ$

Decays of $χ_{c1}$ to vector meson pairs $ϕϕ$, $ωω$ and $ωϕ$ are observed for the first time using $(106\pm4)\times 10^6$ $\psip$ events accumulated at the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times 10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times 10^{-5}$, for $χ_{c1}\to ϕϕ$, $ωω$, and $ωϕ$, respectively. The observation of $χ_{c1}$ decays into a pair of vector mesons $ϕϕ$, $ωω$ and $ωϕ$ indicates that the hadron helicity selection rule is significantly violated in $χ_{cJ}$ decays. In addition, the measurement of $χ_{cJ}\to ωϕ$ gives the rate of doubly OZI-suppressed decay. Branching fractions for $χ_{c0}$ and $χ_{c2}$ decays into other vector meson pairs are also measured with improved precision.

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arXiv2014

Precision measurements of $B(D^+ \rightarrow μ^+ ν_μ)$, the pseudoscalar decay constant $f_{D^+}$, and the quark mixing matrix element $|V_{\rm cd}|$

We report a measurement of the branching fraction $B(D^+ \rightarrow μ^+ ν_μ) = [3.71 \pm 0.19 (\rm stat) \pm 0.06 (\rm sys)]\times 10^{-4}$ based on 2.92 ${\rm fb^{-1}}$ of data accumulated at $\sqrt{s}=3.773$ GeV with the BESIII detector at the BEPCII collider. This measurement, in conjunction with the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\rm cd}|$ determined from a global Standard Model fit, implies a value for the weak decay constant $f_{D^+}=(203.2 \pm 5.3 \pm 1.8)$ MeV. Additionally, using this branching fraction measurement together with a Lattice QCD prediction for $f_{D^+}$, we find $|V_{\rm cd}|=0.2210\pm 0.0058 \pm 0.0047$. In either case, these are the most precise results for these quantities to date.

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arXiv2014

Observation of Electromagnetic Dalitz decays J/ψ\to P e^+e^-

Based on a sample of (225.3\pm2.8)\times 10^{6} J/ψevents collected with the BESIII detector, the electromagnetic Dalitz decays of J/ψ\to P e^+e^-(P=η'/η/π^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/ψ\to η' e^+e^-, J/ψ\to ηe^+e^- and J/ψ\to π^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/ψ\to η' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/ψ\to ηe^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/ψ\to π^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic.

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arXiv2014

Observation of a charged charmoniumlike structure in $e^+e^- \to (D^{} \bar{D}^{})^{\pm} π^\mp$ at $\sqrt{s}=4.26$GeV

We study the process $e^+e^- \to (D^{*} \bar{D}^{*})^{\pm} π^\mp$ at a center-of-mass energy of 4.26GeV using a 827pb$^{-1}$ data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be $(137\pm9\pm15)$pb. We observe a structure near the $(D^{*} \bar{D}^{*})^{\pm}$ threshold in the $π^\mp$ recoil mass spectrum, which we denote as the $Z^{\pm}_c(4025)$. The measured mass and width of the structure are $(4026.3\pm2.6\pm3.7)$MeV/c$^2$ and $(24.8\pm5.6\pm7.7)$MeV, respectively. Its production ratio $\frac{σ(e^+e^-\to Z^{\pm}_c(4025)π^\mp \to (D^{*} \bar{D}^{*})^{\pm} π^\mp)}{σ(e^+e^-\to (D^{*} \bar{D}^{*})^{\pm} π^\mp)}$ is determined to be $0.65\pm0.09\pm0.06$. The first uncertainties are statistical and the second are systematic.

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arXiv2014

Observation of $e^{+} e^{-} \to γX(3872)$ at BESIII

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process $e^{+} e^{-} \to γX(3872)$ is observed for the first time with a statistical significance of $6.3σ$. The measured mass of the $X(3872)$ is ($3871.9\pm 0.7_{\rm stat.}\pm 0.2_{\rm sys.}$) MeV/$c^2$, in agreement with previous measurements. Measurements of the product of the cross section $σ[e^{+} e^{-} \to γX(3872)]$ and the branching fraction $\mathcal{B}[X(3872) \to π^{+} π^{-} J/ψ]$ at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process $Y(4260) \to γX(3872)$.

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arXiv2013

Observation of a charged charmoniumlike structure Z_c(4020) and search for the Z_c(3900) in e+e- to pi+pi-h_c

We study e+e- --> pi+pi-h_c at center-of-mass energies from 3.90 GeV to 4.42 GeV using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies, and are found to be of the same order of magnitude as those of e+e- --> pi+pi-J/psi but with a different line shape. In the π^\pm h_c mass spectrum, a distinct structure, referred to as Z_c(4020), is observed at 4.02 GeV/c^2. The Z_c(4020) carries an electric charge and couples to charmonium. A fit to the π^\pm h_c invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9\pm 0.8\pm 2.7) MeV/c^2 and a width of (7.9\pm 2.7\pm 2.6) MeV for the Z_c(4020), where the first errors are statistical and the second systematic. No significant Z_c(3900) signal is observed, and upper limits on the Z_c(3900) production cross sections in π^\pm h_c at center-of-mass energies of 4.23 and 4.26 GeV are set.

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arXiv2013

Observation of a structure at 1.84 GeV/c$^2$ in the $3(π^+π^-)$ mass spectrum in $J/ψ\rightarrow γ3(π^+π^-)$ decays

With a sample of 225.3 million $J/ψ$ events taken with the BESIII detector, the decay $J/ψ\rightarrow γ3(π^+π^-)$ is analyzed. A structure at 1.84 GeV/c$^2$ is observed in the $3(π^+π^-)$ invariant mass spectrum with a statistical significance of 7.6$σ$ . The mass and width are measured to be $M=1842.2\pm 4.2^{+7.1}_{-2.6}$ MeV/c$^2$ and $Γ=83\pm 14 \pm 11$ MeV. The product branching fraction is determined to be $B(J/ψ\rightarrowγX(1840))\times B(X(1840)\rightarrow 3(π^+π^-))=(2.44\pm0.36^{+0.60}_{-0.74})\times 10^{-5}$. No $η^\prime$ signals are observed in the $3(π^+π^-)$ invariant mass spectrum, and the upper limit of the branching fraction for the decay $η^\prime\rightarrow 3(π^+π^-)$ is set to be $3.1\times10^{-5}$ at a 90% confidence level.

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arXiv2013

Observation of the decay $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{\pm}π^{\mp}+c.c.$

Using a sample of $1.06\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector, we present the first observation of the decays of $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{+}π^{-}+c.c.$ and $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{-}π^{+}+c.c.$. The branching fractions are measured to be $\mathcal{B}(ψ(3686) \rightarrow Λ\barΣ^{+}π^{-} + c.c.)=(1.40\pm 0.03 \pm 0.13)\times10^{-4}$ and $\mathcal{B}(ψ(3686) \rightarrow Λ\barΣ^{-}π^{+}+c.c.)=(1.54\pm 0.04 \pm 0.13)\times10^{-4}$, where the first errors are statistical and the second ones systematic.

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arXiv2013

Precision Measurements of ${\cal B}[ψ(3686) \to π^+π^- J/ψ]$ and ${\cal B}[J/ψ\to l^+l^-]$

Based on $(106.41 \pm 0.86)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, the branching fractions of $ψ(3686) \to π^+π^- J/ψ$, $J/ψ\to e^+e^- $, and $J/ψ\to μ^+μ^-$ are measured. We obtain ${\cal B}[ψ(3686) \to π^+π^-J/ψ]=(34.98\pm 0.02\pm 0.45)%$, ${\cal B}[J/ψ\to e^+e^-] = (5.983 \pm 0.007 \pm 0.037)%$ and ${\cal B}[J/ψ\to μ^+μ^-] = (5.973 \pm 0.007 \pm 0.038)%$. The measurement of ${\cal B}[ψ(3686) \to π^{+}π^{-}J/ψ]$ confirms the CLEO-c measurement, and is apparently larger than the others. The measured $J/ψ$ leptonic decay branching fractions agree with previous experiments within one standard deviation. These results lead to ${\cal B}[J/ψ\to l^+l^-] = (5.978 \pm 0.005 \pm 0.040)%$ by averaging over the $e^{+}e^{-}$ and $μ^{+}μ^{-}$ channels and a ratio of ${\cal B}[J/ψ\to e^+e^-] / {\cal B}[J/ψ\to μ^+μ^-] = 1.0017 \pm 0.0017 \pm 0.0033$, which tests $e$-$μ$ universality at the four tenths of a percent level. All the measurements presented in this paper are the most precise in the world to date.

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arXiv2013

Study of $J/ψ\rightarrow ωp \bar{p}$ at BESIII

The decay $J/ψ\rightarrow ωp \bar{p}$ has been studied, using $225.3\times 10^{6}$ $J/ψ$ events accumulated at BESIII. No significant enhancement near the $p\bar{p}$ invariant-mass threshold (denoted as $X(p\bar{p})$) is observed. The upper limit of the branching fraction $\mathcal{B}(J/ψ\rightarrow ωX(p\bar{p}) \rightarrow ωp \bar{p})$ is determined to be $3.9\times10^{-6}$ at the 95% confidence level. The branching fraction of $J/ψ\rightarrow ωp \bar{p}$ is measured to be $\mathcal{B}(J/ψ\rightarrow ωp \bar{p}) =(9.0 \pm 0.2\ (\text{stat.})\pm 0.9\ (\text{syst.})) \times 10^{-4}$.

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