arXiv subjects

S. Gu

Publications and source records attributed to S. Gu.

At least 127 records · Page 7Linked to original sources

arXiv2018

Amplitude analysis of the $K_{S}K_{S}$ system produced in radiative $J/ψ$ decays

An amplitude analysis of the $K_{S}K_{S}$ system produced in radiative $J/ψ$ decays is performed using the $(1310.6\pm7.0)\times10^{6}$ $J/ψ$ decays collected by the BESIII detector. Two approaches are presented. A mass-dependent analysis is performed by parameterizing the $K_{S}K_{S}$ invariant mass spectrum as a sum of Breit-Wigner line shapes. Additionally, a mass-independent analysis is performed to extract a piecewise function that describes the dynamics of the $K_{S}K_{S}$ system while making minimal assumptions about the properties and number of poles in the amplitude. The dominant amplitudes in the mass-dependent analysis include the $f_{0}(1710)$, $f_{0}(2200)$, and $f_{2}^\prime(1525)$. The mass-independent results, which are made available as input for further studies, are consistent with those of the mass-dependent analysis and are useful for a systematic study of hadronic interactions. The branching fraction of radiative $J/ψ$ decays to $K_{S}K_{S}$ is measured to be $(8.1 \pm 0.4) \times 10^{-4}$, where the uncertainty is systematic and the statistical uncertainty is negligible.

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arXiv2018

Observation of $a^{0}_{0}(980)$-$f_{0}(980)$ Mixing

We report the first observation of $a^{0}_{0}(980)$-$f_{0}(980)$ mixing in the decays of $J/ψ\toϕf_{0}(980)\toϕa^{0}_{0}(980)\toϕηπ^{0}$ and $χ_{c1}\to a^{0}_{0}(980)π^{0}\to f_{0}(980)π^{0}\toπ^{+}π^{-}π^{0}$, using data samples of $1.31\times10^{9}$ $J/ψ$ events and $4.48\times10^{8}$ $ψ(3686)$ events accumulated with the BESIII detector. The signals of $f_{0}(980)\to a^{0}_{0}(980)$ and $a^{0}_{0}(980)\to f_{0}(980)$ mixing are observed at levels of statistical significance of $7.4σ$ and $5.5σ$, respectively. The corresponding branching fractions and mixing intensities are measured and the constraint regions on the coupling constants, $g_{a_{0}K^{+}K^{-}}$ and $g_{f_{0}K^{+}K^{-}}$, are estimated. The results improve the understanding of the nature of $a^{0}_{0}(980)$ and $f_{0}(980)$.

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arXiv2018

Study of the decays $D^+\rightarrowη^{(\prime)} e^+ν_{e}$

The charm semileptonic decays $D^+\toηe^+ν_{e}$ and $D^+\toη'e^+ν_{e}$ are studied with a sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at $\sqrt{s}$ = 3.773 GeV with the BESIII detector. We measure the branching fractions for $D^+\toηe^+ν_{e}$ to be $(10.74\pm0.81\pm0.51)\times10^{-4}$, and for $D^+\toη'e^+ν_{e}$ to be $(1.91\pm0.51\pm0.13)\times10^{-4}$, where the uncertainties are statistical and systematic, respectively. In addition, we perform a measurement of the form factor in the decay $D^+\toηe^+ν_{e}$. All the results are consistent with those obtained by the CLEO-c experiment.

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arXiv2018

Measurement of absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to Λ+ X$

Based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567$\,\rm{pb}^{-1}$ taken at the center-of-mass energy of $\sqrt{s} = 4.6$ GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to Λ+ X$ to be $\mathcal{B}(Λ_{c}^{+} \to Λ+ X)=(38.2^{+2.8}_{-2.2}\pm0.8)\%$ using the double-tag method, where $X$ refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain $\mathcal{A}_{CP} \equiv \frac{\mathcal{B}(Λ_{c}^{+} \to Λ+ X)-\mathcal{B}(\barΛ_{c}^{-} \to \barΛ + X)}{\mathcal{B}(Λ_{c}^{+} \to Λ+ X)+\mathcal{B}(\barΛ_{c}^{-} \to \barΛ + X)} = (2.1^{+7.0}_{-6.6}\pm1.4)\%$, a statistically limited result with no evidence of CP violation.

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arXiv2018

Search for Baryon and Lepton Number Violation in $J/ψ\toΛ_c^+e^-+c.c.$

Using $1.31\times10^9$ $J/ψ$ events collected by the BESIII detector at the Beijing Electron Positron Collider, we search for the process $J/ψ\toΛ_c^+e^-+c.c.$ for the first time. In this process, both baryon and lepton number conservation is violated. No signal is found and the upper limit on the branching fraction $\mathcal{B}(J/ψ\toΛ_c^+e^-+c.c.)$ is set to be $6.9\times10^{-8}$ at the 90\% Confidence Level.

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arXiv2018

Observation of the Semileptonic Decay $D^0 \to a_0(980)^- e^+ ν_e$ and Evidence for $D^+ \to a_0(980)^0 e^+ ν_e$

Using an $e^+e^-$ collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of $D^0 \to a_0(980)^- e^+ ν_e$ and evidence for $D^+ \to a_0(980)^0 e^+ ν_e~$ with significances of $6.4σ$ and $2.9σ$, respectively. The absolute branching fractions are determined to be $\mathcal{B}(D^0 \to a_0(980)^- e^+ ν_e)\times\mathcal{B}(a_0(980)^- \to ηπ^-) = (1.33_{-0.29}^{+0.33}({\rm stat})\pm0.09({\rm syst}))\times10^{-4}~$ and $\mathcal{B}(D^+ \to a_0(980)^0 e^+ ν_e)\times\mathcal{B}(a_0(980)^0 \to ηπ^0) = (1.66_{-0.66}^{+0.81}({\rm stat})\pm0.11({\rm syst}))\times10^{-4}~$. An upper limit of $\mathcal{B}(D^+ \to a_0(980)^0 e^+ ν_e)\times\mathcal{B}(a_0(980)^0 \to ηπ^0)<3.0\times10^{-4}~$ is also determined at the $90\%~$ confidence level.

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arXiv2018

Measurements of the Branching Fractions of the Singly-Cabibbo-Suppressed Decays $D^0\toωη$, $η^{(\prime)}π^0$ and $η^{(\prime)}η$

By analyzing a data sample of 2.93 fb$^{-1}$ collected at $\sqrt s=$ 3.773 GeV with the BESIII detector operated at the BEPCII storage rings, we measure the branching fractions ${\mathcal B}(D^0\toωη)=(2.15\pm0.17_{\rm stat.}\pm0.15_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toηπ^0)=(0.58\pm0.05_{\rm stat.}\pm0.05_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toη^\primeπ^0)=(0.93\pm0.11_{\rm stat.}\pm0.09_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toηη)=(2.20\pm0.07_{\rm stat.}\pm0.06_{\rm sys.})\times 10^{-3}$ and ${\mathcal B}(D^0\toη^\primeη)=(0.94\pm0.25_{\rm stat.}\pm0.11_{\rm sys.})\times 10^{-3}$. We note that ${\mathcal B}(D^0\to ωη)$ is measured for the first time and that ${\mathcal B}(D^0\to ηη)$ is measured with much improved precision.

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arXiv2018

Study of two-photon decays of pseudoscalar mesons via $J/ψ$ radiative decays

Using a sample of $4.48\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons $π^0$, $η$, $η^\prime$, $η(1405)$, $η(1475)$, $η(1760)$, and $X(1835)$ in $J/ψ$ radiative decays using $ψ(3686)\toπ^{+}π^{-}J/ψ$ events. The $π^0$, $η$ and $η^\prime$ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be $B(J/ψ\toγπ^{0}\to3γ)=(3.57\pm0.12\pm0.16)\times10^{-5}$, $B(J/ψ\toγη\to3γ)=(4.42\pm0.04\pm0.18)\times10^{-4}$, and $B(J/ψ\toγη'\to3γ)=(1.26\pm0.02\pm0.05)\times10^{-4}$, where the first errors are statistical and the second systematic. No clear signal for $η(1405)$, $η(1475)$, $η(1760)$ or $X(1835)$ is observed in the two-photon mass spectra, and upper limits at the $90\%$ confidence level on the product branching fractions are obtained.

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arXiv2018

Observation of $e^{+}e^{-} \rightarrow K\bar{K}J/ψ$ at center-of-mass energies from 4.189 to 4.600 GeV

We investigate the process $e^{+}e^{-} \rightarrow K\bar{K}J/ψ$ at center-of-mass energies from 4.189 to 4.600 GeV using 4.7 fb$^{-1}$ of data collected by the BESIII detector at the BEPCII collider. The Born cross sections for the reactions $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ and $K_{S}^{0} K_{S}^{0} J/ψ$ are measured as a function of center-of-mass energy. The energy dependence of the cross section for $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ is shown to differ from that for $π^{+}π^{-}J/ψ$ in the region around the $Y(4260)$. In addition, there is evidence for a structure around 4.5 GeV in the $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ cross section that is not present in $π^{+}π^{-}J/ψ$.

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arXiv2018

Measurement of the matrix elements for the decays $η^{\prime}\rightarrowηπ^+π^-$ and $η^{\prime}\rightarrowηπ^0π^0$

Based on a sample of $1.31\times10^9$ $J/ψ$ events collected with the BESIII detector, the matrix elements for the decays $η^{\prime}\toηπ^{+}π^{-}$ and $η^{\prime}\toηπ^{0}π^{0}$ are determined using 351,016 $η^{\prime}\to(η\toγγ)π^+π^-$ and 56,249 $η^{\prime}\to(η\toγγ)π^0π^0$ events with background levels less than 1\%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between $η^{\prime}\toηπ^{+}π^{-}$ and $η^{\prime}\toηπ^{0}π^{0}$ is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in $η^{\prime}\toηπ^{0}π^{0}$ is observed.

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arXiv2018

Study of $η(1475)$ and $X(1835)$ in radiative $J/ψ$ decays to $γϕ$

The decay $J/ψ\rightarrow γγϕ$ is studied using a sample of $1.31 \times10^{9}$ $J/ψ$ events collected with the BESIII detector. Two structures around 1475 MeV/c$^2$ and 1835 MeV/c$^2$ are observed in the $γϕ$ invariant mass spectrum for the first time. With a fit on the $γϕ$ invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/c$^2$ is found to favor an assignment as the $η(1475)$ and the mass and width for the structure around 1835 MeV/c$^2$ are consistent with the $X(1835)$. The statistical significances of the two structures are $13.5 σ$ and $6.3 σ$, respectively. The results indicate that both $η(1475)$ and $X(1835)$ contain a sizeable $s\bar{s}$ component.

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arXiv2018

Search for $ψ(3686)\to γη_c(η(1405))\to γπ^{+}π^{-}π^{0}$

Using a sample of $448.1\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector, a search for the isospin violating decay $η_{c}\toπ^{+}π^{-}π^{0}$ via $ψ(3686)\toγη_{c}$ is presented. No signal is observed, and the upper limit on $\mathcal{B}(ψ(3686)\to γη_{c}\to γπ^{+}π^{-}π^{0} )$ is determined to be $1.6\times10^{-6}$ at the $90\%$ confidence level. In addition, a search for $η(1405)\to f_{0}(980)π^{0}$ in $ψ(3686)$ radiative decays is performed. No signal is observed, and the branching fraction $\mathcal{B}(ψ(3686)\toγη(1405)\to γf_{0}(980)π^{0}\toγπ^+π^-π^0 )$ is calculated to be less than $ 5.0\times10^{-7}$ at the $90\%$ confidence level.

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arXiv2017

Observation of $χ_{c2}\toη'η'$ and $χ_{c0,2}\toηη'$

Using a sample of $447.9\times 10^6$ $ψ(3686)$ events collected with the BESIII detector in 2009 and 2012, we study the decays $χ_{c0,2}\to$ $η'η'$ and $ηη'$. The decays $χ_{c2}\toη'η'$, $χ_{c0}\toηη'$ and $χ_{c2}\toηη'$ are observed for the first time with statistical significances of $9.6σ$, $13.4σ$ and $7.5σ$, respectively. The branching fractions are determined to be $\mathcal{B}(χ_{c0}\toη'η') =(2.19\pm0.03\pm0.14)\times10^{-3}$, $\mathcal{B}(χ_{c2}\toη'η') = (4.76\pm0.56\pm0.38)\times10^{-5}$, $\mathcal{B}(χ_{c0}\toηη') = (8.92\pm0.84\pm0.65)\times10^{-5}$ and $\mathcal{B}(χ_{c2}\toηη') = (2.27\pm0.43\pm0.25)\times10^{-5}$, where the first uncertainties are statistical and the second systematic. The precision for the measurement of $\mathcal{B}(χ_{c0}\toη'η')$ is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for $χ_{c0,2}$ decays into pseudoscalar meson pairs can be clarified.

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arXiv2017

Branching fraction measurement of $J/ψ\rightarrow K_S K_L$ and search for $J/ψ\rightarrow K_S K_S$

Using a sample of $1.31 \times 10^{9}$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/ψ\rightarrow K_S K_L$ and $K_S K_S$. The branching fraction of$J/ψ\rightarrow K_S K_L$ is determined to be ${\cal B}(J/ψ\rightarrow K_S K_L)=(1.93\pm0.01~(\rm{stat.})\pm0.05~(\rm{syst.}))\times10^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/ψ\rightarrow K_S K_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be ${\cal B}(J/ψ\rightarrow K_S K_S)<1.4\times10^{-8}$, which improves on the previous searches by two orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

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arXiv2017

Measurement of the absolute branching fraction of $D_{s0}^{*\pm}(2317)\to π^0 D_{s}^{\pm}$

The process $e^+ e^- \to D_{s}^{*+} D_{s0}^{*-}(2317)+c.c.$ is observed for the first time with the data sample of 567~pb$^{-1}$ collected with the BESIII detector operating at the BEPCII collider at a center-of-mass energy $\sqrt{s} = 4.6$~GeV. The statistical significance of the $D_{s0}^{*-}(2317)$ signal is $5.8σ$ and the mass is measured to be ($2318.3\pm 1.2\pm 1.2$)~MeV/$c^{2}$. The absolute branching fraction $\mathcal{B}(D_{s0}^{*-}(2317)\to π^0 D_{s}^{-})$ is measured as $1.00^{+0.00}_{-0.14}\pm 0.14$ for the first time. The uncertainties are statistical and systematic, respectively.

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arXiv2017

Measurement of $e^{+}e^{-} \to π^{0}π^{0}ψ(3686)$ at $\sqrt{s}$ from 4.009 to 4.600 GeV and observation of a neutral charmoniumlike structure

Using $e^{+}e^{-}$ collision data collected with the BESIII detector at the BEPCII collider corresponding to an integrated luminosity of 5.2 $fb^{-1}$ at center-of-mass energies ($\sqrt{s}$) from 4.009 to 4.600 GeV, the process $e^{+}e^{-} \to π^{0} π^{0}ψ(3686)$ is studied for the first time. The corresponding Born cross sections are measured and found to be half of those of the reaction $e^{+}e^{-} \to π^{+}π^{-}ψ(3686)$. This is consistent with the expectation from isospin symmetry. Furthermore, the Dalitz plots for $π^{0}π^{0}ψ(3686)$ are accordant with those of $π^{+}π^{-}ψ(3686)$ at all energy points, and a neutral analogue to the structure in $π^\pm ψ(3686)$ around 4040 MeV/$c^{2}$ first observed at $\sqrt{s}$=4.416 GeV is observed in the isospin neutral mode at the same energy.

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arXiv2017

Search for the rare decays $J/ψ\to D^{0} e^{+}e^{-} +c.c.$ and $ψ(3686) \to D^{0} e^{+}e^{-} +c.c.$

Using the data samples of $(1310.6\pm7.2 )\times 10^{6}$ $J/ψ$ events and $(448.1\pm2.9)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector, we search for the rare decays $J/ψ\to D^{0} e^{+}e^{-} +c.c.$ and $ψ(3686) \to D^{0} e^{+}e^{-} +c.c.$. No significant signals are observed and the corresponding upper limits on the branching fractions at the $90\%$ confidence level are determined to be $Br(J/ψ\to D^{0} e^{+}e^{-} +c.c.)< 8.5\times 10^{-8}$ and $Br (ψ(3686) \to D^{0} e^{+}e^{-} +c.c.)<1.4\times 10^{-7}$, respectively. Our limit on $Br(J/ψ\to D^{0} e^{+}e^{-} +c.c.)$ is more stringent by two orders of magnitude than the previous results, and the $Br(ψ(3686) \to D^{0} e^{+}e^{-} +c.c.)$ is measured for the first time.

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arXiv2017

Improved measurements of two-photon widths of the $χ_{cJ}$ states and helicity analysis for $χ_{c2}\toγγ$

Based on $448.1 \times 10^6$ $ψ(3686)$ events collected with the BESIII detector, the decays $ψ(3686)\toγχ_{cJ}, χ_{cJ} \to γγ~(J=0, 1, 2)$ are studied. The decay branching fractions of $χ_{c0,c2} \to γγ$ are measured to be $\mathcal{B}(χ_{c0}\toγγ) = (1.93 \pm 0.08 \pm 0.05 \pm 0.05)\times 10^{-4}$ and $\mathcal{B}(χ_{c2}\toγγ) = (3.10 \pm 0.09 \pm 0.07 \pm 0.11)\times 10^{-4} $, which correspond to two-photon decay widths of $Γ_{γγ}(χ_{c0}) = 2.03 \pm 0.08 \pm 0.06 \pm 0.13 ~\rm{keV}$ and $Γ_{γγ}(χ_{c2}) = 0.60 \pm 0.02 \pm 0.01 \pm 0.04 ~\rm{keV}$ with a ratio of $\mathcal{R}=Γ_{γγ}(χ_{c2})/Γ_{γγ}(χ_{c0})= 0.295 \pm 0.014 \pm 0.007 \pm 0.027$, where the uncertainties are statistical, systematic and associated with the uncertainties of $\mathcal{B}(ψ(3686)\toγχ_{c0,c2})$ and the total widths $Γ(χ_{c0,c2})$, respectively. For the forbidden decay of $χ_{c1}\toγγ$, no signal is observed, and an upper limit on the two-photon width is obtained to be $Γ_{γγ}(χ_{c1})<5.3 ~\rm{eV}$ at the 90\% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay $χ_{c2}\toγγ$ is also measured to be $f_{0/2} = Γ^{λ=0}_{γγ}(χ_{c2})/Γ^{λ=2}_{γγ}(χ_{c2}) = (0.0 \pm 0.6 \pm 1.2)\times 10^{-2}$, where the uncertainties are statistical and systematic, respectively.

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