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Register a new userMeasurement of cross section for $e^{+}e^{-}rightarrowXi^{0}bar{Xi}^{0}$ near threshold
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Using $e^+e^-$ collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb$^{-1}$, we measure the cross sections and effective form factors for the process $e^{+}e^{-}rightarrowXi^{0}bar{Xi}^{0}$ utilizing a single-tag method. A fit to the cross section of $e^{+}e^{-}rightarrowXi^{0}bar{Xi}^{0}$ with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes $e^{+}e^{-}rightarrowXi^{-}bar{Xi}^{+}$ and $Xi^{0}bar{Xi}^{0}$ is calculated using recent BESIII measurement and is found to be compatible with expectation from isospin symmetry.
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The Born cross-sections and effective form factors for process $e^+e^-toXi^-bar{Xi}^+$ are measured at eight center-of-mass energies between 2.644 and 3.080 GeV, using a total integrated luminosity of 363.9 pb$^{-1}$ $e^+e^-$ collision data collected with the BESIII detector at BEPCII. After performing a fit to the Born cross-section of $e^+e^-toXi^-bar{Xi}^+$, no significant threshold effect is observed.
Using a total of 11.0 fb$^{-1}$ of $e^{+}e^{-}$ collision data with center-of-mass energies between 4.009 GeV and 4.6 GeV and collected with the BESIII detector at BEPCII, we measure fifteen exclusive cross sections and effective form factors for the process $e^{+}e^{-}rightarrowXi^{-}barXi^{+}$ by means of a single baryon-tag method. After performing a fit to the dressed cross section of $e^{+}e^{-}rightarrowXi^{-}barXi^{+}$, no significant $psi(4230)$ or $psi(4260)$ resonance is observed in the $Xi^{-}barXi^{+}$ final states, and upper limits at the 90% confidence level on $Gamma_{ee}mathcal{B}$ for the processes $psi(4230)$/$psi(4260)rightarrowXi^{-}barXi^{+}$ are determined. In addition, an excited $Xi$ baryon at 1820 MeV/$c^{2}$ is observed with a statistical significance of 6.2 $sim$ 6.5$sigma$ by including the systematic uncertainty, and the mass and width are measured to be $M = (1825.5 pm 4.7 pm 4.7)$~MeV/$c^{2}$ and $Gamma = (17.0 pm 15.0 pm 7.9)$~MeV, which confirms the existence of the $J^{P}=frac{3}{2}^{-}$ state $Xi(1820)$.
The Born cross section of the $e^{+}e^{-}~rightarrow~Lambda_{c}^{+} bar{Lambda}_{c}^{-}$ process is measured with unprecedented precision using data collected with the BESIII detector at $sqrt{s}=4574.5$, $45580.0$, $4590.0$ and $4599.5$ $mathrm{MeV}$. The non-zero cross section near the $Lambda_{c}^{+} bar{Lambda}_{c}^{-}$ production threshold is discerned. At center-of-mass energies $sqrt{s}=4574.5$ and $4599.5 $ $mathrm{MeV}$, the higher statistics data enable us to measure the $Lambda_{c}$ polar angle distributions. From these, the ratio between the $Lambda_{c}$ electric and magnetic form factors ($|G_{E}/G_{M}|$) is measured for the first time. They are found to be $1.14pm0.14pm0.07$ and $1.23pm0.05pm0.03$ respectively, where the first uncertainties are statistical and the second are systematic.
Using $(10.087pm0.044)times10^{9}$ $J/psi$ events collected by the BESIII detector at the BEPCII collider, we search for the hyperon semileptonic decay $Xi^{-} rightarrow Xi^{0} e^{-} bar{ u}_{e}$. No significant signal is observed and the upper limit on the branching fraction $mathcal B(Xi^{-} rightarrow Xi^{0} e^{-} bar{ u}_{e})$ is set to be $2.59times10^{-4}$ at 90 % confidence level. This result is one order of magnitude more strict than the previous best limit.
The cross sections of the process $e^{+}e^{-} to K_{S}^{0}K_{L}^{0}$ are measured at fifteen center-of-mass energies $sqrt{s}$ from $2.00$ to $3.08~{rm GeV}$ with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results are found to be consistent with those obtained by BaBar. A resonant structure around $2.2~{rm GeV}$ is observed, with a mass and width of $2273.7 pm 5.7 pm 19.3~{rm MeV}/c^2$ and $86 pm 44 pm 51~{rm MeV}$, respectively, where the first uncertainties are statistical and the second ones are systematic. The product of its radiative width ($Gamma_{e^+e^-}$) with its branching fraction to $K_{S}^{0}K_{L}^{0}$ ($Br_{K_{S}^{0}K_{L}^{0}}$) is $0.9 pm 0.6 pm 0.7~{rm eV}$.
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