arXiv subjects

K. L. He

Publications and source records attributed to K. L. He.

At least 37 records · Page 2Linked to original sources

arXiv2021

Determination of the $Λ_c^+$ spin via the reaction $e^+e^-\toΛ_c^+\barΛ_c^-$

We report on a comparison of two possible $Λ_c^+$ spin hypotheses, $J=\frac{1}{2}$ and $\frac{3}{2}$, via the process $e^+e^-\toΛ_c^+\barΛ_c^-$, using the angular distributions of $Λ_c^+$ decays into $pK_S^0$, $Λπ^+$, $Σ^0π^+$, and $Σ^+π^0$. The data were recorded at $\sqrt s = 4.6$ GeV with the BESIII detector and correspond to an integrated luminosity of 587 pb$^{-1}$. The $Λ_c^+$ spin is determined to be $J=\frac{1}{2}$, with this value favored over the $\frac{3}{2}$ hypothesis with a significance corresponding to more than 6 Gaussian standard deviations.

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arXiv2021

Amplitude analysis and branching-fraction measurement of \boldmath $D_{s}^{+} \to K^0_{S}π^{+}π^{0}$

Utilizing a data set corresponding to an integrated luminosity of 6.32~$\rm fb^{-1}$, recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we perform an amplitude analysis of the decay $D_{s}^{+} \to K_{S}^{0}π^{+}π^{0}$ and determine the relative fractions and phase differences of different intermediate processes, which include $K_{S}^{0}ρ(770)^{+}$, $K_{S}^{0}ρ(1450)^{+}$, $K^{*}(892)^{0}π^{+}$, $K^{*}(892)^{+}π^{0}$, and $K^{*}(1410)^{0}π^{+}$. Using a double-tag technique, and making an efficiency correction that relies on our knowledge of the phase-space distribution of the decays coming from the amplitude analysis, the absolute branching fraction is measured to be $\mathcal{B}(D_{s}^{+} \to K_{S}^{0}π^{+}π^{0})=(5.43\pm0.30_{\text{stat}}\pm 0.15_{\text{syst}})\times 10^{-3}$.

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arXiv2021

Study of $e^+e^- \to 2(p\bar{p})$ at center-of-mass energies between 4.0 and 4.6 GeV

Using data taken at 23 center-of-mass energies between 4.0 and 4.6 GeV with the BESIII detector at the BEPCII collider and with a total integrated luminosity of approximately $15$ fb$^{-1}$, the process $e^+e^-\to 2(p \bar{p})$ is studied for the first time. The Born cross sections for $e^+e^-\to 2(p \bar{p})$ are measured, and no significant structure is observed in the lineshape. The baryon pair ($pp$ and $\bar{p}\bar{p}$) invariant mass spectra are consistent with phase space, therefore no hexaquark or di-baryon state is found.

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arXiv2021

Search for the reaction channel $e^+e^- \rightarrow η_cηπ^+π^-$ at center-of-mass energies from 4.23 to 4.60 GeV

Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider, we search for the process $e^+e^-\rightarrow η_cηπ^+π^-$. The search is performed using five large data sets recorded at center-of-mass energies of 4.23, 4.26, 4.36, 4.42, and 4.60 GeV. The $η_c$ meson is reconstructed in 16 exclusive decay modes. No signal is observed in the $η_c$ mass region at any center-of-mass energy. The upper limits on the reaction cross sections are determined to be 6.2, 10.8, 27.6, 22.6 and 23.7 pb at the 90% confidence level at the center-of-mass energies listed above.

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arXiv2021

Observation of a near-threshold structure in the $K^+$ recoil-mass spectra in $e^+e^-\to K^+ (D_s^- D^{0} + D^{-}_s D^0)$

We report a study of the processes of $e^+e^-\to K^+ (D_s^- D^{*0} + D^{*-}_s D^0)$ based on $e^+e^-$ annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7 fb$^{-1}$. An excess over the known contributions of the conventional charmed mesons is observed near the $D_s^- D^{*0}$ and $D^{*-}_s D^0$ mass thresholds in the $K^{+}$ recoil-mass spectrum for events collected at $\sqrt{s}=4.681$ GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as $(3982.5^{+1.8}_{-2.6}\pm2.1)$ MeV/$c^2$ and $(12.8^{+5.3}_{-4.4}\pm3.0)$ MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 $σ$ over the contributions only from the conventional charmed mesons. This is the first candidate of the charged hidden-charm tetraquark with strangeness, decaying into $D_s^- D^{*0}$ and $D^{*-}_s D^0$. However, the properties of the excess need further exploration with more statistics.

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arXiv2021

Evidence for $Z_{c}^{\pm}$ decays into the $ρ^{\pm} η_{c}$ final state

We study $e^{+}e^{-}$ collisions with a $π^{+}π^{-}π^{0}η_{c}$ final state using data samples collected with the BESIII detector at center-of-mass energies $\sqrt{s}=4.226$, $4.258$, $4.358$, $4.416$, and $4.600$ GeV. Evidence for the decay $\zcpm\to\rhopm\etac$ is reported with a statistical significance of $3.9σ$ with various systematic uncertainties taken into account at $\sqrt{s} = 4.226$ GeV, and the Born cross section times branching fraction $σ^{B}(\EE\to \pimp\zcpm)\times \BR(\zcpm\to\rhopm\etac)$ is measured to be $(48 \pm 11 \pm 11)\,\rm{pb}$. The $\zcpm\to \rhopm\etac$ signal is not significant at the other center-of-mass energies and the corresponding upper limits are determined. In addition, no significant signal is observed in a search for $\zcppm\to ρ^{\pm}\etac$ with the same data samples. The ratios $R_{\zc}=\BR(\zcpm\to ρ^{\pm} \etac)/\BR(\zcpm\to π^{\pm} \jpsi)$ and $R_{\zcp}=\BR(\zcppm\to ρ^{\pm} \etac)/\BR(\zcppm\to π^{\pm} \hc)$ are obtained and used to discriminate between different theoretical interpretations of the $\zcpm$ and $\zcppm$.

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arXiv2021

Model independent determination of the spin of the $Ω^{-}$ and its polarization alignment in $ψ(3686)\rightarrowΩ^{-}\barΩ^{+}$

We present an analysis of the process $ψ(3686) \to Ω^- \barΩ^+$ ($Ω^-\to K^-Λ$, $\barΩ^+\to K^+\barΛ$, $Λ\to pπ^-$, $\barΛ\to \bar{p}π^+$) based on a data set of $448\times 10^6$ $ψ(3686)$ decays collected with the BESIII detector at the BEPCII electron-positron collider. The helicity amplitudes for the process $ψ(3686) \to Ω^- \barΩ^+$ and the decay parameters of the subsequent decay $Ω^-\to K^-Λ$ $(\barΩ^+\to K^+\barΛ)$ are measured for the first time by a fit to the angular distribution of the complete decay chain. The branching fraction of $ψ(3686) \to Ω^- \barΩ^+$ is measured to be $(5.82\pm 0.12\pm 0.24)\times 10^{-5}$, with an improved precision compared to previous measurements.

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arXiv2021

Cross section measurement of $e^+e^- \to p\bar{p}η$ and $e^+e^- \to p\bar{p}ω$ at center-of-mass energies between 3.773 GeV and 4.6 GeV

Based on $14.7~\textrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected with the BESIII detector at the BEPCII collider at 17 different center-of-mass energies between $3.7730~\textrm{GeV}$ and $4.5995~\textrm{GeV}$, Born cross sections of the two processes $e^+e^- \to p\bar{p}η$ and $e^+e^- \to p\bar{p}ω$ are measured for the first time. No indication of resonant production through a vector state $V$ is observed, and upper limits on the Born cross sections of $e^+e^- \to V \to p\bar{p}η$ and $e^+e^- \to V \to p\bar{p}ω$ at the $90\%$ confidence level are calculated for a large parameter space in resonance masses and widths. For the current world average parameters of the $ψ(4230)$ of $m=4.2187~\textrm{GeV}/c^{2}$ and $Γ=44~\textrm{MeV}$, we find upper limits on resonant production of the $p\bar{p}η$ and $p\bar{p}ω$ final states of $7.5~\textrm{pb}$ and $10.4~\textrm{pb}$ at the $90\%$ CL, respectively.

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arXiv2020

Observation of di-structures in $e^+e^-\rightarrow{J}/ψ{\rm X}$ at center-of-mass energies around 3.773 GeV

We report a measurement of the observed cross sections of the inclusive $J/ψ$ production in $e^+e^-\rightarrow {J}/ψ{\rm X}$ based on 3.21 fb$^{-1}$ of data accumulated at energies from 3.645 to 3.891 GeV with the BESIII detector operated at the BEPCII collider. The energy-dependent lineshape obtained from the measured cross sections cannot be well described by two Breit-Wigner (BW) amplitudes of the expected decays $ψ(3686)\rightarrow {J}/ψ{\rm X}$ and $ψ(3770)\rightarrow {J}/ψ{\rm X}$. Instead it can be better described with three BW amplitudes of the decays $ψ(3686)\rightarrow {J}/ψ{\rm X}$, $R(3760)\rightarrow {J}/ψ{\rm X}$ and $R(3790)\rightarrow {J}/ψ{\rm X}$ with two distinct structures referred to as $R(3760)$ and $R(3790)$. Under this assumption, we extracted their masses, total widths, and the product of the leptonic width and decay branching fractions to be $M_{R(3760)}= {3761.7\pm 2.2 \pm 1.2}$ MeV/$c^2$, $Γ^{\rm tot}_{R(3760)}= {6.7\pm 11.1 \pm 1.1}$ MeV, $Γ^{ee}_{R(3760)}\mathcal B[R(3760)\rightarrow {J}/ψ{\rm X}]=(4.0\pm 4.3\pm 1.2)$ eV, $M_{R(3790)} = {3784.7\pm 5.7 \pm 1.6}$ MeV/$c^2$, $Γ^{\rm tot}_{R(3790)} = {31.6 \pm 11.9 \pm 3.2}$ MeV, $Γ^{ee}_{R(3790)}\mathcal B[R(3790)\rightarrow {J}/ψ{\rm X}]=(18.1\pm 10.3\pm 4.7)$ eV, where the first uncertainties are statistical and second systematic.

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arXiv2020

Erratum to "Measurement of the $e^+e^-\toπ^+π^-$ cross section between 600 and 900 MeV using initial state radiation"

In Phys. Lett. B 753, 629-638 (2016) [arXiv:1507.08188] the BESIII collaboration published a cross section measurement of the process $e^+e^-\to π^+ π^-$ in the energy range between 600 and 900 MeV. In this erratum we report a corrected evaluation of the statistical errors in terms of a fully propagated covariance matrix. The correction also yields a reduced statistical uncertainty for the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, which now reads as $a_μ^{ππ\mathrm{, LO}}(600 - 900\,\mathrm{MeV}) = (368.2 \pm 1.5_{\rm stat} \pm 3.3_{\rm syst})\times 10^{-10}$. The central values of the cross section measurement and of $a_μ^{ππ\mathrm{, LO}}$, as well as the systematic uncertainties remain unchanged.

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arXiv2020

Observation of a resonant structure in $e^{+}e^{-} \to ωη$ and another in $e^{+}e^{-} \to ωπ^{0}$ at center-of-mass energies between 2.00 and 3.08 GeV

Born cross sections for the processes $e^+e^- \to ωη$ and $e^+e^- \to ωπ^{0}$ have been determined for center-of-mass energies between 2.00 and 3.08 GeV with the BESIII detector at the BEPCII collider. The results obtained in this work are consistent with previous measurements but with improved precision. Two resonant structures are observed. In the $e^{+}e^{-} \to ωη$ cross sections, a resonance with a mass of $(2179 \pm 21 \pm 3)\text{MeV}/c^2$ and a width of $(89 \pm 28 \pm 5)\text{MeV}$ is observed with a significance of 6.1$σ$. Its properties are consistent with the $ϕ(2170)$. In the $e^{+}e^{-} \toωπ^{0}$ cross sections, a resonance denoted $Y(2040)$ is observed with a significance of more than 10$σ$. Its mass and width are determined to be $(2034 \pm 13 \pm 9)\text{MeV}/c^2$ and $(234 \pm 30 \pm 25)\text{MeV}$, respectively, where the first uncertainties are statistical and the second ones are systematic.

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arXiv2020

Study of BESIII Trigger Efficiencies with the 2018 $J/ψ$ Data

Using a dedicated data sample taken in 2018 on the $J/ψ$ peak, we perform a detailed study of the trigger efficiencies of the BESIII detector. The efficiencies are determined from three representative physics processes, namely Bhabha-scattering, dimuon production and generic hadronic events with charged particles. The combined efficiency of all active triggers approaches $100\%$ in most cases with uncertainties small enough as not to affect most physics analyses.

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arXiv2020

Precise Measurements of Branching Fractions for $D_s^+$ Meson Decays to Two Pseudoscalar Mesons

We measure the branching fractions for seven $D_{s}^{+}$ two-body decays to pseudo-scalar mesons, by analyzing data collected at $\sqrt{s}=4.178\sim4.226$ GeV with the BESIII detector at the BEPCII collider. The branching fractions are determined to be $\mathcal{B}(D_s^+\to K^+η^{\prime})=(2.68\pm0.17\pm0.17\pm0.08)\times10^{-3}$, $\mathcal{B}(D_s^+\toη^{\prime}π^+)=(37.8\pm0.4\pm2.1\pm1.2)\times10^{-3}$, $\mathcal{B}(D_s^+\to K^+η)=(1.62\pm0.10\pm0.03\pm0.05)\times10^{-3}$, $\mathcal{B}(D_s^+\toηπ^+)=(17.41\pm0.18\pm0.27\pm0.54)\times10^{-3}$, $\mathcal{B}(D_s^+\to K^+K_S^0)=(15.02\pm0.10\pm0.27\pm0.47)\times10^{-3}$, $\mathcal{B}(D_s^+\to K_S^0π^+)=(1.109\pm0.034\pm0.023\pm0.035)\times10^{-3}$, $\mathcal{B}(D_s^+\to K^+π^0)=(0.748\pm0.049\pm0.018\pm0.023)\times10^{-3}$, where the first uncertainties are statistical, the second are systematic, and the third are from external input branching fraction of the normalization mode $D_s^+\to K^+K^-π^+$. Precision of our measurements is significantly improved compared with that of the current world average values.

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arXiv2020

Observation of a structure in $e^+e^- \to ϕη^{\prime}$ at $\sqrt{s}$ from 2.05 to 3.08 GeV

The process $e^{+}e^{-} \to ϕη^{\prime}$ has been studied for the first time in detail using data sample collected with the BESIII detector at the BEPCII collider at center of mass energies from 2.05 to 3.08 GeV. A resonance with quantum numbers $J^{PC}=1^{--}$ is observed with mass $M$ = (2177.5 $\pm$ 4.8 (stat) $\pm$ 19.5 (syst)) MeV/${ \it{c}^{\mathrm{2}}}$ and width $Γ$ = (149.0 $\pm$ 15.6 (stat) $\pm$ 8.9 (syst)) MeV with a statistical significance larger than 10$σ$. The observed structure could be identified with the $ϕ(2170)$, then the ratio of partial width between the $ϕη^{\prime}$ by BESIII and $ϕη$ by BABAR is ($\mathcal{B}^{R}_{ϕη}Γ^{R}_{ee})/{(\mathcal{B}^{R}_{ϕη^{\prime}}Γ^{R}_{ee})}$ = 0.23 $\pm$ 0.10 (stat) $\pm$ 0.18 (syst), which is smaller than the prediction of the $s\bar{s}g$ hybrid models by several orders of magnitude.

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arXiv2020

Study of open-charm decays and radiative transitions of the X(3872)

The processes $X(3872)\to D^{*0}\bar{D^{0}}+c.c.,~γJ/ψ,~γψ(2S),$ and $γD^{+}D^{-}$ are searched for in a $9.0~\rm fb^{-1}$ data sample collected at center-of-mass energies between $4.178$ and $4.278$ GeV with the BESIII detector. We observe $X(3872)\to D^{*0}\bar{D^{0}}+c.c.$ and find evidence for $X(3872)\toγJ/ψ$ with statistical significances of $7.4σ$ and $3.5σ$, respectively. No evident signals for $X(3872)\toγψ(2S)$ and $γD^{+}D^{-}$ are found, and upper limit on the relative branching ratio $R_{γψ} \equiv\frac{\mathcal{B}(X(3872)\toγψ(2S))}{\mathcal{B}(X(3872)\toγJ/ψ)}<0.59$ is set at 90$\%$ confidence level. Measurements of branching ratios relative to decay $X(3872)\toπ^+π^- J/ψ$ are also reported for decays $X(3872)\to D^{*0}\bar{D^{0}}+c.c., ~γψ(2S),~γJ/ψ$, $γD^{+}D^{-}$, as well as the non-$D^{*0}\bar{D}^{0}$ three-body decays $π^0 D^{0}\bar{D}^{0}$ and $γD^{0}\bar{D}^{0}$.

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arXiv2020

Search for the decay $J/ψ\toγ+ \rm {invisible}$

We search for $J/ψ$ radiative decays into a weakly interacting neutral particle, namely an invisible particle, using the $J/ψ$ produced through the process $ψ(3686)\toπ^+π^-J/ψ$ in a data sample of $(448.1\pm2.9)\times 10^6$ $ψ(3686)$ decays collected by the BESIII detector at BEPCII. No significant signal is observed. Using a modified frequentist method, upper limits on the branching fractions are set under different assumptions of invisible particle masses up to 1.2 $\mathrm{\ Ge\kern -0.1em V}/c^2$. The upper limit corresponding to an invisible particle with zero mass is 7.0$\times 10^{-7}$ at the 90\% confidence level.

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arXiv2020

Measurement of the Born Cross Sections for $e^+e^-\to D_s^+ D_{s1}(2460)^- +c.c.$ and $e^+e^-\to D_s^{\ast +} D_{s1}(2460)^- +c.c.$

The processes $e^+e^-\to D_s^+ D_{s1}(2460)^- +c.c.$ and $e^+e^-\to D_s^{\ast +} D_{s1}(2460)^- +c.c.$ are studied for the first time using data samples collected with the BESIII detector at the BEPCII collider. The Born cross sections of $e^+e^-\to D_s^+ D_{s1}(2460)^- +c.c.$ at nine center-of-mass energies between 4.467\,GeV and 4.600\,GeV and those of $e^+e^-\to D_s^{\ast +} D_{s1}(2460)^- +c.c.$ at ${\sqrt s}=$ 4.590\,GeV and 4.600\,GeV are measured. No obvious charmonium or charmonium-like structure is seen in the measured cross sections.

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arXiv2020

First Measurements of $χ_{cJ}\rightarrow Σ^{-} \barΣ^{+} (J = 0, 1, 2)$ Decays

We measured the branching fractions of the decays $χ_{cJ}\toΣ^{-}\barΣ^{+}$ for the first time using the final states $n\bar{n}π^{+}π^{-}$. The data sample exploited here is $448.1\times10^{6}$ $ψ(3686)$ events collected with BESIII. We find $\mathcal{B}(χ_{cJ}\rightarrowΣ^{-}\barΣ^{+}) = (51.3\pm2.4\pm4.1)\times10^{-5},\, (5.7\pm1.4\pm0.6)\times10^{-5},\, \rm{and}~ (4.4\pm1.7\pm0.5)\times10^{-5}$, for $J=0,1,2$, respectively, where the first uncertainties are statistical and the second systematic.

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