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D. Becker

Publications and source records attributed to D. Becker.

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arXiv2022

Observation of the $J/ψ$ and $ψ(3686)$ decays into $ηΣ^{+}\barΣ^{-}$

The decays $J/ψ\toηΣ^{+}\barΣ{}^-$ and $ψ(3686)\toηΣ^{+}\barΣ{}^-$ are observed for the first time, using $(10087 \pm 44)\times 10^{6}$ $J/ψ$ and $(448.1 \pm 2.9)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. We determine the branching fractions of these two decays to be ${\cal B}(J/ψ\toηΣ^{+}\barΣ{}^-)=(6.34 \pm 0.21 \pm 0.37)\times 10^{-5}$ and ${\cal B}(ψ(3686)\toηΣ^{+}\barΣ{}^-)=(9.59 \pm 2.37 \pm 0.61)\times 10^{-6}$, where the first uncertainties are statistical and the second are systematic. The ratio of these two branching fractions is determined to be $\frac{{\cal B}(ψ(3686)\toηΣ^{+}\barΣ{}^-)}{{\cal B}(J/ψ\toηΣ^{+}\barΣ{}^-)}=(15.1 \pm 3.8)\%$, which is in agreement with the "12\% rule."

hep-ex↗
arXiv2022

Observations of the Cabibbo-Suppressed decays $Λ_{c}^{+}\to nπ^{+}π^{0}$, $nπ^{+}π^{-}π^{+}$ and the Cabibbo-Favored decay $Λ_{c}^{+}\to nK^{-}π^{+}π^{+}$

Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 $\rm{{fb}^{-1}}$, collected by the BESIII detector in the energy region between $4600$ MeV and $4699$ MeV, we report the first observations of the Cabibbo-suppressed decays $Λ_c^+\to nπ^+π^0$, $Λ_c^+\to nπ^+π^-π^+$, and the Cabibbo-favored decay $Λ_c^+\to nK^-π^+π^+$ with statistical significances of $7.9σ$, $7.8σ$, and $>10σ$, respectively. The branching fractions of these decays are measured to be $\mathcal{B}(Λ_{c}^{+}\rightarrow nπ^{+}π^{0})=(0.64\pm0.09\pm0.02)\%$, $\mathcal{B}(Λ_{c}^{+}\rightarrow nπ^{+}π^{-}π^{+})=(0.45\pm0.07\pm0.03)\%$, and $\mathcal{B}(Λ_{c}^{+}\rightarrow nK^{-}π^{+}π^{+})=(1.90\pm0.08\pm0.09)\%$, where the first uncertainties are statistical and the second are systematic. We find that the branching fraction of the decay $Λ_{c}^{+}\rightarrow nπ^{+}π^{0}$ is about one order of magnitude higher than that of $Λ_{c}^{+}\rightarrow nπ^{+}$.

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arXiv2022

Search for the weak radiative decay $Λ_{c}^+\to Σ^+γ$ at BESIII

The Cabibbo-allowed weak radiative decay $Λ_{c}^+\to Σ^+γ$ has been searched for in a sample of $Λ_{c}^+\barΛ_{c}^-$ pairs produced in $e^+e^-$ annihilations, corresponding to an integrated luminosity of $4.5 \mathrm{fb}^{-1}$ collected with the BESIII detector at center-of-mass energies between 4.60 and 4.70 GeV. No excess of signal above background is observed, and we set an upper limit on the branching fraction of this decay to be ${\mathcal B}(Λ_{c}^+\to Σ^+γ)<4.4\times10^{-4}$ at a confidence level of 90\%, which is in agreement with Standard Model expectations.

hep-ex↗
arXiv2022

Measurement of the Branching Fraction of the Singly Cabibbo-Suppressed Decay $Λ_{c}^{+}\toΛK^{+}$

We report a branching fraction measurement of the singly Cabibbo-suppressed decay $Λ_{c}^{+}\toΛK^{+}$ using a data sample collected with the BESIII detector at the BEPCII storage ring. The data span center-of-mass energies from 4.599 to 4.950 GeV and correspond to an integrated luminosity of 6.44 fb$^{-1}$. The branching fraction of $Λ_{c}^{+}\toΛK^{+}$ relative to that of the Cabibbo-favored decay $Λ_{c}^{+}\toΛπ^{+}$ is measured to be $\mathcal{R}=\frac{\mathcal{B}(Λ_{c}^{+}\toΛK^{+})}{\mathcal{B}(Λ_{c}^{+}\toΛπ^{+})}=(4.78\pm0.34\pm0.20)\%$. Combining with the world-average value of $\mathcal{B}(Λ_{c}^{+}\toΛπ^{+})$, we obtain $\mathcal{B}(Λ_c^+\toΛK^+)=(6.21\pm0.44\pm0.26\pm0.34)\times 10^{-4}$. Here the first uncertainties are statistical, the second systematic, and the third comes from the uncertainty of the $Λ_{c}^{+}\toΛπ^{+}$ branching fraction. This result, which is more precise than previous measurements, does not agree with theoretical predictions, and suggests that non-factorizable contributions have been under-estimated in current models.

hep-ex↗
arXiv2022

Partial wave analysis of the charmed baryon hadronic decay $Λ_c^+\toΛπ^+π^0$

Based on $e^+e^-$ collision samples corresponding to an integrated luminosity of 4.4 $\mbox{fb$^{-1}$}$ collected with the BESIII detector at center-of-mass energies between $4.6\,\,\mathrm{GeV}$ and $4.7\,\,\mathrm{GeV}$, a partial wave analysis of the charmed baryon hadronic decay $Λ_c^+\toΛπ^+π^0$ is performed, and the decays $Λ_c^+\toΛρ(770)^{+}$ and $Λ_c^+\toΣ(1385)π$ are studied for the first time. Making use of the world-average branching fraction $\mathcal{B}(Λ_c^+\toΛπ^+π^0)$, their branching fractions are determined to be \begin{eqnarray*} \begin{aligned} \mathcal{B}(Λ_c^+\toΛρ(770)^+)=&(4.06\pm0.30\pm0.35\pm0.23)\times10^{-2},\\ \mathcal{B}(Λ_c^+\toΣ(1385)^+π^0)=&(5.86\pm0.49\pm0.52\pm0.35)\times10^{-3},\\ \mathcal{B}(Λ_c^+\toΣ(1385)^0π^+)=&(6.47\pm0.59\pm0.66\pm0.38)\times10^{-3},\\ \end{aligned} \end{eqnarray*} where the first uncertainties are statistical, the second are systematic, and the third are from the uncertainties of the branching fractions $\mathcal{B}(Λ_c^+\toΛπ^+π^0)$ and $\mathcal{B}(Σ(1385)\toΛπ)$. In addition, %according to amplitudes determined from the partial wave analysis, the decay asymmetry parameters are measured to be $α_{Λρ(770)^+}=-0.763\pm0.053\pm0.045$, $α_{Σ(1385)^{+}π^0}=-0.917\pm0.069\pm0.056$, and $α_{Σ(1385)^{0}π^+}=-0.789\pm0.098\pm0.056$.

hep-ex↗
arXiv2022

First Direct Measurement of the Absolute Branching Fraction of $Σ^+ \to Λe^+ ν_{e}$

The first direct measurement of the absolute branching fraction of $Σ^+ \to Λe^+ ν_{e}$ is reported based on an $e^+e^-$ annihilation sample of $(10087\pm44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at $\sqrt{s}=3.097$ GeV. The branching fraction is determined to be ${\mathcal B}(Σ^+ \to Λe^+ ν_{e}) = [2.93\pm0.74(\rm stat) \pm 0.13(\rm syst)]\times 10^{-5}$, which is the most precise measurement obtained in a single experiment to date and also the first result obtained at a collider experiment. Combining this result with the world average of ${\mathcal B}(Σ^- \to Λe^- \barν_{e})$ and the lifetimes of $Σ^{\pm}$, the ratio, $\frac{Γ(Σ^- \to Λe^- \barν_{e})}{Γ(Σ^+ \to Λe^+ ν_{e})}$, is determined to be $1.06 \pm 0.28$, which is within 1.8 standard deviations of the value expected in the absence of second-class currents that are forbidden in the Standard Model.

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arXiv2022

Study of the Semileptonic Decay $Λ_c^+\rightarrow Λe^+ν_e$

The measurement of the Cabibbo-favored semileptonic decay $Λ_c^+\rightarrow Λe^+ν_e$ is reported using a $4.5~\mathrm{fb}^{-1}$ data sample of $e^+e^-$ annihilations collected at center-of-mass energies ranging from 4.600~GeV to 4.699~GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be $\mathcal{B}(Λ_c^+\rightarrow Λe^+ν_e)=(3.56\pm0.11_{\rm stat.}\pm0.07_{\rm syst.})\%$, which is the most precise measurement to date. Furthermore, we perform an investigation of the internal dynamics in $Λ_c^+\rightarrow Λe^+ν_e$. We provide the first direct comparisons of the differential decay rate and form factors with those predicted from lattice quantum chromodynamics (LQCD) calculations. Combining the measured branching fraction with a $q^2$-integrated rate predicted by LQCD, we determine $|V_{cs}|=0.936\pm0.017_{\mathcal{B}}\pm0.024_{\rm LQCD}\pm0.007_{τ_{Λ_c}}$.

hep-ex↗
arXiv2022

Search for the weak decay $ψ(3686) \to Λ_c^{+} \barΣ^- +c.c$

Using $(448.1 \pm 2.9) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector, we perform the first search for the weak baryonic decay $ψ(3686) \to Λ_c^{+} \barΣ^- +c.c.$. The analysis procedure is optimized using a blinded method. No significant signal is observed, and the upper limit on the branching fraction ($\mathcal B$) of $ψ(3686) \to Λ_c^{+} \barΣ^- +c.c.$ is set to be $1.4\times 10^{-5}$ at the 90\% confidence level.

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arXiv2022

Search for baryon and lepton number violation decay $D^{\pm}\to n(\bar{n})e^{\pm}$

Using a data set of electron-positron collisions corresponding to an integrated luminosity of ${\rm 2.93~fb^{-1}}$ taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, a search for the baryon ($B$) and lepton ($L$) number violating decays $D^{\pm}\to n(\bar{n})e^{\pm}$ is performed. No signal is observed and the upper limits on the branching fractions at the $90\%$ confidence level are set to be $1.43\times10^{-5}$ for the decays $D^{+(-)}\to \bar{n}(n)e^{+(-)}$ with $Δ|B-L|=0$, and $2.91\times10^{-5}$ for the decays $D^{+(-)}\to n(\bar{n})e^{+(-)}$ with $Δ|B-L|=2$ , where $Δ|B-L|$ denotes the change in the difference between baryon and lepton numbers.

hep-ex↗
arXiv2022

Measurement of integrated luminosities at BESIII for data samples at center-of-mass energies between 4.0 and 4.6 GeV

The integrated luminosities of the data samples collected in the BESIII experiment in 2016--2017 at center-of-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events. The integrated luminosities of the old data sets collected in 2010--2014 are updated by considering correction related to the detector performance, offsettting the effect of newly discovered readout errors in the electromagnetic calorimeter that happen haphazardly.

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arXiv2022

Observation of $e^+e^- \to p p \bar{p} \bar{n} π^{-} + c.c.$

Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESIII detector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 $\rm fb^{-1}$, the process $e^+e^- \to p p \bar{p} \bar{n} π^{-} + c.c.$ is observed for the first time with a statistical significance of $11.5σ$. The average Born cross sections in the energy ranges of (4.160, 4.380) GeV, (4.400, 4.600) GeV and (4.610, 4.700) GeV are measured to be $(21.5\pm5.7\pm1.2)$ fb, $(46.3\pm10.6\pm2.5)$ fb and $(59.0\pm9.4\pm3.2)$ fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the $\bar{p}\bar{n}$ and $ppπ^-$ invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.

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arXiv2022

Search for a massless dark photon in $Λ^{+}_{c}\to p γ^{\prime}$ decay

A search for a massless dark photon $γ^{\prime}$ is conducted using 4.5 $\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.600 and 4.699 $\mathrm{GeV}$ with the BESIII detector at BEPCII. No significant signal is observed, and the upper limit on the branching fraction $\mathcal{B}(Λ^{+}_{c}\to p γ^{\prime})$ is determined to be $8.0\times 10^{-5}$ at 90% confidence level.

hep-ex↗
arXiv2022

Search for the lepton flavor violating decay $J/ψ\to eμ$

We present a search for the lepton flavor violating decay $J/ψ\to e^{\pm}μ^{\mp}$ using $8.998\times 10^{9} J/ψ$ events collected with the BESIII detector at the BEPCII $e^+e^-$ storage ring. No excess of signal above background is observed; we therefore set an upper limit on the branching fraction of $\mathcal{B}(J/ψ\to e^{\pm}μ^{\mp})<4.5\times10^{-9}$ at the $90\%$ confidence level. Improving the previous best result by a factor of more than 30, this measurement places the most stringent limit to date on lepton flavor violation in the heavy quarkonium sector.

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arXiv2022

Observation of the $Y(4230)$ and a new structure in $e^+e^- \rightarrow K^+K^-J/ψ$

The cross sections of $e^+e^- \rightarrow K^+K^-J/ψ$ at center-of-mass energies from 4.127 to 4.600~GeV are measured based on 15.6 fb$^{-1}$ data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in the line shape of the cross sections. The mass and width of the first structure are measured to be ($4225.3\pm2.3\pm21.5$) MeV and ($72.9\pm6.1\pm30.8$)~MeV, respectively. They are consistent with those of the established $Y(4230)$. The second structure is observed for the first time with a statistical significance greater than 8$σ$, denoted as $Y(4500)$. Its mass and width are determined to be ($4484.7\pm13.3\pm24.1$) MeV and ($111.1\pm30.1\pm15.2$) MeV, respectively. The first presented uncertainties are statistical and the second ones are systematic. The product of the electronic partial width with the decay branching fraction $ Γ(Y(4230)\to e^+ e^-) \mathcal{B}(Y(4230) \to K^+ K^- J/ψ)$ is reported.

hep-ex↗
arXiv2022

Luminosities and energies of $e^+e^-$ collision data taken between $\sqrt{s}$=4.612 GeV and 4.946 GeV at BESIII

From December 2019 to June 2021, the BESIII experiment collected about 5.85 fb$^{-1}$ of data at center-of-mass energies between 4.61 GeV and 4.95 GeV. This is the highest collision energy BEPCII has reached so far. The accumulated $e^+e^-$ annihilation data samples are useful for studying charmonium(-like) states and charmed-hadron decays. By adopting a novel method of analyzing the production of $Λ_{c}^{+}\barΛ_{c}^{-}$ pairs in $e^+e^-$ annihilation, the center-of-mass energies are measured with a precision of $\sim$0.6 MeV. Integrated luminosities are measured with a precision of better than 1\% by analyzing the events of large-angle Bhabha scattering. These measurements provide important inputs to the analyses based on these data samples.

hep-ex↗
arXiv2022

Study of $ψ(3686)\rightarrowΛ\barΛω$

Based on a data sample of $(448.1\pm2.9)\times10^6$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, the branching fraction of $ψ(3686)\rightarrowΛ\barΛω$ is measured to be $\rm (3.30\pm0.34(stat.)\pm0.29(syst.))\times10^{-5}$ for the first time. In addition, the $Λω$ (or $\barΛω$) invariant mass spectra is studied and the potential presence of excited $Λ$ states has been investigated.

hep-ex↗
arXiv2022

Measurement of $ψ(3686)\toΛ\barΛη$ and $ψ(3686)\toΛ\barΛπ^0$ decays

Based on a sample of $448.1\times10^6\ ψ(3686)$ events collected with the BESIII detector, a study of $ψ(3686)\toΛ\barΛπ^0$ and $ψ(3686)\toΛ\barΛη$ is performed. Evidence of the isospin-violating decay $ψ(3686)\toΛ\barΛπ^0$ is found for the first time with a statistical significance of $3.7σ$, the branching fraction $\mathcal{B}(ψ(3686)\toΛ\barΛπ^0)$ is measured to be $(1.42\pm0.39\pm0.59)\times10^{-6}$, and its corresponding upper limit is determined to be $2.47\times10^{-6}$ at 90\% confidence level. A partial wave analysis of $ψ(3686)\toΛ\barΛη$ shows that the peak around $Λη$ invariant mass threshold favors a $Λ^*$ resonance with mass and width in agreement with the $Λ(1670)$. The branching fraction of the $ψ(3686)\toΛ\barΛη$ is measured to be $(2.34\pm0.18\pm0.52)\times10^{-5}$. The first uncertainties are statistical and the second are systematic.

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