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F. Feldbauer

Publications and source records attributed to F. Feldbauer.

At least 397 records · Page 22Linked to original sources
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 $|V_{cs}|=0.936\pm0.017_{\mathcal{B}}\pm0.024_{\rm LQCD}\pm0.007_{τ_{Λ_c}}$.

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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.

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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

Study of the processes $χ_{cJ} \to Ξ^- \barΞ^+$ and $Ξ^0 \barΞ^0$

Using $448.1\times 10 ^6$ $ψ(3686)$ decays collected with the BESIII detector at the BEPCII $e^+e^-$ storage rings, the branching fractions and angular distributions of the decays $χ_{cJ}\toΞ^-\barΞ^+$ and $Ξ^0\barΞ^0$ $(J = 0, 1, 2)$ are measured based on a partial-reconstruction technique. The decays $χ_{c1}\toΞ^0\barΞ^0$ and $χ_{c2}\toΞ^0\barΞ^0$ are observed for the first time with statistical significances of 7$σ$ and 15$σ$, respectively. The results of this analysis are in good agreement with previous measurements and have significantly improved precision.

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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.

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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 $Ξ^{-}$ Hyperon Transverse Polarization in $ψ(3686)\rightarrowΞ^{-}\barΞ^{+}$

Using a sample of $(448.1~\pm~2.9)$ $\times 10^{6}$ $ψ(3686)$ decays collected with the BESIII detector at BEPCII, we report an observation of $Ξ^{-}$ transverse polarization with a significance of $7.3 σ$ in the decay $ψ(3686)\rightarrowΞ^{-}\barΞ^{+}$ ($Ξ^{-}\rightarrowπ^{-}Λ$, $\barΞ^{+}\rightarrowπ^{+}\barΛ$, $Λ\to pπ^{-}$, $\barΛ\to\bar{p}π^{+}$). The relative phase of the electric and magnetic form factors is determined to be $ΔΦ= (0.667 \pm 0.111 \pm 0.058)$ rad. This is the first measurement of the relative phase for a $ψ(3686)$ decay into a pair of $Ξ^{-}\barΞ^{+}$ hyperons. The $Ξ^{-}$ decay parameters ($α_{Ξ^{-}}$, $ϕ_{Ξ^-}$) and their conjugates ($α_{\barΞ^{+}}$, $ϕ_{\barΞ^{+}}$), the angular-distribution parameter $α_ψ$, and the strong-phase difference $δ_{p}-δ_{s}$ for $Λ$-$π^-$ scattering are measured to be consistent with previous BESIII results.

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arXiv2022

Measurement of $e^+e^-\rightarrowΛ\barΛη$ from 3.5106 to 4.6988 GeV and study of $Λ\barΛ$ mass threshold enhancement

Using data samples with a total integrated luminosity of approximately 18 fb$^{-1}$ collected by the BESIII detector operating at the BEPCII, the process $e^+e^-\rightarrowΛ\barΛ η$ is studied at center-of-mass energies between 3.5106 and 4.6988 GeV. The Born cross section for the process $e^+e^-\rightarrowΛ\barΛη$ is measured. No significant structure is observed in the Born cross section line shape. An enhancement near the $Λ\barΛ$ mass threshold is observed for the first time in the process. The structure can be described by an $S$-wave Breit-Wigner function. Neglecting contribution of excited $Λ$ states and potential interferences, the mass and width are determined to be ($2356\pm 7\pm17$) MeV/$c^2$ and ($304\pm28\pm54$) MeV, respectively, where the first uncertainties are statistical and the second are systematic.

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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.

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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.

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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.

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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.

hep-ex↗
arXiv2022

Measurement of the absolute branching fraction of the singly Cabibbo suppressed decay $Λ^{+}_{c}\to pη^{\prime}$

The singly Cabibbo suppressed decay $Λ^{+}_{c}\to pη^{\prime}$ is measured using 4.5 $\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII. Evidence for $Λ^{+}_{c}\to pη^{\prime}$ with a statistical significance of $3.6σ$ is reported with a double-tag approach. The $Λ^{+}_{c}\to pη^{\prime}$ absolute branching fraction is determined to be $(5.62^{+2.46}_{-2.04} \pm 0.26)\times 10^{-4}$, where the first and second uncertainties are statistical and systematic, respectively. Our result is consistent with the branching fraction obtained by the Belle collaboration within the uncertainty of $1σ$.

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arXiv2022

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

The singly Cabibbo-suppressed decay $D_{s}^{+} \to K^+π^{+}π^{-}π^{0}$ is observed, using a data set corresponding to an integrated luminosity of 6.32 $\rm fb^{-1}$ recorded by the BESIII detector at the centre-of-mass energies between 4.178 and 4.226 GeV. The first amplitude analysis of $D_{s}^{+} \to K^+π^{+}π^{-}π^{0}$ reveals the sub-structures in this decay and determines the fractions and relative phases of different intermediate processes. The dominant intermediate process is $D_s^+ \to K^{*0}ρ^+$, with a fit fraction of $(40.5\pm2.8_{\rm{stat.}}\pm1.5_{\rm{syst.}})\%$. With the detection efficiency based on our amplitude analysis, the absolute branching fraction for $D_{s}^{+} \to K^+π^{+}π^{-}π^{0}$ is measured to be $(9.75\pm0.54_{\rm{stat.}}\pm0.17_{\rm{syst.}})\times 10^{-3}$.

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