arXiv subjects

F. Feldbauer

Publications and source records attributed to F. Feldbauer.

At least 343 records · Page 19Linked to original sources

arXiv2023

Studies of the decay $D^+_s\to K^+K^- μ^+ ν_μ$

The $D^+_s\to K^+K^-μ^+ν_μ$ decay is studied based on 7.33 fb$^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at center-of-mass energies in the range from 4.128 to 4.226 GeV. The absolute branching fraction is measured as ${\mathcal B}(D^+_s\to ϕμ^+ν_μ) = (2.25\pm 0.09 \pm 0.07) \times10^{-2}$, the most precise measurement to date. Combining with the world average of ${\mathcal B}(D^+_s\to ϕe^+ν_e)$, the ratio of the branching fractions obtained is$\frac{{\mathcal B}(D^+_s\to ϕμ^+ν_μ)}{{\mathcal B}(D^+_s\to ϕe^+ν_e)} = 0.94\pm0.08$, in agreement with lepton universality. By performing a partial wave analysis, the hadronic form factor ratios at $q^{2}=0$ are extracted, finding $r_{V}=\frac{V(0)}{A_{1}(0)}=1.58\pm0.17\pm0.02$ and $r_{2}=\frac{A_{2}(0)}{A_{1}(0)}=0.71\pm0.14\pm0.02$, where the first uncertainties are statistical and the second are systematic. No significant $S$-wave contribution from $f_0(980)\to K^+K^-$ is found. The upper limit $\mathcal{B}(D_s^+\to f_0(980)μ^{+}ν_μ) \cdot{\mathcal B}(f_0(980)\to K^+K^-) < 5.45 \times 10^{-4}$ is set at 90\% confidence level.

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arXiv2023

Production of doubly-charged $Δ$ baryon in $e^{+}e^{-}$ annihilation at energies from 2.3094 to 2.6464 GeV

The processes $e^{+}e^{-} \to Δ^{++}\barΔ^{--}$ and $e^{+}e^{-}\to Δ^{++} \bar{p} π^{-} + c.c.$ are studied for the first time with $179~{\rm pb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected with the BESIII detector at center-of-mass energies from $2.3094$ GeV to $2.6464$ GeV. No significant signal for the $e^{+}e^{-}\to Δ^{++}\barΔ^{--}$ process is observed and the upper limit of the Born cross section is estimated at each energy point. For the process $e^{+}e^{-} \to Δ^{++} \bar{p} π^{-} + c.c.$, a significant signal is observed at center-of-mass energies near 2.6454 GeV and the corresponding Born cross section is reported.

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arXiv2023

Measurement of the Energy-Dependent Electromagnetic Form Factors of a Charmed Baryon

We study the process $e^{+}e^{-}\toΛ_{c}^{+}\barΛ_c^{-}$ at twelve center-of-mass energies from $4.6119$ to $4.9509~\mathrm{GeV}$ using data samples collected by the BESIII detector at the BEPCII collider. The Born cross sections and effective form factors ($|G_{\mathrm{eff}}|$) are determined with unprecedented precision after combining the single and double-tag methods based on the decay process $Λ_{c}^{+}\to pK^{-}π^{+}$. Flat cross sections around $4.63~\mathrm{GeV}$ are obtained and no indication of the resonant structure $Y(4630)$, as reported by Belle, is found. In addition, no oscillatory behavior is discerned in the $|G_{\mathrm{eff}}|$ energy-dependence of $Λ_{c}^{+}$, in contrast to what is seen for the proton and neutron cases. Analyzing the cross section together with the polar-angle distribution of the $Λ_{c}^{+}$ baryon at each energy point, the moduli of electric and magnetic form factors ($|G_{E}|$ and $|G_{M}|$) are extracted and separated. For the first time, the energy-dependence of the form factor ratio $|G_{E}/G_{M}|$ is observed, which can be well described by an oscillatory function.

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arXiv2023

First simultaneous measurement of $Ξ^0$ and $\barΞ^0$ asymmetry parameters in $ψ(3686)$ decay

The $Ξ^0$ asymmetry parameters are measured using entangled quantum $Ξ^0$-$\barΞ^0$ pairs from a sample of $(448.1 \pm 2.9) \times 10^6$ $ψ(3686)$ events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the $Ξ^0 \barΞ^0$ helicity states is measured to be $ΔΦ= -0.050 \pm 0.150 \pm 0.020$~rad, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the $Ξ^0$ hyperon $(α_{Ξ^0}, α_{\barΞ^0}, ϕ_{Ξ^0}, ϕ_{\barΞ^0})$ and the angular distribution parameter $(α_{ψ(3686)})$ and $ΔΦ$ are measured simultaneously for the first time. In addition, the $CP$ asymmetry observables are determined to be $A^{Ξ^0}_{CP} = (α_{Ξ^0} + α_{\barΞ^0})/(α_{Ξ^0} - α_{\barΞ^0})$ $= -0.007$ $\pm$ 0.082 $\pm$ 0.025 and $Δϕ^{Ξ^0}_{CP} = (ϕ_{Ξ^0} + ϕ_{\barΞ^0})/2$ $= -0.079$ $\pm$ 0.082 $\pm$ 0.010 rad, which are consistent with $CP$ conservation.

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arXiv2023

Measurement of $e^+e^-\to pK^-\barΛ+c.c.$ cross sections between 4.009 GeV and 4.951 GeV

Using $e^+e^-$ collision datasets corresponding to total integrated luminosity of 21.7 fb$^{-1}$ collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of $e^+e^-\to pK^-\barΛ+c.c.$ are measured for the first time. By fitting these energy-dependent cross sections, we search for the excited $ψ$ states $ψ(4160)$ and $ψ(4415)$, and the vector charmonium-like states $ψ(4230)$, $ψ(4360)$, and $ψ(4660)$. No evidence for these is observed and the upper limits on the branching fractions of these states decaying into $pK^-\bar Λ+c.c.$ are set at the 90\% confidence level.

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arXiv2023

Search for the semi-leptonic decays $Λ_c^+ \to Λπ^+ π^- e^+ ν_e$ and $Λ_c^+ \to p K_S^0 π^- e^+ ν_e$

We search for the semi-leptonic decays $Λ_c^+ \to Λπ^+ π^- e^+ ν_e$ and $Λ_c^+ \to p K_S^0 π^- e^+ ν_e$ in a sample of 4.5 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected in the center-of-mass energy region between 4.600 GeV and 4.699 GeV by the BESIII detector at the BEPCII. No significant signals are observed, and the upper limits on the decay branching fractions are set to be $\mathcal{B}(Λ_c^+ \to Λπ^+ π^- e^+ ν_e)<3.9\times10^{-4}$ and $\mathcal{B}(Λ_c^+ \to p K_S^0 π^- e^+ ν_e)<3.3\times10^{-4}$ at the 90% confidence level, respectively.

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arXiv2023

Measurements of Differential Cross Sections of Inclusive $π^0$ and $K^0_S$ Production in $e^{+}e^{-}$ Annihilation at Energies from 2.2324 to 3.6710 GeV

Based on electron positron collision data collected with the BESIII detector operating at the BEPCII storage rings, the differential cross sections of inclusive $π^0$ and $K^0_S$ production as a function of hadron momentum, normalized by the total cross section of the $e^{+}e^{-} \to$ hadrons process, are measured at six center-of-mass energies from 2.2324 to 3.6710 GeV. Our results with a relative hadron energy coverage from 0.1 to 0.9 significantly deviate from several theoretical calculations based on existing fragmentation functions, especially at lower energies.

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arXiv2023

Study of $Λ_c^+\rightarrow Λμ^+ν_μ$ and Test of Lepton Flavor Universality with $Λ_c^+\rightarrow Λ\ell^+ν_{\ell}$ Decays

The measurement of the Cabibbo-favored semileptonic decay $Λ_c^+\rightarrow Λμ^+ν_μ$ is reported using $4.5~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at center-of-mass energies ranging from 4.600~GeV to 4.699~GeV. The branching fraction of the decay is measured to be $\mathcal{B}(Λ_c^+\rightarrow Λμ^+ν_μ)=(3.48\pm0.14_{\rm stat.}\pm0.10_{\rm syst.})\%$, three times more precise than the prior world average result. Tests of lepton flavor universality using $Λ_c^+\rightarrow Λ\ell^+ν_{\ell}$ ($\ell=e, μ$) decays are reported for the first time, based on measurements of the differential decay rates and the forward-backward asymmetries in separate four-momentum transfer regions. The results are compatible with Standard Model predictions. Furthermore, we improve the determination of the form-factor parameters in $Λ_c^+\rightarrow Λ\ell^+ν_{\ell}$ decays, which provide stringent tests and calibration for lattice quantum chromodynamics (LQCD) calculations.

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arXiv2023

First study of reaction $Ξ^{0}n\rightarrowΞ^{-}p$ using $Ξ^0$-nucleus scattering at an electron-positron collider

Using $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events collected with the BESIII detector at the BEPCII storage ring, the process $Ξ^{0}n\rightarrowΞ^{-}p$ is studied, where the $Ξ^0$ baryon is produced in the process $J/ψ\rightarrowΞ^0\barΞ^0$ and the neutron is a component of the $^9\rm{Be}$, $^{12}\rm{C}$ and $^{197}\rm{Au}$ nuclei in the beam pipe. A clear signal is observed with a statistical significance of $7.1σ$. The cross section of the reaction $Ξ^0+{^9\rm{Be}}\rightarrowΞ^-+p+{^8\rm{Be}}$ is determined to be $σ(Ξ^0+{^9\rm{Be}}\rightarrowΞ^-+p+{^8\rm{Be}})=(22.1\pm5.3_{\rm{stat}}\pm4.5_{\rm{sys}})$ mb at the $Ξ^0$ momentum of $0.818$ GeV/$c$, where the first uncertainty is statistical and the second is systematic. No significant $H$-dibaryon signal is observed in the $Ξ^-p$ final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

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arXiv2023

Determination of spin and parity of $D^{*}_{(s)}$ mesons

The spin and parity of the charmed mesons $D_{s}^{*+}$, $D^{*0}$ and $D^{*+}$ are determined for the first time to be $J^P=1^{-}$ with significances greater than 10$σ$ over other hypotheses of $2^{+}$ and $3^{-}$, using an $e^+e^-$ collision data sample with an integrated luminosity of 3.19 fb$^{-1}$ collected by the BESIII detector at a center-of-mass energy of 4.178 GeV. Different spin-parity hypotheses for $D_{s}^{*+}$, $D^{*0}$, and $D^{*+}$ mesons are tested via a helicity amplitude analysis of the processes $e^+e^-\to D^{*+}_{s}D^{-}_{s}$, $D^{*0}D^{0}$ and $D^{*+}D^{-}$, with $D^{*+}_{s}\to D^{+}_{s} γ$, $D^{*0}\to D^{0}π^{0}$, and $D^{*+}\to D^{+}π^{0}$. The results confirm the quark model predictions.

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arXiv2023

Precision Measurement of the Decay $Σ^{+} \rightarrow pγ$ in the Process $J/ψ\rightarrow Σ^{+}\barΣ^{-}$

Using $(10\:087\pm44)\times10^{6}$ $J/ψ$ events collected with the BESIII detector, the radiative hyperon decay $Σ\rightarrow pγ$ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be $\left(0.996 \pm 0.021_{\rm stat.}\pm 0.018_{\rm syst.}\right)\times 10^{-3}$, which is lower than its world average value by $4.2$ standard deviations. Its decay asymmetry parameter is determined to be $-0.652 \pm 0.056_{\rm stat.}\pm 0.020_{\rm syst.}$. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by $78\%$ and $34\%$, respectively.

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arXiv2023

Precision measurement of the matrix elements for $η\toπ^+π^-π^0$ and $η\toπ^0π^0π^0$ decays

A precision measurement of the matrix elements for $η\toπ^+π^-π^0$ and $η\toπ^0π^0π^0$ decays is performed using a sample of $(10087\pm44)\times10^6$ $J/ψ$ decays collected with the BESIII detector. The decay $J/ψ\to γη$ is used to select clean samples of 631,686 $η\toπ^+π^-π^0$ decays and 272,322 $η\toπ^0π^0π^0$ decays. The matrix elements for both channels are in reasonable agreement with previous measurements. The non-zero $gX^2Y$ term for the decay mode $η\toπ^+π^-π^0$ is confirmed, as reported by the KLOE Collaboration, while the other higher-order terms are found to be insignificant. Dalitz plot asymmetries in the $η\toπ^+π^-π^0$ decay are also explored and are found to be consistent with charge conjugation invariance. In addition, a cusp effect is investigated in the $η\toπ^0π^0π^0$ decay, and no obvious structure around the $π^+π^-$ mass threshold is observed.

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arXiv2023

Search for baryon and lepton number violating decays of $Ξ^{0}$ hyperons

Using $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events collected by the BESIII detector at the BEPCII collider, we report the first search for the baryon and lepton number violating decays $Ξ^{0} \rightarrow K^{-} e^{+}$ with $Δ(B-L)=0$ and $Ξ^{0} \rightarrow K^{+} e^{-}$ with $|Δ(B-L)|=2$, where $B$ ($L$) is the baryon (lepton) number. While no signal is observed, the upper limits on the branching fractions of these two decays are set to $\mathcal B(Ξ^{0} \rightarrow K^{-} e^{+})<3.6\times10^{-6}$ and $\mathcal B(Ξ^{0} \rightarrow K^{+} e^{-})<1.9\times10^{-6}$ at the 90\% confidence level, respectively. These results offer a direct probe of baryon number violating interactions involving a strange quark.

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arXiv2023

Determination of the $C\!P$-even fraction of $D^0\rightarrow K_S^0π^+π^-π^0$

Quantum-correlated $D\bar{D}$ pairs collected by the BESIII experiment at the $ψ(3770)$ resonance, corresponding to an integrated luminosity of 2.93 fb$^{-1}$, are used to study the $D^0 \rightarrow K^{0}_Sπ^{+} π^{-} π^{0}$ decay mode. The $C\!P$-even fraction of $D^0 \rightarrow K^{0}_Sπ^{+} π^{-} π^{0}$ decays is determined to be $0.235\pm 0.010\pm 0.002$, where the first uncertainty is statistical and the second is systematic.

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arXiv2023

Test of $C\!P$ Symmetry in Hyperon to Neutron Decays

The quantum entangled $J/ψ\to Σ^{+}\barΣ^{-}$ pairs from $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events taken by the BESIII detector are used to study the non-leptonic two-body weak decays $Σ^{+} \to n π^{+}$ and $\barΣ^{-} \to \bar{n} π^{-}$. The $C\!P$-odd weak decay parameters of the decays $Σ^{+} \to n π^{+}$ ($α_{+}$) and $\barΣ^{-} \to \bar{n} π^{-}$ ($\barα_{-}$) are determined to be $-0.0565\pm0.0047_{\rm stat}\pm0.0022_{\rm syst}$ and $0.0481\pm0.0031_{\rm stat}\pm0.0019_{\rm syst}$, respectively. The decay parameter $\barα_{-}$ is measured for the first time, and the accuracy of $α_{+}$ is improved by a factor of four compared to the previous results. The simultaneously determined decay parameters allow the first precision $C\!P$ symmetry test for any hyperon decay with a neutron in the final state with the measurement of $A_{C\!P}=(α_{+}+\barα_{-})/(α_{+}-\barα_{-})=-0.080\pm0.052_{\rm stat}\pm0.028_{\rm syst}$. Assuming $C\!P$ conservation, the average decay parameter is determined as $\left< α_{+}\right>=(α_{+}- \barα_{-})/2 = -0.0506\pm0.0026_{\rm stat}\pm0.0019_{\rm syst}$, while the ratios $α_{+}/α_{0}$ and $\barα_{-}/\barα_{0}$ are $-0.0490\pm0.0032_{\rm stat}\pm0.0021_{\rm syst}$ and $-0.0571\pm0.0053_{\rm stat}\pm0.0032_{\rm syst}$, where $α_{0}$ and $\barα_{0}$ are the decay parameters of the decays $Σ^{+} \to p π^{0}$ and $\barΣ^{-} \to \bar{p} π^{0}$, respectively.

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arXiv2023

Measurement of $e^+ e^- \rightarrow ϕη^{\prime}$ cross sections at center-of-mass energies between 3.508 and 4.600 GeV

We present a measurement of the dressed cross sections for $e^+ e^- \rightarrow ϕη^{\prime}$ at different center-of-mass energies between 3.508 and 4.600 GeV based on 15.1 fb$^{-1}$ of $e^+ e^-$ annihilation data collected with the BESIII detector operating at the BEPCII collider. In addition, a search for the decay $Y(4230) \to ϕη^{\prime}$ is performed. No clear signal is observed and the corresponding upper limit is provided.

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arXiv2023

First Experimental Study of the Purely Leptonic Decay $D_s^{*+}\to e^+ν_e$

Using $7.33~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data taken with the BESIII detector at the BEPCII collider, we report the first experimental study of the purely leptonic decay $D_s^{*+}\to e^+ν_e$. A signal for the decay $D_s^{*+}\to e^+ν_e$ is observed with a statistical significance of $2.9σ$. The branching fraction of ${D_s^{*+}\to e^+ν_e}$ is measured to be $(2.1{^{+1.2}_{-0.9}}_{\rm stat.}\pm0.2_{\rm syst.})\times 10^{-5}$, corresponding to an upper limit of $4.0\times10^{-5}$ at the 90\% confidence level. Taking the total width of the $D_s^{*+}$~(($0.070\pm0.028$) keV) predicted by lattice quantum chromodynamics as input, the decay constant of the $D^{*+}_s$ is determined to be $f_{D_s^{*+}}=(213.6{^{+61.0}_{-45.8}}_{\rm stat.}\pm43.9_{\rm syst.})$ MeV, corresponding to an upper limit of 353.8 MeV at the 90\% confidence level.

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arXiv2023

Measurement of Branching Fractions of Singly Cabibbo-suppressed Decays $Λ_c^+ \rightarrow Σ^{0} K^+$ and $Σ^{+} K_{S}^0$

Based on a sample of 4.4 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected in the energy region between 4.6 GeV and 4.7 GeV with the BESIII detector at BEPCII, two singly Cabibbo-suppressed decays $Λ_c^+ \rightarrow Σ^0 K^+$ and $Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0$ are studied. The ratio of the branching fraction $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 K^+)$ relative to $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 π^+)$ is measured to be $0.0361 \pm 0.0073(\mathrm{stat.}) \pm 0.0005(\mathrm{syst.})$, and the ratio of $\mathcal{B}(Λ_c^+ \rightarrow Σ^+ K_{S}^0)$ relative to $\mathcal{B}(Λ_{c}^{+} \rightarrow Σ^+ π^+ π^-)$ is measured to be $0.0106 \pm 0.0031(\mathrm{stat.}) \pm 0.0004(\mathrm{syst.})$. After taking the world-average branching fractions of the reference decay channels, the branching fractions $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 K^+)$ and $\mathcal{B}(Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0)$ are determined to be $(4.7\pm 0.9(\mathrm{stat.})\pm 0.1(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$ and $(4.8\pm 1.4(\mathrm{stat.})\pm 0.2(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$, respectively. The branching fraction of the $Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0$ decay is measured for the first time.

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