arXiv subjects

F. Feldbauer

Publications and source records attributed to F. Feldbauer.

At least 649 records · Page 36Linked to original sources

arXiv2017

Measurement of the integrated luminosity and the center-of-mass energy of the data taken by BESIII at $\sqrt{s} = 2.125$ GeV

To study the nature of the state $Y(2175)$, a dedicated data set of $e^+e^-$ collision data was collected at the center-of-mass energy of 2.125 GeV with the BESIII detector at the BEPCII collider. By analyzing large-angle Bhabha scattering events, the integrated luminosity of this data set is determined to be $108.49\pm0.02\pm0.85$ pb$^{-1}$, where the first uncertainty is statistical and the second one is systematic. In addition, the center-of-mass energy of the data set is determined with radiative dimuon events to be $2126.55\pm0.03\pm0.85$ MeV, where the first uncertainty is statistical and the second one is systematic.

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arXiv2017

Improved measurements of two-photon widths of the $χ_{cJ}$ states and helicity analysis for $χ_{c2}\toγγ$

Based on $448.1 \times 10^6$ $ψ(3686)$ events collected with the BESIII detector, the decays $ψ(3686)\toγχ_{cJ}, χ_{cJ} \to γγ~(J=0, 1, 2)$ are studied. The decay branching fractions of $χ_{c0,c2} \to γγ$ are measured to be $\mathcal{B}(χ_{c0}\toγγ) = (1.93 \pm 0.08 \pm 0.05 \pm 0.05)\times 10^{-4}$ and $\mathcal{B}(χ_{c2}\toγγ) = (3.10 \pm 0.09 \pm 0.07 \pm 0.11)\times 10^{-4} $, which correspond to two-photon decay widths of $Γ_{γγ}(χ_{c0}) = 2.03 \pm 0.08 \pm 0.06 \pm 0.13 ~\rm{keV}$ and $Γ_{γγ}(χ_{c2}) = 0.60 \pm 0.02 \pm 0.01 \pm 0.04 ~\rm{keV}$ with a ratio of $\mathcal{R}=Γ_{γγ}(χ_{c2})/Γ_{γγ}(χ_{c0})= 0.295 \pm 0.014 \pm 0.007 \pm 0.027$, where the uncertainties are statistical, systematic and associated with the uncertainties of $\mathcal{B}(ψ(3686)\toγχ_{c0,c2})$ and the total widths $Γ(χ_{c0,c2})$, respectively. For the forbidden decay of $χ_{c1}\toγγ$, no signal is observed, and an upper limit on the two-photon width is obtained to be $Γ_{γγ}(χ_{c1})<5.3 ~\rm{eV}$ at the 90\% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay $χ_{c2}\toγγ$ is also measured to be $f_{0/2} = Γ^{λ=0}_{γγ}(χ_{c2})/Γ^{λ=2}_{γγ}(χ_{c2}) = (0.0 \pm 0.6 \pm 1.2)\times 10^{-2}$, where the uncertainties are statistical and systematic, respectively.

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arXiv2017

Study of $J/ψ$ and $ψ(3686)$ decays to $π^+π^-η^\prime$

Using the data samples of $1.31\times 10^9$ $J/ψ$ events and $4.48\times 10^8$ $ψ(3686)$ events collected with the BESIII detector, partial wave analyses on the decays $J/ψ$ and $ψ(3686) \to π^+π^-η^\prime$ are performed with a relativistic covariant tensor amplitude approach. The dominant contribution is found to be $J/ψ$ and $ψ(3686)$ decays to $ρη^\prime$. In the $J/ψ$ decay, the branching fraction ${\cal B}(J/ψ\to ρη^\prime)$ is determined to be $(7.90\pm0.19(\mathrm{stat})\pm0.49(\mathrm{sys}))\times 10^{-5}$. Two solutions are found in the $ψ(3686)$ decay, and the corresponding branching fraction ${\cal B}(ψ(3686)\to ρη^\prime)$ is $(1.02\pm0.11(\mathrm{stat})\pm0.24(\mathrm{sys}))\times 10^{-5}$ for the case of constructive interference, and $(5.69\pm1.28(\mathrm{stat})\pm2.36(\mathrm{sys}))\times 10^{-6}$ for destructive interference. As a consequence, the ratios of branching fractions between $ψ(3686)$ and $J/ψ$ decays to $ρη^\prime$ are calculated to be $(12.9\pm1.4(\mathrm{stat})\pm3.1(\mathrm{sys}))$\% and $(7.2\pm1.6(\mathrm{stat})\pm3.0(\mathrm{sys}))$\%, respectively. We also determine the inclusive branching fractions of $J/ψ$ and $ψ(3686)$ decays to $π^+π^-η^\prime$ to be $(1.36\pm0.02(\mathrm{stat})\pm0.08(\mathrm{sys}))\times 10^{-4}$ and $(1.51\pm0.14(\mathrm{stat})\pm 0.23(\mathrm{sys}))\times 10^{-5}$, respectively.

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arXiv2017

Observation of $e^+ e^- \to ηY(2175)$ at center-of-mass energies above 3.7$\sim$GeV

The state $Y(2175)$ is observed in the process $e^+ e^- \to ηY(2175)$ at center-of-mass energies between 3.7 and 4.6$\sim$GeV with a statistical significance larger than $10σ$ using data collected with the BESIII detector operating at the BEPCII storage ring. This is the first observation of the $Y(2175)$ in this process. The mass and width of the $Y(2175)$ are determined to be ($2135\pm 8\pm 9$)~MeV/$c^2$ and ($104\pm 24\pm 12$)~MeV, respectively, and the production cross section of $e^+ e^- \to ηY(2175)\to ηϕf_{0}(980)\to ηϕπ^+ π^-$ is at a several hundred femtobarn level. No significant signal for the process $e^+ e^- \to η' Y(2175)$ is observed and the upper limit on $σ(e^+ e^- \to η' Y(2175))/σ(e^+ e^- \to ηY(2175))$ is estimated to be 0.43 at the 90\% confidence level. We also search for $ψ(3686) \to ηY(2175)$. No significant signal is observed, indicating a strong suppression relative to the corresponding $J/ψ$ decay, in violation of the "12\% rule."

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arXiv2017

Determination of the number of $ψ(3686)$ events at BESIII

The numbers of $ψ(3686)$ events accumulated by the BESIII detector for the two rounds of data taking during 2009 and 2012 are determined to be $(107.0\pm0.8)\times 10^6$ and $(341.1\pm 2.1)\times 10^6$, respectively, by counting inclusive hadronic events, where the uncertainty is dominated by systematics and the statistical uncertainty is negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of $ψ(3686)$ events for the two data-taking periods is $(448.1\pm2.9)\times10^6$.

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arXiv2017

Measurements of the branching fractions for the semi-leptonic decays $D^+_s\toϕe^{+}ν_{e}$, $ϕμ^{+}ν_μ$, $ημ^{+}ν_μ$ and $η'μ^{+}ν_μ$

By analyzing 482 pb$^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy $\sqrt s=4.009$ GeV with the BESIII detector, we measure the %absolute branching fractions for the semi-leptonic decays $D_{s}^{+}\to ϕe^{+}ν_{e}$, $ϕμ^{+}ν_μ$, $ημ^{+}ν_μ$ and $η'μ^{+}ν_μ$ to be ${\mathcal B}(D_{s}^{+}\toϕe^{+}ν_{e})=(2.26\pm0.45\pm0.09)$\%, ${\mathcal B}(D_{s}^{+}\toϕμ^{+}ν_μ)=(1.94\pm0.53\pm0.09)$\%, ${\mathcal B}(D_{s}^{+}\toημ^{+}ν_μ)=(2.42\pm0.46\pm0.11)$\% and ${\mathcal B}(D_{s}^{+}\toη'μ^{+} ν_μ) = (1.06\pm0.54\pm0.07)$\%, where the first and second uncertainties are statistical and systematic, respectively. The branching fractions for the three semi-muonic decays $D_s^+\toϕμ^+ν_μ, ημ^+ν_μ$ and $η' μ^+ν_μ$ are determined for the first time and that of $D^+_s\to ϕe^+ν_e$ is consistent with the world average value within uncertainties.

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arXiv2017

Measurement of cross sections of the interactions $e^+e^-\rightarrow ϕϕω$ and $e^+e^-\rightarrow ϕϕϕ$ at center-of-mass energies from 4.008 to 4.600 GeV

Using data samples collected with the BESIII detector at the BEPCII collider at six center-of-mass energies between 4.008 and 4.600 GeV, we observe the processes $e^+e^-\rightarrow ϕϕω$ and $e^+e^-\rightarrow ϕϕϕ$. The Born cross sections are measured and the ratio of the cross sections $σ(e^+e^-\rightarrow ϕϕω)/σ(e^+e^-\rightarrow ϕϕϕ)$ is estimated to be $1.75\pm0.22\pm0.19$ averaged over six energy points, where the first uncertainty is statistical and the second is systematic. The results represent first measurements of these interactions.

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arXiv2017

Search for the rare decay $D^+ \to D^0 e^+ν_e$

We search for the rare decay $D^+\to D^0 e^+ν_{e}$, using a data set with an integrated luminosity of 2.93 $\rm fb^{-1}$ collected at $\sqrt{s}=3.773$ GeV with the BESIII detector operating at the BEPCII storage rings. No signals are observed. We set the upper limit on the branching fraction for $D^+\to D^0 e^+ν_e$ to be $1.0\times 10^{-4}$ at the 90\% confidence level.

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arXiv2017

Measurement of branching fractions for $ψ(3686)\rightarrowγη',γη$ and $γπ^{0}$

Using a data sample of $448\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII storage ring, the decays $ψ(3686)\rightarrowγη$ and $ψ(3686)\rightarrowγπ^{0}$ are observed with a statistical significance of $7.3σ$ and $ 6.7σ$, respectively. The branching fractions are measured to be $\mathcal{B}(ψ(3686)\rightarrowγη)=(0.85\pm0.18\pm0.05)\times10^{-6}$ and $\mathcal{B}(ψ(3686)\rightarrowγπ^{0})=(0.95\pm0.16\pm0.05)\times10^{-6}$. In addition, we measure the branching fraction of $ψ(3686)\rightarrowγη'$ to be $\mathcal{B}(ψ(3686)\rightarrowγη')=(125.1\pm2.2\pm6.2)\times 10^{-6}$, with improved precision compared to previous results.

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arXiv2017

Observation of the doubly radiative decay $η^{\prime}\to γγπ^0$

Based on a sample of $1.31$ billion $J/ψ$ events collected with the BESIII detector, we report the study of the doubly radiative decay $η^\prime\to γγπ^0$ for the first time, where the $η^\prime$ meson is produced via the $J/ψ\to γη^\prime$ decay. The branching fraction of $η^\prime\to γγπ^0$ inclusive decay is measured to be ${\cal B}(η^\prime\to γγπ^0)_{\text{Incl.}}$ = $(3.20\pm0.07\mbox{(stat)}\pm0.23\mbox{(sys)})\times 10^{-3}$, while the branching fractions of the dominant process $η^\prime\rightarrowγω$ and the non-resonant component are determined to be ${\cal B}(η^\prime\to γω)\times {\cal B}(ω\to γπ^0) = (23.7 \pm1.4\mbox{(stat)}\pm1.8\mbox{(sys)})\times 10^{-4}$ and ${\cal B}(η^\prime\to γγπ^0)_{\text{NR}} = (6.16\pm0.64\mbox{(stat)} \pm0.67\mbox{(sys)})\times 10^{-4}$, respectively. In addition, the $M^2_{γγ}$-dependent partial widths of the inclusive decay are also presented.

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arXiv2017

Observation of $e^{+}e^{-} \to ηh_{c}$ at center-of-mass energies from 4.085 to 4.600 GeV

We observe for the first time the process $e^{+}e^{-} \rightarrow ηh_c$ with data collected by the BESIII experiment. Significant signals are observed at the center-of-mass energy $\sqrt{s}=4.226$ GeV, and the Born cross section is measured to be $(9.5^{+2.2}_{-2.0} \pm 2.7)$ pb. Evidence for $ηh_c$ is observed at $\sqrt{s}=4.358$ GeV with a Born cross section of $(10.0^{+3.1}_{-2.7} \pm 2.6)$ pb, and upper limits on the production cross section at other center-of-mass energies between 4.085 and 4.600 GeV are determined.

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arXiv2017

Branching fraction measurements of $ψ(3686) \to γχ_{cJ}$

Using a sample of 106 million $ψ(3686)$ decays, the branching fractions of $ψ(3686) \to γχ_{c0}, ψ(3686) \to γχ_{c1}$, and $ψ(3686) \to γχ_{c2}$ are measured with improved precision to be $(9.389 \pm 0.014 \pm 0.332)\,\%$, $(9.905 \pm 0.011 \pm 0.353)\,\% $, and $(9.621 \pm 0.013 \pm 0.272)\,\% $, respectively, where the first uncertainties are statistical and the second ones are systematic. The product branching fractions of $ψ(3686) \to γχ_{c1}, χ_{c1} \to γJ/ψ$ and $ψ(3686) \to γχ_{c2}, χ_{c2} \to γJ/ψ$ and the branching fractions of $χ_{c1} \to γJ/ψ$ and $χ_{c2} \to γJ/ψ$ are also presented.

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arXiv2017

Evidence for the singly-Cabibbo-suppressed decay $Λ_{c}^{+} \to pη$ and search for $Λ_{c}^{+} \to pπ^{0}$

We study the singly-Cabibbo-suppressed decays $Λ_c^{+}\to pη$ and $Λ_{c}^{+}\to pπ^{0}$ using $Λ_{c}^{+}Λ_{c}^{+}$ pairs produced by $e^+e^-$ collisions at a center-of-mass energy of $\sqrt{s} = 4.6\; GeV$. The data sample was collected by the BESIII detector at the BEPCII collider and corresponds to an integrated luminosity of 567 $pb^{-1}$. We find the first evidence for the decay $Λ_{c}^{+}\to p η$ with a statistical significance of $4.2σ$ and measure its branching fraction to be $\mathcal{B}(Λ_c^+\to pη)= (1.24\pm0.28({\rm{stat.}})\pm0.10({\rm{syst.}}))\times10^{-3}$. No significant $Λ_c^+ \to pπ^0$ signal is observed. We set an upper limit on its branching fraction $\mathcal{B}(Λ_c^+ \to pπ^{0}) < 2.7 \times 10^{-4}$ at the 90% confidence level.

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arXiv2017

Observation of the helicity-selection-rule suppressed decay of the $χ_{c2}$ charmonium state

The decays of $χ_{c2}\to K^{+}K^{-}π^{0}$, $K_{S} K^{\pm}π^{\mp}$ and $π^{+}π^{-}π^{0}$ are studied with the $ψ(3686)$ data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of $χ_{c2}\to K^{\ast}\overline{K}$, $χ_{c2}\to a_{2}^{\pm}(1320)π^{\mp}/a_{2}^{0}(1320)π^{0}$ and $χ_{c2}\to ρ(770)^{\pm}π^{\mp}$ are measured. Here $K^{\ast}\overline{K}$ denotes both $K^{\ast\pm}K^{\mp}$ and $K^{\ast 0}\overline{K}{}^{0}+c.c.$, and $K^{\ast}$ denotes the resonances $K^{\ast}(892)$, $K^{\ast}_{2}(1430)$ and $K^{\ast}_{3}(1780)$. The observations indicate a strong violation of the helicity selection rule in $χ_{c2}$ decays into vector and pseudoscalar meson pairs. The measured branching fractions of $χ_{c2}\to K^{\ast}(892)\overline{K}$ are more than 10 times larger than the upper limit of $χ_{c2}\to ρ(770)^{\pm}π^{\mp}$, which is so far the first direct observation of a significant $U$-spin symmetry breaking effect in charmonium decays.

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arXiv2017

Determination of spin and parity of the $Z_c(3900)$

The spin and parity of the $Z_c(3900)^\pm$ state are determined to be $J^P=1^+$ with a statistical significance larger than $7σ$ over other quantum numbers in a partial wave analysis of the process $e^+e^-\to π^+π^-J/ψ$. We use a data sample of 1.92 fb$^{-1}$ accumulated at $\sqrt{s}=4.23$ and 4.26 GeV with the BESIII experiment. When parameterizing the $Z_c(3900)^\pm$ with a Flatte-like formula, we determine its pole mass $M_\textrm{pole}=(3881.2\pm4.2_\textrm{stat}\pm52.7_\textrm{syst})\textrm{MeV}/c^2$ and pole width $Γ_\textrm{pole}=(51.8\pm4.6_\textrm{stat}\pm36.0_\textrm{syst})\textrm{MeV}$. We also measure cross sections for the process $e^+e^-\to Z_c(3900)^+π^-+c.c.\to J/ψπ^+π^-$ and determine an upper limit at the 90\% confidence level for the process $e^+e^-\to Z_c(4020)^+π^-+c.c.\to J/ψπ^+π^-$.

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arXiv2017

Study of $J/ψ$ and $ψ(3686)\rightarrowΣ(1385)^{0}\barΣ(1385)^{0}$ and $Ξ^0\barΞ^{0}$

We study the decays of $J/ψ$ and $ψ(3686)$ to the final states $Σ(1385)^{0}\barΣ(1385)^{0}$ and $Ξ^0\barΞ^{0}$ based on a single baryon tag method using data samples of $(1310.6 \pm 7.0) \times 10^{6}$ $J/ψ$ and $(447.9 \pm 2.9) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. The decays to $Σ(1385)^{0}\barΣ(1385)^{0}$ are observed for the first time. The measured branching fractions of $J/ψ$ and $ψ(3686)\rightarrowΞ^0\barΞ^{0}$ are in good agreement with, and much more precise, than the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for $J/ψ\rightarrowΣ(1385)^{0}\barΣ(1385)^{0}$, $α=-0.64 \pm 0.03 \pm 0.10$, is found to be negative, different to the other decay processes in this measurement. In addition, the "12\% rule" and isospin symmetry in the $J/ψ$ and $ψ(3686)\rightarrowΞ\barΞ$ and $Σ(1385)\barΣ(1385)$ systems are tested.

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arXiv2017

Evidence for $e^{+}e^{-} \to γη_c(1S)$ at center-of-mass energies between 4.01 and 4.60 GeV

We present first evidence for the process $e^+e^-\to γη_c(1S)$ at six center-of-mass energies between 4.01 and 4.60~GeV using data collected by the BESIII experiment operating at BEPCII. These data sets correspond to a total integrated luminosity of 4.6~fb$^{-1}$. We measure the Born cross section at each energy using a combination of twelve $η_c(1S)$ decay channels. Because the significance of the signal is marginal at each energy ($\le3.0σ$), we also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the $Y(4260)$, we measure a peak Born cross section $σ_{\mathrm{ peak}}(e^+e^-\toγη_c(1S)) = 2.11 \pm 0.49 (\mathrm{stat.}) \pm 0.36 (\mathrm{syst.})$~pb with a statistical significance of 4.2$σ$.

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arXiv2017

Observation of $ψ(3686) \rightarrow e^{+}e^{-}χ_{cJ}$ and $χ_{cJ} \rightarrow e^{+}e^{-}J/ψ$

Using $4.479 \times 10^{8}$ $ψ(3686)$ events collected with the BESIII detector, we search for the decays $ψ(3686) \rightarrow e^{+}e^{-}χ_{c0,1,2}$ and $χ_{c0,1,2} \rightarrow e^{+}e^{-}J/ψ$. The decays $ψ(3686) \rightarrow e^{+}e^{-}χ_{c0,1,2}$ and $χ_{c0,1,2} \rightarrow e^{+}e^{-}J/ψ$ are observed for the first time. The measured branching fractions are $\mathcal{B}(ψ(3686) \rightarrow e^{+}e^{-}χ_{c0,1,2}) = (11.7 \pm 2.5 \pm 1.0)\times10^{-4}$, $(8.6 \pm 0.3 \pm 0.6)\times10^{-4}$, $(6.9 \pm 0.5 \pm 0.6)\times10^{-4}$, and $\mathcal{B}(χ_{c0,1,2} \rightarrow e^{+}e^{-}J/ψ) = (1.51 \pm 0.30 \pm 0.13)\times10^{-4}$, $(3.73 \pm 0.09 \pm 0.25)\times10^{-3}$, $(2.48 \pm 0.08 \pm 0.16)\times10^{-3}$. The ratios of the branching fractions $\frac{\mathcal{B}(ψ(3686) \rightarrow e^{+}e^{-}χ_{c0,1,2})}{\mathcal{B}(ψ(3686) \rightarrow γχ_{c0,1,2})}$ and $\frac{\mathcal{B}(χ_{c0,1,2} \rightarrow e^{+}e^{-}J/ψ)}{\mathcal{B}(χ_{c0,1,2} \rightarrow γJ/ψ)}$ are also reported.

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