arXiv subjects

T. Held

Publications and source records attributed to T. Held.

At least 127 records · Page 7Linked to original sources

arXiv2015

Measurement of the form factors in the decay $D^+ \to ωe^+ ν_{e}$ and search for the decay $D^+ \to ϕe^+ ν_{e}$

Using 2.92 fb$^{-1}$ of electron-positron annihilation data collected at a center-of-mass energy of $\sqrt{s}= 3.773$ GeV with the BESIII detector, we present an improved measurement of the branching fraction $\mathcal{B}(D^+ \to ωe^+ ν_{e}) = (1.63\pm0.11\pm0.08)\times 10^{-3}$. The parameters defining the corresponding hadronic form factor ratios at zero momentum transfer are determined for the first time, we measure them to be $r_V = 1.24\pm0.09\pm0.06$ and $r_2 = 1.06\pm0.15 \pm 0.05$. The first and second uncertainties are statistical and systematic, respectively. We also search for the decay $D^+ \to ϕe^+ ν_{e}$. An improved upper limit $\mathcal{B}(D^+ \to ϕe^+ ν_{e}) < 1.3 \times 10^{-5}$ is set at 90\% confidence level.

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arXiv2015

Observation of $η^{\prime}\toωe^{+} e^{-}$

Based on a sample of \etapr mesons produced in the radiative decay $J/ψ\toγη^{\prime}$ in $1.31\times 10^9$ $J/ψ$ events collected with the BESIII detector, the decay $η^{\prime}\toωe^{+} e^{-}$ is observed for the first time, with a statistical significance of $8σ$. The branching fraction is measured to be $\mathcal{B}(η^{\prime}\toωe^{+} e^{-})=(1.97\pm0.34(\text{stat})\pm0.17(\text{syst}))\times10^{-4}$, which is in agreement with theoretical predictions. The branching fraction of $η^{\prime}\toωγ$ is also measured to be $(2.55\pm0.03(\text{stat})\pm0.16(\text{syst}))\times10^{-2}$, which is the most precise measurement to date, and the relative branching fraction $\frac{\mathcal{B}(η^{\prime}\to ωe^{+}e^{-})}{\mathcal{B}(η^{\prime}\to ωγ)}$ is determined to be $(7.71\pm1.34(\text{stat})\pm0.54(\text{syst}))\times10^{-3}$.

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arXiv2015

Observation of the isospin-violating decay $J/ψ\to ϕπ^{0}f_{0}(980)$

Using a sample of 1.31 billion $J/ψ$ events collected with the BESIII detector at the BEPCII collider, the decays $J/ψ\to ϕπ^{+}π^{-}π^{0}$ and $J/ψ\to ϕπ^{0}π^{0}π^{0}$ are investigated. The isospin violating decay $J/ψ\to ϕπ^{0} f_{0}(980)$ with $f_{0}(980) \to ππ$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $π^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/ψ\to ϕη'$, the branching fractions of $η' \to π^{+}π^{-}π^{0}$ and $η' \to π^{0}π^{0}π^{0}$, as well as their ratio, are also measured.

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arXiv2015

Search for $Z_c(3900)^\pm\toωπ^\pm$

The decay $Z_c(3900)^\pm\toωπ^\pm$ is searched for using data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s}=4.23$ and $4.26$~GeV. No significant signal for the $Z_c(3900)^\pm$ is found, and upper limits at the 90\% confidence level on the Born cross section for the process $e^+e^-\to Z_c(3900)^\pmπ^\mp\toωπ^+π^-$ are determined to be $0.26$ and $0.18$ pb at $\sqrt{s}=4.23$ and 4.26 GeV, respectively.

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arXiv2015

Searches for isospin-violating transitions $χ_{c0,2} \rightarrow π^{0} η_{c}$

We present the first upper-limit measurement of the branching fractions of the isospin-violating transitions $χ_{c0,2} \rightarrow π^{0} η_{c}$. The measurements are performed using $106\times 10^{6}$ $ψ(3686)$ events accumulated with the BESIII detector at the BEPCII $e^{+}e^{-}$ collider at a center-of-mass energy corresponding to the $ψ(3686)$ mass. We obtained upper limits on the branching fractions at a 90\% confidence level of $B(χ_{c0} \rightarrow π^{0} η_{c}) < 1.6 \times 10^{-3}$ and $B(χ_{c2} \rightarrow π^{0} η_{c}) < 3.2 \times 10^{-3}$.

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arXiv2015

Search for $D^0\toγγ$ and improved measurement of the branching fraction for $D^0 \to π^0π^0$

Using $2.92$ fb$^{-1}$ of electron-positron annihilation data collected at $\sqrt{s} = 3.773$~GeV with the BESIII detector, we report the results of a search for the flavor-changing neutral current process $D^0\toγγ$ using a double-tag technique. We find no signal and set an upper limit at $90\%$ confidence level for the branching fraction of $B(D^0\toγγ) < 3.8\times10^{-6}$. We also investigate $D^0$-meson decay into two neutral pions, obtaining a branching fraction of $B(D^0\toπ^0π^0) = (8.24\pm0.21(\text{stat.})\pm0.30(\text{syst.}))\times10^{-4}$, the most precise measurement to date and consistent with the current world average

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arXiv2015

Measurement of the Matrix Elements for the Decays $η\rightarrow π^{+}π^{-}π^0$ and $η/η^{\prime}\rightarrowπ^0π^0π^0$

Based on a sample of $1.31 \times 10^9$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider, Dalitz plot analyses of selected 79,625 $η\rightarrowπ^{+}π^{-}π^0$ events, 33,908 $η\rightarrowπ^0π^0π^0$ events and 1,888 $η^{\prime}\rightarrowπ^0π^0π^0$ events are performed. The measured matrix elements of $η\rightarrowπ^+π^-π^0$ are in reasonable agreement with previous measurements. The Dalitz plot slope parameters of $η\rightarrowπ^0π^0π^0$ and $η^{\prime}\rightarrowπ^0π^0π^0$ are determined to be $-0.055 \pm 0.014 \pm 0.004$ and $-0.640 \pm 0.046 \pm 0.047$, respectively, where the first uncertainties are statistical and the second systematic. Both values are consistent with previous measurements, while the precision of the latter one is improved by a factor of three. Final state interactions are found to have an important role in those decays.

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arXiv2015

Observation of the electromagnetic doubly OZI-suppressed decay $J/ψ\rightarrow ϕπ^{0}$

Using a sample of $1.31$ billion $J/ψ$ events accumulated with the BESIII detector at the BEPCII collider, we report the observation of the decay $J/ψ\rightarrow ϕπ^{0}$, which is the first evidence for a doubly Okubo-Zweig-Iizuka suppressed electromagnetic $J/ψ$ decay. A clear structure is observed in the $K^{+} K^{-}$ mass spectrum around 1.02 GeV/$c^2$, which can be attributed to interference between $J/ψ\rightarrow ϕπ^{0}$ and $J/ψ\rightarrow K^{+}K^{-}π^{0}$ decays. Due to this interference, two possible solutions are found. The corresponding measured values of the branching fraction of $J/ψ\to ϕπ^{0}$ are $[2.94 \pm 0.16\text{(stat.)} \pm 0.16\text{(syst.)}] \times 10^{-6}$ and $[1.24 \pm 0.33\text{(stat.)} \pm 0.30\text{(syst.)}] \times 10^{-7}$.

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arXiv2015

Measurement of the proton form factor by studying $e^{+} e^{-}\rightarrow p\bar{p}$

Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of $e^{+}e^{-}\rightarrow p\bar{p}$ at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal $(|G_{E}|= |G_{M}|)$. In addition, the ratio of electric to magnetic form factors, $|G_{E}/G_{M}|$, and $|G_{M}|$ are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at $\sqrt{s}=$ 2232.4 and 2400.0 MeV and a combined sample at $\sqrt{s}$ = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BaBar, improving the overall uncertainty by about 30\%. The $|G_{E}/G_{M}|$ ratios are close to unity and consistent with BaBar results in the same $q^{2}$ region, which indicates the data are consistent with the assumption that $|G_{E}|=|G_{M}|$ within uncertainties.

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arXiv2015

Measurement of $\mathcal B(ψ(3770)\toγχ_{c1})$ and search for $ψ(3770)\toγχ_{c2}$

We report a measurement of the branching fraction of $ψ(3770)\toγχ_{c1}$ and search for the transition $ψ(3770)\rightarrow γχ_{c2}$ based on 2.92~fb$^{-1}$ of $e^+e^-$ data accumulated at $\sqrt{s}=3.773$~GeV with the BESIII detector at the BEPCII collider. The measured branching fraction of $ψ(3770) \rightarrow γχ_{c1}$ is $\mathcal B(ψ(3770) \rightarrow γχ_{c1})=(2.48 \pm 0.15 \pm 0.23) \times 10^{-3}$, which is the most precise measurement to date. The upper limit on the branching fraction of $ψ(3770)\rightarrow γχ_{c2}$ at a $90\%$ confidence level is $\mathcal B(ψ(3770) \rightarrow γχ_{c2})<0.64 \times 10^{-3}$. The corresponding partial widths are $Γ(ψ(3770) \to γχ_{c1}) =(67.5\pm 4.1\pm 6.7)$~keV and $Γ(ψ(3770) \to γχ_{c2}) < 17.4$~keV.

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arXiv2015

Observation of the $ψ(1^3D_2)$ state in $e^+e^-\toπ^+π^-γχ_{c1}$ at BESIII

We report the observation of the $X(3823)$ in the process $e^+e^-\to π^+π^-X(3823) \to π^+π^-γχ_{c1}$ with a statistical significance of $6.2σ$, in data samples at center-of-mass energies $\sqrt{s}=$4.230, 4.260, 4.360, 4.420 and 4.600~GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the $X(3823)$ is $(3821.7\pm 1.3\pm 0.7)$~MeV/$c^2$, where the first error is statistical and the second systematic, and the width is less than $16$~MeV at the 90\% confidence level. The products of the Born cross sections for $e^+e^-\to π^+π^-X(3823)$ and the branching ratio $\mathcal{B}[X(3823)\to γχ_{c1,c2}]$ are also measured. These measurements are in good agreement with the assignment of the $X(3823)$ as the $ψ(1^3D_2)$ charmonium state.

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arXiv2015

An Improved Limit for Gamma_ee of X(3872) and Gamma_ee Measurement of psi(3686)

Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e+e- -> gamma_ISR X(3872) -> gamma_ISR pi+pi-J/psi via the Initial State Radiation technique. The production of a resonance with quantum numbers J^PC = 1^++ such as the X(3872) via single photon e+e- annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction Gamma_ee^X(3872)Br(X(3872) -> pi+pi-Jψ) < 0.13 eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the psi(3686) to be Gamma_ee^psi(3686) = 2231 +- 18 +- 99 eV.

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arXiv2015

Measurement of $y_{CP}$ in $D^0-\overline{D}^0$ oscillation using quantum correlations in $e^+e^-\to D^0\overline{D}^0$ at $\sqrt{s}$ = 3.773\,GeV

We report a measurement of the parameter $y_{CP}$ in $\ensuremath{D^0}\xspace-\ensuremath{\overline{D}^{0}}\xspace$ oscillations performed by taking advantage of quantum coherence between pairs of $\ensuremath{D^0}\xspace \ensuremath{\overline{D}^{0}}\xspace$ mesons produced in $e^+e^-$ annihilations near threshold. In this work, doubly-tagged $\ensuremath{D^0}\xspace \ensuremath{\overline{D}^{0}}\xspace$ events, where one $D$ decays to a $CP$ eigenstate and the other $D$ decays in a semileptonic mode, are reconstructed using a data sample of 2.92\,fb$^{-1}$ collected with the BESIII detector at the center-of-mass energy of $\sqrt{s}$ = 3.773\,GeV. We obtain $y_{CP} = (-2.0\pm1.3\pm0.7)\%$, where the first uncertainty is statistical and the second is systematic. This result is compatible with the current world average.

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arXiv2015

Observation of the Dalitz Decay $η' \to γe^+e^-$

We report the first observation of the Dalitz decay $η' \to γe^+e^-$, based on a data sample of 1.31 billion $J/ψ$ events collected with the BESIII detector. The $η'$ mesons are produced via the $J/ψ\to γη'$ decay process. The ratio $Γ(η' \to γe^+ e^-)/Γ(η'\toγγ)$ is measured to be $(2.13\pm0.09(\text{stat.})\pm0.07(\text{sys.}))\times10^{-2}$. This corresponds to a branching fraction ${\cal B}(η' \to γe^+e^-)= (4.69 \pm0.20(\text{stat.})\pm0.23(\text{sys.}))\times10^{-4}$. The transition form factor is extracted and different expressions are compared to the measured dependence on the $e^+e^-$ invariant mass. The results are consistent with the prediction of the Vector Meson Dominance model.

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arXiv2015

Measurements of $ψ(3686) \to K^{-} Λ\barΞ^{+} +c.c.$ and $ψ(3686) \to γK^{-} Λ\barΞ^{+} +c.c$

Using a sample of $1.06\times10^8\ \psip$ events produced in $e^+e^-$ collisions at $\sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $\klx+c.c.$ and $\gklx+c.c.$. We observe two hyperons, $Ξ(1690)^-$ and $Ξ(1820)^-$, in the $K^-Λ$ invariant mass distribution in the decay $\klx+c.c.$ with significances of $4.9 σ$ and $6.2 σ$, respectively. The branching fractions of $\klx+c.c.$, $\ksx+c.c.$, $\psip\toγχ_{cJ}\to γK^- Λ\barΞ^+ +c.c.$ $(J=0,\ 1,\ 2)$, and $\psip\to Ξ(1690/1820)^{-} \barΞ^++c.c$ with subsequent decay $Ξ(1690/1820)^-\to K^-Λ$ are measured for the first time.

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arXiv2015

Measurement of the $e^{+}e^{-} \to ηJ/ψ$ cross section and search for $e^{+}e^{-} \to π^{0} J/ψ$ at center-of-mass energies between 3.810 and 4.600~GeV

Using data samples collected with the BESIII detector operating at the BEPCII collider at center-of-mass energies from 3.810 to 4.600 GeV, we perform a study of $e^{+}e^{-} \to ηJ/ψ$ and $π^0 J/ψ$. Statistically significant signals of $e^{+}e^{-} \to ηJ/ψ$ are observed at $\sqrt{s}$ = 4.190, 4.210, 4.220, 4.230, 4.245, 4.260, 4.360 and 4.420 GeV, while no signals of $e^{+}e^{-} \to π^{0} J/ψ$ are observed. The measured energy-dependent Born cross section for $e^{+}e^{-} \to ηJ/ψ$ shows an enhancement around 4.2~GeV. The measurement is compatible with an earlier measurement by Belle, but with a significantly improved precision.

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arXiv2015

Precision measurement of the integrated luminosity of the data taken by BESIII at center of mass energies between 3.810 GeV and 4.600 GeV

From December 2011 to May 2014, about 5 $\rm fb^{-1}$ of data were taken with the BESIII detector at center-of-mass energies between 3.810 GeV and 4.600 GeV to study the charmoniumlike states and higher excited charmonium states. The time integrated luminosity of the collected data sample is measured to a precision of 1% by analyzing events produced by the large-angle Bhabha scattering process.

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arXiv2015

Observation of $e^+e^-\to π^0π^0 h_c$ and a neutral charmoniumlike structure $Z_c(4020)^0$

Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of $\sqrt{s}=4.23$, 4.26, and 4.36~GeV, we observe $\EE\to \pphc$ for the first time. The Born cross sections are measured and found to be about half of those of $\EE\to π^+π^-h_c$ within less than 2$σ$. In the $π^0h_c$ mass spectrum, a structure at 4.02~GeV/$c^2$ is found. It is most likely to be the neutral isospin partner of the $\zcp^{\pm}$ observed in the process of $\EE\to π^+π^-h_c$ is found. A fit to the $π^0 h_c$ invariant mass spectrum, with the width of the $\zcpn$ fixed to that of its charged isospin partner and possible interferences with non-$\zcpn$ amplitudes neglected, gives a mass of ($4023.9\pm 2.2 \pm 3.8$)~MeV/$c^2$ for the $\zcpn$, where the first error is statistical and the second systematic.

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