arXiv subjects

X. K. Chu

Publications and source records attributed to X. K. Chu.

At least 127 records · Page 7Linked to original sources

arXiv2016

Improved measurement of the absolute branching fraction of $D^{+}\rightarrow \bar K^0 μ^{+}ν_μ$

By analyzing 2.93 fb$^{-1}$ of data collected at $\sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction ${\mathcal B}(D^{+}\rightarrow\bar K^0μ^{+}ν_μ)=(8.72 \pm 0.07_{\rm stat.} \pm 0.18_{\rm sys.})\%$, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of ${\mathcal B}(D^0\to K^-μ^+ν_μ)$, ${\mathcal B}(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})$, and the lifetimes of the $D^0$ and $D^+$ mesons with the value of ${\mathcal B}(D^{+}\rightarrow\bar K^0 μ^{+}ν_μ)$ measured in this work, we determine the following ratios of partial widths: $Γ(D^0\to K^-μ^+ν_μ)/Γ(D^{+}\rightarrow\bar K^0μ^{+}ν_μ)=0.963\pm0.044$ and $Γ(D^{+}\rightarrow\bar K^0 μ^{+}ν_μ)/Γ(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})=0.988\pm0.033$.

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arXiv2016

Observation of $e^{+}e^{-} \to η^{\prime} J/ψ$ at center-of-mass energies between 4.189 and 4.600 GeV

The process $e^{+}e^{-}\to η^{\prime} J/ψ$ is observed for the first time with a statistical significance of $8.6σ$ at center-of-mass energy $\sqrt{s} = 4.226$ GeV and $7.3σ$ at $\sqrt{s} = 4.258$ GeV using data samples collected with the BESIII detector. The Born cross sections are measured to be $(3.7 \pm 0.7 \pm 0.3)$ and $(3.9 \pm 0.8 \pm 0.3)$ pb at $\sqrt{s} = 4.226$ and $4.258$ GeV, respectively, where the first errors are statistical and the second systematic. Upper limits at the 90% confidence level of the Born cross sections are also reported at other 12 energy points.

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arXiv2016

Measurement of the absolute branching fraction of $D^{+}\rightarrow\bar K^0 e^{+}ν_{e}$ via $\bar K^0\toπ^0π^0$

By analyzing 2.93 fb$^{-1}$ data collected at the center-of-mass energy $\sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay $D^+\rightarrow\bar K^0 e^{+}ν_{e}$ to be ${\mathcal B}(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})=(8.59 \pm 0.14 \pm 0.21)\%$ using $\bar K^0\to K^0_S\to π^0π^0$, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties.

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arXiv2016

Observation of an anomalous line shape of the $η^{\prime}π^{+}π^{-}$ mass spectrum near the $p\bar{p}$ mass threshold in $J/ψ\rightarrowγη^{\prime}π^{+}π^{-}$

Using $1.09\times10^{9}$ $J/ψ$ events collected by the BESIII experiment in 2012, we study the $J/ψ\rightarrowγη^{\prime}π^{+}π^{-}$ process and observe a significant abrupt change in the slope of the $η^{\prime}π^{+}π^{-}$ invariant mass distribution at the proton-antiproton ($p\bar{p}$) mass threshold. We use two models to characterize the $η^{\prime}π^{+}π^{-}$ line shape around $1.85~\text{GeV}/c^{2}$: one which explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another which is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around $1.85~\text{GeV}/c^{2}$ with strong couplings to $p\bar{p}$ final states or a narrow state just below the $p\bar{p}$ mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a $p\bar{p}$ molecule-like state or bound state with greater than $7σ$ significance.

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arXiv2016

Study of $ψ$ decays to the $Ξ^{-}\barΞ^{+}$ and $Σ(1385)^{\mp}\barΣ(1385)^{\pm}$ final states

We study the decays of the charmonium resonances $J/ψ$ and $ψ(3686)$ to the final states $Ξ^{-}\barΞ^{+}$, $Σ(1385)^{\mp}\barΣ(1385)^{\pm}$ based on a single baryon tag method using data samples of $(223.7 \pm 1.4) \times 10^{6}$ $J/ψ$ and $(106.4 \pm 0.9) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. The decay $ψ(3686)\rightarrowΣ(1385)^{\mp}\barΣ(1385)^{\pm}$ is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with and much more precise than the previously published results. Additionally, the ratios $\frac{\cal{B}(ψ(3686)\rightarrowΞ^{-}\barΞ^{+})}{\cal{B}(J/ψ\rightarrowΞ^{-}\barΞ^{+})}$, $\frac{\cal{B}(ψ(3686)\rightarrowΣ(1385)^{-}\barΣ(1385)^{+})}{\cal{B}(J/ψ\rightarrowΣ(1385)^{-}\barΣ(1385)^{+})}$ and $\frac{\cal{B}(ψ(3686)\rightarrowΣ(1385)^{+}\barΣ(1385)^{-})}{\cal{B}(J/ψ\rightarrowΣ(1385)^{+}\barΣ(1385)^{-})}$ are determined.

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arXiv2016

Study of $J/ψ\to p\bar{p}ϕ$ at BESIII

Using a data sample of $1.31 \times 10^{9}$ $J/ψ$ events accumulated with the BESIII detector, the decay $J/ψ\to p\bar{p}ϕ$ is studied via two decay modes, $ϕ\to K^{0}_{S}K^{0}_{L}$ and $ϕ\to K^{+}K^{-}$. The branching fraction of $J/ψ\to p\bar{p}ϕ$ is measured to be $\mathcal{B}(J/ψ\to p\bar{p}ϕ)=[5.23\pm0.06(\mbox{stat})\pm0.33(\mbox{syst})]\times10^{-5}$, which agrees well with a previously published measurement, but with a significantly improved precision. No evident enhancement near the $p\bar{p}$ mass threshold, denoted as $X(p\bar{p})$, is observed, and the upper limit on the branching fraction of $J/ψ\to X(p\bar{p})ϕ\to p\bar{p}ϕ$ is determined to be $\mathcal{B}(J/ψ\to X(p\bar{p})ϕ\to p\bar{p}ϕ)<2.1\times10^{-7}$ at the 90\% confidence level.

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arXiv2016

Search for the weak decay $η^{\prime}\to K^{\pm}π^{\mp}$ and precise measurement of the branching fraction ${\cal B}(J/ψ\toϕη^{\prime})$

We present the first search for the rare decay of $η^\prime$ into $K^{\pm}π^{\mp}$ in $J/ψ\toϕη^{\prime}$, using a sample of $1.3\times10^{9}$ $J/ψ$ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90\% confidence level for the ratio $\frac{{\cal B}(η^{\prime}\to K^{\pm}π^{\mp})}{{\cal B}(η^{\prime}\toγπ^{+}π^{-})}$ is determined to be $1.3\times10^{-4}$. In addition, we report the measurement of the branching fraction of $J/ψ\toϕη^{\prime}$ to be $(5.10\pm0.03(\text{stat.})\pm0.32(\text{syst.}))\times10^{-4}$, which agrees with previous results from BESII.

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arXiv2016

Measurements of absolute hadronic branching fractions of $Λ_{c}^{+}$ baryon

Using $567\rm{pb}^{-1}$ of $e^+e^-$ collisions recorded at $\sqrt{s}=4.599\rm{GeV}$ with the BESIII detector, we report first measurements of absolute hadronic branching fractions of Cabibbo-favored decays of the $Λ_{c}^{+}$ baryon with a double-tag technique. A global least-square fitter is utilized to improve the measured precision. Among the measurements for twelve $Λ_{c}^{+}$ decay modes, the branching fraction for $Λ_{c}^{+} \rightarrow pK^-π^+$ is determined to be $(5.84\pm0.27\pm0.23)\%$, where the first uncertainty is statistical and the second is systematic. In addition, the measurements of the branching fractions of the other eleven Cabbibo-favored hadronic decay modes are significantly improved.

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arXiv2016

Measurement of azimuthal asymmetries in inclusive charged dipion production in $e^+e^-$ annihilations at $\sqrt{s}$ = 3.65 GeV

We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^-\rightarrow ππX$ based on a data set of 62 $\rm{pb}^{-1}$ at the center-of-mass energy $\sqrt{s}=3.65$ GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.

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arXiv2015

Observation of the Singly Cabibbo-Suppressed Decay $D^{+}\toωπ^{+}$ and Evidence for $D^{0}\toωπ^{0}$

Based on 2.93 fb$^{-1}$ $e^+e^-$ collision data taken at center-of-mass energy of 3.773 GeV by the BESIII detector, we report searches for the singly Cabibbo-suppressed decays $D^{+}\toωπ^{+}$ and $D^{0}\toωπ^{0}$. A double tag technique is used to measure the absolute branching fractions $\mathcal{B}(D^{+}\toωπ^{+})=(2.79\pm0.57\pm0.16)\times 10^{-4}$ and $\mathcal{B}(D^{0}\toωπ^{0})=(1.17\pm0.34\pm0.07)\times 10^{-4}$, with statistical significances of $5.5σ$ and $4.1σ$, respectively. We also present measurements of the absolute branching fractions for the related $ηπ$ decay modes. We find $\mathcal{B}(D^{+}\toηπ^{+})=(3.07\pm0.22\pm0.13)\times10^{-3}$ and $\mathcal{B}(D^{0}\toηπ^{0})=(0.65\pm0.09\pm0.04)\times10^{-3}$, which are consistent with the current world averages. The first and second uncertainties are statistical and systematic, respectively.

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arXiv2015

Measurement of the branching fraction for $ψ(3770) \to γχ_{c0}$

By analyzing a data set of 2.92 fb$^{-1}$ of $e^+e^-$ collision data taken at $\sqrt s= 3.773~\rm GeV$ and 106.41$\times 10^{6}$ $ψ(3686)$ decays taken at $\sqrt s= 3.686~\rm GeV$ with the BESIII detector at the BEPCII collider, we measure the branching fraction and the partial decay width for $ψ(3770)\toγχ_{c0}$ to be ${\mathcal B}(ψ(3770)\toγχ_{c0})=(6.88\pm0.28\pm0.67)\times 10^{-3}$ and $Γ[ψ(3770)\toγχ_{c0}]=(187\pm8\pm19)~\rm keV$, respectively. These are the most precise measurements to date.

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arXiv2015

Search for the isospin violating decay $Y(4260)\rightarrow J/ψηπ^{0}$

Using data samples collected at center of mass energies of $\sqrt{s}$ = 4.009, 4.226, 4.257, 4.358, 4.416 and 4.599 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the isospin violating decay $Y(4260)\rightarrow J/ψηπ^{0}$. No signal is observed, and upper limits on the cross section $σ(e^{+}e^{-}\rightarrow J/ψηπ^{0})$ at the 90\% confidence level are determined to be 3.6, 1.7, 2.4, 1.4, 0.9 and 1.9 pb, respectively.

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arXiv2015

Study of decay dynamics and $CP$ asymmetry in $D^+ \to K^0_L e^+ ν_e$ decay

Using 2.92~fb$^{-1}$ of electron-positron annihilation data collected at $\sqrt{s} = 3.773$~GeV with the BESIII detector, we obtain the first measurements of the absolute branching fraction $\mathcal{B}(D^+ \to K^0_L e^+ ν_e) = (4.481 \pm 0.027(\mathrm{stat.}) \pm 0.103(\mathrm{sys.}))\%$ and the $CP$ asymmetry $A_{CP}^{D^+ \to K^0_L e^+ ν_e} = (-0.59 \pm 0.60(\mathrm{stat.}) \pm 1.48(\mathrm{sys.}))\%$. From the $D^+ \to K^0_L e^+ ν_e$ differential decay rate distribution, the product of the hadronic form factor and the magnitude of the CKM matrix element, $f_{+}^{K}(0)|V_{cs}|$, is determined to be $0.728 \pm 0.006(\mathrm{stat.}) \pm 0.011(\mathrm{sys.})$. Using $|V_{cs}|$ from the SM constrained fit with the measured $f_{+}^{K}(0)|V_{cs}|$, $f_{+}^{K}(0) = 0.748 \pm 0.007(\mathrm{stat.}) \pm 0.012(\mathrm{sys.})$ is obtained, and utilizing the unquenched LQCD calculation for $f_{+}^{K}(0)$, $|V_{cs}| = 0.975 \pm 0.008(\mathrm{stat.}) \pm 0.015(\mathrm{sys.}) \pm 0.025(\mathrm{LQCD})$.

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arXiv2015

Observation of a Neutral Structure near the $D\bar{D}^{}$ Mass Threshold in $e^{+}e^{-}\to (D \bar{D}^)^0π^0$ at $\sqrt{s}$ = 4.226 and 4.257 GeV

A neutral structure in the $D\bar{D}^{*}$ system around the $D\bar{D}^{*}$ mass threshold is observed with a statistical significance greater than 10$σ$ in the processes $e^{+}e^{-}\rightarrow D^{+}D^{*-}π^{0}+c.c.$ and $e^{+}e^{-}\rightarrow D^{0}\bar{D}^{*0}π^{0}+c.c.$ at $\sqrt{s}$ = 4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as $Z_{c}(3885)^{0}$. Assuming the presence of a resonance, its pole mass and width are determined to be ($3885.7^{+4.3}_{-5.7}$(stat)$\pm 8.4$(syst)) MeV/$c^{2}$ and ($35^{+11}_{-12}$(stat)$ \pm 15$(syst)) MeV, respectively. The Born cross sections are measured to be $σ(e^{+}e^{-}\to Z_{c}(3885)^{0}π^{0}, Z_{c}(3885)^{0} \to D\bar{D}^{*})=(77 \pm 13$(stat)$\pm 17$(syst)) pb at 4.226 GeV and ($47 \pm 9$(stat)$ \pm 10$(syst)) pb at 4.257 GeV. The ratio of decay rates $\frac{\mathcal{B}({Z_{c}(3885)^{0} \to D^{+}D^{*-}+c.c.})}{\mathcal{B}({Z_{c}(3885)^{0} \to D^{0}\bar{D}^{*0}+c.c.})}$ is determined to be $0.96 \pm 0.18$(stat)$\pm 0.12$(syst), consistent with no isospin violation in the process $Z_{c}(3885)^{0}\to D\bar{D}^*$.

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arXiv2015

Measurement of the $\mathrm e^+\mathrm e^-\rightarrow\mathrmπ^+\mathrmπ^-$ Cross Section between 600 and 900 MeV Using Initial State Radiation

We extract the $e^+e^-\rightarrow π^+π^-$ cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb$^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor $|F_π|^2$ as well as the contribution of the measured cross section to the leading order hadronic vacuum polarization contribution to $(g-2)_μ$. We find this value to be $a_μ^{ππ,\rm LO}(600-900\;\rm MeV) = (368.2 \pm 2.5_{\rm stat} \pm 3.3_{\rm sys})\cdot 10^{-10}$.

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arXiv2015

Confirmation of a charged charmoniumlike state $Z_c(3885)^{\mp}$ in $e^+e^-\toπ^{\pm}(D\bar{D}^*)^\mp$ with double $D$ tag

We present a study of the process $e^+e^-\toπ^{\pm}(D\bar{D}^*)^{\mp}$ using data samples of 1092~pb$^{-1}$ at $\sqrt{s}=4.23$~GeV and 826~pb$^{-1}$ at $\sqrt{s}=4.26$~GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the $D$ meson pair and the bachelor $π^{\pm}$ in the final state, we confirm the existence of the charged structure $Z_c(3885)^{\mp}$ in the $(D\bar{D}^*)^{\mp}$ system in the two isospin processes $e^+e^-\toπ^+D^0D^{*-}$ and $e^+e^-\toπ^+D^-D^{*0}$. By performing a simultaneous fit, the statistical significance of $Zc(3885)^{\mp}$ signal is determined to be greater than 10$σ$, and its pole mass and width are measured to be $M_{\rm{pole}}$=(3881.7$\pm$1.6(stat.)$\pm$1.6(syst.))~MeV/$c^2$ and $Γ_{\rm{pole}}$=(26.6$\pm$2.0(stat.)$\pm$2.1(syst.))~MeV, respectively. The Born cross section times the $(D\bar{D}^*)^{\mp}$ branching fraction ($σ(e^+e^-\toπ^{\pm}Z_{c}(3885)^{\mp}) \times Br(Z_{c}(3885)^{\mp}\to(D\bar{D}^*)^{\mp})$) is measured to be $(141.6\pm7.9(\text{stat.})\pm12.3(\text{syst.}))~\text{pb}$ at $\sqrt{s}=4.23$~GeV and $(108.4\pm6.9(\text{stat.})\pm8.8(\text{syst.}))~\text{pb}$ at $\sqrt{s}=4.26$~GeV. The polar angular distribution of the $π^{\pm}$-$Z_c(3885)^{\mp}$ system is consistent with the expectation of a quantum number assignment of $J^P=1^+$ for $Z_c(3885)^{\mp}$.

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arXiv2015

Measurement of the center-of-mass energies at BESIII via the di-muon process

From 2011 to 2014, the BESIII experiment collected about 5 fb$^{-1}$ data at center-of-mass energies around 4 GeV for the studies of the charmonium-like and higher excited charmonium states. By analyzing the di-muon process $e^{+}e^{-}\rightarrowγ_{\rm ISR/FSR}μ^{+}μ^{-}$, the center-of-mass energies of the data samples are measured with a precision of 0.8 MeV. The center-of-mass energy is found to be stable for most of time during the data taking.

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arXiv2015

Measurement of the branching fractions of $D_{s}^{+}\rightarrow η'X$ and $D_{s}^{+}\rightarrow η'ρ^{+}$ in $e^+e^-\to D^+_{s}D^-_{s}$

We study $D_{s}^{+}$ decays to final states involving the $η'$ with a 482$\,$pb$^{-1}$ data sample collected at $\sqrt{s}$ = 4.009$\,$GeV with the \mbox{BESIII} detector at the BEPCII collider. We measure the branching fractions $\mathcal{B}(D^+_{s}\rightarrow η'X)$ = (8.8$\pm$1.8$\pm$0.5)$\%$ and $\mathcal{B}(D_{s}^{+}\rightarrow η'ρ^{+})$ = ($5.8\pm1.4\pm0.4$)$\%$ where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the non-resonant branching ratio $\mathcal{B}(D_{s}^{+}\rightarrow η'π^+π^0)<5.1\%$ at the 90$\%$ confidence level. Our results are consistent with CLEO's recent measurements and help to resolve the disagreement between the theoretical prediction and CLEO's previous measurement of $\mathcal{B}(D_{s}^{+}\rightarrow η'ρ^{+})$.

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