arXiv subjects

F. Cossio

Publications and source records attributed to F. Cossio.

At least 541 records · Page 30Linked to original sources

arXiv2021

Measurement of the branching fraction of leptonic decay $D_s^+\toτ^+ν_τ$ via $τ^+\toπ^+π^0\bar ν_τ$

By analyzing $6.32~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at the center-of-mass energies between 4.178 and 4.226\,GeV with the BESIII detector, we determine the branching fraction of the leptonic decay $D_s^+\toτ^+ν_τ$ with $τ^+\toπ^+π^0\bar ν_τ$, to be $\mathcal{B}_{D_s^+\toτ^+ν_τ}=(5.29\pm0.25_{\rm stat}\pm0.20_{\rm syst})\%$. We estimate the product of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ and the $D_s^+$ decay constant $f_{D^+_s}$ to be $f_{D_s^+}|V_{cs}|=(244.8\pm5.8_{\rm stat}\pm4.8_{\rm syst})~\mathrm{MeV}$ using the known values of the $τ^+$ and $D_s^+$ masses as well as the $D_s^+$ lifetime, together with our branching fraction measurement. Combining with the value of $|V_{cs}|$ obtained from a global fit in the standard model and $f_{D_s^+}$ from lattice quantum chromodynamics, we obtain $f_{D_s^+}=(251.6\pm5.9_{\rm stat}\pm4.9_{\rm syst})$\,MeV and $|V_{cs}| = 0.980\pm0.023_{\rm stat}\pm0.019_{\rm syst}$.

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arXiv2021

Measurement of cross section for $e^{+}e^{-}\rightarrowΞ^{0}\barΞ^{0}$ near threshold

Using $e^+e^-$ collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb$^{-1}$, we measure the cross sections and effective form factors for the process $e^{+}e^{-}\rightarrowΞ^{0}\barΞ^{0}$ utilizing a single-tag method. A fit to the cross section of $e^{+}e^{-}\rightarrowΞ^{0}\barΞ^{0}$ with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes $e^{+}e^{-}\rightarrowΞ^{-}\barΞ^{+}$ and $Ξ^{0}\barΞ^{0}$ is calculated using recent BESIII measurement and is found to be compatible with expectation from isospin symmetry.

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arXiv2021

Measurements of Born Cross Sections of $e^+e^-\to D_s^{*+} D_{sJ}^{-} +c.c.$

The Born cross sections are measured for the first time for the processes $e^+e^-\to D_s^{*+}D_{s0}^*(2317)^- +c.c.$ and $e^+e^-\to D_s^{*+}D_{s1}(2460)^- +c.c.$ at the center-of-mass energy $\sqrt{s}=$ 4.600~GeV, 4.612~GeV, 4.626~GeV, 4.640~GeV, 4.660~GeV, 4.68~GeV, and 4.700~GeV, and for $e^+e^-\to D_s^{*+}D_{s1}(2536)^- +c.c.$ at $\sqrt{s}=$ 4.660~GeV, 4.680~GeV, and 4.700~GeV, using data samples collected with the BESIII detector at the BEPCII collider. No structures are observed in cross-section distributions for any of the processes.

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arXiv2021

Amplitude analysis and branching fraction measurement of $D_{s}^{+} \rightarrow K^{+}K^{-}π^{+}$

We report an amplitude analysis and branching fraction measurement of $D_{s}^{+} \rightarrow K^{+}K^{-}π^{+}$ decay using a data sample of 3.19 $\rm fb^{-1}$ recorded with BESIII detector at a center-of-mass energy of 4.178 GeV. We perform a model-independent partial wave analysis in the low $K^{+}K^{-}$ mass region to determine the $K^{+}K^{-}$ S-wave lineshape, followed by an amplitude analysis of our very pure high-statistics sample. The amplitude analysis provides an accurate determination of the detection efficiency allowing us to measure the branching fraction ${\cal B}(D_{s}^{+} \rightarrow K^{+}K^{-}π^{+}) = (5.47\pm0.08_{\rm stat}\pm0.13_{\rm sys})\%$.

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arXiv2021

Study of the decay $D^+\to K^*(892)^+ K_S^0$ in $D^+\to K^+ K_S^0 π^0$

Based on an $e^{+}e^{-}$ collision data sample corresponding to an integrated luminosity of 2.93 $\mathrm{fb}^{-1}$ collected with the BESIII detector at $\sqrt{s}=3.773 \mathrm{GeV}$, the first amplitude analysis of the singly Cabibbo-suppressed decay $D^{+}\to K^+ K_S^0 π^0$ is performed. From the amplitude analysis, the $K^*(892)^+ K_S^0$ component is found to be dominant with a fraction of $(57.1\pm2.6\pm4.2)\%$, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction $\mathcal{B}(D^+\to K^+ K_S^0 π^0)$ measured by BESIII, we obtain $\mathcal{B}(D^+\to K^*(892)^+ K_S^0)=(8.69\pm0.40\pm0.64\pm0.51)\times10^{-3}$, where the third uncertainty is due to the branching fraction $\mathcal{B}(D^+\to K^+ K_S^0 π^0)$. The precision of this result is significantly improved compared to the previous measurement.

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arXiv2021

First Measurement of the Absolute Branching Fraction of $Λ\to p μ^- \barν_μ$

The absolute branching fraction of $Λ\to p μ^- \barν_μ$ is reported for the first time based on an $e^+e^-$ annihilation sample of ten billion $J/ψ$ events collected with the BESIII detector at $\sqrt{s}=3.097$ GeV. The branching fraction is determined to be ${\mathcal B}(Λ\to pμ^- \barν_μ) = [1.48\pm0.21(\rm stat) \pm 0.08(\rm syst)]\times 10^{-4}$, which is a significant improvement in precision over the previous indirect measurements. Combining this result with the world average of ${\mathcal B}(Λ\to p e^- \barν_{e})$, we obtain the ratio, $\frac{Γ(Λ\to p μ^- \barν_μ)}{Γ(Λ\to p e^- \barν_{e})}$, to be $0.178 \pm 0.028$, which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of $Λ\to p μ^- \barν_μ$ and $\barΛ \to \bar{p} μ^+ ν_μ$ is also determined, and no evidence for $CP$ violation is found.

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arXiv2021

Study of the process $e^{+}e^{-}\rightarrowϕη$ at center-of-mass energies between 2.00 and 3.08 GeV

The process $e^{+}e^{-} \rightarrow ϕη$ is studied at 22 center-of-mass energy points ($\sqrt{s}$) between 2.00 and 3.08 GeV using 715 pb$^{-1}$ of data collected with the BESIII detector. The measured Born cross section of $e^{+}e^{-} \rightarrow ϕη$ is found to be consistent with {\textsl{BABAR}} measurements, but with improved precision. A resonant structure around 2.175 GeV is observed with a significance of 6.9$σ$ with mass ($2163.5\pm6.2\pm3.0$) MeV/$c^{2}$ and width ($31.1_{-11.6}^{+21.1}\pm1.1$) MeV, where the first uncertainties are statistical and the second are systematic.

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arXiv2021

Search for the rare semi-leptonic decay $J/ψ\to D^{-}e^{+}ν_{e}+c.c.$

Using $10.1\times10^{9}$ $J/ψ$ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $\sqrt{s}=3.097~\rm{GeV}$ and collected with the BESIII detector, we present a search for the rare semi-leptonic decay $J/ψ\to D^{-}e^{+}ν_{e}+c.c.$. No excess of signal above background is observed, and an upper limit on the branching fraction $\mathcal{B}(J/ψ\to D^{-}e^{+}ν_{e}+c.c.)<7.1\times10^{-8}$ is obtained at $90\%$ confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.

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arXiv2021

Search for the lepton number violating decay $Σ^{-} \to p e^{-} e^{-}$ and the rare inclusive decay $Σ^{-} \to Σ^{+} X$

Using a data sample of $(1310.6 \pm 7.0) \times 10^{6}$ $J/ψ$ events taken with the BESIII detector at the center-of-mass energy of 3.097 GeV, we search for the first time for the lepton number violating decay $Σ^{-} \to p e^{-} e^{-}$ and the rare inclusive decay $Σ^{-} \to Σ^{+} X$, where $X$ denotes any possible particle combination. The $Σ^-$ candidates are tagged in $J/ψ\to \barΣ(1385)^+Σ^-$ decays. No signal candidates are found, and the upper limits on the branching fractions at the 90\% confidence level are determined to be $\mathcal{B}(Σ^{-} \to p e^{-} e^{-}) < 6.7 \times 10^{-5}$ and $\mathcal{B}(Σ^{-} \to Σ^{+} X) < 1.2 \times 10^{-4}$.

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arXiv2021

Observation of the decays $χ_{cJ}\to n K^{0}_{S}\barΛ+ c.c.$

By analyzing $4.48\times10^8$ $ψ(3686)$ events collected with the BESIII detector, we observe the decays $χ_{cJ} \to n K^0_S\barΛ+ c.c.$ ($J=0$, 1, 2) for the first time, via the radiative transition $ψ(3686) \to γχ_{cJ}$. The branching fractions are determined to be $(6.67 \pm 0.26_{\rm stat} \pm 0.41_{\rm syst})\times10^{-4}$, $(1.71 \pm 0.12_{\rm stat} \pm 0.12_{\rm syst})\times10^{-4}$, and $(3.66 \pm 0.17_{\rm stat} \pm 0.23_{\rm syst})\times10^{-4}$ for $J=0$, 1, and 2, respectively.

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arXiv2021

Search for the charged lepton flavor violating decay $J/ψ\to eτ$

A search for the charged lepton flavor violating decay $J/ψ\to e^{\pm}τ^{\mp}$ with $τ^{\mp} \to π^{\mp}π^0ν_τ$ is performed with about $10$ billion $J/ ψ$ events collected with the BESIII detector at the BEPCII. No significant signal is observed, and an upper limit is set on the branching fraction $\mathcal{B}(J/ψ\to e^{\pm}τ^{\mp})<7.5\times10^{-8}$ at the 90$\%$ confidence level. This improves the previously published limit by two orders of magnitude.

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arXiv2021

Study of $e^+e^- \rightarrow π^{0}X(3872)γ$ and search for $Z_c(4020)^{0}\rightarrow X(3872)γ$

Using data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.178 to 4.600 GeV, we study the process $e^+e^-\rightarrowπ^{0}X(3872)γ$ and search for $Z_c(4020)^{0}\rightarrow X(3872)γ$. We find no significant signal and set upper limits on $σ(e^+e^-\rightarrowπ^{0}X(3872)γ)\cdot\mathcal{B}(X(3872)\rightarrowπ^{+}π^{-}J/ψ)$ and $σ(e^+e^-\rightarrowπ^{0}Z_c(4020)^{0})\cdot\mathcal{B}(Z_c(4020)^{0}\rightarrow X(3872)γ)\cdot\mathcal{B}(X(3872)\rightarrowπ^{+}π^{-}J/ψ)$ for each energy point at $90\%$ confidence level, which is of the order of several tenths pb.

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arXiv2021

Measurement of the doubly Cabibbo-suppressed decay $D^+\to K^+π^+π^-π^0$ with semileptonic tags

Using an $e^+e^-$ annihilation data sample corresponding to an integrated luminosity of $2.93\,\rm fb^{-1}$ collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the doubly Cabibbo-suppressed decay $D^+\to K^+π^+π^-π^0$ is studied with a semileptonic tag method. After removing the decays containing narrow intermediate resonances, $D^+\to K^+η$, $D^+\to K^+ω$, and $D^+\to K^+ϕ$, the branching fraction for the decay $D^+\to K^+π^+π^-π^0$ is determined to be $(1.03 \pm 0.12_{\rm stat} \pm 0.06_{\rm syst})\times 10^{-3}$. The ratio of the branching fraction for $D^+\to K^+π^+π^-π^0$ to its Cabibbo-favored counterpart $D^+\to K^-π^+π^+π^0$ is measured to be $ (1.65\pm0.21)\%$, corresponding to $(5.73\pm0.73)\tan^4θ_C$, where $θ_C$ is the Cabibbo mixing angle. These results are consistent with our previous measurement with hadronic tags but are significantly larger than other doubly Cabibbo-suppressed decays in the charm sector.

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arXiv2021

Cross section measurement of $e^{+}e^{-} \to K_{S}^{0}K_{L}^{0}$ at $\sqrt{s}=2.00-3.08~{\rm GeV}$

The cross sections of the process $e^{+}e^{-} \to K_{S}^{0}K_{L}^{0}$ are measured at fifteen center-of-mass energies $\sqrt{s}$ from $2.00$ to $3.08~{\rm GeV}$ with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results are found to be consistent with those obtained by BaBar. A resonant structure around $2.2~{\rm GeV}$ is observed, with a mass and width of $2273.7 \pm 5.7 \pm 19.3~{\rm MeV}/c^2$ and $86 \pm 44 \pm 51~{\rm MeV}$, respectively, where the first uncertainties are statistical and the second ones are systematic. The product of its radiative width ($Γ_{e^+e^-}$) with its branching fraction to $K_{S}^{0}K_{L}^{0}$ ($Br_{K_{S}^{0}K_{L}^{0}}$) is $0.9 \pm 0.6 \pm 0.7~{\rm eV}$.

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arXiv2021

Weak phases and CP-symmetry tests in sequential decays of entangled double-strange baryons

Using a sample of $1.31\times10^9$ $J/ψ$ events collected with the BESIII detector at the electron-positron collider BEPCII, we analyse the full $J/ψ\to$ $Ξ^-\overlineΞ^+$, $Ξ^-\to Λπ^-$, $Λ\to pπ^-$, $\overlineΞ^+\to\overlineΛπ^+$, $\overlineΛ\to\overline{p}π^+$ decay chain. A new method, exploiting the fact that the $Ξ^-\overlineΞ^+$ pair is entangled and sequentially decaying, and where the complete decay chains are reconstructed, is applied for the first time. This enables precision measurements of the decay parameters for the $Ξ^-\toΛπ^-$ decay ($α_Ξ$, $ϕ_Ξ$) as well as the $\overlineΞ^+\to\overlineΛπ^+$ decay ($\overlineα_Ξ$, $\overlineϕ_Ξ$). From the decay parameters, two independent CP tests were performed, quantified by the observables $A_{\rm CP}^Ξ$ and $Δϕ_Ξ$. Our results, $A_{\rm CP}^Ξ$ = $(6.0\pm13.4\pm5.6)\times10^{-3}$ and $Δϕ_Ξ= (-4.8\pm13.7\pm2.9)\times10^{-3}~{\rm rad}$, are consistent with CP symmetry. Furthermore, our method enables a separation of strong and weak $Ξ\toΛπ$ decay amplitudes. This results in the first direct measurement of the weak phase difference for any baryon decay. The result is found to be $(ξ_{P} - ξ_{S}) = (1.2\pm3.4\pm0.8)\times10^{-2}$ rad and is one of the most precise tests of CP symmetry for strange baryons. The strong phase difference is measured to be $(δ_P - δ_S) = (-4.0\pm3.3\pm1.7)\times10^{-2}$ rad. In addition, we provide an independent measurement of the recently debated $Λ$ decay parameter, $α_Λ = 0.757 \pm 0.011 \pm 0.008 $. The $Λ\overlineΛ$ asymmetry is measured to be $A_{\rm CP}^Λ = (-3.7\pm11.7\pm9.0)\times10^{-3}$.

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arXiv2021

Search for new decay modes of the $ψ_2(3823)$ and the process $e^+e^-\rightarrowπ^0π^0ψ_2(3823)$

The decays $ψ_2(3823)\rightarrowγχ_{c0,1,2}, π^+π^-J/ψ, π^0π^0J/ψ, ηJ/ψ$, and $π^0J/ψ$ are searched for using the reaction $e^+e^-\rightarrowπ^+π^-ψ_2(3823)$ in a 19 fb$^{-1}$ data sample collected at center-of-mass energies between 4.1 and 4.7 GeV with the BESIII detector. The process $ψ_2(3823)\rightarrowγχ_{c1}$ is observed in a 9 fb$^{-1}$ data sample in the center-of-mass energy range 4.3 to 4.7 GeV, which confirms a previous observation but with a higher significance of $11.8σ$, and evidence for $ψ_2(3823)\rightarrowγχ_{c2}$ is found with a significance of $3.2σ$ for the first time. The branching-fraction ratio $\frac{\mathcal{B}(ψ_2(3823)\rightarrowγχ_{c2})}{\mathcal{B}(ψ_2(3823)\rightarrowγχ_{c1})}$ is determined. No significant $ψ_2(3823)$ signals are observed for any of the other decay channels. Upper limits of branching-fraction ratios for $ψ_2(3823)\rightarrowπ^+π^-J/ψ, π^0π^0J/ψ, ηJ/ψ, π^0J/ψ, γχ_{c0}$ relative to $ψ_2(3823)\rightarrowγχ_{c1}$ are reported. The process $e^+e^-\rightarrowπ^0π^0ψ_2(3823)$ is also searched for, and we find evidence for the process with a significance of $4.3σ$. The average cross-section ratio $\frac{σ(e^+e^-\rightarrowπ^0π^0ψ_2(3823))}{σ(e^+e^-\rightarrowπ^+π^-ψ_2(3823))}$ is also determined.

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arXiv2021

Measurements of the branching fractions of $ψ(3686)\rightarrow\barΣ^{0}Λ+c.c.$ and $χ_{cJ (J = 0,1,2)} \rightarrow Λ\barΛ$

Based on $4.481\times10^8$ $ψ(3686)$ events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay $ψ(3686)\rightarrow\barΣ^{0}Λ+c.c.$ is measured to be $(1.60 \pm 0.31 \pm 0.13~\pm~0.58) \times 10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays $χ_{cJ} \rightarrowΛ\barΛ$ are measured via $ψ(3686)\rightarrowγχ_{cJ}$, and the branching fractions are determined to be $\mathcal{B}\left(χ_{c0}\rightarrowΛ\barΛ\right)=(3.64 \pm 0.10 \pm 0.10 \pm 0.07)\times 10^{-4}$, $\mathcal{B}\left(χ_{c1}\rightarrowΛ\barΛ\right)=(1.31\pm0.06 \pm 0.06 \pm0.03)\times 10^{-4}$, $\mathcal{B}\left(χ_{c2}\rightarrowΛ\barΛ\right)=(1.91\pm0.08 \pm 0.17 \pm0.04)\times 10^{-4}$, where the third uncertainties are systematic due to the $ψ(3686) \rightarrow γχ_{c J}$ branching fractions.

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arXiv2021

Measurement of the absolute branching fraction of inclusive semielectronic $D_s^+$ decays

We measure the inclusive semielectronic decay branching fraction of the $D_s^+$ meson. A double-tag technique is applied to $e^+e^-$ annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range $4.178 - 4.230$ GeV. We select positrons from $D_s^+\rightarrow Xe^{+}ν_e$ with momenta greater than 200 MeV/$c$, and determine the laboratory momentum spectrum, accounting for the effects of detector efficiency and resolution. The total positron yield and semielectronic branching fraction are determined by extrapolating this spectrum below the momentum cutoff. We measure the $D_s^+$ semielectronic branching fraction to be $\mathcal{B}\left(D_s^+\rightarrow Xe^{+}ν_e\right)=\left(6.30\pm0.13\;(\text{stat.})\pm 0.10\;(\text{syst.})\right)\%$, showing no evidence for unobserved exclusive semielectronic modes. We combine this result with external data taken from literature to determine the ratio of the $D_s^+$ and $D^0$ semielectronic widths, $\frac{Γ(D_{s}^{+}\rightarrow Xe^+ν_e)}{Γ(D^0\rightarrow Xe^+ν_e)}=0.790\pm 0.016\;(\text{stat.})\pm0.020\;(\text{syst.})$. Our results are consistent with and more precise than previous measurements.

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