arXiv subjects

F. Feldbauer

Publications and source records attributed to F. Feldbauer.

At least 361 records · Page 20Linked to original sources

arXiv2023

Observation of the decay $χ_{cJ} \to Ω^- \barΩ^+$

Using an $e^+e^-$ collision data sample of $(27.08 \pm 0.14) \times 10^{8}$ $ψ(3686)$ events collected by the BESIII detector, we report the first observation of $χ_{cJ} \to Ω^- \barΩ^+$ ($J=0,\,1,\,2$) decays with significances of $5.6σ$, $6.4σ$, and $18σ$, respectively, where the $χ_{cJ}$ mesons are produced in the radiative $ψ(3686)$ decays. The branching fractions are determined to be $\mathcal{B}(χ_{c0} \to Ω^- \barΩ^+) = (3.51 \pm 0.54 \pm 0.29) \times 10^{-5}$, $\mathcal{B}(χ_{c1} \to Ω^- \barΩ^+) = (1.49 \pm 0.23 \pm 0.10) \times 10^{-5}$, and $\mathcal{B}(χ_{c2} \to Ω^- \barΩ^+) = (4.52 \pm 0.24 \pm 0.18) \times 10^{-5}$, where the first and second uncertainties are statistical and systematic, respectively.

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arXiv2023

Evidence for $η_c$(2S)$\to\pipieta$ decay

The decay $η_c(2S)\to\pipieta$ is searched for through the radiative transition $ψ(3686) \toγη_c(2S)$ using 448 million $ψ$(3686) events accumulated at the BESIII detector. The first evidence of $η_c(2S)\toπ^+π^-η$ is found with a statistical significance of 3.5$σ$. The product of the branching fractions of $ψ(3686)\toγη_c(2S)$ and $η_c(2S)\to\pipieta$ is measured to be $Br(ψ(3686)\toγη_c(2S))\times Br(η_c(2S)\to\pipieta)=(2.97\pm0.81\pm0.26)\times10^{-6}$, where the first uncertainty is statistical and the second one is systematic. The branching fraction of the decay $η_c(2S)\to\pipieta$ is determined to be $Br(η_c(2S)\to\pipieta)=(42.4\pm11.6\pm3.8\pm30.3)\times10^{-4}$, where the third uncertainty is transferred from the uncertainty of the branching fraction of $ψ(3686)\toγη_c(2S)$.

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arXiv2023

Cross section measurements of $e^+e^- \to ΦK^+ K^-$ and $e^+ e^- \to ΦK_S^0 K_S^0$ at center-of-mass energies between 3.7730 GeV and 4.7008 GeV

Based on 22.7 fb$^{-1}$ of $e^+e^-$ annihilation data collected at 33 different center-of-mass energies between 3.7730 GeV and 4.7008 GeV with the BESIII detector at the BEPCII collider, Born cross sections of the two processes $e^+e^-\to ϕK^+ K^-$ and $e^+ e^- \to ϕK_{S}^{0} K_{S}^{0}$ are measured for the first time. No indication of resonant production through an intermediate vector state $V$ is observed, and the upper limits on the product of the electronic width $Γ_{e^+e^-}$ and the branching fraction $Br(V\rightarrow ϕK \bar{K})$ of the processes $e^+e^- \to V \to ϕK^+ K^-$ and $e^+e^- \to V \to ϕK_S^0K_S^0$ at the $90\%$ confidence level are obtained for a large parameter space in resonance masses and widths. For the current world average mass and width of the $ψ(4230)$ of $m=4.2187$ GeV$/c^2$ and $Γ=44$ MeV, we set upper limits on the $ϕK^+ K^-$ and $ϕK_S^0K_S^0$ final states of 1.75 eV and 0.47 eV at the $90\%$ confidence level, respectively.

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arXiv2023

Observation of a New $X(3872)$ Production Process $e^+e^-\toωX(3872)$

Using $4.7~\rm fb^{-1}$ of $e^+e^-$ collision data at center-of-mass energies from 4.661 to 4.951 GeV collected by the BESIII detector at the BEPCII collider, we observe the $X(3872)$ production process $e^{+}e^{-}\toωX(3872)$ for the first time. The significance is $7.8σ$, including both the statistical and systematic uncertainties. The $e^+e^-\toωX(3872)$ Born cross section and the corresponding upper limit at 90\% confidence level at each energy point are reported. The line shape of the cross section indicates that the $ωX(3872)$ signals may be from the decays of some non-trivial structures.

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arXiv2023

Search for an axion-like particle in radiative $J/ψ$ decays

We search for an axion-like particle (ALP) $a$ through the process $ψ(3686)\rightarrowπ^+π^-J/ψ$, $J/ψ\rightarrowγa$, $a\rightarrowγγ$ in a data sample of $(2.71\pm0.01)\times10^9$ $ψ(3686)$ events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay $J/ψ\rightarrowγa$ and the ALP-photon coupling constant $g_{aγγ}$ are set at 95% confidence level in the mass range of $0.165\leq m_a\leq2.84\,\mbox{GeV}/c^2$. The limits on $B(J/ψ\rightarrowγa)$ range from $8.3\times10^{-8}$ to $1.8\times10^{-6}$ over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for $0.165\leq m_a\leq1.468\,\mbox{GeV}/c^2$.

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arXiv2023

Measurements of the electric and magnetic form factors of the neutron for time-like momentum transfer

We present the first measurements of the electric and magnetic form factors of the neutron in the time-like (positive $q^2$) region as function of four-momentum transfer. We explored the differential cross sections of the reaction $e^+e^- \rightarrow \bar{n}n$ with data collected with the BESIII detector at the BEPCII accelerator, corresponding to an integrated luminosity of 354.6 pb$^{-1}$ in total at twelve center-of-mass energies between $\sqrt{s} = 2.0 - 2.95$ GeV. A relative uncertainty of 18% and 12% for the electric and magnetic form factors, respectively, is achieved at $\sqrt{s} = 2.3935$ GeV. Our results are comparable in accuracy to those from electron scattering in the comparable space-like (negative $q^2$) region of four-momentum transfer. The electromagnetic form factor ratio $R_{\rm em}\equiv |G_E|/|G_M|$ is within the uncertainties close to unity. We compare our result on $|G_E|$ and $|G_M|$ to recent model predictions, and the measurements in the space-like region to test the analyticity of electromagnetic form factors.

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arXiv2023

Observation of the $Y(4230)$ and evidence for a new vector charmonium-like state $Y(4710)$ in $e^{+}e^{-}\to K_{S}^{0} K_{S}^{0} J/ψ$

Cross sections for the process $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J/ψ$ at center-of-mass energies from $4.128$ to $4.950$ GeV are measured using data samples with a total integrated luminosity of 21.2 fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring. The $Y(4230)$ state is observed in the energy dependence of the $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J/ψ$ cross section for the first time with a statistical significance of 26.0$σ$. In addition, an enhancement around $4.710$ GeV, called the $Y(4710)$, is seen with a statistical significance of 4.2$σ$. There is no clear structure around $4.484$ GeV. Using a fit with a coherent sum of three Breit-Wigner functions, we determine the mass and width of the $Y(4230)$ state to be $4226.9 \pm 6.6 \pm 21.9$ MeV/$c^{2}$ and $71.7 \pm 16.2 \pm 31.4$ MeV, respectively, and the mass and width of the $Y(4710)$ state to be $4704.0 \pm 52.3 \pm 69.5$ MeV/$c^{2}$ and $183.2 \pm 114.0 \pm 90.8$ MeV, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the average Born cross section ratio of $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J/ψ$ to $e^{+} e^{-} \to K^{+} K^{-} J/ψ$ is measured to be $0.388_{-0.028}^{+0.035}\pm0.016$, or $0.426_{-0.031}^{+0.038}\pm0.018$ if three-body phase space is considered.

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arXiv2023

Study of the $h_c$($1^1P_1$) meson via $ψ(2S) \rightarrow π^0 h_c$ decays at BESIII

Using 448 million $ψ(2S)$ events, the spin-singlet $P$-wave charmonium state $h_c$(1$^1P_1$) is studied via the $ψ(2S) \rightarrow π^0 h_c$ decay followed by the $h_c \to γη_c$ transition. The branching fractions are measured to be $\mathcal{B}_{\rm Inc}(ψ(2S) \rightarrow π^0h_c) \times \mathcal{B}_{\rm Tag}(h_c \rightarrow γη_c) = (4.22 ^{+0.27}_{-0.26} \pm 0.19) \times 10^{-4}$ , $\mathcal{B}_{\rm Inc}(ψ(2S) \rightarrow π^0h_c) = (7.32 \pm 0.34 \pm 0.41) \times 10^{-4}$, and $\mathcal{B}_{\rm Tag}(h_c \rightarrow γη_c) = (57.66 ^{+3.62}_{-3.50} \pm 0.58)\%$, where the uncertainties are statistical and systematic, respectively. The $h_c$(1$^1P_1$) mass and width are determined to be $M = (3525.32 \pm 0.06 \pm 0.15)~\rm{MeV}/c^{\rm{2}}$ and ${\mathit Γ} = (0.78 ^{+0.27}_{-0.24} \pm 0.12)~\rm{MeV}$. Using the center of gravity mass of the three $χ_{cJ}$(1$^3 P_J$) mesons ($M(\rm c.o.g.)$), the $1P$ hyperfine mass splitting is estimated to be $Δ_{\rm hyp} = M(h_c) - M(\rm c.o.g.) = (0.03 \pm 0.06 \pm 0.15) ~ \rm{MeV}/c^{\rm{2}}$, which is consistent with the expectation that the $1P$ hyperfine splitting is zero at the lowest-order.

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arXiv2023

Observation of Three Charmoniumlike States with $J^{PC}=1^{--}$ in $e^{+}e^{-}\to D^{0}D^{-}π^{+}$

The Born cross sections of the process $e^{+}e^{-}\to D^{*0}D^{*-}π^{+}$ at center-of-mass energies from 4.189 to 4.951 GeV are measured for the first time. The data samples used correspond to an integrated luminosity of $17.9\,{\rm fb}^{-1}$ and were collected by the BESIII detector operating at the BEPCII storage ring. Three enhancements around 4.20, 4.47 and 4.67 GeV are visible. The resonances have masses of $4209.6\pm4.7\pm5.9\,{\rm MeV}/c^{2}$, $4469.1\pm26.2\pm3.6\,{\rm MeV}/c^{2}$ and $4675.3\pm29.5\pm3.5\,{\rm MeV}/c^{2}$ and widths of $81.6\pm17.8\pm9.0\,{\rm MeV}$, $246.3\pm36.7\pm9.4\,{\rm MeV}$, and $218.3\pm72.9\pm9.3\,{\rm MeV}$, respectively, where the first uncertainties are statistical and the second systematic. The first and third resonances are consistent with the $ψ(4230)$ and $ψ(4660)$ states, respectively, while the second one is compatible with the $ψ(4500)$ observed in the $e^{+}e^{-}\to K^{+}K^{-}J/ψ$ process. These three charmoniumlike $ψ$ states are observed in $e^{+}e^{-}\to D^{*0}D^{*-}π^{+}$ process for the first time.

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arXiv2023

Improved measurement of the absolute branching fraction of inclusive semileptonic $Λ_c^+$ decay

Using $4.5 \mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data samples collected at center-of-mass energies ranging from 4.600 to 4.698 GeV with the BESIII detector at the BEPCII collider, we measured the absolute branching fraction for the inclusive semileptonic decay $Λ_c^+\rightarrow Xe^+ν_e$, where $X$ refers to any possible particle system. The branching fraction of the decay is determined to be $\mathcal{B}({\it Λ}^+_c\rightarrow Xe^+ν_e)=(4.06\pm0.10_{\rm stat.}\pm0.09_{\rm syst.})\%$. Our result improves the precision of previous measurement of $\mathcal{B}({\it Λ}^+_c\rightarrow Xe^+ν_e)$ by more than threefold. Using the known $Λ_c^+$ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons, we measure the ratio of inclusive semileptonic decay widths $Γ(Λ_c^+\rightarrow X e^+ν_e)/\barΓ(D\rightarrow Xe^+ν_e)=1.28\pm0.05$, where statistical and systematic uncertainties are combined.

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arXiv2023

Study of the $e^+e^- \to π^{+}π^{-}ω$ process at center-of-mass energies between 4.0 and 4.6 GeV

Using $15.6$ $\rm fb^{-1}$ of $e^+e^-$ collision data collected at twenty-four center-of-mass energies from $4.0$ to $4.6$ GeV with the BESIII detector, the helicity amplitudes of the process $e^+e^-\to π^{+}π^{-}ω$ are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5$σ$ are presented, such as $f_{0}(500)$, $f_{0}(980)$, $f_{2}(1270)$, $f_{0}(1370)$, $b_{1}(1235)^{\pm}$, and $ρ(1450)^{\pm}$. In addition, evidence of a resonance state in $e^+e^-\to π^+π^-ω$ production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/$c^2$, which is consistent with the production of $ψ(4160)$ or $Y(4220)$.

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arXiv2023

Measurement of the Branching Fraction for the Decay $ψ(3686) \rightarrow ϕK_{S}^{0} K_{S}^{0}$

Based on $(448.1 \pm 2.9 )\times 10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decay $ψ(3686)\rightarrow ϕK_{S}^{0} K_{S}^{0}$ is observed for the first time. Taking the interference between $ψ(3686)$ decay and continuum production into account, the branching fraction of this decay is measured to be $\mathcal{B}(ψ(3686)\rightarrowϕK_S^0 K_S^0 )$ = $(3.53 $ $\pm$ $0.20$ $\pm$ $0.21$)$\times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. Combining with the world average value for ${\mathcal B}(J/ψ\to ϕK^0_SK^0_S)$, the ratio $\mathcal{B}(ψ(3686)\rightarrow ϕK_{S}^{0} K_{S}^{0})/\mathcal{B}(J/ψ\rightarrow ϕK_{S}^{0} K_{S}^{0}) $ is determined to be $(6.0\pm 1.6)$%, which is suppressed relative to the 12% rule.

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arXiv2023

Measurement of the $e^{+}e^{-}\rightarrowΛ\barΛ$ cross section from threshold to 3.00 GeV using events with initial-state radiation

Using initial-state radiation events from a total integrated luminosity of 11.957 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at BEPCII, the cross section for the process $e^{+}e^{-}\rightarrowΛ\barΛ$ is measured in 16 $Λ\barΛ$ invariant mass intervals from the production threshold up to 3.00 GeV$/c^{2}$. The results are consistent with previous results from BaBar and BESIII, but with better precision and with narrower $Λ\barΛ$ invariant mass intervals than BaBar.

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arXiv2023

Helicity amplitude analysis of $χ_{cJ} \rightarrow ϕϕ$

Using (447.9 $\pm$ 2.3) million $ψ$(3686) events collected with the BESIII detector, the decays of $χ_{cJ} \rightarrow ϕϕ$ ($J$=0, 1, 2) have been studied via the decay $ψ(3686)\rightarrowγχ_{cJ}$. The branching fractions of the decays $χ_{cJ} \rightarrow ϕϕ$ ($J$=0, 1, 2) are determined to be $(8.48\pm0.26\pm0.27)\times10^{-4}$, $(4.36\pm0.13\pm0.18)\times10^{-4}$, and $(13.36\pm0.29\pm0.49)\times10^{-4}$, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process $ψ(3686) \rightarrow γχ_{cJ}, χ_{cJ}\rightarrow ϕϕ, ϕ\rightarrow K^{+}K^{-}$, the polarization parameters of the $χ_{cJ} \rightarrow ϕϕ$ decays are determined for the first time.

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arXiv2023

Study of $e^+e^-\rightarrowΩ^{-}\barΩ^{+}$ at center-of-mass energies from 3.49 to 3.67 GeV

Using data samples of $e^+e^-$ collisions collected with the BESIII detector at eight center-of-mass energy points between 3.49 and 3.67 GeV, corresponding to an integrated luminosity of 670 pb$^{-1}$, we present the upper limits of Born cross sections and the effective form factor for the process $e^+e^-\rightarrowΩ^{-}\barΩ^{+}$. A fit to the cross sections using a pQCD-derived energy dependent function shows no significant threshold effect. The upper limit on the measured effective form factor is consistent with a theoretical prediction within the uncertainty of 1$σ$. These results provide new experimental information on the production mechanism of $Ω$.

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arXiv2023

Partial wave analysis of $J/ψ\rightarrowγηη'$

Based on a sample of (10.09$\pm$0.04)$\times$10$^{9}$ $J/ψ$ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay $J/ψ\rightarrow γηη'$ is performed. An isoscalar state with exotic quantum numbers $J^{PC}=1^{-+}$, denoted as $η_1(1855)$, has been observed for the first time with statistical significance larger than 19$σ$. Its mass and width are measured to be (1855$\pm$9$_{-1}^{+6}$)~MeV/$c^{2}$ and (188$\pm$18$_{-8}^{+3}$)~MeV, respectively. The product branching fraction ${\cal B}(J/ψ$$\rightarrow$$ γη_1(1855)$$\rightarrow$$γηη')$ is measured to be (2.70$\pm 0.41 _{-0.35}^{+0.16}) \times$10$^{-6}$. The first uncertainties are statistical and the second are systematic. In addition, an upper limit on the branching ratio ${\cal B}(f_0(1710)$$\rightarrow$$ηη')$/${\cal B}(f_0(1710)$$\rightarrow$$ππ)$ is determined to be $1.61 \times 10^{-3}$ at 90\% confidence level, which lends support to the hypothesis that the $f_0(1710)$ has a large glueball component.

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arXiv2023

Observation of an isoscalar resonance with exotic $J^{PC}=1^{-+}$ quantum numbers in $J/ψ\rightarrowγηη'$

Using a sample of (10.09$\pm$0.04)$\times$10$^{9}$ $J/ψ$ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay $J/ψ\rightarrow γηη'$ is performed. The first observation of an isoscalar state with exotic quantum numbers $J^{PC}=1^{-+}$, denoted as $η_1(1855)$, is reported in the process $J/ψ\rightarrow γη_1(1855)$ with $η_1(1855)\rightarrowηη'$. Its mass and width are measured to be (1855$\pm$9$_{-1}^{+6}$)MeV/$c^{2}$ and (188$\pm$18$_{-8}^{+3}$)MeV, respectively, where the first uncertainties are statistical and the second are systematic, and its statistical significance is estimated to be larger than 19$σ$.

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arXiv2023

Study of $η(1405)/η(1475)$ in $J/ψ\toγK^{0}_{S} K^{0}_{S}π^{0}$ decay

Using a sample of $(10.09\pm0.04)\times10^{9}$ $J/ψ$ decays collected with the BESIII detector, partial wave analyses of the decay $J/ψ\toγK^{0}_{S} K^{0}_{S}π^{0}$ are performed within the $K^{0}_{S}K^{0}_{S}π^{0}$ invariant mass region below $1.6\mathrm{\ Ge\kern -0.1em V}/c^2$. The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the $K^{0}_{S}K^{0}_{S}π^{0}$ invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, ${\it i.e.}$, the $η(1405)$ with a mass of $1391.7\pm0.7_{-0.3}^{+11.3}\mathrm{\ Me\kern -0.1em V}/c^2$ and a width of $60.8\pm1.2_{-12.0}^{+5.5}\mathrm{\ Me\kern -0.1em V}$, and the $η(1475)$ with a mass of $1507.6\pm1.6_{-32.2}^{+15.5}\mathrm{\ Me\kern -0.1em V}/c^2$ and a width of $115.8\pm2.4_{-10.9}^{+14.8}\mathrm{\ Me\kern -0.1em V}$. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the $K^{0}_{S}K^{0}_{S}π^{0}$ invariant mass spectrum deteriorates significantly.

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