arXiv subjects

R. Baldini Ferroli

Publications and source records attributed to R. Baldini Ferroli.

At least 37 records · Page 2Linked to original sources

arXiv2023

Measurement of Branching Fractions of Singly Cabibbo-suppressed Decays $Λ_c^+ \rightarrow Σ^{0} K^+$ and $Σ^{+} K_{S}^0$

Based on a sample of 4.4 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected in the energy region between 4.6 GeV and 4.7 GeV with the BESIII detector at BEPCII, two singly Cabibbo-suppressed decays $Λ_c^+ \rightarrow Σ^0 K^+$ and $Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0$ are studied. The ratio of the branching fraction $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 K^+)$ relative to $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 π^+)$ is measured to be $0.0361 \pm 0.0073(\mathrm{stat.}) \pm 0.0005(\mathrm{syst.})$, and the ratio of $\mathcal{B}(Λ_c^+ \rightarrow Σ^+ K_{S}^0)$ relative to $\mathcal{B}(Λ_{c}^{+} \rightarrow Σ^+ π^+ π^-)$ is measured to be $0.0106 \pm 0.0031(\mathrm{stat.}) \pm 0.0004(\mathrm{syst.})$. After taking the world-average branching fractions of the reference decay channels, the branching fractions $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 K^+)$ and $\mathcal{B}(Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0)$ are determined to be $(4.7\pm 0.9(\mathrm{stat.})\pm 0.1(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$ and $(4.8\pm 1.4(\mathrm{stat.})\pm 0.2(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$, respectively. The branching fraction of the $Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0$ decay is measured for the first time.

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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

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

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

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

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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arXiv2023

Search for invisible decays of a dark photon using $e^+e^-$ annihilation data at BESIII

We report a search for a dark photon using $14.9$~fb$^{-1}$ of $e^+e^-$ annihilation data taken at center-of-mass energies from 4.13 to 4.60~GeV with the BESIII detector operated at the BEPCII storage ring. The dark photon is assumed to be produced in the radiative annihilation process of $e^+e^-$ and to predominantly decay into light dark matter particles, which escape from the detector undetected. The mass range from 1.5 to 2.9~GeV is scanned for the dark photon candidate, and no significant signal is observed. The mass dependent upper limits at the 90$\%$ confidence level on the coupling strength parameter $ε$ for a dark photon coupling with an ordinary photon vary between $1.6\times 10^{-3}$ and $5.7\times10^{-3}$.

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arXiv2023

Improved measurement of the branching fractions of the inclusive decays $D^+ \to K_S^0X $ and $D^0 \to K_S^0X $

By analyzing 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, the branching fractions of the inclusive decays $D^+\to K^0_S X$ and $D^0\to K^0_S X$ are measured to be $(32.78\pm 0.13\pm 0.27)\%$ and $(20.54\pm 0.12\pm 0.18)\%$, respectively, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world averages of previous measurements, but with improved precision.

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arXiv2023

Evidence for the Cusp Effect in $η'$ Decays into $ηπ^0π^0$

Using a sample of $4.3\times 10^5$ $η'\toηπ^0π^0$ events selected from the ten billion $J/ψ$ event dataset collected with the BESIII detector, we study the decay $η'\toηπ^0π^0$ within the framework of nonrelativistic effective field theory. Evidence for a structure at $π^+π^-$ mass threshold is observed in the invariant mass spectrum of $π^0π^0$ with a statistical significance of around $3.5σ$, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the $ππ$ scattering length combination $a_0-a_2$ is determined to be $\rm 0.226\pm0.060_{stat}\pm0.013_{syst}$, which is in good agreement with theoretical calculation of $0.2644\pm0.0051$.

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arXiv2023

Observation of $e^+e^-\toπ^0π^0ψ_2(3823)$

Using a data sample corresponding to an integrated luminosity of 11.3 $\rm fb^{-1}$ collected at center-of-mass energies from $4.23$ to $4.70$~GeV with the BESIII detector, we observe the process $e^+e^-\toπ^0π^0ψ_2(3823)$ for the first time with a statistical significance of $6.0σ$. The ratio of average cross sections for $e^+e^-\toπ^0π^0ψ_2(3823)$ over $π^+π^-ψ_2(3823)$ is determined to be $\mathcal{R}=\frac{σ[e^+e^-\toπ^0π^0ψ_2(3823)]}{σ[e^+e^-\toπ^+π^-ψ_2(3823)]}=0.57\pm 0.14\pm0.05$, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the $ψ_2(3823)$ is measured to be $M[ψ_2(3823)]=3824.5\pm 2.4\pm 1.0$~MeV/$c^2$. Due to the limited statistics, the intrinsic width of the $ψ_2(3823)$ is measured as an upper limit of $18.8$~MeV at $90\%$ confidence level.

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arXiv2023

Observation of the decay $D^+_s\to ωπ^+η$

Using 7.33 fb$^{-1}$ of $e^+e^-$ collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226~GeV, we observe for the first time the decay $D^{\pm}_s\to ωπ^{\pm}η$ with a statistical significance of 7.6$σ$. The measured branching fraction of this decay is $(0.54\pm0.12\pm0.04)\%$, where the first uncertainty is statistical and the second is systematic.

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arXiv2023

Study of $e^+e^-\toγϕJ/ψ$ from $\sqrt{s}=4.600$ to $4.951$ GeV

Using data samples with an integrated luminosity of $6.4$~fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring, the process of $e^+e^-\toγϕJ/ψ$ is studied. The processes of $e^+e^-\toϕχ_{c1,c2}$, $χ_{c1,c2}\toγJ/ψ$ are observed with a significance of more than $10σ$. The $\sqrt{s}$-dependent cross section of $e^+e^- \to ϕχ_{c1,c2}$ is measured between 4.600 and 4.951~GeV, and evidence of a resonance structure is found for the first time in the $ϕχ_{c2}$ process. We also search for the processes of $e^+e^-\toγX(4140)$, $γX(4274)$ and $γX(4500)$ via the $γϕJ/ψ$ final state, but no obvious structures are found. The upper limits on the production cross section times the branching fraction for these processes at the 90% confidence level are reported.

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