arXiv subjects

G. Chelkov

Publications and source records attributed to G. Chelkov.

At least 181 records · Page 10Linked to original sources

arXiv2024

First observation of the decay $Λ^+_c\to nK^{0}_{S}π^+π^0$

Based on 4.5 fb$^{-1}$ of $e^{+}e^{-}$ collision data accumulated at center-of-mass energies between $4599.53$ MeV and $4698.82$ MeV with the BESIII detector, the decay $Λ_{c}^{+}\to nK_{S}^{0}π^+π^0$ is observed for the first time with a significance of $9.2σ$. The branching fraction is measured to be $(0.85\pm0.13\pm0.03)\%$, where the first uncertainty is statistical and the second systematic, which differs from the theoretical prediction based on isospin by 4.4$σ$. This indicates that there may be resonant contributions or some unknown dynamics in this decay.

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arXiv2024

Observation of $D^{+}\to K_{S}^{0}a_{0}(980)^{+}$ in the amplitude analysis of $D^{+} \to K_{S}^{0}π^+η$

We perform for the first time an amplitude analysis of the decay $D^{+}\to K_{S}^{0}π^+η$ and report the observation of the decay $D^{+}\to K_{S}^{0}a_{0}(980)^{+}$ using 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector. As the only W-annihilation free decay among $D$ to $a_{0}(980)$-pseudoscalar, $D^{+}\to K_{S}^{0}a_{0}(980)^{+}$ is the ideal decay to extract the contributions of the external and internal $W$-emission amplitudes involving $a_{0}(980)$ and study the final-state interactions. The absolute branching fraction of $D^{+}\to K_{S}^{0}π^+η$ is measured to be $(1.27\pm0.04_{\rm stat.}\pm0.03_{\rm syst.})\%$. The product branching fractions of $D^{+}\to K_{S}^{0}a_{0}(980)^{+}$ with $a_{0}(980)^{+}\to π^+η$ and $D^{+}\to π^+ K_0^*(1430)^0$ with $K_0^*(1430)^0\to K_{S}^{0}η$ are measured to be $(1.33\pm0.05_{\rm stat.}\pm0.04_{\rm syst.})\%$ and $(0.14\pm0.03_{\rm stat.}\pm0.01_{\rm syst.})\%$, respectively.

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arXiv2024

Observation of the semileptonic decays $D^0\rightarrow K_S^0π^-π^0 e^+ ν_e$ and $D^+\rightarrow K_S^0π^+π^- e^+ ν_e$

By analyzing $e^+e^-$ annihilation data corresponding to an integrated luminosity of 2.93 $\rm fb^{-1}$ collected at a center-of-mass energy of 3.773 GeV with the \text{BESIII} detector, the first observation of the semileptonic decays $D^0\rightarrow K_S^0π^-π^0 e^+ ν_e$ and $D^+\rightarrow K_S^0π^+π^- e^+ ν_e$ is reported. With a dominant hadronic contribution from $K_1(1270)$, the branching fractions are measured to be $\mathcal{B}(D^0\rightarrow {K}_1(1270)^-(\to K^0_Sπ^-π^0)e^+ν_e)=(1.69^{+0.53}_{-0.46}\pm0.15)\times10^{-4}$ and $\mathcal{B}(D^+\to \bar{K}_1(1270)^0(\to K^0_Sπ^+π^-)e^+ν_e)=(1.47^{+0.45}_{-0.40}\pm0.20)\times10^{-4}$ with statistical significance of 5.4$σ$ and 5.6$σ$, respectively. When combined with measurements of the $K_1(1270)\to K^+π^-π$ decays, the absolute branching fractions are determined to be $\mathcal{B}(D^0\to K_1(1270)^-e^+ν_e)=(1.05^{+0.33}_{-0.28}\pm0.12\pm0.12)\times10^{-3}$ and $\mathcal{B}(D^+\to \bar{K}_1(1270)^0e^+ν_e)=(1.29^{+0.40}_{-0.35}\pm0.18\pm0.15)\times10^{-3}$. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainties originate from the assumed branching fractions of the $K_1(1270)\to Kππ$ decays.

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arXiv2024

Observation of structures in the processes $e^+e^-\rightarrowωχ_{c1}$ and $ωχ_{c2}$

We present measurements of the Born cross sections for the processes $e^+e^-\rightarrowωχ_{c1}$ and $ωχ_{c2}$ at center-of-mass energies $\sqrt{s}$ from 4.308 to 4.951 GeV. The measurements are performed with data samples corresponding to an integrated luminosity of 11.0 $\rm{fb}^{-1}$ collected with the BESIII detector operating at the BEPCII storage ring. Assuming the $e^+e^-\rightarrowωχ_{c2}$ signals come from a single resonance, the mass and width are determined to be $M=(4413.6\pm9.0\pm0.8)$ MeV/$c^2$ and $Γ=(110.5\pm15.0\pm2.9)$ MeV, respectively, which is consistent with the parameters of the well-established resonance $ψ(4415)$. In addition, we also use one single resonance to describe the $e^+e^-\rightarrowωχ_{c1}$ lineshape, and determine the mass and width to be $M=(4544.2\pm18.7\pm1.7)$ MeV/$c^2$ and $Γ=(116.1\pm33.5\pm1.7)$ MeV, respectively. The structure of this lineshape, observed for the first time, requires further understanding.

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arXiv2024

Measurement of $Λ$ transverse polarization in $e^{+}e^{-}$ collisions at $\sqrt{s}= 3.68-3.71$ GeV

With data samples collected with the BESIII detector at seven energy points at $\sqrt{s}= 3.68 - 3.71$ GeV, corresponding to an integrated luminosity of 333 pb$^{-1}$, we present a study of the $Λ$ transverse polarization in the $e^+e^-\toΛ\barΛ$ reaction. The significance of polarization by combining the seven energy points is found to be 2.6$σ$ including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the $Λ\barΛ$ helicity states. The modulus ratio and the relative phase of EM-$psionic$ form factors combined with all energy points are measured to be $R^Ψ =$ 0.71$^{+0.10}_{-0.10}$ $\pm$ 0.03 and $ΔΦ^Ψ$ = (23$^{+8.8}_{-8.0}$ $\pm$ 1.6$)^\circ$, where the first uncertainties are statistical and the second systematic.

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arXiv2024

Precise measurement of the $e^+e^-\to D_s^+D_s^-$ cross sections at center-of-mass energies from threshold to 4.95 GeV

Using the $e^+e^-$ collision data collected with the BESIII detector operating at the BEPCII collider, at center-of-mass energies from the threshold to $4.95$~GeV, we present precise measurements of the cross sections for the process $e^+e^-\to D_s^+D_s^-$ using a single tag method. The resulting cross section lineshape exhibits several new structures, thereby offering an input for coupled channel analysis and model tests, which are critical to understand vector charmonium-like states with masses between 4 and 5~GeV.

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arXiv2024

Observation of the decay $h_{c}\to3(π^{+}π^{-})π^{0}$

Based on $(2712.4\pm14.1)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector, we study the decays $h_{c}\to3(π^{+}π^{-})π^{0}$, $h_{c}\to2(π^{+}π^{-})ω$, $h_{c}\to2(π^{+}π^{-})π^{0}η$, $h_{c}\to2(π^{+}π^{-})η$, and $h_{c}\to p\bar{p}$ via $ψ(3686)\toπ^{0}h_{c}$. The decay channel $h_{c}\to3(π^{+}π^{-})π^{0}$ is observed for the first time, and its branching fraction is determined to be $\left( {9.28\pm 1.14 \pm 0.77} \right) \times {10^{ - 3}}$, where the first uncertainty is statistical and the second is systematic. In addition, first evidence is found for the modes $h_{c} \to 2(π^{+}π^{-})π^{0}η$ and $h_{c}\to2(π^{+}π^{-})ω$ with significances of 4.8$σ$ and 4.7$σ$, and their branching fractions are determined to be $(7.55\pm1.51\pm0.77)\times10^{-3}$ and $\left( {4.00 \pm 0.86 \pm 0.35}\right) \times {10^{ - 3}}$, respectively. No significant signals of $h_c\to 2(π^+π^-)η$ and $h_{c}\to p\bar{p}$ are observed, and the upper limits of the branching fractions of these decays are determined to be $<6.19\times10^{-4}$ and $<4.40\times10^{-5}$ at the 90% confidence level, respectively.

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arXiv2024

Determination of the $Σ^{+}$ Timelike Electromagnetic Form Factors

Based on data samples collected with the BESIII detector at the BEPCII collider, the process $e^{+}e^{-} \to Σ^{+}\barΣ^{-}$ is studied at center-of-mass energies $\sqrt{s}$ = 2.3960, 2.6454, and 2.9000 GeV. Using a fully differential angular description of the final state particles, both the relative magnitude and phase information of the $Σ^{+}$ electromagnetic form factors in the timelike region are extracted. The relative phase between the electric and magnetic form factors is determined to be $\sinΔΦ$ = -0.67~$\pm$~0.29~(stat)~$\pm$~0.18~(syst) at $\sqrt{s}$ = 2.3960 GeV, $ΔΦ$ = 55$^{\circ}$~$\pm$~19$^{\circ}$~(stat) $\pm$~14$^{\circ}$~(syst) at $\sqrt{s}$ = 2.6454 GeV, and 78$^{\circ}$~$\pm$~22$^{\circ}$~(stat) $\pm$~9$^{\circ}$~(syst) at $\sqrt{s}$ = 2.9000 GeV. For the first time, the phase of the hyperon electromagnetic form factors is explored in a wide range of four-momentum transfer. The evolution of the phase along with four-momentum transfer is an important input for understanding its asymptotic behavior and the dynamics of baryons.

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arXiv2024

Observation of $ψ(3686)\to 3ϕ$

Using $(2.712\pm0.014)\times 10^9$ $ψ(3686)$ events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of $ψ(3686)\to 3ϕ$ decay with a significance larger than 10$σ$. The branching fraction of this decay is determined to be $(1.46\pm0.05\pm0.17)\times10^{-5}$, where the first uncertainty is statistical and the second is systematic. No significant structure is observed in the $ϕϕ$ invariant mass spectra.

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arXiv2024

Updated measurement of the branching fraction of $D_s^+\to τ^+ν_τ$ via $τ^+\toπ^+\barν_τ$

This paper reports the study of $D_s^+\to τ^+ν$ via $τ^+\toπ^+\barν_τ$ using a boosted decision tree method, with $7.33$ fb$^{-1}$ of $e^{+}e^{-}$ collision data collected by the BESIII detector at center-of-mass energies between $4.128$ and $4.226$~GeV. The branching fraction of $D_s^+\to τ^+ν_τ$ is determined to be $(5.44\pm0.17_{\rm stat}\pm0.13_{\rm syst})\%$. The product of the $D_s^+$ decay constant $f_{D_s^+}$ and the CKM matrix element $|V_{cs}|$ is $f_{D_s^+}|V_{cs}| = (248.3\pm3.9_{\rm stat}\pm3.1_{\rm syst}\pm1.0_{\rm input})~\mathrm{MeV}$. Combining with the $|V_{cs}|$ value obtained from the Standard Model global fit or the $f_{D_s^+}$ from the lattice quantum chromodynamics, we determine $|V_{cs}| = 0.993\pm0.015_{\rm stat}\pm0.012_{\rm syst}\pm0.004_{\rm input}$ and $f_{D_s^+} = (255.0\pm4.0_{\rm stat}\pm3.2_{\rm syst}\pm1.0_{\rm input})~\text{MeV}$. The first uncertainty is statistical, the second one is systematic and the third one is due to the input parameters, mainly the lifetime of $D_s^+$. All results obtained in this work supersede the BESIII previous results based on 6.32 fb$^{-1}$ of $e^+e^-$ collision data taken at center-of-mass energies between $4.178$ and $4.226$~GeV.

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arXiv2024

Observation of $D^+_s\to η^\prime μ^+ν_μ$, Precision Test of Lepton Flavor Universality with $D^+_s\to η^{(\prime)} \ell^+ν_\ell$, and First Measurements of $D^+_s\to η^{(\prime)}μ^+ν_μ$ Decay Dynamics

By analyzing 7.33 fb$^{-1}$ of $e^+e^-$ annihilation data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we report the observation of the semileptonic decay $D^+_s\to η^\prime μ^+ν_μ$, with a statistical significance larger than 10$σ$, and the measurements of the $D_s^+ \to ημ^+ν_μ$ and $D_s^+ \to η^\primeμ^+ν_μ$ decay dynamics for the first time. The branching fractions of $D_s^+ \to ημ^+ν_μ$ and $D_s^+ \to η^\primeμ^+ν_μ$ are determined to be $(2.235\pm0.051_{\rm stat}\pm0.052_{\rm syst})\%$ and $(0.801\pm0.055_{\rm stat}\pm0.028_{\rm syst})\%$, respectively, with precision improved by factors of 6.0 and 6.6 compared to the previous best measurements. Combined with the results for the decays $D_s^+ \to ηe^+ν_e$ and $D_s^+ \to η^\prime e^+ν_e$, the ratios of the decay widths are examined both inclusively and in several $\ell^+ν_\ell$ four-momentum transfer ranges. No evidence for lepton flavor universality violation is found within the current statistics. The products of the hadronic form factors $f_{+,0}^{η^{(\prime)}}(0)$ and the $c\to s$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ are determined. The results based on the two-parameter series expansion are $f^η_{+,0}(0)|V_{cs}| = 0.452\pm0.010_{\rm stat}\pm0.007_{\rm syst}$ and $f^{η^{\prime}}_{+,0}(0)|V_{cs}| = 0.504\pm0.037_{\rm stat}\pm0.012_{\rm syst}$, which help to constrain present models on $f_{+,0}^{η^{(\prime)}}(0)$. The forward-backward asymmetries are determined to be $\langle A_{\rm FB}^η\rangle=-0.059\pm0.031_{\rm stat}\pm0.005_{\rm syst}$ and $\langle A_{\rm FB}^{η^\prime}\rangle=-0.064\pm0.079_{\rm stat}\pm0.006_{\rm syst}$ for the first time, which are consistent with the theoretical calculation.

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arXiv2024

Measurement of the $e^{+}e^{-} \to K_{S}^{0} K_{L}^{0} π^{0}$ cross sections from $\sqrt{s}=$ 2.000 to 3.080 GeV

Based on $e^{+}e^{-}$ collision data collected at center-of-mass energies from 2.000 to 3.080 GeV by the BESIII detector at the BEPCII collider, a partial wave analysis is performed for the process $e^{+}e^{-}\to K_{S}^{0} K_{L}^{0} π^{0}$. The results allow the Born cross sections of the process $e^{+}e^{-}\to K_{S}^{0} K_{L}^{0} π^{0}$, as well as its subprocesses $e^{+}e^{-}\to K^{*}(892)^{0}\bar{K}^{0}$ and $K^{*}_{2}(1430)^{0}\bar{K}^{0}$ to be measured. The Born cross sections for $e^{+}e^{-}\to K_{S}^{0}K_{L}^{0}π^{0}$ are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the process $e^{+}e^{-}\to K^{*}(892)^{0}\bar{K}^{0}$ is consistent with a vector meson state around 2.2 GeV with a significance of 3.2$σ$. A Breit-Wigner fit determines its mass as $M_Y=(2164.7\pm9.1\pm3.1)~{\rm{MeV}}/c^{2}$ and its width as $Γ_{Y}=(32.4\pm21.0\pm1.8)~\rm{MeV}$.

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arXiv2024

First observation of $Λ_c^+\rightarrowΛK^+π^0$ and evidence of $Λ_c^+\rightarrowΛK^+π^+π^-$

We present the first observation of the singly Cabibbo-suppressed decay $Λ_c^+ \rightarrow ΛK^+π^0$ with a significance of $5.7σ$ and the first evidence of $Λ_c^+ \rightarrow ΛK^+π^+π^-$ decay with a significance of $3.1σ$, based on $e^+e^-$ annihilation data recorded by the BESIII detector at the BEPCII collider. The data correspond to an integrated luminosity of $6.4~{\rm fb^{-1}}$, in the center-of-mass energy range from $4.600~{\rm GeV}$ to $4.950~{\rm GeV}$. We determine the branching fractions of $Λ_c^+ \rightarrow ΛK^+π^0$ and $Λ_c^+ \rightarrow ΛK^+π^+π^-$ relative to their Cabibbo-favored counterparts to be $\frac{\mathcal{B}(Λ_c^+ \rightarrow ΛK^+π^0)}{\mathcal{B}(Λ_c^+ \rightarrow Λπ^+π^0)} = (2.09\pm0.39_{\mathrm{stat.}}\pm0.07_{\mathrm{syst.}}) \times 10^{-2}$ and $\frac{\mathcal{B}(Λ_c^+ \rightarrow ΛK^+π^+π^-)}{\mathcal{B}(Λ_c^+ \rightarrow Λπ^+π^+π^-)} = (1.13\pm0.41_{\mathrm{stat.}}\pm0.06_{\mathrm{syst.}}) \times 10^{-2}$, respectively. Moreover, by combining our measured result with the world average of $\mathcal{B}(Λ^+_c\to Λπ^+π^0)$, we obtain the branching fraction $\mathcal{B}(Λ_c^+ \to ΛK^+π^0) = (1.49\pm0.27_{\mathrm{stat.}}\pm0.05_{\mathrm{syst.}}\pm0.08_{\mathrm{ref.}}) \times 10^{-3}$. This result significantly departs from theoretical predictions based on quark $SU(3)$ flavor symmetry, which is underpinned by the presumption of meson pair $S$-wave amplitude dominance.

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arXiv2024

Search for a muonphilic scalar $X_{0}$ or vector $X_{1}$ via $J/ψ\toμ^+μ^-+\rm{invisible}$ decays at BESII

A light scalar $X_{0}$ or vector $X_{1}$ particles have been introduced as a possible explanation for the $(g-2)_μ$ anomaly and dark matter phenomena. Using $(8.998\pm 0.039)\times10^9$ $\jpsi $ events collected by the BESIII detector, we search for a light muon philic scalar $X_{0}$ or vector $X_{1}$ in the processes $J/ψ\toμ^+μ^- X_{0,1}$ with $X_{0,1}$ invisible decays. No obvious signal is found, and the upper limits on the coupling $g_{0,1}'$ between the muon and the $X_{0,1}$ particles are set to be between $1.1\times10^{-3}$ and $1.0\times10^{-2}$ for the $X_{0,1}$ mass in the range of $1<M(X_{0,1})<1000$ MeV$/c^2$ at 90$\%$ confidence level.

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arXiv2024

Study of light scalar mesons through $D_s^+ \to π^0 π^0 e^+ ν_e$ and $K_S^0 K_S^0 e^+ ν_e$ decays

Using 6.32~fb$^{-1}$ of $e^+e^-$ collision data recorded by the BESIII detector at center-of-mass energies between $4.178$ to $4.226$ GeV, we present the first measurement of the decay $D_s^+\to f_0(980)e^+ν_e,\,f_0(980)\to π^0π^0$. The product branching fraction of $D_s^+\to f_0(980)e^+ν_e,\,f_0(980)\to π^0π^0$ is measured to be $(7.9\pm1.4_{\rm stat} \pm0.3_{\rm syst})\times 10^{-4}$, with a statistical significance of $7.8σ$. Furthermore, the upper limits on the product branching fractions of $D_s^+\to f_0(500)e^+ν_e$ with $f_0(500)\to π^0π^0$ and the branching fraction of $D_s^+\to K_{S}^{0}K_{S}^{0}e^+ν_e$ are set to be $7.3\times 10^{-4}$ and $3.8\times 10^{-4}$ at 90\% confidence level, respectively. Our results provide valuable inputs to the understanding of the structures of light scalar mesons.

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arXiv2024

Search for the production of deuterons and antideuterons in e^+e^- annihilation at center-of-mass energies between 4.13 and 4.70 GeV

Using a data sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 19 fb$^{-1}$ collected with the BESIII detector at the BEPCII collider, we search for the production of deuterons and antideuterons via $e^+e^-\to ppπ^-\bar{d}+c.c.$ for the first time at center-of-mass energies between 4.13 and 4.70 GeV. No significant signal is observed and the upper limit of the $e^+e^-\to ppπ^-\bar{d}+c.c.$ cross section is determined to be from 9.0 to 145 fb depending on the center-of-mass energy at the $90\%$ confidence level.

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arXiv2024

Measurement of the Electromagnetic Transition Form-factors in the decays $η'\rightarrowπ^+π^-l^+l^-$

With a sample of $(10087\pm44)\times10^{6}$ $J/ψ$ events accumulated with the BESIII detector, we analyze the decays $η'\rightarrowπ^+π^-l^+l^-(l=e,$ $μ)$ via the process $J/ψ\rightarrowγη'$. The branching fractions are measured to be $\mathcal{B}(η'\rightarrowπ^+π^-e^+e^-)=(2.45\pm0.02(\rm{stat.})\pm0.08(\rm{syst.})) \times10^{-3}$ and $\mathcal{B}(η'\rightarrowπ^+π^-μ^+μ^-)=(2.16\pm0.12(\rm{stat.})\pm0.06(\rm{syst.}))\times10^{-5}$, and the ratio is $\frac{\mathcal{B}(η'\rightarrowπ^{+}π^{-}e^{+}e^{-})}{\mathcal{B}(η'\rightarrowπ^{+}π^{-}μ^{+}μ^{-})} = 113.4\pm0.9(\rm{stat.})\pm3.7(\rm{syst.})$. In addition, by combining the $η'\rightarrowπ^+π^-e^+e^-$ and $η'\rightarrowπ^+π^-μ^+μ^-$ decays, the slope parameter of the electromagnetic transition form factor is measured to be $b_{η'}=1.30\pm0.19\ (\mathrm{GeV}/c^{2})^{-2}$, which is consistent with previous measurements from BESIII and theoretical predictions from the VMD model. The asymmetry in the angle between the $π^+π^-$ and $l^+l^-$ decay planes, which has the potential to reveal the $CP$-violation originating from an unconventional electric dipole transition, is also investigated. The asymmetry parameters are determined to be $\mathcal{A}_{CP}(η'\rightarrowπ^+π^-e^+e^-)=(-0.21\pm0.73(\rm{stat.})\pm0.01(\rm{syst.}))\%$ and $\mathcal{A}_{CP}(η'\rightarrowπ^+π^-μ^+μ^-)=(0.62\pm4.71(\rm{stat.})\pm0.08(\rm{syst.}))\%$, implying that no evidence of $CP$-violation is observed at the present statistics. Finally, an axion-like particle is searched for via the decay $η'\rightarrowπ^+π^-a, a\rightarrow e^+e^-$, and upper limits of the branching fractions are presented for the mass assumptions of the axion-like particle in the range of $0-500\ \mathrm{MeV}/c^{2}$.

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arXiv2024

Study of $e^{+}e^{-}\rightarrowπ^{+}π^{-}π^{0}$ at $\sqrt{s}$ from 2.00 to 3.08 GeV at BESIII

With the data samples taken at center-of-mass energies from 2.00 to 3.08 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis on the $e^{+}e^{-}\rightarrowπ^{+}π^{-}π^{0}$ process is performed. The Born cross sections for $e^{+}e^{-}\rightarrowπ^{+}π^{-}π^{0}$ and its intermediate processes $e^{+}e^{-}\rightarrowρπ$ and $ρ(1450)π$ are measured as functions of $\sqrt{s}$. The results for $e^{+}e^{-}\rightarrowπ^{+}π^{-}π^{0}$ are consistent with previous results measured with the initial state radiation method within one standard deviation, and improve the uncertainty by a factor of ten. By fitting the line shapes of the Born cross sections for the $e^{+}e^{-}\rightarrowρπ$ and $ρ(1450)π$, a structure with mass $M = 2119\pm11\pm15\ {\rm MeV}/c^2$ and width $Γ=69\pm30\pm5 {\rm MeV}$ is observed with a significance of $5.9σ$, where the first uncertainties are statistical and the second ones are systematic. This structure can be intepreteted as an excited $ω$ state.

hep-ex↗