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We measure the Born cross section for the reaction e+eββΞ·hc from sβ=4.129 to 4.600~GeV using data sets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross section line shape near 4.200~GeV is observed with a statistical significance of 7Ο. The parameters of this resonance are measured to be \MeasMass\ and \MeasWidth, where the first uncertainties are statistical and the second systematic.
Based on 4.5 fbβ1 of e+eβ collision data accumulated at center-of-mass energies between 4599.53 MeV and 4698.82 MeV with the BESIII detector, the decay Ξ+cβnK0SΟ+Ο0 is observed for the first time with a significance of 9.2Ο. The branching fraction is measured to be (0.85Β±0.13Β±0.03)%, where the first uncertainty is statistical and the second systematic, which differs from the theoretical prediction based on isospin by 4.4Ο. This indicates that there may be resonant contributions or some unknown dynamics in this decay.
Search for eβΊeβ»βββKβΊKβ»Ο(3770) at center-of-mass energies from 4.84 to 4.95 GeV
(2024)
Using e+eβ collision data, corresponding to an integrated luminosity of 892pbβ1 collected at center-of-mass energies from 4.84 to 4.95\,GeV with the BESIII detector, we search for the process e+eββK+KβΟ(3770) by reconstructing two charged kaons and one D meson from Ο(3770). No significant signal of e+eββK+KβΟ(3770) is found and the upper limits of the Born cross sections are reported at 90\% confidence level.
Based on 4.5 fbβ1 of e+eβ collision data accumulated at center-of-mass energies between 4599.53 MeV and 4698.82 MeV with the BESIII detector, the decay Ξ+cβnK0SΟ+Ο0 is observed for the first time with a significance of 9.2Ο. The branching fraction is measured to be (0.85Β±0.13Β±0.03)%, where the first uncertainty is statistical and the second systematic, which differs from the theoretical prediction based on isospin by 4.4Ο. This indicates that there may be resonant contributions or some unknown dynamics in this decay.
The process π+β’πββΞ£+β’Β―Ξ£β is studied from threshold up to 3.04ββGeV/π2 via the initial-state radiation technique using data with an integrated luminosity of 12.0ββfbβ1, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of Ξ£ are measured in eleven Ξ£+Β―Ξ£β invariant mass intervals from threshold to 3.04ββGeV/π2. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays π½/πβΞ£+β’Β―Ξ£β and πβ‘(3686)βΞ£+β’Β―Ξ£β are determined and the obtained results are consistent with the previous results of BESIII.
The process e+eββΞ£+Σ¯β is studied from threshold up to 3.04 GeV/c2 via the initial-state radiation technique using data with an integrated luminosity of 12.0 fbβ1, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of Ξ£ are measured in eleven Ξ£+Σ¯β invariant mass intervals from threshold to 3.04 GeV/c2. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays J/ΟβΞ£+Σ¯β and Ο(3686)βΞ£+Σ¯β are determined and the obtained results are consistent with the previous results of BESIII.
Amplitude analysis of the decays Dβ° β ΟβΊΟβΟβΊΟβ» and Dβ° β ΟβΊΟβ»Οβ°Οβ°
(2023)
Using e+eβ annihilation data corresponding to an integrated luminosity of 2.93 fbβ1 taken at the center-of-mass energy sβ=3.773~GeV with the BESIII detector, a joint amplitude analysis is performed on the decays D0βΟ+ΟβΟ+Οβ and D0βΟ+ΟβΟ0Ο0(non-Ξ·). The fit fractions of individual components are obtained, and large interferences among the dominant components of D0βa1(1260)Ο, D0βΟ(1300)Ο, D0βΟ(770)Ο(770) and D0β2(ΟΟ)S are found in both channels. With the obtained amplitude model, the CP-even fractions of D0βΟ+ΟβΟ+Οβ and D0βΟ+ΟβΟ0Ο0(non-Ξ·) are determined to be (75.2Β±1.1stat.Β±1.5syst.)% and (68.9Β±1.5stat.Β±2.4syst.)%, respectively. The branching fractions of D0βΟ+ΟβΟ+Οβ and D0βΟ+ΟβΟ0Ο0(non-Ξ·) are measured to be (0.688Β±0.010stat.Β±0.010syst.)% and (0.951Β±0.025stat.Β±0.021syst.)%, respectively. The amplitude analysis provides an important model for binning strategy in the measurements of the strong phase parameters of D0β4Ο when used to determine the CKM angle Ξ³(Ο3) via the BββDKβ decay.
Amplitude analysis of the decays Dβ° β ΟβΊΟβΟβΊΟβ» and Dβ° β ΟβΊΟβ»Οβ°Οβ°
(2024)
Using e+eβ annihilation data corresponding to an integrated luminosity of 2.93 fbβ1 taken at the center-of-mass energy sβ=3.773~GeV with the BESIII detector, a joint amplitude analysis is performed on the decays D0βΟ+ΟβΟ+Οβ and D0βΟ+ΟβΟ0Ο0(non-Ξ·). The fit fractions of individual components are obtained, and large interferences among the dominant components of D0βa1(1260)Ο, D0βΟ(1300)Ο, D0βΟ(770)Ο(770) and D0β2(ΟΟ)S are found in both channels. With the obtained amplitude model, the CP-even fractions of D0βΟ+ΟβΟ+Οβ and D0βΟ+ΟβΟ0Ο0(non-Ξ·) are determined to be (75.2Β±1.1stat.Β±1.5syst.)% and (68.9Β±1.5stat.Β±2.4syst.)%, respectively. The branching fractions of D0βΟ+ΟβΟ+Οβ and D0βΟ+ΟβΟ0Ο0(non-Ξ·) are measured to be (0.688Β±0.010stat.Β±0.010syst.)% and (0.951Β±0.025stat.Β±0.021syst.)%, respectively. The amplitude analysis provides an important model for binning strategy in the measurements of the strong phase parameters of D0β4Ο when used to determine the CKM angle Ξ³(Ο3) via the BββDKβ decay.
Using 7.33~fbβ1 of e+eβ collision data collected by the BESIII detector at center-of-mass energies in the range of sβ=4.128β4.226~GeV, we search for the rare decays D+sβh+(h0)e+eβ, where h represents a kaon or pion. By requiring the e+eβ invariant mass to be consistent with a Ο(1020), 0.98<M(e+eβ)<1.04 ~GeV/c2, the decay D+sβΟ+Ο,Οβe+eβ is observed with a statistical significance of 7.8Ο, and evidence for the decay D+sβΟ+Ο,Οβe+eβ is found for the first time with a statistical significance of 4.4Ο. The decay branching fractions are measured to be B(D+sβΟ+Ο,Οβe+eβ)=(1.17+0.23β0.21Β±0.03)Γ10β5, and B(D+sβΟ+Ο,Οβe+eβ)=(2.44+0.67β0.62Β±0.16)Γ10β5, where the first uncertainties are statistical and the second systematic. No significant signal for the three four-body decays of D+sβΟ+Ο0e+eβ, D+sβK+Ο0e+eβ, and D+sβK0SΟ+e+eβ is observed. For D+sβΟ+Ο0e+eβ, the Ο mass region is vetoed to minimize the long-distance effects. The 90% confidence level upper limits set on the branching fractions of these decays are in the range of (7.0β8.1)Γ10β5.
Search for eβΊeβ»βββKβΊKβ»Ο(3770) at center-of-mass energies from 4.84 to 4.95 GeV
(2024)
Using e+eβ collision data, corresponding to an integrated luminosity of 892pbβ1 collected at center-of-mass energies from 4.84 to 4.95\,GeV with the BESIII detector, we search for the process e+eββK+KβΟ(3770) by reconstructing two charged kaons and one D meson from Ο(3770). No significant signal of e+eββK+KβΟ(3770) is found and the upper limits of the Born cross sections are reported at 90\% confidence level.
Precision measurement of the branching fraction of J/Ο β KβΊKβ» via Ο(2S) β ΟβΊΟβ»J/Ο
(2024)
Using a sample of 448.1Γ106 Ο(2S) events collected with the BESIII detector, we perform a study of the decay J/ΟβK+Kβ via Ο(2S)βΟ+ΟβJ/Ο.
The branching fraction of J/ΟβK+Kβ is determined to be BK+Kβ=(3.072Β±0.023(stat.)Β±0.050(syst.))Γ10β4, which is consistent with previous measurements but with significantly improved precision.
A light scalar X0 or vector X1 particles have been introduced as a possible explanation for the (gβ2)ΞΌ anomaly and dark matter phenomena.
Using (8.998Β±0.039)Γ109 $\jpsi$ events collected by the BESIII detector, we search for a light muon philic scalar X0 or vector X1 in the processes J/ΟβΞΌ+ΞΌβX0,1 with X0,1 invisible decays. No obvious signal is found, and the upper limits on the coupling gβ²0,1 between the muon and the X0,1 particles are set to be between 1.1Γ10β3 and 1.0Γ10β2 for the X0,1 mass in the range of 1<M(X0,1)<1000~MeV/c2 at 90% confidence level.
Based on (10.09Β±0.04)Γ109 J/Ο events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/ΟβΟΟ0Ξ· is performed. We observe for the first time two new structures on the ΟΞ· invariant mass distribution, with statistical significances of 24.0Ο and 16.9Ο; the first with JPC = 1+β, mass M = (1911 Β± 6 (stat.) Β± 14 (sys.))~MeV/c2, and width Ξ= (149 Β± 12 (stat.) Β± 23 (sys.))~MeV, the second with JPC = 1ββ, mass M = (1996 Β± 11 (stat.) Β± 30 (sys.))~MeV/c2, and width Ξ = (148 Β± 16 (stat.) Β± 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f0(980)βa0(980)0 mixing signal in J/ΟβΟf0(980)βΟa0(980)0 and the corresponding electromagnetic decay J/ΟβΟa0(980)0 are measured with improved precision, providing crucial information to understand the nature of a0(980)0 and f0(980).
Based on (10.09Β±0.04)Γ109 J/Ο events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/ΟβΟΟ0Ξ· is performed. We observe for the first time two new structures on the ΟΞ· invariant mass distribution, with statistical significances of 24.0Ο and 16.9Ο; the first with JPC = 1+β, mass M = (1911 Β± 6 (stat.) Β± 14 (sys.))~MeV/c2, and width Ξ= (149 Β± 12 (stat.) Β± 23 (sys.))~MeV, the second with JPC = 1ββ, mass M = (1996 Β± 11 (stat.) Β± 30 (sys.))~MeV/c2, and width Ξ = (148 Β± 16 (stat.) Β± 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f0(980)βa0(980)0 mixing signal in J/ΟβΟf0(980)βΟa0(980)0 and the corresponding electromagnetic decay J/ΟβΟa0(980)0 are measured with improved precision, providing crucial information to understand the nature of a0(980)0 and f0(980).
A light scalar X0 or vector X1 particles have been introduced as a possible explanation for the (gβ2)ΞΌ anomaly and dark matter phenomena.
Using (8.998Β±0.039)Γ109 $\jpsi$ events collected by the BESIII detector, we search for a light muon philic scalar X0 or vector X1 in the processes J/ΟβΞΌ+ΞΌβX0,1 with X0,1 invisible decays. No obvious signal is found, and the upper limits on the coupling gβ²0,1 between the muon and the X0,1 particles are set to be between 1.1Γ10β3 and 1.0Γ10β2 for the X0,1 mass in the range of 1<M(X0,1)<1000 MeV/c2 at 90% confidence level.
A search has been performed for the semileptonic decays D0βK0SKβe+Ξ½e, D+βK0SK0Se+Ξ½e and D+βK+Kβe+Ξ½e, using 7.9 fbβ1 of e+eβ annihilation data collected at the center-of-mass energy sβ=3.773 GeV by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits are set at the 90\% confidence level of 2.13Γ10β5, 1.54Γ10β5 and 2.10Γ10β5 for the branching fractions of D0βK0SKβe+Ξ½e, D+βK0SK0Se+Ξ½e and D+βK+Kβe+Ξ½e, respectively.
The Cabbibo-favored decay Ξ+cβΞ0K+Ο0 is studied for the first time using 6.1 fbβ1 of e+eβ collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay Ξ+cβΞ0K+Ο0 is measured to be (7.79Β±1.46Β±0.71)Γ10β3, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Ξ+cβΞ(1530)0K+ is (5.99Β±1.04Β±0.29)Γ10β3, which is consistent with the previous result of (5.02Β±0.99Β±0.31)Γ10β3. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Ξ+cβnK+Ο0 is 7.1Γ10β4 at the 90% confidence level. The upper limits on the branching fractions of Ξ+cβΞ£0K+Ο0 and ΞK+Ο0 are also determined to be 1.8Γ10β3 and 2.0Γ10β3, respectively.
The Cabbibo-favored decay Ξ+cβΞ0K+Ο0 is studied for the first time using 6.1 fbβ1 of e+eβ collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay Ξ+cβΞ0K+Ο0 is measured to be (7.79Β±1.46Β±0.71)Γ10β3, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Ξ+cβΞ(1530)0K+ is (5.99Β±1.04Β±0.29)Γ10β3, which is consistent with the previous result of (5.02Β±0.99Β±0.31)Γ10β3. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Ξ+cβnK+Ο0 is 7.1Γ10β4 at the 90% confidence level. The upper limits on the branching fractions of Ξ+cβΞ£0K+Ο0 and ΞK+Ο0 are also determined to be 1.8Γ10β3 and 2.0Γ10β3, respectively.
The Cabbibo-favored decay Ξ+cβΞ0K+Ο0 is studied for the first time using 6.1 fbβ1 of e+eβ collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay Ξ+cβΞ0K+Ο0 is measured to be (7.79Β±1.46Β±0.71)Γ10β3, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Ξ+cβΞ(1530)0K+ is (5.99Β±1.04Β±0.29)Γ10β3, which is consistent with the previous result of (5.02Β±0.99Β±0.31)Γ10β3. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Ξ+cβnK+Ο0 is 7.1Γ10β4 at the 90% confidence level. The upper limits on the branching fractions of Ξ+cβΞ£0K+Ο0 and ΞK+Ο0 are also determined to be 1.8Γ10β3 and 2.0Γ10β3, respectively.
The absolute branching fraction of the decay Ξc(2625)+βΞ+cΟ+Οβ is measured for the first time to be (50.7Β±5.0stat.Β±4.9syst.)% with 368.48 pbβ1 of e+eβ collision data collected by the BESIII detector at the center-of-mass energies of sβ=4.918 and 4.950 GeV. This result is lower than the naive prediction of 67\%, obtained from isospin symmetry, by more than 2Ο, thereby indicating that the novel mechanism referred to as the \textit{threshold effect}, proposed for the strong decays of Ξc(2595)+, also applies to Ξc(2625)+. This measurement is necessary to obtain the coupling constants for the transitions between s-wave and p-wave charmed baryons in heavy hadron chiral perturbation theory. In addition, we search for the decay Ξc(2595)+βΞ+cΟ+Οβ. No significant signal is observed, and the upper limit on its branching fraction is determined to be 80.8\% at the 90\% confidence level.
We search for the di-photon decay of a light pseudoscalar axion-like particle, a, in radiative decays of the J/Ο, using 10 billion J/Ο events collected with the BESIII detector. We find no evidence of a narrow resonance and set upper limits at the 95% confidence level on the product branching fraction B(J/ΟβΞ³a)ΓB(aβΞ³Ξ³) and the axion-like particle photon coupling constant gaΞ³Ξ³ in the ranges of (3.6β49.8)Γ10β8 and (2.2β103.8)Γ10β4 GeVβ1, respectively, for 0.18β€maβ€2.85 GeV/c2. These are the most stringent limits to date in this mass region.
Using data samples with an integrated luminosity of 22.42 fbβ1 collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the $e^{+}e^{-}\rightarrow\etaJ/\psi$ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with Ο(4040), two additional resonances, and a non-resonant component is performed. The mass and width of the first additional state are (4219.7Β±2.5Β±4.5)MeV/c2 and (80.7Β±4.4Β±1.4)MeV, respectively, consistent with the Ο(4230). For the second state, the mass and width are (4386Β±13Β±17)MeV/c2 and (177Β±32Β±13)MeV, respectively, consistent with the Ο(4360). The first uncertainties are statistical and the second ones are systematic. The statistical significance of Ο(4040) is 8.0Ο and those for Ο(4230) and Ο(4360) are more than 10.0Ο.
Using data samples with an integrated luminosity of 22.42ββfbβ1 collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the π+β’πββπβ’π½/π process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with πβ‘(4040), two additional resonances, and a nonresonant component are performed. The mass and width of the first additional state are (4219.7Β±2.5Β±4.5)ββMeV/π2 and (80.7Β±4.4Β±1.4)ββMeV, respectively, consistent with the πβ‘(4230). For the second state, the mass and width are (4386Β±13Β±17)ββMeV/π2 and (177Β±32Β±13)ββMeV, respectively, consistent with the πβ‘(4360). The first uncertainties are statistical, and the second ones are systematic. The statistical significance of πβ‘(4040) is 8.0β’π and those for πβ‘(4230) and πβ‘(4360) are more than 10.0β’π.
First observation of ΞcβΊβββΞKβΊΟβ° and evidence of ΞcβΊβββΞKβΊΟβΊΟβ»
(2023)
We present the first observation of the singly Cabibbo-suppressed decay Ξ+cβΞK+Ο0 with a significance of 5.7Ο and the first evidence of Ξ+cβΞK+Ο+Οβ decay with a significance of 3.1Ο, based on e+eβ annihilation data recorded by the BESIII detector at the BEPCII collider. The data correspond to an integrated luminosity of 6.4 fbβ1, in the center-of-mass energy range from 4.600 GeV to 4.950 GeV. We determine the branching fractions of Ξ+cβΞK+Ο0 and Ξ+cβΞK+Ο+Οβ relative to their Cabibbo-favored counterparts to be B(Ξ+cβΞK+Ο0)B(Ξ+cβΞΟ+Ο0)=(2.09Β±0.39stat.Β±0.07syst.)Γ10β2 and B(Ξ+cβΞK+Ο+Οβ)B(Ξ+cβΞΟ+Ο+Οβ)=(1.13Β±0.41stat.Β±0.06syst.)Γ10β2, respectively. Moreover, by combining our measured result with the world average of B(Ξ+cβΞΟ+Ο0), we obtain the branching fraction B(Ξ+cβΞK+Ο0)=(1.49Β±0.27stat.Β±0.05syst.Β±0.08ref.)Γ10β3. 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.
First observation of ΞcβΊβββΞKβΊΟβ° and evidence of ΞcβΊβββΞKβΊΟβΊΟβ»
(2024)
We present the first observation of the singly Cabibbo-suppressed decay Ξ+πβΞβ’πΎ+β’π0 with a significance of 5.7β’π and the first evidence of Ξ+πβΞβ’πΎ+β’π+β’πβ decay with a significance of 3.1β’π, based on π+β’πβannihilation data recorded by the BESIII detector at the BEPCII collider. The data correspond to an integrated luminosity of 6.4ββfbβ1, in the center-of-mass energy range from 4.600 to 4.950 GeV. We determine the branching fractions of Ξ+πβΞβ’πΎ+β’π0 and Ξ+πβΞβ’πΎ+β’π+β’πβ relative to their Cabibbo-favored counterparts to be β¬β‘(Ξ+πβΞβ’πΎ+β’π0)β¬β‘(Ξ+πβΞβ’π+β’π0) = (2.09Β±0.3β’9statΒ±0.0β’7syst)Γ10β2 and β¬β‘(Ξ+πβΞβ’πΎ+β’π+β’πβ)β¬β‘(Ξ+πβΞβ’π+β’π+β’πβ) = (1.13Β±0.4β’1statΒ±0.0β’6syst)Γ10β2, respectively. Moreover, by combining our measured result with the world average of β¬β‘(Ξ+πβΞβ’π+β’π0), we obtain the branching fraction β¬β‘(Ξ+πβΞβ’πΎ+β’π0) = (1.49Β±0.2β’7statΒ±0.0β’5systΒ±0.0β’8ref)Γ10β3. This result significantly departs from theoretical predictions based on quark πβ’πβ‘(3) flavor symmetry, which is underpinned by the presumption of meson pair π-wave amplitude dominance.
First observation of ΞcβΊβββΞKβΊΟβ° and evidence of ΞcβΊβββΞKβΊΟβΊΟβ»
(2024)
We present the first observation of the singly Cabibbo-suppressed decay Ξ+cβΞK+Ο0 with a significance of 5.7Ο and the first evidence of Ξ+cβΞK+Ο+Οβ decay with a significance of 3.1Ο, based on e+eβ annihilation data recorded by the BESIII detector at the BEPCII collider. The data correspond to an integrated luminosity of 6.4 fbβ1, in the center-of-mass energy range from 4.600 GeV to 4.950 GeV. We determine the branching fractions of Ξ+cβΞK+Ο0 and Ξ+cβΞK+Ο+Οβ relative to their Cabibbo-favored counterparts to be B(Ξ+cβΞK+Ο0)B(Ξ+cβΞΟ+Ο0)=(2.09Β±0.39stat.Β±0.07syst.)Γ10β2 and B(Ξ+cβΞK+Ο+Οβ)B(Ξ+cβΞΟ+Ο+Οβ)=(1.13Β±0.41stat.Β±0.06syst.)Γ10β2, respectively. Moreover, by combining our measured result with the world average of B(Ξ+cβΞΟ+Ο0), we obtain the branching fraction B(Ξ+cβΞK+Ο0)=(1.49Β±0.27stat.Β±0.05syst.Β±0.08ref.)Γ10β3. 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.
Based on 7.33ββfbβ1 of π+β’πβ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, the experimental studies of the doubly Cabibbo-suppressed decays π·+π βπΎ+β’πΎ+β’πβ and π·+π βπΎ+β’πΎ+β’πββ’π0 are reported. We determine the absolute branching fraction of π·+π βπΎ+β’πΎ+β’πβ to be (1.2β’4+0.28β0.26β’(stat)Β±0.06β’(syst))Γ10β4. No significant signal of π·+π βπΎ+β’πΎ+β’πββ’π0 is observed and the upper limit on its decay branching fraction at 90% confidence level is set to be 1.7Γ10β4.
Based on 7.33 fbβ1 of e+eβ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, the experimental studies of the doubly Cabibbo-suppressed decays D+sβK+K+Οβ and D+sβK+K+ΟβΟ0 are reported. We determine the absolute branching fraction of D+sβK+K+Οβ to be (1.23+0.28β0.25(stat)Β±0.06(syst)) Γ10β4. No significant signal of D+sβK+K+ΟβΟ0 is observed and the upper limit on its decay branching fraction at 90\% confidence level is set to be 1.7Γ10β4.
We present cross sections for the reaction e+eββK0SK0L at center-of-mass energies ranging from 3.51 GeV to 4.95 GeV using data samples collected in the BESIII experiment, corresponding to a total integrated luminosity of 26.5 fbβ1. The ratio of neutral-to-charged kaon form factors at large momentum transfers (12 GeV2<Q2<25 GeV2) is determined to be 0.21Β±0.01, which indicates a small but significant effect of flavor-SU(3) breaking in the kaon wave function, and consequently excludes the possibility that flavor-SU(3) breaking is the primary reason for the strong experimental violation of the pQCD prediction |F(ΟΒ±)|/|F(KΒ±)|=f2Ο/f2K, where F(ΟΒ±) and F(KΒ±) are the form factors, and fΟ and fK are the decay constants of charged pions and kaons, respectively. We also observe a significant signal for the charmless decay Ο(3770)βK0SK0L for the first time. Within a 1Ο contour of the likelihood value, the the branching fraction for Ο(3770)βK0SK0L is determined to be B=(2.63+1.40β1.59)Γ10β5, and the relative phase between the continuum and Ο(3770) amplitudes is Ο=(β0.39+0.05β0.10)Ο. The branching fraction is in good agreement with the S- and D-wave charmonia mixing scheme proposed in the interpretation of the "ΟΟ puzzle" between J/Ο and Ο(3686) decays.
Using (10087Β±44)Γ106 J/Ο events collected with the BESIII detector, numerous Ξβ and Ξ decay asymmetry parameters are simultaneously determined from the process J/ΟβΞβΞΒ―+βΞ(pΟβ)ΟβΞΒ―(nΒ―Ο0)Ο+ and its charge-conjugate channel. The precisions of Ξ±0 for ΞβnΟ0 and Ξ±Β―0 for ΞΒ―βnΒ―Ο0 compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of ΞβnΟ0 to that of ΞβpΟβ, β¨Ξ±0β©/β¨Ξ±Ξββ©, is determined to be 0.873Β±0.012+0.011β0.010, where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity more than 5Ο, which signifies the existence of the ΞI=3/2 transition in Ξ for the first time. Beside, we test for CP violation in ΞββΞΟβ and in ΞβnΟ0 with the best precision to date.
We report the measurement of the cross sections for e+eββhadrons at center-of-mass (c.m.) energies from 3.645 to 3.871 GeV. We observe a new resonance R(3810) in the cross sections for the first time, and observe the R(3760) resonance with high significance in the cross sections. The R(3810) has a mass of (3804.5Β±0.9Β±0.9) ~MeV/c2, a total width of (5.4Β±3.5Β±3.2)~MeV, and an electronic partial width of (19.4Β±7.4Β±12.1)~eV. Its significance is 7.7Ο. The R(3810) could be interpreted as a hadro-charmonium resonance predicted by Quantum Chromodynamics (QCD). In addition, we measure the mass (3751.9Β±3.8Β±2.8) ~MeV/c2, the total width (32.8Β±5.8Β±8.7)~MeV, and the electronic partial width (184Β±75Β±86)~eV with improved precision for the R(3760). Furthermore, for the R(3780) we measure the mass (3778.7Β±0.5Β±0.3) ~MeV/c2 and total width (20.3Β±0.8Β±1.7)~MeV with improved precision, and the electronic partial width (265Β±69Β±83)~eV. The R(3780) can be interpreted as the 13D1 state of charmonium. Its mass and total width differ significantly from the corresponding fitted values given by the Particle Data Group in 2022 by 7.1 and 3.2 times the uncertainties for Ο(3770), respectively. Ο(3770) has been interpreted as the 13D1 state for 45 years.
Using a sample of (10087Β±44)Γ106 J/Ο events, which is about 45 times larger than that was previously analyzed, a further investigation on the J/ΟβΞ³3(Ο+Οβ) decay is performed. A significant distortion at 1.84 GeV/c2 in the line-shape of the 3(Ο+Οβ) invariant mass spectrum is observed for the first time, which could be resolved by two overlapping resonant structures, X(1840) and X(1880). The new state X(1880) is observed with a statistical significance larger than 10Ο. The mass and width of X(1880) are determined to be 1882.1Β±1.7Β±0.7 MeV/c2 and 30.7Β±5.5Β±2.4 MeV, respectively, which indicates the existence of a ppΒ― bound state.
Using a sample of (10087Β±44)Γ106 J/Ο events, which is about fifty times larger than that was previously analyzed, a further investigation on the J/ΟβΞ³3(Ο+Οβ) decay is performed. A significant distortion at 1.84 GeV/c2 in the line-shape of the 3(Ο+Οβ) invariant mass spectrum is observed for the first time, which is analogous to the behavior of X(1835) and could be resolved by two overlapping resonant structures, X(1840) and X(1880). The new state X(1880) is observed with a statistical significance of 14.7Ο. The mass and width of X(1880) are determined to be 1882.1Β±1.7Β±0.7 MeV/c2 and 30.7Β±5.5Β±2.4 MeV, respectively, which indicates the existence of a ppΒ― bound state.
Using a sample of (10087Β±44)Γ106ββπ½/π events, which is about 45 times larger than that was previously analyzed, a further investigation on the π½/πβπΎβ’3β’(π+β’πβ) decay is performed. A significant distortion at 1.84ββGeV/π2 in the line shape of the 3β’(π+β’πβ) invariant mass spectrum is observed for the first time, which could be resolved by two overlapping resonant structures, πβ‘(1840) and πβ‘(1880). The new state πβ‘(1880) is observed with a statistical significance larger than 10β’π. The mass and width of πβ‘(1880) are determined to be 1882.1Β±1.7Β±0.7ββMeV/π2 and 30.7Β±5.5Β±2.4ββMeV, respectively, which indicates the existence of a πβ’Β― π bound state.
Measurement of the eβΊeβ» β Kβ°SKβ°LΟβ° cross sections from βs = 2.000 to 3.080 GeV
(2024)
Based on e+eβ 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 isperformed for the process e+eβ β K0SK0LΟ0. The results allow the Born cross sections of the process e+eβ β K0SK0LΟ0, as well as its subprocesses e+eβ β Kβ(892)0KΒ― 0 and Kβ2(1430)0KΒ― 0 to be measured. The Born cross sections for e+eβ β K0SK0 LΟ 0 are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the process e+e β β Kβ(892)0KΒ― 0 is consistent with a vector meson state around 2.2 GeV with a signifcance of 3.2Ο. A Breit-Wigner ft determines its mass as MY = (2164.7 Β± 9.1 Β± 3.1) MeV/c2 and its width as ΞY = (32.4 Β± 21.0 Β± 1.8) MeV.
Measurement of the eβΊeβ» β Kββ°KLβ°Οβ° cross sections from βs = 2.000 to 3.080 GeV
(2023)
Based on e+eβ 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+eββK0SK0LΟ0. The results allow the Born cross sections of the process e+eββK0SK0LΟ0, as well as its subprocesses e+eββKβ(892)0KΒ― and Kβ2(1430)0KΒ― to be measured. The Born cross sections for e+eββK0SK0LΟ0 are consistent with previous measurements by BaBar and SND, but with substantially improved precision. The Born cross section lineshape of the process e+eββKβ(892)0KΒ― is consistent with a vector meson state around 2.2 GeV with a statistical significance of 3.2Ο. A Breit-Wigner fit determines its mass as MY=(2164.1Β±9.6Β±3.1) MeV/c2 and its width as ΞY=(32.4Β±21.1Β±1.5) MeV, where the first uncertainties are statistical and the second ones are systematic, respectively.
Measurement of the eβΊeβ» β Kββ°KLβ°Οβ° cross sections from βs = 2.000 to 3.080 GeV
(2022)
Based on e+eβ 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+eββK0SK0LΟ0. The results allow the Born cross sections of the process e+eββK0SK0LΟ0, as well as its subprocesses e+eββKβ(892)0KΒ―0 and Kβ2(1430)0KΒ―0 to be measured. The Born cross sections for e+eββK0SK0LΟ0 are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the process e+eββKβ(892)0KΒ―0 is consistent with a vector meson state around 2.2 GeV with a significance of 3.2Ο. A Breit-Wigner fit determines its mass as MY=(2164.7Β±9.1Β±3.1) MeV/c2 and its width as ΞY=(32.4Β±21.0Β±1.8) MeV.
Using (10087Β±44)Γ106 J/Ο events collected with the BESIII detector, numerous Ξβ and Ξ decay asymmetry parameters are simultaneously determined from the process J/ΟβΞβΞΒ―+βΞ(pΟβ)ΟβΞΒ―(nΒ―Ο0)Ο+ and its charge-conjugate channel. The precisions of Ξ±0 for ΞβnΟ0 and Ξ±Β―0 for ΞΒ―βnΒ―Ο0 compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of ΞβnΟ0 to that of ΞβpΟβ, β¨Ξ±0β©/β¨Ξ±Ξββ©, is determined to be 0.873Β±0.012+0.011β0.010, where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity more than 5Ο, which signifies the existence of the ΞI=3/2 transition in Ξ for the first time. Beside, we test for CP violation in ΞββΞΟβ and in ΞβnΟ0 with the best precision to date.
Using (10087Β±44)Γ106 J/Ο events collected with the BESIII detector, numerous Ξβ and Ξ decay asymmetry parameters are simultaneously determined from the process J/ΟβΞβΞΒ―+βΞ(pΟβ)ΟβΞΒ―(nΒ―Ο0)Ο+ and its charge-conjugate channel. The precisions of Ξ±0 for ΞβnΟ0 and Ξ±Β―0 for ΞΒ―βnΒ―Ο0 compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of ΞβnΟ0 to that of ΞβpΟβ, β¨Ξ±0β©/β¨Ξ±Ξββ©, is determined to be 0.873Β±0.012+0.011β0.010, where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity, which is predicted by the ΞI=1/2 rule, with a statistical significance of more than 5Ο. We test for CP violation in ΞββΞΟβ and in ΞβnΟ0 with the best precision to date.
By analyzing e+eβ annihilation da ta corresponding to an integrated luminosity of 2.93 fbβ1 collected at a center-of-mass energy of 3.773 GeV with the \text{BESIII} detector, the first observation of the semileptonic decays D0βK0SΟβΟ0e+Ξ½e and D+βK0SΟ+Οβe+Ξ½e is reported. With a dominant hadronic contribution from K1(1270), the branching fractions are measured to be B(D0βK1(1270)β(βK0SΟβΟ0)e+Ξ½e) = (1.69+0.53β0.46Β±0.15)Γ10β4 and B(D+βKΒ―1(1270)0(βK0SΟ+Οβ)e+Ξ½e) = (1.47+0.45β0.40Β±0.20)Γ10β4 with statistical significance of 5.4Ο and 5.6Ο, respectively. When combined with measurements of the K1(1270)βK+ΟβΟ decays, the absolute branching fractions are determined to be B(D0βK1(1270)βe+Ξ½e) = (1.05+0.33β0.28Β±0.12Β±0.12)Γ10β3 and B(D+βKΒ―1(1270)0e+Ξ½e) = (1.29+0.40β0.35Β±0.18Β±0.15)Γ10β3. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainties originate from the assumed branching fractions of the K1(1270)βKΟΟ decays.
Amplitude analysis and branching fraction measurement of the decay DβΊ β Kββ°ΟβΊΟβ°Οβ°
(2023)
Using 2.93 fbβ1 of e+eβ collision data collected with the BESIII detector at the center-of-mass energy 3.773 GeV, we perform the first amplitude analysis of the decay D+ β Ο+Ο0Ο0 and determine the relative magnitudes and phases of different intermediate processes. The absolute branching fraction of D+ β Ο+Ο0Ο0 is measured to be (2.888 Β± 0.058stat. Β± 0.069syst.)%. The dominant intermediate processes are D+ β a1(1260)+(β Ο+Ο0) and D+ β *0Ο+, with branching fractions of (8.66 Β± 1.04stat. Β± 1.39syst.) Γ 10β3 and (9.70 Β± 0.81stat. Β± 0.53syst.) Γ 10β3, respectively.
The quantum entangled J/ΟβΞ£+Σ¯β pairs from (1.0087Β±0.0044)Γ1010 J/Ο events taken by the BESIII detector are used to study the non-leptonic two-body weak decays Ξ£+βnΟ+ and Σ¯ββnΒ―Οβ. The CP-odd weak decay parameters of the decays Ξ£+βnΟ+ (Ξ±+) and Σ¯ββnΒ―Οβ (Ξ±Β―β) are determined to be β0.0565Β±0.0047statΒ±0.0022syst and 0.0481Β±0.0031statΒ±0.0019syst, respectively. The decay parameter Ξ±Β―β is measured for the first time, and the accuracy of Ξ±+ is improved by a factor of four compared to the previous results. The simultaneously determined decay parameters allow the first precision CP symmetry test for any hyperon decay with a neutron in the final state with the measurement of ACP=(Ξ±++Ξ±Β―β)/(Ξ±+βΞ±Β―β) = β0.080Β±0.052statΒ±0.028syst. Assuming CP conservation, the average decay parameter is determined as β¨Ξ±+β©=(Ξ±+βΞ±Β―β)/2 = β0.0506Β±0.0026statΒ±0.0019syst, while the ratios Ξ±+/Ξ±0 and Ξ±Β―β/Ξ±Β―0 are β0.0490Β±0.0032statΒ±0.0021syst and β0.0571Β±0.0053statΒ±0.0032syst, where Ξ±0 and Ξ±Β―0 are the decay parameters of the decays Ξ£+βpΟ0 and Σ¯ββpΒ―Ο0, respectively.
The quantum entangled J=Ο β ΣþΣ¯ β pairs from Γ°1.0087 0.0044Γ Γ 1010 J=Ο events taken by the BESIII detector are used to study the nonleptonic two-body weak decays Σþ β nΟΓΎ and Σ¯ β β nΒ―Οβ. The CP-odd weak decay parameters of the decays Σþ β nΟΓΎ (Ξ±ΓΎ) and Σ¯ β β nΒ―Οβ (Ξ±Β―β) are determined to be 0.0481 0.0031stat 0.0019syst and β0.0565 0.0047stat 0.0022syst, respectively. The decay parameter Ξ±Β―β is measured for the first time, and the accuracy of Ξ±ΓΎ is improved by a factor of 4 compared to the previous results. The simultaneously determined decay parameters allow the first precision CP symmetry test for any hyperon decay with a neutron in the final state with the measurement of ACP ΒΌ ðαþ ΓΎ Ξ±Β―βΓ=ðαþ β Ξ±Β―βΓ ΒΌ β0.080 0.052stat 0.028syst. Assuming CP conservation, the average decay parameter is determined as hΞ±ΓΎi¼ðαþ β Ξ±Β―βΓ=2 ΒΌ β0.0506 0.0026stat 0.0019syst, while the ratios Ξ±ΓΎ=Ξ±0 and Ξ±Β―β=Ξ±Β― 0 are β0.0490 0.0032stat 0.0021syst and β0.0571 0.0053stat 0.0032syst, where Ξ±0 and Ξ±Β― 0 are the decay parameters of the decays Σþ β pΟ0 and Σ¯ β β pΒ― Ο0, respectively.
Quantum-correlated π·β’Β―π· pairs collected by the BESIII experiment at the πβ‘(3770) resonance corresponding to an integrated luminosity of 2.93ββfbβ1 are used to study the π·0βπΎ0πβ’π+β’πββ’π0 decay mode. The πΆβ’π-even fraction of π·0βπΎ0πβ’π+β’πββ’π0 decays is determined to be 0.235Β±0.010Β±0.002, where the first uncertainty is statistical and the second is systematic.
Using (1.0087Β±0.0044)Γ1010ββπ½/π events collected by the BESIII detector at the BEPCII collider, we report the first search for the baryon and lepton number violating decays Ξ0βπΎββ’π+ with Ξβ’(π΅βπΏ)=0 and Ξ0βπΎ+β’πβ with |Ξβ’(π΅βπΏ)|=2, where π΅ (πΏ) is the baryon (lepton) number. While no signal is observed, the upper limits on the branching fractions of these two decays are set to β¬β‘(Ξ0βπΎββ’π+)<3.6Γ10β6 and β¬β‘(Ξ0βπΎ+β’πβ)<1.9Γ10β6 at the 90% confidence level, respectively. These results offer a direct probe of baryon number violating interactions involving a strange quark.
Using Γ°1.0087 0.0044Γ Γ 1010 J=Ο events collected with the BESIII detector at the BEPCII storage ring, the process Ξ0n β Ξβp is studied, where the Ξ0 baryon is produced in the process J=Ο β Ξ0ΞΒ― 0 and the neutron is a component of the 9 Be, 12C, and 197Au nuclei in the beam pipe. A clear signal is observed with a statistical significance of 7.1Ο. The cross section of the reaction Ξ0 ΓΎ 9 Be β Ξβ ΓΎ p ΓΎ 8 Be is determined to be ΟΓ°Ξ0 ΓΎ 9 Be β Ξβ ΓΎ p ΓΎ 8 BeΓΒΌΓ°22.1 5.3stat 4.5sysΓ mb at the Ξ0 momentum of 0.818 GeV=c, where the first uncertainty is statistical and the second is systematic. No significant H-dibaryon signal is observed in the Ξβp final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.
Using an π+β’πβ collision data sample of (27.08Β±0.14)Γ108ββπβ‘(3686) events collected by the BESIII detector, we report the first observation of ππβ’π½βΞ©ββ’Β―Ξ©+ (π½=0, 1, 2) decays with significances of 5.6β’π, 6.4β’π, and 18β’π, respectively, where the ππβ’π½ mesons are produced in the radiative πβ‘(3686) decays. The branching fractions are determined to be β¬β‘(ππβ’0βΞ©ββ’Β―Ξ©+) = (3.51Β±0.54Β±0.29)Γ10β5, β¬β‘(ππβ’1βΞ©ββ’Β―Ξ©+)=(1.49Β±0.23Β±0.10)Γ10β5, and β¬β‘(ππβ’2βΞ©ββ’Β―Ξ©+)=(4.52Β±0.24Β±0.18)Γ10β5, where the first and second uncertainties are statistical and systematic, respectively.
The Ξ0 asymmetry parameters are measured using entangled quantum Ξ0 β ΞΒ― 0 pairs from a sample of Γ°448.1 2.9Γ Γ 106 ΟΓ°3686Γ events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the Ξ0ΞΒ― 0 helicity states is measured to be ΞΞ¦ ΒΌ β0.050 0.150 0.020 rad, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the Ξ0 hyperon ðαΞ0 ; Ξ±ΞΒ― 0 ; ΟΞ0 ; ΟΞΒ― 0 Γ and the angular distribution parameter Β½Ξ±ΟΓ°3686Γ and ΞΞ¦ are measured simultaneously for the first time. In addition, the CP asymmetry observables are determined to be AΞ0 CP ΒΌ ðαΞ0 ΓΎ Ξ±ΞΒ― 0 Γ=ðαΞ0 β Ξ±ΞΒ― 0 Γ ΒΌ β0.007 0.082 0.025 and ΞΟΞ0 CP ΒΌ Γ°ΟΞ0 ΓΎ ΟΞΒ― 0 Γ=2 ΒΌ β0.079 0.082 0.010 rad, which are consistent with CP conservation.
Precision measurements of DβΊβ β πeβΊβ’πβ and DβΊβ β πβ²β’eβΊβ’πβ
(2023)
Precision measurements of the semileptonic decays π·+π βπβ’π+β’ππ and π·+π βπβ²β’π+β’ππ are performed with 7.33ββfbβ1 of π+β’πβ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector. The branching fractions obtained are β¬β‘(π·+π βπβ’π+β’ππ) = (2.255Β±0.03β’9statΒ±0.05β’1syst)% and β¬β‘(π·+π βπβ²β’π+β’ππ)=(0.810Β±0.03β’8statΒ±0.02β’4syst)%. Combining these results with the β¬β‘(π·+βπβ’π+β’ππ) and β¬β‘(π·+βπβ²β’π+β’ππ) obtained from previous BESIII measurements, the πβπβ² mixing angle in the quark flavor basis is determined to be πP=(40.0Β±2.0statΒ±0.6syst)Β°. Moreover, from the fits to the partial decay rates of π·+π βπβ’π+β’ππ and π·+π βπβ²β’π+β’ππ, the products of the hadronic transition form factors ππ(β²)+β‘(0) and the modulus of the πβπ Cabibbo-Kobayashi-Maskawa matrix element |ππβ’π | are determined by using different hadronic transition form factor parametrizations. Based on the two-parameter series expansion, the products ππ+β‘(0)β’|ππβ’π | = 0.4519Β±0.007β’1statΒ±0.006β’5syst and ππβ²+β‘(0)β’|ππβ’π | = 0.525Β±0.02β’4statΒ±0.00β’9syst are extracted. All results determined in this work supersede those measured in the previous BESIII analyses based on the 3.19ββfbβ1 subsample of data at 4.178 GeV.
Measurement of branching fractions of _Ξ__(c)βΊ decays to Ξ£+K+Kβ, Ξ£+Ο and Ξ£+K+Οβ(Ο0)
(2023)
Based on 4.5 fbβ1 data taken at seven center-of-mass energies ranging from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we measure the branching fractions of Ξ + c β Ξ£ + + hadrons relative to Ξ + c β Ξ£ +Ο +Ο β. Combining with the world average branching fraction of Ξ + c β Ξ£ +Ο +Ο β, their branching fractions are measured to be (0.377 Β± 0.042 Β± 0.020 Β± 0.021)% for Ξ + c β Ξ£ +K+Kβ, (0.200 Β± 0.023 Β± 0.011 Β± 0.011)% for Ξ + c β Ξ£+K+Οβ, (0.414 Β± 0.080 Β± 0.030 Β± 0.023)% for Ξ + c β Ξ£ +Ο and (0.197 Β± 0.036 Β± 0.009 Β± 0.011)% for Ξ + c β Ξ£ +K+Kβ(non-Ο). In all the above results, the first uncertainties are statistical, the second are systematic and the third are from external input of the branching fraction of Ξ + c β Ξ£ +Ο +Ο β. Since no signal for Ξ + c β Ξ£ +K+ΟβΟ 0 is observed, the upper limit of its branching fraction is determined to be 0.13% at the 90% confidence level.