First simultaneous measurement of Ξ 0 and Ξ ¯ 0 asymmetry parameters in ψ ( 3686 ) decay
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79 ASTRONOMY AND ASTROPHYSICS↗
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Study of Λ c + → Λ μ + ν μ and test of lepton flavor universality with Λ c + → Λ ℓ + ν ℓ decays
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79 ASTRONOMY AND ASTROPHYSICS↗
Measurements of the absolute branching fractions of Ω − decays and test of the Δ I = 1 / 2 rule
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Astronomy & Astrophysics↗
Measurement of the cross sections for e + e − → η π + π − at center-of-mass energies between 2.00 and 3.08 GeV
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Astronomy & Astrophysics↗
Measurement of the e + e − → Λ Σ ¯ 0 + c . c . cross sections at s from 2.3094 to 3.0800 GeV
The Born cross sections and effective form factors of the process e + e − → Λ Σ ¯ 0 + c . c . are measured at 14 center-of-mass energy points from 2.3094 to 3.0800 GeV, based on data corresponding to an integrated luminosity of ( 478.5 ± 4.8 ) pb − 1 collected with the BESIII detector. A nonzero Born cross section is observed at the center-of-mass energy of 2.3094 GeV with a statistical significance of more than five standard deviations, and the cross sections at other energies are obtained with improved precision compared to earlier measurements from the Collaboration. The Born cross-section line shape is described better by a shape considering the strong-interaction effects than by a pQCD motivated functional form. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Observation and branching fraction measurement of the decay J / ψ → p ¯ Σ + K S 0 + c . c .
The first observation of the decays J / ψ → p ¯ Σ + K S 0 and J / ψ → p Σ ¯ − K S 0 is reported using ( 10087 ± 44 ) × 10 6 J / ψ events recorded by the BESIII detector at the BEPCII storage ring. The branching fractions of each channel are determined to be B ( J / ψ → p ¯ Σ + K S 0 ) = ( 1.361 ± 0.006 ± 0.025 ) × 10 − 4 , and B ( J / ψ → p Σ ¯ − K S 0 ) = ( 1.352 ± 0.006 ± 0.025 ) × 10 − 4 . The combined result is B ( J / ψ → p ¯ Σ + K S 0 + c . c . ) = ( 2.725 ± 0.009 ± 0.050 ) × 10 − 4 , where the first uncertainty is statistical and the second systematic. The results presented are in good agreement with the branching fractions of the isospin partner decay J / ψ → p K − Σ ¯ 0 + c . c . Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Observation of the decay J / ψ → e + e − η ( 1405 ) with η ( 1405 ) → π 0 f 0 ( 980 )
Using a data sample of ( 10087 ± 44 ) × 10 6 J / ψ events collected by the BESIII detector in 2009, 2012, 2018 and 2019, the electromagnetic Dalitz process J / ψ → e + e − η ( 1405 ) is observed via the decay η ( 1405 ) → π 0 f 0 ( 980 ) , f 0 ( 980 ) → π + π − , with a significance of about 9.8 σ . The branching fraction of this decay is measured to be B ( J / ψ → e + e − η ( 1405 ) → e + e − π 0 f 0 ( 980 ) → e + e − π 0 π + π − ) = ( 2.04 ± 0.20 ( stat ) ± 0.08 ( syst ) ) × 10 − 7 . The branching fraction ratio B ( J / ψ → e + e − η ( 1405 ) ) / B ( J / ψ → γ η ( 1405 ) ) is determined to be ( 1.36 ± 0.17 ( stat ) ± 0.06 ( syst ) ) × 10 − 2 . Furthermore, an e + e − invariant mass dependent transition form factor of J / ψ → e + e − η ( 1405 ) is presented for the first time. The obtained result provides input for different theoretical models and is valuable for the improved understanding the intrinsic structure of the η ( 1405 ) meson. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
First observation of Λ c + → Λ K + π 0 and evidence of Λ c + → Λ K + π + π −
We present the first observation of the singly Cabibbo-suppressed decay Λ c + → Λ K + π 0 with a significance of 5.7 σ and the first evidence of Λ c + → Λ K + π + π − decay with a significance of 3.1 σ , 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 fb − 1 , in the center-of-mass energy range from 4.600 to 4.950 GeV. We determine the branching fractions of Λ c + → Λ K + π 0 and Λ c + → Λ K + π + π − relative to their Cabibbo-favored counterparts to be B ( Λ c + → Λ K + π 0 ) B ( Λ c + → Λ π + π 0 ) = ( 2.09 ± 0.3 9 stat ± 0.0 7 syst ) × 10 − 2 and B ( Λ c + → Λ K + π + π − ) B ( Λ c + → Λ π + π + π − ) = ( 1.13 ± 0.4 1 stat ± 0.0 6 syst ) × 10 − 2 , respectively. Moreover, by combining our measured result with the world average of B ( Λ c + → Λ π + π 0 ) , we obtain the branching fraction B ( Λ c + → Λ K + π 0 ) = ( 1.49 ± 0.2 7 stat ± 0.0 5 syst ± 0.0 8 ref ) × 10 − 3 . This result significantly departs from theoretical predictions based on quark S U ( 3 ) flavor symmetry, which is underpinned by the presumption of meson pair S -wave amplitude dominance. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Updated measurements of the M1 transition ψ ( 3686 ) → γ η c ( 2 S ) with η c ( 2 S ) → K K ¯ π
Based on a data sample of ( 2712.4 ± 14.3 ) × 10 6 ψ ( 3686 ) events collected with the BESIII detector at the BEPCII collider, the M1 transition ψ ( 3686 ) → γ η c ( 2 S ) with η c ( 2 S ) → K K ¯ π is studied, where K K ¯ π is K + K − π 0 or K S 0 K ± π ∓ . The mass and width of the η c ( 2 S ) are measured to be ( 3637.8 ± 0.8 ( stat ) ± 0.2 ( syst ) ) MeV / c 2 and ( 10.5 ± 1.7 ( stat ) ± 3.5 ( syst ) ) MeV , respectively. The product branching fraction B ( ψ ( 3686 ) → γ η c ( 2 S ) ) × B ( η c ( 2 S ) → K K ¯ π ) is determined to be ( 0.97 ± 0.06 ( stat ) ± 0.09 ( syst ) ) × 10 − 5 . Using B ( η c ( 2 S ) → K K ¯ π ) = ( 1.8 6 − 0.49 + 0.68 ) % , we obtain the branching fraction of the radiative transition to be B ( ψ ( 3686 ) → γ η c ( 2 S ) ) = ( 5.2 ± 0.3 ( stat ) ± 0.5 ( syst ) − 1.4 + 1.9 ( extr ) ) × 10 − 4 , where the third uncertainty is due to the quoted B ( η c ( 2 S ) → K K ¯ π ) . Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Improved measurement of the decays η ′ → π + π − π + ( 0 ) π − ( 0 ) and search for the rare decay η ′ → 4 π 0
Using a sample of 10 billion J / ψ events collected with the BESIII detector, the decays η ′ → π + π − π + π − , η ′ → π + π − π 0 π 0 and η ′ → 4 π 0 are studied via the process J / ψ → γ η ′ . The branching fractions of η ′ → π + π − π + π − and η ′ → π + π − π 0 π 0 are measured to be ( 8.56 ± 0.25 ( stat ) ± 0.23 ( syst ) ) × 10 − 5 and ( 2.12 ± 0.12 ( stat ) ± 0.10 ( syst ) ) × 10 − 4 , respectively, which are consistent with previous measurements but with improved precision. No significant η ′ → 4 π 0 signal is observed, and the upper limit on the branching fraction of this decay is determined to be less than 1.24 × 10 − 5 at the 90% confidence level. In addition, an amplitude analysis of η ′ → π + π − π + π − is performed to extract the doubly virtual isovector form factor α for the first time. The measured value of α = 1.22 ± 0.33 ( stat ) ± 0.04 ( syst ) , is in agreement with the prediction of the vector meson dominance model. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Study of the doubly Cabibbo-suppressed decays D s + → K + K + π − and D s + → K + K + π − π 0
Based on 7.33 fb − 1 of e + e − 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 s + → K + K + π − and D s + → K + K + π − π 0 are reported. We determine the absolute branching fraction of D s + → K + K + π − to be ( 1.2 4 − 0.26 + 0.28 ( stat ) ± 0.06 ( syst ) ) × 10 − 4 . No significant signal of D s + → K + K + π − π 0 is observed and the upper limit on its decay branching fraction at 90% confidence level is set to be 1.7 × 10 − 4 . Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Measurements of Σ electromagnetic form factors in the timelike region using the untagged initial-state radiation technique
The process e + e − → Σ + Σ ¯ − is studied from threshold up to 3.04 GeV / c 2 via the initial-state radiation technique using data with an integrated luminosity of 12.0 fb − 1 , 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 Σ are measured in eleven Σ + Σ ¯ − invariant mass intervals from threshold to 3.04 GeV / c 2 . The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays J / ψ → Σ + Σ ¯ − and ψ ( 3686 ) → Σ + Σ ¯ − are determined and the obtained results are consistent with the previous results of BESIII. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Measurement of the absolute branching fraction of the three-body decay Λ c + → Ξ 0 K + π 0 and search for Λ c + → n K + π 0 , Σ 0 K + π 0 , and Λ K + π 0
The Cabbibo-favored decay Λ c + → Ξ 0 K + π 0 is studied for the first time using 6.1 fb − 1 of e + e − 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 Λ c + → Ξ 0 K + π 0 is measured to be ( 7.79 ± 1.46 ± 0.95 ) × 10 − 3 , where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Λ c + → Ξ ( 1530 ) 0 K + is ( 5.99 ± 1.04 ± 0.32 ) × 10 − 3 , which is consistent with the previous result of ( 5.02 ± 0.99 ± 0.31 ) × 10 − 3 . In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Λ c + → n K + π 0 is 7.1 × 10 − 4 at the 90% confidence level. The upper limits on the branching fractions of Λ c + → Σ 0 K + π 0 and Λ K + π 0 are also determined to be 1.8 × 10 − 3 and 2.0 × 10 − 3 , respectively. Published by the American Physical Society 2024
Ablikim, M.↗
First observation of the decay Λ c + → n K S 0 π + π 0
Based on 4.5 fb − 1 of e + e − collision data accumulated at center-of-mass energies between 4599.53 and 4698.82 MeV with the BESIII detector, the decay Λ c + → n K S 0 π + π 0 is observed for the first time with a significance of 9.2 σ . The branching fraction is measured to be ( 0.85 ± 0.13 ± 0.03 ) % , where the first uncertainty is statistical and the second is 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. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Improved measurements of the Dalitz decays η / η ′ → γ e + e −
Based on a data sample of 10 billion J / ψ events collected with the BESIII detector, improved measurements of the Dalitz decays η / η ′ → γ e + e − are performed, where the η and η ′ are produced through the radiative decays J / ψ → γ η / η ′ . The branching fractions of η → γ e + e − and η ′ → γ e + e − are measured to be ( 7.07 ± 0.05 ± 0.23 ) × 10 − 3 and ( 4.83 ± 0.07 ± 0.14 ) × 10 − 4 , respectively. Within the single-pole model, the parameter of electromagnetic transition form factor for η → γ e + e − is determined to be Λ η = ( 0.749 ± 0.027 ± 0.007 ) GeV / c 2 . Within the multipole model, we extract the electromagnetic transition form factors for η ′ → γ e + e − to be Λ η ′ = ( 0.802 ± 0.007 ± 0.008 ) GeV / c 2 and γ η ′ = ( 0.113 ± 0.010 ± 0.002 ) GeV / c 2 . The results are consistent with both theoretical predictions and previous measurements. The characteristic sizes of the interaction regions for the η and η ′ are calculated to be ( 0.645 ± 0.023 ± 0.007 ) fm and ( 0.596 ± 0.005 ± 0.006 ) fm , respectively. In addition, we search for the dark photon in η / η ′ → γ e + e − , and the upper limits of the branching fractions as a function of the dark photon are given at 90% confidence level. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Search for D 0 → K S 0 K − e + ν e , D + → K S 0 K S 0 e + ν e , and D + → K + K − e + ν e
A search has been performed for the semileptonic decays D 0 → K S 0 K − e + ν e , D + → K S 0 K S 0 e + ν e , and D + → K + K − e + ν e , using 7.9 fb − 1 of e + e − annihilation data collected at the center-of-mass energy s = 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 2.13 × 10 − 5 , 1.54 × 10 − 5 , and 2.10 × 10 − 5 for the branching fractions of D 0 → K S 0 K − e + ν e , D + → K S 0 K S 0 e + ν e , and D + → K + K − e + ν e , respectively. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Study of excited Ξ states in ψ ( 3686 ) → K − Λ Ξ ¯ + + c . c .
Based on a sample of ( 448.1 ± 2.9 ) × 10 6 ψ ( 3686 ) events collected with the BESIII detector at BEPCII, the decays of ψ ( 3686 ) → K − Λ Ξ ¯ + + c . c . with Ξ ¯ + → Λ ¯ π + , Λ ¯ → p ¯ π + are studied. We investigate the two excited resonances, Ξ ( 1690 ) − and Ξ ( 1820 ) − , which are each observed with large significance ( ≫ 10 σ ) in the K − Λ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of Ξ ( 1690 ) − and Ξ ( 1820 ) − are measured to be 1 2 − and 3 2 − , respectively. The masses, widths, and product branching fractions of Ξ ( 1690 ) − and Ξ ( 1820 ) − are also measured. Published by the American Physical Society 2024
Astronomy & Astrophysics↗