Engineering topics

Bettoni, D.

Publications and source records attributed to Bettoni, D..

At least 109 records · Page 6

DOE OSTI2024

Search for η c ( 2 S ) → π + π − η c and η c ( 2 S ) → π + π − K S 0 K ± π ∓ decays

Based on ( 27.12 ± 0.14 ) × 10 8 ψ ( 2 S ) events collected by the BESIII detector, we search for the decay η c ( 2 S ) → π + π − η c via ψ ( 2 S ) → γ η c ( 2 S ) . No significant signal is observed, and the upper limit on the product branching fraction B ( ψ ( 2 S ) → γ η c ( 2 S ) ) × B ( η c ( 2 S ) → π + π − η c ) is determined to be 2.21 × 10 − 5 at the 90% confidence level. In addition, the η c ( 2 S ) → π + π − K S 0 K ± π ∓ decay is studied via ψ ( 2 S ) → γ η c ( 2 S ) and is observed with a statistical significance of 10 σ for the first time. The branching fraction of η c ( 2 S ) → π + π − K S 0 K ± π ∓ is determined to be ( 1.33 ± 0.11 ± 0.40 ± 0.95 ) × 10 − 2 , where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the quoted B ( ψ ( 2 S ) → γ η c ( 2 S ) ) . Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Observation of ψ ( 3686 ) → 3 ϕ

Using ( 2.712 ± 0.014 ) × 10 9 ψ ( 3686 ) events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of ψ ( 3686 ) → 3 ϕ decay with a significance larger than 10 σ . The branching fraction of this decay is determined to be ( 1.46 ± 0.05 ± 0.17 ) × 10 − 5 , where the first uncertainty is statistical and the second is systematic. No significant structure is observed in the ϕ ϕ invariant mass spectra. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Observation of Structures in the Processes e + e − → ω χ c 1 and ω χ c 2

We present measurements of the Born cross sections for the processes e + e − → ω χ c 1 and ω χ c 2 at center-of-mass energies s from 4.308 to 4.951 GeV. The measurements are performed with data samples corresponding to an integrated luminosity of 11.0 fb − 1 collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring. Assuming the e + e − → ω χ c 2 signals come from a single resonance, the mass and width are determined to be M = ( 4413.6 ± 9.0 ± 0.8 ) MeV / c 2 and Γ = ( 110.5 ± 15.0 ± 2.9 ) 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 − → ω χ c 1 line shape and determine the mass and width to be M = ( 4544.2 ± 18.7 ± 1.7 ) MeV / c 2 and Γ = ( 116.1 ± 33.5 ± 1.7 ) MeV , respectively. The structure of this line shape, observed for the first time, requires further understanding. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

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↗

DOE OSTI2024

Measurement of branching fractions for Λ c + → n K S 0 π + and Λ c + → n K S 0 K +

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, we measure the absolute branching fraction of the Cabibbo-favored decay Λ c + → n K S 0 π + with the precision improved by a factor of 2.8 and report the first evidence for the singly-Cabibbo-suppressed decay Λ c + → n K S 0 K + . The branching fractions for Λ c + → n K S 0 π + and Λ c + → n K S 0 K + are determined to be ( 1.86 ± 0.08 ± 0.04 ) × 10 − 2 and ( 3. 9 − 1.4 + 1.7 ± 0.3 ) × 1 0 − 4 , respectively, where the first uncertainties are statistical and the second ones are systematic. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Coupled-Channel Analysis of the χ c 1 ( 3872 ) Line Shape with BESIII Data

We perform a study of the χ c 1 ( 3872 ) line shape using the data samples of e + e − → γ χ c 1 ( 3872 ) , χ c 1 ( 3872 ) → D 0 D ¯ 0 π 0 , and π + π − J / ψ collected with the BESIII detector. The effects of the coupled channels and the off-shell D * 0 are included in the parametrization of the line shape. The line shape mass parameter is obtained to be M X = ( 3871.63 ± 0.1 3 − 0.05 + 0.06 ) MeV . Two poles are found on the first and second Riemann sheets corresponding to the D * 0 D ¯ 0 branch cut. The pole location on the first sheet is much closer to the D * 0 D ¯ 0 threshold than the other, and is determined to be 7.04 ± 0.1 5 − 0.08 + 0.07 MeV above the D 0 D ¯ 0 π 0 threshold with an imaginary part − 0.19 ± 0.0 8 − 0.19 + 0.14 MeV . Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Observation of the Anomalous Shape of X ( 1840 ) in J / ψ → γ 3 ( π + π − ) Indicating a Second Resonance Near p p ¯ Threshold

Using a sample of ( 10087 ± 44 ) × 10 6 J / ψ events, which is about 45 times larger than that was previously analyzed, a further investigation on the J / ψ → γ 3 ( π + π − ) decay is performed. A significant distortion at 1.84 GeV / c 2 in the line shape of the 3 ( π + π − ) 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 10 σ . The mass and width of X ( 1880 ) are determined to be 1882.1 ± 1.7 ± 0.7 MeV / c 2 and 30.7 ± 5.5 ± 2.4 MeV , respectively, which indicates the existence of a p p ¯ bound state. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Search for the decay χ c 1 ( 3872 ) → π + π − χ c 1

Using a data sample corresponding to an integrated luminosity of 10.9 fb − 1 collected at center-of-mass energies from 4.16 to 4.34 GeV with the BESIII detector, we search for the decay χ c 1 ( 3872 ) → π + π − χ c 1 in the radiative production e + e − → γ χ c 1 ( 3872 ) . No significant signal is observed, and the ratio for the branching fraction of χ c 1 ( 3872 ) → π + π − χ c 1 to χ c 1 ( 3872 ) → π + π − J / ψ is measured as R ≡ B [ χ c 1 ( 3872 ) → π + π − χ c 1 ] B [ χ c 1 ( 3872 ) → π + π − J / ψ ] < 0.18 at 90% confidence level. An upper limit on the product of the cross section σ [ e + e − → γ χ c 1 ( 3872 ) ] and the branching fraction B [ χ c 1 ( 3872 ) → π + π − χ c 1 ] at each center-of-mass energy is also given. These measurements favor the nonconventional charmonium nature of the χ c 1 ( 3872 ) state. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

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↗

DOE OSTI2024

Study of the f 0 ( 980 ) and f 0 ( 500 ) Scalar Mesons through the Decay D s + → π + π − e + ν e

Using e + e − collision data corresponding to an integrated luminosity of 7.33 fb − 1 recorded by the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, we present an analysis of the decay D s + → π + π − e + ν e , where the D s + is produced via the process e + e − → D s * ± D s ∓ . We observe the f 0 ( 980 ) in the π + π − system and the branching fraction of the decay D s + → f 0 ( 980 ) e + ν e with f 0 ( 980 ) → π + π − measured to be ( 1.72 ± 0.1 3 stat ± 0.1 0 syst ) × 10 − 3 , where the uncertainties are statistical and systematic, respectively. The dynamics of the D s + → f 0 ( 980 ) e + ν e decay are studied with the simple pole parametrization of the hadronic form factor and the Flatté formula describing the f 0 ( 980 ) in the differential decay rate, and the product of the form factor f + f 0 ( 0 ) and the c → s Cabibbo-Kobayashi-Maskawa matrix element | V c s | is determined for the first time to be f + f 0 ( 0 ) | V c s | = 0.504 ± 0.01 7 stat ± 0.03 5 syst . Furthermore, the decay D s + → f 0 ( 500 ) e + ν e is searched for the first time but no signal is found. The upper limit on the branching fraction of D s + → f 0 ( 500 ) e + ν e , f 0 ( 500 ) → π + π − decay is set to be 3.3 × 10 − 4 at 90% confidence level. Published by the American Physical Society 2024

Ablikim, M.↗

DOE OSTI2024

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↗

DOE OSTI2024

Observation of ψ(3686) → $$ {\varOmega}^{-}{K}^{+}{\overline{\Xi}}^0 $$ + c.c.

Abstract Using (27.12±0.14)×10 8 ψ(3686) events collected with the BESIII detector at BEPCII, the decay ofψ(3686)→$$ {\varOmega}^{-}{K}^{+}{\overline{\Xi}}^0 $$ Ω − K + Ξ ¯ 0 + c.c.is observed for the first time. The branching fraction of this decay is measured to be$$ {\mathcal{B}}_{\psi (3686)\to {\varOmega}^{-}{K}^{+}{\overline{\Xi}}^0+\textrm{c}.\textrm{c}.} $$ B ψ 3686 → Ω − K + Ξ ¯ 0 + c . c . = (2.78 ± 0.40 ± 0.18) × 10 −6 , where the first uncertainty is statistical and the second is systematic. Possible baryon excited states are searched for in this decay, but no evident intermediate state is observed with the current sample size.

Physics↗

DOE OSTI2024

Observation of D + → K S 0 a 0 ( 980 ) + in the Amplitude Analysis of D + → K S 0 π + η

We perform for the first time an amplitude analysis of the decay D + → K S 0 π + η and report the observation of the decay D + → 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 + → K S 0 a 0 ( 980 ) + is the ideal decay in extracting the contributions of the W -emission amplitudes involving a 0 ( 980 ) and to study the final-state interactions. The absolute branching fraction of D + → K S 0 π + η is measured to be ( 1.27 ± 0.0 4 stat ± 0.0 3 syst ) % . The branching fractions of intermediate processes D + → K S 0 a 0 ( 980 ) + with a 0 ( 980 ) + → π + η and D + → π + K ¯ 0 * ( 1430 ) 0 with K ¯ 0 * ( 1430 ) 0 → K S 0 η are measured to be ( 1.33 ± 0.0 5 stat ± 0.0 4 syst ) % and ( 0.14 ± 0.0 3 stat ± 0.0 1 syst ) % , respectively. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

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↗

DOE OSTI2024

Observation of Significant Flavor-SU(3) Breaking in the Kaon Wave Function at 12 < Q 2 < 25 GeV 2 and Discovery of the Charmless Decay ψ ( 3770 ) → K S 0 K L 0

We present cross sections for the reaction e + e − → K S 0 K L 0 at center-of-mass energies ranging from 3.51 to 4.95 GeV using data samples collected in the BESIII experiment, corresponding to a total integrated luminosity of 26.5 fb − 1 . The ratio of neutral-to-charged kaon form factors at large momentum transfers ( 12 < Q 2 < 25 GeV 2 ) is determined to be 0.21 ± 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 ( π ± ) | / | F ( K ± ) | = f π 2 / f K 2 , where F ( π ± ) and F ( K ± ) are the form factors, and f π and f K are the decay constants of charged pions and kaons, respectively. We also observe a significant signal for the charmless decay ψ ( 3770 ) → K S 0 K L 0 for the first time. Within a 1 σ contour of the likelihood value, the branching fraction for ψ ( 3770 ) → K S 0 K L 0 is determined to be B = ( 2.6 3 − 1.59 + 1.40 ) × 10 − 5 , and the relative phase between the continuum and ψ ( 3770 ) amplitudes is ϕ = ( − 0.3 9 − 0.10 + 0.05 ) π . The branching fraction is in good agreement with the S - and D -wave charmonia mixing scheme proposed in the interpretation of the “ ρ π puzzle” between J / ψ and ψ ( 3686 ) decays. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Observation of J / ψ decays to e + e − e + e − and e + e − μ + μ −

Using a data sample of 4.481 × 10 8 ψ ( 3686 ) events collected with the BESIII detector, we report the first observation of the four-lepton-decays J / ψ → e + e − e + e − and J / ψ → e + e − μ + μ − utilizing the process ψ ( 3686 ) → π + π − J / ψ . The branching fractions are determined to be [ 5.48 ± 0.31 ( stat ) ± 0.45 ( syst ) ] × 10 − 5 and [ 3.53 ± 0.22 ( stat ) ± 0.13 ( syst ) ] × 10 − 5 , respectively. The results are consistent with theoretical predictions. No significant signal is observed for J / ψ → μ + μ − μ + μ − , and an upper limit on the branching fraction is set at 1.6 × 10 − 6 at the 90% confidence level. A C P asymmetry observable is constructed for the first two channels, which is measured to be ( − 0.012 ± 0.054 ± 0.010 ) and ( 0.062 ± 0.059 ± 0.006 ) , respectively. No evidence for C P violation is observed in this process. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

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.↗

DOE OSTI2024

Investigation of the Δ I = 1 / 2 Rule and Test of C P Symmetry through the Measurement of Decay Asymmetry Parameters in Ξ − Decays

Using ( 10 087 ± 44 ) × 10 6 J / ψ events collected with the BESIII detector, numerous Ξ − and Λ decay asymmetry parameters are simultaneously determined from the process J / ψ → Ξ − Ξ ¯ + → Λ ( p π − ) π − Λ ¯ ( n ¯ π 0 ) π + and its charge-conjugate channel. The precisions of α Λ 0 for Λ → n π 0 and α ¯ Λ 0 for Λ ¯ → n ¯ π 0 compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of Λ → n π 0 to that of Λ → p π − , ⟨ α Λ 0 ⟩ / ⟨ α Λ − ⟩ , is determined to be 0.873 ± 0.01 2 − 0.010 + 0.011 , where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity more than 5 σ , which signifies the existence of the Δ I = 3 / 2 transition in Λ for the first time. Besides, we test for C P symmetry in Ξ − → Λ π − and in Λ → n π 0 with the best precision to date. Published by the American Physical Society 2024

Physics↗