Engineering topics
Geng, C.
Publications and source records attributed to Geng, C..
Search for hadronic transition χ cJ →η c π + π - and observation of χ cJ →KK̄ πππ
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Precision measurements of branching fractions for ψ ′ → π 0 J / ψ and η J / ψ
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Observation of e⁺e⁻→ηJ/ψ at center-of-mass energy √s=4.009 GeV
Using a 478 pb⁻¹ data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring at a center-of-mass energy of s√=4.009 GeV, the production of e⁺e⁻→ηJ/ψ is observed for the first time with a statistical significance of greater than 10σ. The Born cross section is measured to be (32.1±2.8±1.3) pb, where the first error is statistical and the second systematic. Assuming the ηJ/ψ signal is from a hadronic transition of the ψ(4040), the fractional transition rate is determined to be B(ψ(4040)→ηJ/ψ)=(5.2±0.5±0.2±0.5)×10⁻³, where the first, second, and third errors are statistical, systematic, and the uncertainty from the ψ(4040) resonant parameters, respectively. The production of e⁺e⁻→π0J/ψ is searched for, but no significant signal is observed, and B(ψ(4040)→π⁰J/ψ)<2.8×10⁻⁴ is obtained at the 90% confidence level.
Measurement of χ cj decaying into pn̄π⁻ and pn̄π⁻π⁰
Using a data sample of 1.06×10⁸ ψ' events collected with the BESIII detector in 2009, the branching fractions of χ cJ →pn̄π⁻ and χ cJ →pn̄π⁻π⁰ (J=0, 1, 2) are measured. (Throughout the text, inclusion of charge conjugate modes is implied if not stated otherwise.) The results for χ c⁰ →pn̄π⁻ and χ c² →pn̄π⁻ are consistent with, but much more precise than, those of previous measurements. The decays of χ c1 →pn̄π⁻ and χ cJ →pn̄π⁻π⁰ are observed for the first time.
Observation of χ cJ decays to ΛΛ¯¯¯π⁺π⁻
Decays of the χ cJ states (J=0, 1, 2) to ΛΛ¯¯¯π⁺π⁻, including processes with intermediate Σ(1385), are studied through the E1 transition ψ'→γχ cJ using 106×10⁶ ψ' events collected with the BESIII detector at BEPCII. This is the first observation of χcJ decays to the final state ΛΛ¯¯¯π⁺π⁻. The branching ratio of the intermediate process χ cJ →Σ(1385) ± Σ¯¯¯(1385) ∓ is also measured for the first time, and the results agree with the theoretical predictions based on the color-octet effect.
Study of J/ψ→pp̄ and J/ψ→nn̄
The decays J/ψ→pp̄ and J/ψ→nn̄ have been investigated with a sample of 225.2×10⁶ J/ψ events collected with the BESIII detector at the BEPCII e⁺e⁻ collider. The branching fractions are determined to be B(J/ψ→pp̄)=(2.112±0.004±0.031)×10⁻³ and B(J/ψ→nn̄)=(2.07±0.01±0.17)×10⁻³. Distributions of the angle θ between the proton or antineutron and the beam direction are well described by the form 1+αcos ²θ, and we find α=0.595±0.012±0.015 for J/ψ→pp̄ and α=0.50±0.04±0.21 for J/ψ→nn̄. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the J/ψ→NN¯¯¯ decay.
First observation of the isospin violating decay J/ψ→ΛΣ̄⁰+c.c.
Using a sample of (225.2±2.8)×10⁶ J/ψ events collected with the BESIII detector, we present results of a study of J/ψ→γΛΛ¯¯¯ and report the first observation of the isospin violating decay J/ψ→ΛΣ¯¯¯⁰+c.c., in which Σ¯¯¯⁰ decays to γΛ¯¯¯. The measured branching fractions are B(J/ψ→Λ¯¯¯Σ⁰)=(1.46±0.11±0.12)×10⁻⁵ and B(J/ψ→ΛΣ¯¯¯⁰)=(1.37±0.12±0.11)×10⁻⁵. We search for Λ(1520)→γΛ decay, and find no evident signal, and an upper limit for the product branching fraction B(J/ψ→ΛΛ¯¯¯(1520)+c.c.)×B(Λ(1520)→γΛ)<4.1×10⁻⁶ is set at the 90% confidence level. We also report the observation of η c →ΛΛ¯¯¯ in J/ψ→γη c , η c →ΛΛ¯¯¯ and measure the branching fraction B(η c →ΛΛ¯¯¯)=(1.16±0.12(stat)±0.19(syst)±0.28(PDG))×10⁻³.