Engineering topics
Han, S.
Publications and source records attributed to Han, S..
Measurement of higher-order multipole amplitudes in ψ ( 3686 ) → γ χ c 1 , 2 with χ c 1 , 2 → γ J / ψ and search for the transition η c ( 2 S ) → γ J / ψ
Using 106 ×10 6 ψ (3686) events collected with the BESIII detector, we measure multipole amplitudes for the decay ψ (3686) → γχ c1,2 → γγ J/ψ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for ψ (3686) → γχ c1,2 → γγ J/ψ and the normalized electric-octupole amplitudes for ψ ( 3686 ) → γχ c2 , χ c2 → γJ/ψ are determined. The M2 amplitudes for ψ (3686) → γ χ c1 and χ c1,2 → γ J / ψ are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of ψ ( 3686 ) and J /ψ decays to χ c1,2 , b$1\atop{2}$/ b$2\atop{2}$ = 1.35 ± 0.72 and a$1\atop{2}$/a$2\atop{2}$ = 0.617 ± 0.083 , which agree well with theoretical expectations. By considering the multipole contributions of χ c 1 , 2 , we measure the product branching fractions for the cascade decays ψ ( 3686 ) → γχ c0,1,2 → γγJ/ψ and search for the process η c (2S) → γJ/ψ through ψ ( 3686 ) → γη c (2S). The product branching fraction for ψ (3686) → γχ c0 → γγJ/ψ is 3σ larger than published measurements, while those of ψ (3686) → γχ c1,2 → γγJ/ψ are consistent. In conclusion, no significant signal for the decay ψ ( 3686 ) → γη c (2S) → γγJ/ψ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.
Measurement of the absolute branching fraction for Λ c + → Λ μ + ν μ
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Precise Measurement of the e + e - → π + π - J / ψ Cross Section at Center-of-Mass Energies from 3.77 to 4.60 GeV
The statistical significance of this resonance is estimated to be larger than 7.6 σ . The mass and width of the second resonance agree with the Y(4360) resonance reported by the BABAR and Belle experiments within errors. Finally, the Y ( 4008 ) resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.
Evidence of Two Resonant Structures in e + e - → π + π - h c
The cross sections of e + e - →π + π - h c at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e + e - →π + π - J/ψ and e + e - →π + π - ψ (2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e + e - → π + π - h c cross sections around 4.22 and 4.39 GeV / c 2 , which we call Y ( 4220 ) and Y ( 4390 ) , respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4 $+5.5\atop{-4.5 ± 0.9) MeV/c 2 and a width of 66.0$+12.3\atop-8.3$±0.4 MeV for the Y (4220), and a mass of (4391.5 $+6.3\atop-16.8$ ± 1.0) MeV/c 2 and a width of (139.5$+16.2\atop-20.6 ± 0.6) MeV for the Y (4390), where the first uncertainties are statistical and the second ones systematic. The statistical significance of Y ( 4220 ) and Y(4390) is 10σ over one structure assumption.
Luminosity measurements for the R scan experiment at BESIII
By analyzing the large-angle Bhabha scattering events e + e - → (γ)e + e - and diphoton events e + e - → (γ)γγ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. Finally, the results are important inputs for the R value and J/ψ resonance parameter measurements.
Amplitude Analysis of the Decays η ' → π + π - π 0 and η ' → π 0 π 0 π 0
Based on a sample of 1.31 × 10 9 J / ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η'→ π + π - π 0 and η' → π 0 π 0 π 0 is performed. A significant P-wave contribution from η'→ ρ ± π ∓ is observed for the first time in η' → π + π - π 0 . The branching fraction is determined to be B ( η'→ ρ ± π ∓ ) = ( 7.44 ± 0.60 ± 1.26 ± 1.84 ) × 10 -4 , where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S -wave component, there is a significant σ meson component. The branching fractions of the combined S -wave components are determined to be B ( η' → π + π - π 0 ) S = ( 37.63 ± 0.77 ± 2.22 ± 4.48 ) × 10 -4 and B ( η' → π 0 π 0 π 0 ) = ( 35.22 ± 0.82 ± 2.54 ) × 10 -4 , respectively. Finally, the latter one is consistent with previous BESIII measurements.
Modeling Iridium-Based Trilayer and Bilayer Transition-Edge Sensors
Here, we report a model that can be used to calculate superconducting transition temperature of a transition-edge sensor (TES), which is either a normal metal-superconductor-normal metal trilayer or a normal metal-superconductor bilayer. The model allows the T C estimation of a trilayer when the normal metals at the bottom and at the top are different. Furthermore, the model includes the spin flip time of the normal metals. We also use the T C calculations from this model for selected Ir-based trilayers and bilayers to help understand potential designs of low T C TESs. A Au/Ir/Au trilayer can have a low T C because the superconducting order parameter is reduced with normal metals at both sides. On the other hand, an Ir/Pt bilayer can have a low T C because the much larger electron density of states of Pt reduces the superconducting order parameter more effectively. Moreover, the spin flip scattering of paramagnetic Pt also contributes to the T C reduction.
Measurements of the branching fractions for D + → K S 0 K S 0 K + , K S 0 K S 0 π + and D 0 → K S 0 K S 0 , K S 0 K S 0 K S 0
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Measurements of the absolute branching fractions for D s + → η e + ν e and D s + → η ′ e + ν e
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Measurement of Singly Cabibbo Suppressed Decays Λ c + → p π + π − and Λ c + → p K + K −
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Measurement of the absolute branching fraction of D + → $\bar{K}$ 0 e + ν e via $\bar{K}$ 0 → π 0 π 0
By analyzing 2.93 fb–1 data collected at the center-of-mass energy with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay D+ → $\bar{K}$0 e+νe to be Β(D + → $\bar{K}$ 0 e + ν e ) = (8.59 ± 0.14 ± 0.21)% using $\bar{K}$ 0 → K 0 s → π 0 π 0 , where the first uncertainty is statistical and the second systematic. Finally, our result is consistent with previous measurements within uncertainties..