Search NASA⌕ Search

Engineering topics

Han, Y. L.

Publications and source records attributed to Han, Y. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

The {sup 95}Zr( n , γ ){sup 96}Zr Cross Section from the Surrogate Ratio Method and Its Effect on s -process Nucleosynthesis

The {sup 95}Zr( n , γ ){sup 96}Zr reaction cross section is crucial in the modeling of s -process nucleosynthesis in asymptotic giant branch stars because it controls the operation of the branching point at the unstable {sup 95}Zr and the subsequent production of {sup 96}Zr. We have carried out the measurement of the {sup 94}Zr({sup 18}O, {sup 16}O) and {sup 90}Zr({sup 18}O, {sup 16}O) reactions and obtained the γ -decay probability ratio of {sup 96}Zr* and {sup 92}Zr* to determine the {sup 95}Zr( n , γ ){sup 96}Zr reaction cross sections with the surrogate ratio method. Our deduced Maxwellian-averaged cross section of 66 ± 16 mb at 30 keV is close to the value recommended by Bao et al., but 30% and more than a factor of two larger than the values proposed by Toukan and Käppeler and Lugaro et al., respectively, and routinely used in s -process models. We tested the new rate in stellar models with masses between 2 and 6 M {sub ⊙} and metallicities of 0.014 and 0.03. The largest changes—up to 80% variations in {sup 96}Zr—are seen in models of mass 3–4 M {sub ⊙}, where the {sup 22}Ne neutron source is mildly activated. The new rate can still provide a match to data from meteoritic stardust silicon carbide grains, provided that the maximum mass of the parent stars is below 4 M {sub ⊙}, for a metallicity of 0.03.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Determination of the number of ψ(3686) events at BESIII

The numbers of ψ(3686) events accumulated by the BESIII detector for the data taken during 2009 and 2012 are determined to be $(107.0\pm 0.8)\times {10}^{6}$ and $(341.1\pm 2.1)\times {10}^{6}$, respectively, by counting inclusive hadronic events, where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is $(448.1\pm 2.9)\times {10}^{6}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of e + e – → γ χ c J via initial state radiation at Belle

The process e + e – → γχ cJ (J = 1, 2) is studied via initial state radiation using 980 fb –1 of data at and around the Υ(nS) (n = 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e + e – collider. Here, no significant signal is observed except from ψ(2S) decays. Upper limits on the cross sections between √s = 3.80 and 5.56 GeV are determined at the 90% credibility level, which range from a few pb to a few tens of pb. We also set upper limits on the decay rate of the vector charmonium [ψ(4040), ψ(4160), and ψ(4415)] and charmoniumlike [Y(4260), Y(4360), and Y(4660)] states to γχ cJ .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗