排序方式: 共有51条查询结果,搜索用时 15 毫秒
1.
A large fraction of 4-jet events inZ 0 decays evolve fromq \(\bar q\) gg parton states. These configurations allow us to test the triple gluon coupling which is a consequence of the non-Abelian nature of QCD. The strength and the form of this coupling determine the quark-gluon decomposition of the final state as well as angular correlations between the jets. A critical assessment of the sensitivity of these observables to theggg vertex is presented under realistic experimental conditions. Methods to improve the sensitivity in large samples ofZ 0 decays are suggested. 相似文献
2.
John Bethke Jürgen Kopf Paul Margaretha Bernard Pignon Léon Dupont Léon E. Christiaens 《Helvetica chimica acta》1997,80(6):1865-1868
Irradiation (λ = 350 nm) of 1H-[2]benzothiopyran-1-one ( 2 ) in the solid state affords selectively and in good yield 6aα, 6bα, 12bα, 12cα -tetrahydrocyclobuta[1, 2-c:4, 3-c′]bis([2]benzothiopyran)-5, 8-dione ( 3 ), the head-to-head (HH) cis-cisoid-cis-cyclodimer of 2 , X-Ray analysis of 2 confirms that this reaction proceeds according to the well-established topochemical principles. The same dimer 3 is obtained in low yields on irradiation of 10−1 M solutions of 2 in either MeOH or MeCN, while no conversion at all is observed in benzene. On irradiation of 2 in MeCN in the presence of tetrachloroethene, the [2 + 2] photocycloadduct 4 is formed in good yield, the conversion 2 → 4 being efficiently quenched by naphthalene. In contrast, no reaction is observed -on irradiation of 2 in the presence of 2, 3-dimethylbut-2-ene, neither in polar nor in apolar solvents. 相似文献
3.
Soderstrom E McKenna JA Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R 《Physical review letters》1990,64(25):2980-2983
4.
Komamiya S Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gatto C Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R 《Physical review letters》1990,64(24):2881-2884
5.
6.
7.
8.
9.
Upon irradiation at wavelengths above 390 nm in the presence of 2,3‐dimethylbut‐2‐ene, both the newly synthesized pyranoquinolinedione 8 and thiinobenzopyrandione 9 selectively afford one of two possible photocycloadducts, 23 and 24 , respectively. 相似文献
10.
Siegfried Bethke 《The European Physical Journal C - Particles and Fields》2009,64(4):689-703
Measurements of α
s, the coupling strength of the Strong Interaction between quarks and gluons, are summarised and an updated value of the world
average of as(MZ0)\alpha_{\mathrm{s}}(M_{\mathrm{Z}^{0}}) is derived. Special emphasis is laid on the most recent determinations of α
s. These are obtained from τ-decays, from global fits of electroweak precision data and from measurements of the proton structure function F2, which are based on perturbative QCD calculations up to O(as4)\mathcal{O}(\alpha_{\mathrm{s}}^{4}); from hadronic event shapes and jet production in e+e− annihilation, based on O(as3)\mathcal{O}(\alpha_{\mathrm{s}}^{3}) QCD; from jet production in deep inelastic scattering and from ϒ decays, based on O(as2)\mathcal{O}(\alpha_{\mathrm{s}}^{2}) QCD; and from heavy quarkonia based on unquenched QCD lattice calculations. A pragmatic method is chosen to obtain the world
average and an estimate of its overall uncertainty, resulting in
as(MZ0)=0.1184±0.0007.\alpha_\mathrm{s}(M_{\mathrm{Z}^0})=0.1184\pm 0.0007. 相似文献 |