Search for Down-Type Fourth Generation Quarks with the ATLAS Detector in Events with One Lepton and Hadronically Decaying W Bosons

This Letter presents a search for pair production of heavy down-type quarks decaying via b^{'}→Wt in the lepton+jets channel, as b^{'}b[over ˉ]^{'}→W^{-}tW^{+}t[over ˉ]→bb[over ˉ]W^{+}W^{-}W^{+}W^{-}→l^{±}νbb[over ˉ]qq[over ˉ]qq[over ˉ]qq[over ˉ]. In addition to requiring exactly one lepton, large missing transverse momentum, and at least six jets, the invariant mass of nearby jet pairs is used to identify high transverse momentum W bosons. In data corresponding to an integrated luminosity of 1.04 fb^{-1} from pp collisions at sqrt[s]=7 TeV recorded with the ATLAS detector, a heavy down-type quark with mass less than 480?GeV can be excluded at the 95% confidence level.     

5‐aminothiazolium salts as potential cyclic azomethine ylides: Base‐induced cycloaddition reactions with aryl,alkyl, and benzoyl isothiocyanates

Reactions of the in situ generated thiazoles 2 with aryl and alkyl isothiocyanates appear to be totally regioselective and give the unexpected 5‐(phenylthio)imidazolium‐4‐thiolates 3 . Such rapid interconversion of mesoionic compounds is explained by a 1,3‐dipolar addition to the C=N bond of the heterocumulene followed by tBuNCS elimination. Similar interactions with benzoyl isothiocyanate exclusively proceed on the C=S unsaturation of the heteroallene moiety and produce the 4‐(phenylthio)thiazolium‐5‐amidines 12 . Structural assignment of isolated imidazoles and thiazoles is based on ¹³C NMR data and chemically confirmed by the NaBH₄ reduction of the alkylated derivatives 5 and 13 . Efforts to isomerize the starting mesoionic thiazole 2a without the use of tBuNCS are unsuccessful. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 10:16–26, 2000