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51.
OPAL Collaboration G. Alexander J. Allison N. Altekamp K. Ametewee K. J. Anderson S. Anderson S. Arcelli S. Asai D. Axen et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):543-560
Symmetric three-jet events are selected from hadronic Z0 decays such that the two lower energy jets are each produced at an angle of about 150° with respect to the highest energy
jet. In some cases, a displaced secondary vertex is reconstructed in one of the two lower energy jets, which permits the other
lower energy jet to be identified as a gluon jet through anti-tagging. In other cases, the highest energy jet is tagged as
a b jet or as a light quark (uds) jet using secondary vertex or track impact parameter and momentum information. Comparing
the two lower energy jets of the events with a tag in the highest energy jet to the anti-tagged gluon jets yields a direct
comparison of b, uds and gluon jets, which are produced with the same energy of about 24 GeV and under the same conditions.
We observe b jets and gluon jets to have similar properties as measured by the angular distribution of particle energy around
the jet directions and by the fragmentation functions. In contrast, gluon jets are found to be significantly broader and to
have a markedly softer fragmentation function than uds jets. For thek
⊥ jet finder withy
cut=0.02, we find
as the ratios of the mean charged particle multiplicity in the gluon jets compared to the b and uds jets. Results are also
reported using the cone jet finder. 相似文献
52.
The charge transfer compound TDAE-C60 (TDAE — tetrakis-dimethylamino-ethylene) is so far the only known C60 based molecular ferromagnet. The ESR spectra of TDAE-C60 single crystals demonstrate that freshly grown regularly shaped single crystals show at first an AFM (antiferromagnetic)-like behavior which changes upon annealing at room temperature in vacuum to a FM (ferromagnetic) one. It thus seems that annealing induces a change in the relative orientation of the distorted C 60 ? ions resulting in a change in the sign of the effective magnetic interactions between neighboring C 60 ? ions. A structural transition in the TDAE methyl protons at 250 K seems to be connected with this process. Here we review the structure, the ESR spectra, the proton NMR spectra and the13C NMR spectra of TDAE-C60. 相似文献
53.
ALEPH Collaboration D. Buskulic I. De Bonis D. Decamp P. Ghez C. Goy J. P. Lees A. Lucotte M. N. Minard P. Odier et al. 《Zeitschrift fur Physik C Particles and Fields》1996,71(3):357-378
The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and
backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the
period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing
the original quark and antiquark is measured for
and
events in subsamples selected by their long lifetimes or using fastD*’s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation
between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is
shown that differences between light quark charge separations and the measured average can be determined using hadronisation
models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons andΛ’s. The separations are used to measure the electroweak mixing angle precisely as sin2
ϑ
w
eff
=0.2322±0.0008(exp.stat.) ±0.0007(exp.syst.)±0.0008(sep.). The first two errors are due to purely experimental sources whereas
the third stems from uncertainties in the quark charge separations.
Supported by Dirección General de Investigación Científica y Técnica, Spain 相似文献
54.
ALEPH Collaboration D. Buskulic I. De Bonis D. Decamp P. Ghez C. Goy J. P. Lees A. Lucotte M. N. Minard P. Odier et al. 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):31-44
The lifetimes of theB
0 andB
+ mesons have been measured with theAleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991–1994. In the first of three
methods, semileptonic decays ofB
0 andB
+ mesons were partially reconstructed by identifying events containing a lepton with an associatedD*− or meson. The second method used fully reconstructedB
0 andB
+ mesons. The third method, used to measure theB
0 lifetime, employed a partial reconstruction technique to identifyB
0→D*−
π
+
X decays. 相似文献
55.
White DB Tippens WB Abegg R Baldisseri A Boudard A Briscoe W Fabbro B Garçon M Hermes EA Jacobs WW Kessler RS Lytkin L Mayer B Nefkens BM Niebuhr C Petrov AM Poitou J Saudinos J Tomasi-Gustafsson E van der Schaaf A van Oers WT Vigdor SE Wang M 《Physical review D: Particles and fields》1996,53(11):6658-6661
56.
Workman JA Garrido NP Sançon J Roberts E Wessel HP Sweeney JB 《Journal of the American Chemical Society》2005,127(4):1066-1067
The first examples of highly enantioselective [2,3]-sigmatropic rearrangements of acyclic allylic ammonium ylids are reported. Thus, a range of N-{2'-[(N'-allyl-N',N'-dialkyl)ammonium]}acetyl camphor sultams undergo rearrangement at 0 degrees C in DME solution with high diastereofacial control (up to 99:1 dr) to give allylglycines in generally high yield. The power of the method has been demonstrated in a rapid and efficient synthesis of (R)-allyl glycine. 相似文献
57.
DENG Shui-Quan HUANG Xiao-Yin ZHUANG Hong-HuiHUANG Jin-LingState Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian ChinaLIN Zhen-GuangDepartment of Chemistry Fujian Teachers'''' University Fuzhou Fujian China 《中国化学》1994,12(3):270-276
An open chain compound was obtained by reaction of benzil with thiocarbohy-drazide in acidic condition. Its derivative, namely, benzil bis-(5-isopropylidene-3-thiocarbohydrazone) has been structurally characterized by X-ray single crystal diffraction method. Crystallographic data: C22H26N8S2, Mr=466.62, monoclinic, space group C2/c, a=12.215(3), b=11.473(2), c=17.032 (3)A, B=98.96(2)0, V=2357.7(9)A3, Z=4, Dc=1.32 g/cm3, F(000)=1040, u(Mo Ka)=2.43 cm-1. Final R=0.050, Rw=0.061 for 1103 unique and observed reflections with I> 3o(I). The effect of the structures on the formation of the open-chain intermediates during the cyclization of (2:2) Schiff base macrocyclic compound has been discussed and a possible mechanism for the ring closure has been suggested. 相似文献
58.
59.
Pandya SU Garçon C Chavant PY Py S Vallée Y 《Chemical communications (Cambridge, England)》2001,(18):1806-1807
The vinylzinc reagents derived from hydrozirconation of alkynes and transmetallation add readily to nitrones to yield pure (E)-N-allylhydroxylamines; some of these rearrange into O-allylhydroxylamines. 相似文献
60.
Résumé L'analyse de coupes lourdes (huile de distillation sous vide et huile issue du séparateur à chaud) provenant de l'hydroliquéfaction
catalytique du charbon a été réalisée par mise en ouvre de différentes techniques chromatographiques. L'identification des
principales structures résulte de l'application de la chromatographie par couplage de transfert de charge en mode HPLC et
des spectroscopies UV et de masse.
Donotor-acceptor complex chromatography —Application to analysis of coal liquefaction products by HPLC
Summary A Vacuum gas oil and the corresponding residue of a coal liquefaction product were investigated by means of HPLC and MS. Nearly a complete identification was performed by chromatographic, UV-spectroscopic methods and MS.
相似文献