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  • 1
    Electronic Resource
    Electronic Resource
    Correlations between D and $${\overline D}$$ mesons produced in 500 GeV/cπ−-nucleon interactions (2000)
    Springer
    EPJ direct 1 (2000), S. 1-67 
    Details
    ISSN: 1435-3725
    Keywords: 12.38.-t ; 13.85.-t ; 13.87.Ce ; 13.87.Fh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a study of correlations between D and $${\overline D}$$ mesons produced in 500 GeV/cπ−-nucleon interactions, based on data from experiment E791 at Fermilab. We have fully reconstructed 791 ± 44 charm meson pairs to study correlations between the transverse and longitudinal momenta of the two D mesons and the relative production rates for different types of D meson pairs. We see slight correlations between the longitudinal momenta of the D and the $${\bar D}$$ , and significant correlations between the azimuthal angle of the D and the $${\bar D}$$ . The experimental distributions are compared to a next-to-leading-order QCD calculation and to predictions of the PYTHIA/JETSET Monte Carlo event generator. We observe less correlation between transverse momenta and different correlations between longitudinal momenta than these models predict for the default values of the model parameters. Better agreement between data and theory might be achieved by tuning the model parameters or by adding higher order perturbative terms, thus contributing to a better understanding of charm production. The relative production rates for the four sets of charm pairs, $$D^0{{\overline D}^0}, D^0 D^{-}, D^+{{\overline D}^0}, D^+ D^{-}$$ as calculated in the PYTHIA/JETSET event generator with the default parameters, agree with data as far as the relative ordering, but predict too many $$D^+ {{\overline D}^0}$$ pairs and too few $$D^+ D^{-}$$ pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101059900c0004
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Correlations between D and $${\overline D}$$ mesons produced in 500 GeV/cπ−-nucleon interactions (1999)
    Springer
    EPJ direct 1 (1999), S. 1-67 
    Details
    ISSN: 1435-3725
    Keywords: 12.38.-t ; 13.85.-t ; 13.87.Ce ; 13.87.Fh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a study of correlations between D and $${\overline D}$$ mesons produced in 500 GeV/cπ−-nucleon interactions, based on data from experiment E791 at Fermilab. We have fully reconstructed 791 ± 44 charm meson pairs to study correlations between the transverse and longitudinal momenta of the two D mesons and the relative production rates for different types of D meson pairs. We see slight correlations between the longitudinal momenta of the D and the $${\bar D}$$ , and significant correlations between the azimuthal angle of the D and the $${\bar D}$$ . The experimental distributions are compared to a next-to-leading-order QCD calculation and to predictions of the PYTHIA/JETSET Monte Carlo event generator. We observe less correlation between transverse momenta and different correlations between longitudinal momenta than these models predict for the default values of the model parameters. Better agreement between data and theory might be achieved by tuning the model parameters or by adding higher order perturbative terms, thus contributing to a better understanding of charm production. The relative production rates for the four sets of charm pairs, $$D^0{{\overline D}^0}, D^0 D^{-}, D^+{{\overline D}^0}, D^+ D^{-}$$ as calculated in the PYTHIA/JETSET event generator with the default parameters, agree with data as far as the relative ordering, but predict too many $$D^+ {{\overline D}^0}$$ pairs and too few $$D^+ D^{-}$$ pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101059900c0004
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on diphenylguanidine-accelerated sulfur vulcanization of styrene butadiene rubber in the presence and absence of dicumylperoxide (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2971-2983 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diphenylguanidine (DPG) raises the rate of decomposition of dicumylperoxide (DCP) and the crosslinking maxima due to DCP is lowered to some extent by DPG. When the molar proportion of DPG-S is approximately 1:1, no additive results of crosslink formation (as reported for NR) are observed. Zinc oxide and stearic acid increase the rate of crosslinking as well as the crosslinking maxima. In the present study it appears most probable that DPG-accelerated sulfuration of SBR is an ionic process. At a constant level of DCP and sulfur crosslink density increases when the amount of DPG is increased; a constant level of DCP and DPG crosslinking increases with rising sulfur concentration.An increase in the concentration of DPG or sulfur leads to greater formation of the complex as well as a change in its composition. The effect of DPG is more pronounced, for by reducing the number of sulfur atoms more sulfur is available for crosslinking. Sulfur absorbs little SO2 or H2S; if it is already saturated, there is no perceptible effect. DPG does absorb H2S or SO2 and the rate and maxima of crosslinks is increased. The effect of SO2 is higher because of the higher Ka values of H2SO3 and consequently higher concentration of HSO3-. Reversion is a free-radical process inhibited by free DPG present in the system. In the presence of zinc oxide and stearic acid the reaction follows a polar mechanism as well as a radical mechanism.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.170161122
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Studies of vulcanization with tetramethylthiuram disulfide and sulfur vulcanization accelerated by tetramethylthiuram disulfide of styrene-butadiene rubber in presence and absence of dicumyl peroxide (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2255-2268 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The salient features of nonelemental sulfur vulcanization by tetramethylthiuram disulfide (TMTD) and elemental sulfur vulcanization promoted by TMTD both in presence and absence of ZnO and stearic acid have been studied. In stock containing TMTD, a higher rate constant value for dicumyl peroxide (DCP) decomposition was observed. TMTD decreases the crosslinking density due to DCP depending on its concentration. An entirely radical mechanism has been advanced in the absence of ZnO. ZnO or ZnO-stearic acid seems to alter the entire course of reaction. The rate of crosslinking increases in the presence of ZnO or ZnO-stearic acid. Moreover, crosslinks are formed additively (further supported from the activation energy data), and mixed crosslink formation has been confirmed by the methyl iodide test of the vulcanizates. Stearic acid has no effect on crosslink formation. An ionic chain mechanism has been postulated in the presence of ZnO, as suggested by British authors.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150916
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Studies of accelerated sulfur vulcanization of styrene-butadiene rubber by N-cyclohexylbenzothiazol-2-sulfenamide in the presence and absence of dicumyl peroxide (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2773-2784 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study embodies the results and discussion of a comprehensive and systematic investigation of the mechanism of sulfuration of styrene-butadiene rubber accelerated by N-cyclohexylbenzothiazole-2-sulfenamide (CBS) with and without activators. Dicumyl peroxide (DCP) has been taken as a chemical aid to distinguish between free-radical and polar mechanisms of sulfuration. The rate constant for DCP decomposition in presence of CBS and the reduction in crosslink density by CBS have also been studied. With a constant amount of DCP and sulfur the crosslink density increases with increasing CBS concentration. In the presence of ZnO and stearic acid, crosslinking proceeds faster than in a similar system without these ingredients, and with DCP the crosslinks are found to be formed nearly additively as confirmed by methyl iodide treatment of the vulcanizates. In the absence of DCP, the crosslinking is characterized by an induction period, even in presence of ZnO and stearic acid. In the presence of sulfur, the 2-mercaptobenzothiazole (MSH) or amine or amine salt form crosslinkins by ionic reaction.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170151121
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    Paper (German National Licenses)
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