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41.
We analyse the proton electromagnetic form factor ratioR(Q 2 ) =QF 2 (Q 2 )/F 1 (Q 2 ) as a function of momentum transferQ 2 within perturbative QCD. We find that the prediction for (R(Q 2 ) at large momentum transferQ depends on the exclusive quark wave functions, which are unknown. For a wide range of wave functions we find thatQF 2 F 1 ~ const. at large momentum transfer, which is in agreement with recent JLAB data. 相似文献
42.
W. Wittek M. Aderholz P. Allport N. Armenise J. P. Baton M. Berggren F. W. Bullock M. Calicchio E. F. Clayton T. Coghen A. M. Cooper-Sarkar O. Erriquez P. Fitch N. Giannakopoulos J. Guy E. Hoffmann P. O. Hulth G. T. Jones P. Kasper U. F. Katz J. Kern H. Klein P. Marage E. Matsinos D. R. O. Morrison M. Neveu M. A. Parker N. Schmitz E. Simopoulou K. Varvell A. Vayaki W. Venus H. Wachsmuth BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(2):231-251
The average multiplicities of charged hadrons and of π+, π? and π0 mesons, produced in \(\bar v\) Ne and νNe charged current interactions in the forward and backward hemispheres of theW ±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (y Lab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π0 multiplicity accurately. The ratio of average π multiplicities \(\frac{{2\left\langle {n_{\pi ^O } } \right\rangle }}{{[\left\langle {n_{\pi ^ + } } \right\rangle + \left\langle {n_{\pi ^ - } } \right\rangle ]}}\) is consistent with 1. In the backward hemisphere \(\left\langle {n_{\pi ^O } } \right\rangle \) is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between \(\mathop v\limits^{( - )} \) and \(\mathop v\limits^{( - )} \) , \(\mathop v\limits^{( - )} \) scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial \(\mathop v\limits^{( - )} \) interaction. 相似文献
43.
T. A. Armstrong M. Benayoun W. Beusch I. J. Bloodworth J. N. Carney R. Childs B. R. French B. Ghidini A. Jacholkowski J. Kahane J. B. Kinson A. Kirk K. Knudson V. Lenti Ph. Leruste A. Malamant J. L. Narjoux F. Navach A. Palano E. Quercigh N. Redaelli L. Rossi M. Sené R. Sené M. Stassinaki M. T. Trainor G. Vassiliadis O. Villalobos Baillie M. F. Votruba G. Zito R. Zitoun WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1990,46(3):405-410
The reactionpp→p f (K + K -π+π-)p s , where theK + K ? π+π- system is centrally produced, has been studied at 300 GeV/c. TheK *0 \(K^{*0} \bar K^{*0} \) final state has been observed and the cross sections for its central production are found to be the same at 300 and 85 GeV/c. TheK *0 \(K^{*0} \bar K^{*0} \) final state appears to be produced as a non-resonant threshold enhancement. 相似文献
44.
Susan J. Burrell Andrew E. Derome Michael S. Edenborough Laurence M. Harwood Sarah A. Leeming Neil S. Isaacs 《Tetrahedron letters》1985,26(18):2229-2232
Furan undergoes intramolecular Diels-Alder reaction when subjected to high (14kbar) pressures to give a mixture of and adducts in which the adduct is formed as the kinetic product, at variance with the expected course of events. 相似文献
45.
Gerald O. Schulz H. James Harwood 《Journal of polymer science. Part A, Polymer chemistry》1974,12(7):1451-1460
Pyrolysis of poly(tert-butyl N-vinylcarbamate) at 185–200°C in bulk yields a rigid foam containing cyclic urea units, primary amine units, and a small amount of urea crosslinks. The yield of primary amine units (ca. 13%) and the yields of carbon dioxide (ca. 57%), isobutylene (ca. 57%), and tert-butanol formed in this reaction indicate that it involves pairwise decomposition of adjacent carbamate units to form cyclic urea units, tert-butanol, carbon dioxide, and isobutylene. The vinyl amine units are formed from carbamate units that become flanked by urea units. The amounts of amine units and residual carbamate units were determined as a function of degree of pyrolysis by an ion-exchange technique and agreed with values expected for a random cyclization process. The pyrolyzed polymers are useful as ion-exchange resins and as rigid foams having good thermal stability. 相似文献
46.
K. Varvell A. M. Cooper-Sarkar M. A. Parker R. A. Sansum M. Aderholz N. Armenise J. P. Baton F. W. Bullock M. Berggren D. Bertrand V. Brisson W. Burkot M. Calcchio E. F. Claytoh T. Coghen O. Erriquez P. J. Fitch G. Gerbier J. Guy P. O. Hulth G. Iaselli G. T. Jones P. Kasper H. Klein C. Kochowski P. Marage M. Mermikides R. P. Middleton D. R. O. Morrison M. M. Mobayyen S. Natali M. Neveu S. Nuzzo S. W. O'Neale P. Petiau A. Petrides F. Ruggieri J. Sacton E. Simopoulou C. Vallee A. Vayaki W. A. Venus H. Wachsmuth J. Wells W. Wittek BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1987,36(1):1-13
The isoscalar nucleon structure functionsF 2(x, Q 2) andxF 3(x, Q 2) are measured in the range 0<Q 2<64 GeV2, 1.7<W 2<250 GeV2,x<0.7 using ν and \(\bar v\) interactions on neon in BEBC. The data are used to evaluate possible higher twist contributions and to determine their impact on the evaluation of the QCD parameter Λ. In contrast to previous analyses reaching to such lowW 2 values, it is found that a low \(\Lambda _{\overline {MS} } \) value in the neighbourhood of 100 MeV describes the data adequately and that the contribution of dynamical higher twist effects is small and negative. 相似文献
47.
T. A. Armstrong I. J. Bloodworth J. N. Carney B. R. French B. Ghidini J. B. Kinson V. Lenti A. Palano I. C. Print G. Vassiliadis O. Villalobos Baillie M. F. Votruba G. Zito R. Zitoun WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1987,34(1):33-38
The reactions π+ p→π+(K + K ? π+ π? p andpp→p(K + K ? π+ π?)p where the (K + K ? π+ π?) system is centrally produced have been studied at 85 GeV/c. 48% of the final state proceeds through single or double vector meson resonant production i.e.,K *0(890) (37%), ? (4%),ρ 0 (7%). Evidence is found for associatedK *0 (890) \(\bar K\) *o (890) production (6.4±1.1%) with a cross section ten times higher than that found for associated ? ? production in the same experiment. 相似文献
48.
[reaction: see text] The trimeric quinone framework of conocurvone is crucial for its potent anti-HIV activity. A new synthesis of trimeric quinones based on stepwise substitution of the halogens in 2,3-dihaloquinones by hydroxyquinone anions is described. Chlorinated biquinones are key intermediates that undergo regiospecific substitution reactions to yield trimeric quinone monomethyl ethers. 相似文献
49.
Zinc with a trace of zinc chloride in methanol, ethanol, dioxane or diethyl ether is one of the most common dehalogenating agents1–4. However, the use of such low boiling solvents causes difficulties when the dehalogenated products have boiling points similar to these solvents, when they form azeotropic mixtures with the solvents or when the products tend to polymerize in the reaction mixture and it is desirable to remove them as formed. 相似文献
50.
The WA Collaboration M.I.?Adamovich et al. 《The European Physical Journal C - Particles and Fields》2001,22(1):47-54
We report on a measurement of the differential cross sections of inclusive production in and neutron beams. A strong leading particle effect was observed for production by . The measured –distributions are compared with calculations based on the Lund model (PYTHIA) and the quark-gluon string model.
Received: 6 August 2001 / Revised version: 3 September 2001 / Published online: 5 October 2001 相似文献