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991.
A.L.S. Angelis H.-J. Besch B.J. Blumenfeld L. Camilleri T.J. Chapin R.L. Cool C. del Papa L. Di Lella Z. Dimčovski R.J. Hollebeek L.M. Lederman D.A. Levinthal J.T. Linnemann C.B. Newman N. Phinney B.G. Pope S.H. Pordes K.K. Young 《Nuclear Physics B》1982,209(2):284-300
We present data on proton-proton collisions, obtained at the CERN Intersecting Storage Rings, in which two roughly back-to-back π0's of high transverse momentum (pT) were produced. The angular distribution of the dipion axis relative to the collision axis is found to be independent of both the effective mass m of the dipion system and the centre-of-mass energy √s of the proton-proton collision. The cross-sections at the values of √s satisfy a scaling law of the form . We show from our data that the leading π0 carries most of the momentum of the scattered parton. Given this fact, the axis of the dipion system follows closely the direction of the scattered constituents, and we exploit this to determine the angular dependence of the hard-scattering subprocess. We also compare our data with the lowest order QCD predictions using structure functions as determined in deep-inelastic scattering and fragmentation functions from electron-positron annihilation. 相似文献
992.
Bruce D Jacobs Soon-Jae Kwon Leslie D Field Robert K Norris David Randles Karen Wilson Timothy A Wright 《Tetrahedron letters》1985,26(29):3495-3498
The SRN1 reaction between sterically hindered p-nitrobenzylic substrates and tertiary carbanions gives C-alkylated products whose yields depend on the steric bulk of both the benzylic substrate and the carbanion, and on the nature of the groups in the carbanion. 相似文献
993.
The surface and subsurface speciation of carbon-supported vapor-deposited films, prepared by resistively heating manganese chips in the sample chamber of an HP 5950A ESCA spectrometer, have been studied using XPS and argon ion etching. It is shown that the oxide formed in poor vacuum is MnO. Under improved experimental conditions, a mixture of Mn metal and MnO is obtained, but the metal is very reactive to oxygen. For very thick films formed in poor vacuum, the oxide covers a layer of manganese metal. The oxide is no longer evident after 60 h of etching. For the layer of manganese remaining, we have found that the Mn3s multiplet splitting is smaller than that reported in the literature. The present result is shown to be consistent with magnetic susceptibility measurements on α-Mn. For discontinuous MnO films, argon ion etching causes the Mn2p binding energy to shift to higher energy. This is inconsistent with reduction to Mn metal, as the binding energy would shift to a lower value for this case. 相似文献
994.
Necessary and sufficient conditions are found for a multiplier operator to be bounded on L2 of the line with weight |x|2α. This paper is concerned primarily with the case . Multiplier operators are defined on these spaces by using the usual definition on a subspace that is shown to be dense in the space. The case is treated by duality; is briefly treated using a recent result on fractional integrals. The periodic case is also sketched. 相似文献
995.
The uncertainty in the subtraction of electromagnetic effects from S-wave proton-proton scattering potentials is studied in two models using unitarily transformed potentials. Restrictions on these models caused by theoretical, off-shell and deuteron constraints are imposed. The probable uncertainty of physical interest is found to be small. It is typically only a few parts per thousand of the one-pion exchange potential. It has relatively little effect on Coulomb displacement energies. Phenomenological charge-symmetry-breaking potentials are constructed which both fit the experimental neutron-neutron (nn) scattering length (?16.4 fm). and give roughly the needed Coulomb displacement energies. These phenomenological potentials are found to contain a short-range repulsion and a strong long-range attraction for a neutron pair. The need for experimental information on the shape and state dependence of the nn force is emphasized. These can probably be obtained from precise nn scattering measurements. 相似文献
996.
The oscillatory phenomenon was observed in aqueous solution during the oxidation of ascorbic acid by oxygen. Even though the exact number and amplitude of the oscillations could not be exactly duplicated for each and every run, such factors as temperature, concentration of ascorbic acid, cupric ions, and pH affecting the oscillatory behavior were studied, and those regions where oscillations occurred were delineated. A mechanism consistent with the oscillatory behavior is proposed and discussed. 相似文献
997.
Paul S. Braterman Ronald J. Cross Ljubica Manojlović-Muir Kenneth W. Muir G.Brent Young 《Journal of organometallic chemistry》1975,84(3):C40-C42
The X-ray crystal structure analysis of cis-[PtPh2(Ph2PCH2PPh2)] suggests that the unusually low PtP coupling constant is a consequence of distortion of the valency angles at the platinum and phosphorus atoms; the restrictive geometry of the chelate ring does not effect the lengths of the metal—ligand bonds. 相似文献
998.
The problem of file organization which we consider involves altering the placement of records on pages of a secondary storage device. In addition, we want this reorganization to be done in-place, i.e., using the file's original storage space for the newly reorganized file. The motivation for such a physical change is to improve the database system's performance. For example, by placing frequently and jointly accessed records on the same page or pages, we can try to minimize the number of page accesses made in answering a set of queeries. The optimal assignment (or reassignment) of records to clusters is exactly what record clustering algorithms attempt to do. However, record clustering algorithms usually do not solve the entire problem, i.e., they do not specify how to efficiently reorganize the file to reflect the clustering assignment which they determine. Our algorithm is a companion to general record clustering algorithms since it actually transforms the file. The problem of optimal file reorganization isNP-hard. Consequently, our reorganization algorithm is based on heuristics. The algorithm's time and space requirements are reasonable and its solution is near optimal. In addition, the reorganization problem which we consider in this paper is similar to the problem of join processing when indexes are used.The research of this author was partially supported by the National Science Foundation under grant IST-8696157. 相似文献
999.
If A is an m×m and ? is an analytic function, then ?(A) depends only on the values of ? and its first m?1 derivatives on the spectrum of A. In this paper we estimate 6?(A)6, for certain matrix norms 6·6, in terms of the maximum moduli of these derivatives on the convex hull of the spectrum of A. 相似文献
1000.
R. Albrecht T. C. Awes C. Baktash P. Beckmann G. Claesson F. Berger R. Bock L. Dragon R. L. Ferguson A. Franz S. Garpman R. Glasow H. ?. Gustafsson H. H. Gutbrod K. H. Kampert B. W. Kolb P. Kristiansson I. Y. Lee H. L?hner I. Lund F. E. Obenshain A. Oskarsson I. Otterlund T. Peitzmann S. Persson F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter R. Santo H. R. Schmidt T. Siemiarczuk S. P. Sorensen E. Stenlund G. R. Young WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,38(1):109-115
Target remnants withZ<3 from proton-nucleus and16O-nucleus reactions at 60 and 200 GeV/nucleon were measured in the angular range from 30° to 160° (?1.7<η<1.3) employing the Plastic Ball detector. The excitation energy of the target spectator matter in central oxygen-induced collisions is found to be high enough to allow for complete disintegration of the target nucleus into fragments withZ<3. The average longitudinal momentum transfer per proton to the target in central collisions is considerably higher in the case of16O-induced reactions (≈300 MeV/c) than in proton-induced reactions (≈130 MeV/c). The baryon rapidity distributions are roughly in agreement with one-fluid hydrodynamical calculations at 60 GeV/nucleon16O+Au but are in disagreement at 200 GeV/nucleon, indicating the higher degree of transparency at the higher bombarding energy. Both, the transverse momenta of target spectators and the entropy produced in the target fragmentation region are compared to those attained in head-on collisions of two heavy nuclei at Bevalac energies. They are found to be comparable or do even exceed the values for the participant matter at beam energies of about 1–2 GeV/nucleon. 相似文献