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P.J. Bussey C. Raine J.G. Rutherglen P.S.L. Booth L.J. Carroll P.R. Daniel C.J. Hardwick J.R. Holt J.N. Jackson J.H. Norem W.H. Range F.H. Combley W. Galbraith V.H. Rajaratnam C. Sutton M.C. Thorne P. Waller 《Nuclear Physics B》1976,104(2):253-276
An experiment has been completed at the Daresbury synchrotron to measure the asymmetry in the photoproduction cross section of neutral pions on hydrogen, for photons polarised normal to and in the production plane. The source of polarised photons was coherent bremsstrahlung of electrons traversing the lattice structure of diamond and the polarisation P of the γ beam was calculated from the measured intensity of the coherent spike. The asymmetry parameter Σ, defined as Σ = (σ⊥ ? σ|)/(σ⊥ + σ|) where σ⊥(σ|) are the cross sections for photons polarised perpendicular (parallel) to the production plane, has been measured over a range of photon energies from 1.2 to 2.8 GeV and over a range of ?t (the square of the four-momentum transfer) from 0.13 (GeV/c)2 to 1.4 (GeV/c)2. A marked energy variation in the value of Σ is found over the energy region 1.6–1.8 GeV. 相似文献
73.
P.J. Bussey C. Raine J.G. Rutherglen P.S.L. Booth L.J. Carroll P.R. Daniel A.W. Edwards C.J. Hardwick J.R. Holt J.N. Jackson J. Norem W.H. Range W. Galbraith V.H. Rajaratnam C. Sutton M.C. Thorne P. Waller 《Physics letters. [Part B]》1976,61(5):479-482
Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t-values between ?0.2 (GeV/c)2 and ?1.2 (GeV/c)2. The values of Σ are close to +1 for values of |t| less than 0.7 (GeV/c)2, showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments. 相似文献
74.
G. H. Grosch B. Freytag K.-J. Range U. Rssler 《International journal of quantum chemistry》1994,52(4):919-926
Within the framework of density functional theory (DFT ), we calculate the ground-state electronic properties of CdxSn1–x Te using norm-conserving pseudopotentials in connection with the local density (LDA ) and virtual crystal approximation (VCA ). Our particular interest is in the influence of the Cd-4d and the Sn-4d electrons by comparing results obtained with pseudopotentials, which either consider the d-electrons explicitly or in the frozen core. In the mixed crystal system CdxSn1–x Te, the transition from a ten- (x = 0) to an eight-electron (x = 1) system is realized, which is accompanied by a change of the crystal structure from rock salt (SnTe) to zinc blende (CdTe). By calculating the ground-state energies, we find the equilibrium lattice constant as the function of x and the bulk modulus, as well as the crossover value of x for the transition from rock-salt to zinc blende. The calculated lattice constants and bulk moduli are in much closer agreement with experimental data if the d-electrons are taken into account explicitly, whereas the crossover is rather insensitive with respect to the d-electrons. In view of the electronic charge density, we demonstrate the decrease of ionicity for increasing x. © 1994 John Wiley & Sons, Inc. 相似文献
75.
M. Bonesini E. Bonvin P. S. L. Boóth D. Bortoletto L. J. Carroll A. J. Cass D. Cavalli G. Costa M. Donnat P. A. Dorsaz D. N. Edwards J. R. Fischer L. Fluri D. Frame F. Gianotti S. Jack J. N. Jackson M. Kelly M. N. Kienzle-Focacci R. Lucock J. G. Lynch L. Mandelli M. Martin L. Mathys A. Maxwell M. Mazzanti J. J. Myerscough P. J. Negus S. Pensotti-Rancoita L. Perini D. Perrin G. Polesello W. H. Range L. Rosselet S. W. Snow M. Tamborini A. S. Thompson R. M. Turnbull J. Wells M. Werlen WA -Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,37(4):535-544
The inclusive cross sections for prompt photon production by π? and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx F ranges covered are 4.0<p T <7.0GeV/c and ?0.45<x F <0.55 respectively. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed. 相似文献
76.
A.D.J. Banks P.S.L. Booth P.T. Campbell L.J. Carroll R.A. Donald D.N. Edwards S. Geer M.A. Houlden J.N. Jackson J. Lewis J. Pinfold W.H. Range J.A. Richardson T. Armstrong B. Baccari B.R. French G. Rudolph 《Physics letters. [Part B]》1981,100(2):191-194
A search has been made for narrow structures in p, pπ? and Λ0 systems. No significant structures are seen. The upper limit at the 99.5% confidence level for production of narrow states in the p system in the mass range 2.0–2.2 GeV is 40 nb. 相似文献
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