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Discovery mass reach for topgluons decaying to t{bar t} at the Tevatron

Description: In topcolor assisted technicolor, topgluons are massive gluons which couple mainly to top and bottom quarks. We estimate the mass reach for topgluons decaying to {ital t{anti t}} at the Tevatron as a function of integrated luminosity. The mass reach for topgluons decreases with increasing topgluon width, and is 1.0 - 1.1 TeV for Run H (2 fb{sup - 1}) and 1.3 - 1.4 TeV for TeV33 (30 fb{sup -1}).
Date: September 1, 1996
Creator: Harris, R.M.
Partner: UNT Libraries Government Documents Department

Instant two-body equation in Breit frame

Description: A quasipotential formalism for elastic scattering from relativistic bound states is based on applying an instant constraint to both initial and final states in the Breit frame. This formalism is advantageous for the analysis of electromagnetic interactions because current conservation and four momentum conservation are realized within a three-dimensional formalism. Wave functions are required in a frame where the total momentum is nonzero, which means that the usual partial wave analysis is inapplicable. In this work, the three-dimensional equation is solved numerically, taking into account the relevant symmetries. A dynamical boost of the interaction also is needed for the instant formalism, which in general requires that the boosted interaction be defined as the solution of a four-dimensional equation. For the case of a scalar separable interaction, this equation is solved and the Lorentz invariance of the three-dimensional formulation using the boosted interaction is verified. For more realistic interactions, a simple approximation is used to characterize the boost of the interaction.
Date: January 1, 1995
Creator: Devine, N. K. & Wallace, S. J.
Partner: UNT Libraries Government Documents Department

Extension of the Application of the generalized pole representation to the treatment of resonance cross sections.

Description: One reliable and convenient way of processing the cross sections in the resolved energy region is by use of the generalized pole representation, whereby the Doppler-broadening calculation can be carried out rigorously using the analytical approach. So far, its applications have been limited to cases with resonance parameters specified by the Reich-Moore formalism. Although such an approach, in principle, can be extended to all three remaining representations of resolved resonance parameters specified by the ENDF data format, there is no computational tool for handling such a task at present. Given that Breit-Wigner formalisms are probably the most widely used by any evaluated nuclear data library to represent cross sections, a special effort has to be made to convert the single level and multilevel Breit-Wigner resonance parameters to pole parameters. A FORTRAN computer code BW2PR has been developed for this purpose. Extensive calculations have been performed to demonstrate that the proposed method ensures the conservation of the information contained originally in Breit-Wigner resonance parameters. This will make it possible to apply the exact Doppler-broadening method to a larger collection of nuclides.
Date: March 12, 1999
Creator: Hwang, R. N. & Jammes, C.
Partner: UNT Libraries Government Documents Department

Production of {phi} mesons in Au-Au collisions at the AGS.

Description: The first measurements of {phi} meson production in Au-Au collisions at AGS energies are presented via the decay to K{sup +} K{sup {minus}}. A measurement of the centrality dependence of the yield shows an increase similar to that seen for the K{sup {minus}} with a spectral shape consistent with a relativistic Breit-Wigner distribution within the statistical errors of the present data set. Future analysis using the full data set with 4 times the statistics will allow a more accurate determination of the yields, slopes and spectral shapes.
Date: August 10, 1999
Creator: Back, B. B.; Betts, R. R.; Chang, J.; Collaboration, E917; Gillitzer, A.; Henning, W. F. et al.
Partner: UNT Libraries Government Documents Department

Status of the O{alpha} calculation of e{sup +}e{sup -} {yields} W{sup +}W{sup -} {yields} 4f(gamma)

Description: We consider the full process e{sup +}e{sup {minus}} {yields} W{sup +}W{sup {minus}} {yields} 4f. We show that the off-shell effect are sizable and comparable to radiative effects. We give the exact results for hard bremsstrahlung processes e{sup +}e{sup {minus}} {yields} (4f + {gamma}) and the results of the O({alpha}) improved cross sections for e{sup +}e{sup {minus}} {yields} W{sup +}W{sup {minus}} including photon radiation. The status of the virtual corrections to the 4f-process is described.
Date: November 1, 1991
Creator: Aeppli, A.
Partner: UNT Libraries Government Documents Department

ACTIVATION CROSS SECTION OF Na$sup 23$ AROUND 3 KEV

Description: The activation cross section of sodium in the range from thermal energy through the 3-kev resonance is generally assumed to be given by the one-level BreitWigner formula, the GAMMA /sub gamma / being selected to describe correctly the known thermal absorption cross section. The contribution of this resonance to the resonance activation integral then turns out to be 0.12 barns. This somewhat indirectly inferred value is considerably larger than the value given by Dancoff et al., in an old paper, the latter value being based on experimental work. It is shown in the present memo, that Dancoff's actual measurements are quite consistent with the Breit-Wigner formula and the above mentioned GAMMA /sub gamma /. The discrepancy is a result of Dancoff's transition from the actual measurements to the resonance integral, this transition being based on data that is now obsolete. (auth)
Date: February 1, 1957
Creator: Ergen, W.K.
Partner: UNT Libraries Government Documents Department

A Statistical Model of Nuclear Level Spacings

Description: A generalization of Wigner's simple model for the distribution of nuclear level spacings is studied. The generalization is based on a stochastic process which reproduces the correct joint probabllity distribution of N energy levels for small spacings. The case N = 3, which includes the effect of the correlation between adjacent spacings, is discussed in detail. The resulting distribution and the correlation coefflcient are compared with experimental data. No definite conclusion can be drawn except that the effect of the correlations on the spacing distribution is very small. (auth)
Date: December 1, 1960
Creator: Dresner, L. & Inonu, E.
Partner: UNT Libraries Government Documents Department

Stochastic Nuclear Reaction Theory: Breit-Wigner nuclear noise

Description: The purpose of this paper is the application of various statistical tests for the detection of the intermediate structure, which lies immersed in the Breit-Wigner ''noise'' arising from the superposition of many compound nucleus resonances. To this end, neutron capture cross sections are constructed by Monte-Carlo simulations of the compound nucleus, hence providing the ''noise'' component. In a second step intermediate structure is added to the Breit-Wigner noise. The performance of the statistical tests in detecting the intermediate structure is evaluated using mocked-up neutron cross sections as the statistical samples. Afterwards, the statistical tests are applied to actual nuclear cross section data. 10 refs., 1 fig., 2 tabs.
Date: January 1, 1988
Creator: de Saussure, G. & Perez, R.B.
Partner: UNT Libraries Government Documents Department

Revised evaluations for ENDF/B-VI Revision 2

Description: The purpose of this paper is to report on revised cross-section evaluations for 17 nuclides that have been prepared for ENDF/B-VI Revision 2. The nuclides considered include five fission products and various isotopes of cadmium and hafnium. The previous ENDF/B-VI evaluations for these 17 nuclides were carried over from ENDF/B-V and were completed in the 1974--1980 time period. By utilizing the experimental data that have become available since 1980 the revised evaluations will result in significant improvements in the evaluated nuclear data files. The primary emphasis was placed on the resolved and unresolved resonance regions, but new experimental data were also used to improve the cross sections for energies above the unresolved resonance region. Negative elastic scattering cross sections were encountered in some of the previous evaluations; since the revised evaluations use multilevel Breit-Wigner (MLBW) parameters, rather than single-level Breit-Wigner (SLBW), this problem is eliminated.
Date: March 1, 1993
Creator: Wright, R. Q.
Partner: UNT Libraries Government Documents Department

Use of R-matrix theory in light element evaluations

Description: R-matrix theory is a general framework for describing nuclear reactions (neutron- and charged-particle-induced) that is particularly well-suited for including resonances. We will review some unconventional properties of resonances that arise from this theory, including non-Breit-Wigner (BW) resonances and shadow poles, and discuss their physical consequences. Examples will be given from the analyses of several light systems that have been used in ENDF evaluations, including {sup 4}He, {sup 5}He, {sup 15}N, and {sup 17}O. The resonances in the helium systems tend to be significantly non-BW in character, while almost all the resonances in {sup 15}N and {sup 17}O are Breit-Wigner. An interesting exception in the case of {sup 15}N indicates that some of the sub-threshold levels that have been assumed to be bound might be virtual. We find that fitting data from all possible reactions simultaneously results in level schemes for the compound systems that differ in some cases significantly from the ``accepted`` published level information.
Date: December 31, 1992
Creator: Hale, G. M.
Partner: UNT Libraries Government Documents Department

New results in the partial wave analysis of the K{sup {minus}}{omega} system in the reaction K{sup {minus}}p {yields} K{sup {minus}}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0}p

Description: Preliminary results are presented from the first large-statistics partial wave analysis of K{sup {minus}}{omega} system produced in the reaction K{sup {minus}p {yields} K{sup {minus}}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0}p at 11 GeV/c observed with the LASS spectrometer at SLAC. The analysis is based on the moments of the joint angular distributions of the decay to the K{sup {minus}}{omega}} system, with subsequent {omega} decay to {pi}{sup +}{pi}{sup {minus}}{pi}{sub 0}. The resulting J{sup P} = 2{sup {minus}}, 2{sup +} and 3{sup {minus}} amplitudes exhibit resonant behavior, and are discussed in the context of the relevant Briet-Wigner fits.
Date: August 1, 1991
Creator: Aston, D.; Bienz, T.; Bird, F.; Dunwoodie, W.; Johnson, W.; Kunz, P. et al.
Partner: UNT Libraries Government Documents Department

RBU: A COMBINED MONTE CARLO REACTOR-BURNUP PROGRAM FOR THE IBM 709

Description: RBU is a digital computer program for the detailed calculation of the neutron, reactivity, and isotopic history of a reactor in which relatively exact models of the geometry and physical processes are included to permit reliable pre dictions of fuel costs and reactor performance. The program uses the Monte Carlo method to obtain the fine structure of the neutron flux in three space dimensions and energy. Using this fine structure, cross sections are averaged over space and energy to obtain the neutronic properties for equivalent homogeneous one- dimensional regions of space and ranges of energy. These are used in diffusion calculations to obtain the macroscopic flux distribution throughout the reactor. The consumption and production of isotopes is computed for a time step by the solution of sets of partial differential equations involving both the macroscopic and microscopic fluxes. With the new concentrations, diffusion calculations are performed again to obtain macroscopic fluxes for the next time step. At variable intervals, Monte Carlo calculations are again performed to determine the changes in microscopic flux distributions. The cycle is repeated until conditions on the reactivity or other properties dictate the end of the calculation. Programmed control rod manipulation may be included in the calculation. The Monte Carlo, diffusion, or burnup portions of the program may be used separately. The unresolved resonance range is treated by random selection of resonance parameters from appropriate distributions using the Doppler broadened single level Breit- Wigner formula. Resolved resonances are treated similarly with the exception that specific values of the resonance parameters are used. The effects of molecular binding and thermal motion of the nuclei on near-thermal scattering are treated by a simple model capable of incorporating the pertinent physical theory and data. (auth)
Date: September 30, 1959
Creator: Leshan, E.J.; Burr, J.R.; Temme, M.; Thompson, G.T. & Triplett, J.R.
Partner: UNT Libraries Government Documents Department

Rbu-Calculation of Reactor History Including the Details of Isotopic Concentration. Part 1. The Method

Description: RBU is a digital computer program for the detailed calculaticn of the neutron, reactivity, and isotopic history of a reactor in which relatively exact models of the geometry and physical processes are included to permit reliable predictions of fuel costs and reactor performance. The program uses the Monte Carlo method to obtain the fine structure of the neutron flux in three space dimensions and energy. Using this fine structure, cross sections are averaged over space and energy to obtain the neutronic properties for equivalent homogeneous one-dimensional regions of space and ranges of energy. These are used in diffusion calculations to obtain the macroscopic fiux distribution throughout the reactor. The consumption and production of isotopes are computed for a time step by the solution of sets of partial differential equations involving both the macroscopic and microscopic fluxes. With the new concentrations, diffusion calculations are performed again to obtain macroscopic fluxes for the next time step. At variable intervals Monte Carlo calculations are again performed to determine the changes in microscopic flux distributions. The cycle is repeated until conditions on the reactivity or other properties dictate thc end of the calculation. Programmed control rod manipulation or fuel transfers may be included in the calculation. The Monte Carlos diffusions or burnup portions of the program may be used separately, on the IBM 704 as well as on the IBM 709 for which the complete program is written. The unresolved resonance range is treated by random selection of resonance parameters from appropriate distributions using the Doppler broadened single level Breit-Wigner formula. Resolved resonances are treated similarly with the exception that specific values of the resonance parameters are used. The effects of molecular binding and thermal motion of the nuclei on nearthermal scattering are treated by a simple model capable of incorporating the pertinent physical ...
Date: December 1, 1958
Creator: Leshan, E. J.; Burr, J. R.; Temme, M.; Morrison, R.; Thompson, G. T. & Triplett, J. R.
Partner: UNT Libraries Government Documents Department