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Tables and graphs of photon interaction cross sections from 1.0 keV to 100 MeV derived from the LLL Evaluated Nuclear Data Library

Description: Energy-dependent evaluated photon interaction cross sections and related parameters are presented for the elements H through Cf (Z = 1 to 98). Data are given over the energy range from 1 keV to 100 MeV. The related parameters include form factors and average energy deposits per collision (with and without fluorescence). Fluorescence information is given for all atomic shells that can emit a photon with a kinetic energy of 1 keV or more. In addition, the following macroscopic properties are given: total mean free path and energy deposit per centimeter. This information is derived from the Livermore Evaluated Nuclear Data Library (ENDL) as of Oct. 1975. (auth)
Date: October 31, 1975
Creator: Plechaty, E.F.; Cullen, D.E. & Howerton, R.J.
Partner: UNT Libraries Government Documents Department

Impact ionization in GaAs: A screened exchange density-functional approach

Description: Results are presented of a fully ab initio calculation of impact ionization rates in GaAs within the density functional theory framework, using a screened-exchange formalism and the highly precise all-electron full-potential linearized augmented plane wave method. The calculated impact ionization rates show a marked orientation dependence in k space, indicating the strong restrictions imposed by the conservation of energy and momentum. This anisotropy diminishes as the impacting electron energy increases. A Keldysh type fit performed on the energy-dependent rate shows a rather soft edge and a threshold energy greater than the direct band gap. The consistency with available Monte Carlo and empirical pseudopotential calculations shows the reliability of our approach and paves the way to ab initio calculations of pair production rates in new and more complex materials.
Date: August 13, 2001
Creator: Picozzi, S., Asahi, R., Geller, C.B., Continenza, A., and Freeman, A.J.
Partner: UNT Libraries Government Documents Department

Relativistic Quark Clustering in the gamma gamma -> pi^+ pi^- and pi^0 pi^0 reactions

Description: Cross section for pion pair production by photon-photon collisions are estimated near the threshold using a relativitic quark clustering model.A realistic qq wave function of the pion was determined by fitting the pion charge form factor up to q^2 = 4 ~ 6 GeV^2/c^2, the weak decay constant and the pion charge radius.The composite structure of the pion provides a simple explanation for the energy dependence and magnitudes of pi^+pi^- and pi^0 pi^0 pair productions.
Date: January 1, 1988
Creator: Gross, Franz; Ito, Hiroshi & Buck, Warren
Partner: UNT Libraries Government Documents Department

A Proposal to Search for Charmed Particles Originating from the Interactions of 400 GeV/c Protons in Emulsion Nuclei

Description: There has been much recent discussion of the possibility of the existence of 'charmed' particles, hadrons which possess non-zero values of 'charm', a further additive quantum number. These particles may be generated either in the three triplet model of Han and Nambu or by the postulate of a fourth, charm-bearing quark. On the assumption that charm, like strangeness, is conserved in strong and electromagnetic interactions (the opposite assumption would necessitate charmed particles coupling strongly to ordinary hadrons and the existence of yet undiscovered states, e.g. Z*s) but not conserved in weak interactions one might expect their production either singly in neutrino interactions or in pairs in associated production in high energy hadron collisions, to be followed by their subsequent, relatively slow, decay into 'uncharmed' particles. Various estimates as to mass, lifetime, production cross-sections and decay modes have been made for these particles. However their failure to appear as di-lepton events among the neutrino interactions of the Brookhaven A.G.S. and CERN P.S. experiments might suggest that their masses are in excess of 2 GeV/c{sup 2} the other hand, such particles would have been expected to have been observed directly in bubble chamber studies at FNAL had their lifetimes been greater than 10{sup -11}s as suggested by some authors. This proposal, which may be thought of as complementary to that of Burhop et al, is for a straightforward exposure of a stack of emulsions to a 400 GeV/c proton beam to look for evidence of the pair production of charmed particles. The spatial resolution of the emulsion technique is about one micron with the consequence that the decays of particles of mean lives in the range 10{sup -11} to 10{sup -14} s should be readily observable.
Date: November 1, 1974
Creator: Sacton, J.
Partner: UNT Libraries Government Documents Department


Description: The objectives of research activities in particle theory are predicting the production cross section and decay branching fractions of Higgs bosons and new particles at hadron colliders, developing techniques and computer software to discover these particles and to measure their properties, and searching for new phenomena and new interactions at the Fermilab Tevatron and the CERN Large Hadron Collider. The results of our project could lead to the discovery of Higgs bosons, new particles, and signatures for new physics, or we will be able to set meaningful limits on important parameters in particle physics. We investigated the the prospects for the discovery at the CERN Large Hadron Collider of Higgs bosons and supersymmetric particles. Promising results are found for the CP-odd pseudoscalar ($A^0$) and the heavier CP-even scalar ($H^0$) Higgs bosons with masses up to 800 GeV. Furthermore, we study properties of the lightest neutralino ($\chi^0$) and calculate its cosmological relic density in a supersymmetric $U(1)'$ model as well as the muon anomalous magnetic moment $a_\mu = (g_\mu - 2)/2$ in a supersymmetric $U(1)'$ model. We found that there are regions of the parameter space that can explain the experimental deviation of $a_\mu$ from the Standard Model calculation and yield an acceptable cold dark matter relic density without conflict with collider experimental constraints. % Recently, we presented a complete next-to-leading order (NLO) calculation for the total cross section of inclusive Higgs pair production via bottom-quark fusion ($b\bar{b} \to hh$) at the CERN Large Hadron Collider (LHC) in the Standard Model and the minimal supersymmetric model. We plan to predict the Higgs pair production rate and to study the trilinear coupling among the Higgs bosons. % In addition, we have made significant contributions in B physics, single top production, charged Higgs search at the Fermilab as well as in grid computing ...
Date: September 5, 2007
Creator: Kao, Chung
Partner: UNT Libraries Government Documents Department

Current quarks, constituent quarks, and symmetries of resonance decays

Description: The transformation between ''current'' quarks and ''constituent'' quarks recently suggested by Melosh is examined with respect to its predictions for pionic decays of resonances. It implies the use of SU(6)/sub W/ for classifying particle states but not for describing decay processes. lnstead, pion emission proceeds via DELTA L/sub z/ = 0, plus or minus 1, where L is the internal (''quark'') orbital angular momentum. This decay symmetry is called SU(6)/sub W/ (DELTA L/sub z/ = 0, plus or minus 1). It is proven equivalent for any decay A yields B + pi (where A, B are arbitrary qq-bar or qqq hadrons) to the /sup 3/P/sub 0/ quark-pair creation model for such decays, as formulated by Micu, Colglazier, Petersen and Rosner. The roles of final orbital angular momenta l and of SU(3) x SU(3) subgroups of SU(6)w are also discussed, and some new predictions are made for decays of meson resonances below 1700 MeV. (auth)
Date: April 18, 1973
Creator: Hey, A.J.G.; Rosner, J.L. & Weyers, J.
Partner: UNT Libraries Government Documents Department


Description: The status of experiments on electron scattering, photoproduction of mesons, wide-angle muon pair production, photoproduction of pairs with large momentum transfers, photoproduction of sigma particles, pion production in peripheral processes, wide-angle electron pair production, and the Compton effect at 1 to 3 Bev is summarized. The status of shielding studies, spark chamber studies of photoproduction, and bubble chamber investigations are also included. Magnets, targets, ejection-type vacuum chambers, photon-beam drift tubes and collimators, detectors, cables, cryogenic cooling equipment, radiation detectors, and construction of supplementary shielding walls were involved in design efforts and procurement of equipment and facilities. Modifications and improvements at the accelerator proper were made on the magnet power supply, the r-f system, the Drivac high-vacuum pumps and other components and facilities. Operation at energies up to 6.2 Bev and with intensities up to 30% of design intensity (6 x 10/ sup 12/ electrons/sec) was achieved. Data of a technical nature are very limited. (D.C.W.)
Date: February 1, 1963
Partner: UNT Libraries Government Documents Department

The Direct Production of Electron Pairs in Nuclear Emulsion by 100 and 200 GeV Protons

Description: It is proposed to study the direct production of electron pairs produced when a high energy proton interacts with the Coulomb field of a nucleus. This process occurs at fourth order in quantum electrodynamics. This phenomena, called trident production when the incident particle is an electron, is characterized by a single incident primary track and three emerging tracks. Accelerator experiments on direct pair production by protons have not been previously reported, due to the small cross-sections at energies less than 100 GeV. However, at an energy of 100 GeV the cross-section for the direct creation of electron pairs by protons in emulsion is about 10{sup -25}cm{sup 2}.
Date: July 20, 1972
Creator: Cary, A.S. & College, /Harvey Mudd
Partner: UNT Libraries Government Documents Department

Internally Cooled Molten-Salt Reactors

Description: The initial and long-term nuclear characteristics of two internally cooled heteroingeneous graphite-moderated two-region molten-salt reactors were studied. The reactors have doubling times of 22.5 and 27.5 years. Methods of decreasing the doubling times by removing the Pa/sup 233/ from the core and by increasing the specific power of the reactor are described. (auth)
Date: June 22, 1959
Creator: Lackey, M. E.
Partner: UNT Libraries Government Documents Department

Photoproduction Experiment at Fermilab

Description: The authors propose to continue and extend the program of photoproduction and pair production studies currently being carried out in Experiment E-87. The goals of the physics program they propose are: (1) to look for {mu}{sup {+-}}+e{sup {-+}}{nu}'s final states; (2) to study the mass spectra of hadronic final states which are produced in association with a single charged lepton (electron or muon); and (3) to determine the properties of a selected number of photoproduced multi-body hadronic final states; in particular: {gamma} + A {yields} ({bar p}p{pi}{sup +}{pi}{sup -}) + A {yields} ({pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0}) + A {yields} (K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}) + A {yields} (K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0}) + A etec., etc. The need for a heavy lepton pair production experiment is more crucial today than when they first proposed this experiment five years ago. The {mu}e pairs observed recently at SPEAR can be interpreted as arising from the decay of 2 GeV/c{sup 2} heavy leptons. They feel there is a compelling need to demonstrate that such {mu}e pairs are observed in at least one other reaction before such an interpretation can be considered completely satisfactory. To the best of their knowledge, the only independent reaction in which one might expect to observe such events is the pair production of heavy leptons. The broad band photon beam at Fermilab is perhaps the only beam in which such a pair production experiment is feasible. In addition, the probability of mis-identifying two hadrons as a {mu}e pair is extremely small (10{sup -6}) at Fermilab energies - several orders of magnitude smaller than at SPEAR. The primary motivation for examining the photoproduced hadronic final states such as {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} and K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} is to search for structure in ...
Date: October 1, 1975
Creator: Knapp, B.; Lee, W.; Moscoso, L.; Sokolsky, P.; U., /Columbia; Gladding, G. et al.
Partner: UNT Libraries Government Documents Department


Description: Research progress on pair production, photoproduction, beta scattering by protons and deuterons, meson ( pi ) production, shielding, polarized photon production, and photonproton scattering is reported. Developments of experimental equipment and facilities are also summarized, together with accelerator improvements and operation. (D.C.W.)
Date: January 17, 1964
Partner: UNT Libraries Government Documents Department