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Perl, M.L.

Stanford Linear Accelerator Center, Menlo Park, CA (United States). Funding organisation: USDOE, Washington, DC (United States)

Stanford Linear Accelerator Center, Menlo Park, CA (United States). Funding organisation: USDOE, Washington, DC (United States)

AbstractAbstract

[en] The status of the Landau, Pomeranchuk, Migdal Effect is briefly reviewed. A recent experiment at the Stanford Linear Accelerator Center substantially agrees with the existing theoretical formulation. However, that formulation suffers from an imprecise foundation and a lack of generality. The difficulty of finding a simple, explanatory picture of the 1/√K behavior of the Effect is also noted

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May 1994; 15 p; 1994 Physics encounters of the Aosta Valley; La Thuile (Italy); 6-12 Mar 1994; CONF-9403127--1; CONTRACT AC03-76SF00515; Also available from OSTI as DE94013798; NTIS; US Govt. Printing Office Dep

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AbstractAbstract

[en] Bremsstrahlung cross section calculations are still attracting attention because of the inadequacy of the existing formulae. The Sommerfeld-Elwert formula holds good up to 0.1 MeV. Bethe and Heitler gave a relativistic expression for the bremsstrahlung cross sections using Dirac's electron theory and Born approximation. Coulomb and screening effects were not included in their calculations. Calculations of the bremsstrahlung cross sections using the B-H formula are tedious. Approximations of the B-H formula in the nonrelativistic and extreme relativistic regions exist. But no such approximation is available in the intermediate energy region. An attempt is made to obtain an approximation of the B-H formula in the intermediate energy region. Several approximations are made to reduce the B-H formula into a polynomial in x, the ratio of the photon energy to the total energy of the incident electron. The coefficients of the polynomial turn out to be a long series of terms which are functions of incident electron energy. The validity of the approximate formula in the intermediate energy region will be discussed

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International symposium on radiation physics; Calcutta, India; 30 Nov 1974; See CONF-741109--.

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Natl. Bur. Stand. (U.S.), Spec. Publ; (no.461); p. 60-63

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AbstractAbstract

[en] Complete text of publication follows. With the maturity of high-power laser technology, we can realize an extremely high intensity of photons in a tiny space. About 10 kJ of 1 eV photons (10

^{22}photons) can be squeezed in a space of several micro matter during 10 fs (10^{-14}s). This means the density of photons of 10^{34}/cm^{3}. Photon is boson and can be squeezed to a tiny space. We expect that we can design unique experiments of the collective effects of elementary particles and such lasers can also be used for a new type of experiments. The physics will be wider with the combination of the conventional accelerators. I briefly describe what we have carried out as academic research related to high energy astrophysics. One is the possibility of laboratory high-energy astrophysics experiment with use of the electron-positron plasma produced by laser irradiation on high-Z material. Regarding the electron-positron plasma, we had started the analysis of the experimental data obtained by Tom Cowan et al. It was around the year of 2000. We have carried out a computational simulation of the positron production based on the Fokker-Planck type kinetic equation. In such a situation, most of the laser energy is converted to the energy of relativistic electrons, while it was found that the direct production of the positrons via the Trident process is relatively inefficient. The most of positrons are found to be produced, however, via Bethe-Heitler process. In this process, the electron energy is once converted to that of γ-ray via bremmstrahlung process and γ-ray efficiently produces the pairs via interaction with nuclei. In the later work, we found that the plasma effect through the ambipolar electric field is found to be essential in comparing with the Cowan's experimental data. With the promising, recent experimental results, I will explain the physics of positron production and modeling high-energy astrophysical plasma with experimental pair plasma.Primary Subject

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Hungarian Academy of Sciences, Budapest (Hungary). KFKI Research Institute for Particle and Nuclear Physics; [140 p.]; 2010; p. 63; 31. European Conference on Laser Interaction with Matter; Budapest (Hungary); 6-10 Sep 2010; 5 refs.

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AbstractAbstract

[en] The effect of influence of multiple scattering on electron Bremsstrahlung in amorphous medium is called the Landau-Pomeranchuk-Migdal effect (the LPM effect). Experimental data are analysed and compared with theoretical models. (K.A.)

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Tran Thanh Van, J. (ed.); [687 p.]; ISBN 2-86332-225-7; ; 1997; p. 547-552; 32. Moriond Particle Physics Meeting; Les Arcs, Savoie (France); 22-29 Mar 1997; 18 refs.

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AbstractAbstract

[en] Recent measurements of inclusive and exclusive semi-leptonic b branching ratios are reviewed. Model-independent analyses from ARGUS and CLEO confirm the value BR(b → lνX) 0 10.4%, while new analyses from ALEPH obtain higher values above 11%. The difference is not consistent with measured values of b hadron lifetime. New measurements of BR(B → D

^{*}lν) from CLEO and ALEPH are in good agreement. First measurements of B → D^{*}πlν branching ratios from OPAL, DELPHI, and ALEPH confirm indirect evidence for a large D^{**}component in semi-leptonic B decaysPrimary Subject

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6. international symposium on heavy-flavour physics; Pisa (Italy); 6-10 Jun 1995

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Maximon, L.C.; Miniac, Arlette de; Aniel, Thierry.

CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Service de la Metrologie et de la Physique Neutroniques Fondamentales

CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Service de la Metrologie et de la Physique Neutroniques Fondamentales

AbstractAbstract

[en] We consider in detail the differential cross section for bremsstrahlung for angles and energies in the range of interest for a tagging system. We derive a high energy, small angle approximation for the differential cross section for bremsstrahlung. We use this approximation to determine the maxima and minimum of the cross section and to evaluate it at these extremes. It is shown that the differential cross section has a very sharp dip in the region of small momentum transfers. Coulomb corrections to be Born approximation are considered, and do not fill in this dip. Some particular cases are quantitatively described in the range of interest corresponding to the tagged photon facility planned at the 'Accelerateur Lineaire de Saclay' namely: energy of the incoming electron, E

_{1}=140 MeV - energy of the tagged photon, k=95 MeV - angle between the incoming electron and the outgoing tagged photon, theta_{1}from 0 to 2 degrees - characteristic angles of the tagging electron, theta_{2}from 0 to 6 degrees and phi from 0 to 2 degreesOriginal Title

bremsstrahlung differential cross sections

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Mar 1981; 146 p

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Singh, Tajinder; Singh, Amit; Kahlon, K.S.; Dhaliwal, A.S., E-mail: tajinder_singh2k2@yahoo.com

Proceedings of the international conference on radiation environment - assessment, measurement and its impact: abstract and souvenir

Proceedings of the international conference on radiation environment - assessment, measurement and its impact: abstract and souvenir

AbstractAbstract

[en] Z-dependence of spectral shape of total Bremsstrahlung spectra i.e. the sum of ordinary Bremsstrahlung (OB) and polarization Bremsstrahlung (PB), in thick target materials (Al, Cu, Sn and Pb), produced by beta particles of

^{147}Pm and^{45}Ca, has been studied in the photon energy region of 5-10 keV. It has been established that the spectral shape of total Bremsstrahlung spectra, in terms of S (k, Z) i.e. the number of photons of energy k per m_{0}c^{2}per beta disintegration, is not linearly dependent on the atomic number (Z) of the target material and rather it is proportional to Z^{n}. It has been found that the index 'n' values obtained from modified Elwert factor (relativistic) Bethe-Heitler theory, which include the contribution PB into OB, are in agreement with the experimentally measured results by using X-PIPS Si(Li) detector. In the studied photon energy region, the index values 'n' of Z-dependence are much higher than unity, which is due to the larger contribution of PB into OB. The decrease in 'n' values with increase of photon energy is due to the decrease in contribution of PB into OB. Hence the contribution of polarization Bremsstrahlung plays a vital role into the formation of a spectral shape of total Bremsstrahlung spectra. (author)Primary Subject

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Babasaheb Bhimrao Ambedkar University, Lucknow (India); 170 p; 2012; p. 74; RADENVIRON-2012: international conference on radiation environment - assessment, measurement and its impact; Lucknow (India); 12-14 Apr 2012; This record replaces 44066663

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ALKALINE EARTH ISOTOPES, BETA DECAY RADIOISOTOPES, BETA-MINUS DECAY RADIOISOTOPES, CALCIUM ISOTOPES, DAYS LIVING RADIOISOTOPES, ELECTROMAGNETIC RADIATION, EVEN-ODD NUCLEI, INTERMEDIATE MASS NUCLEI, ISOTOPES, NUCLEI, ODD-EVEN NUCLEI, PROMETHIUM ISOTOPES, RADIATIONS, RADIOISOTOPES, RARE EARTH NUCLEI, SPECTRA, YEARS LIVING RADIOISOTOPES

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AbstractAbstract

[en] The differential cross-section is calculated for the bremsstrahlung of photons from magnetic moments of protons or neutrons decelerated in an external static nuclear (vector) potential. The lowest-order perturbative approximation is used (both with respect to the magnetic moment and external potential). The recent hypothesis of a new magnetic-type interaction of nucleons is also considered in the context of possible bremsstrahlung of a new kind from the corresponding nucleon magnetic moments. (author)

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Gevorkyan, S.R.; Grigiryan, S

Abstracts of the third international conference on modern problems of nuclear physics

Abstracts of the third international conference on modern problems of nuclear physics

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No abstract available

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Uzbekistan Academy of Sciences, Institute of Nuclear Physics, Tashkent (Uzbekistan); Bukhara State Univ., Bukhara (Uzbekistan); Samarkand State Univ., Samarkand (Uzbekistan); Tashkent State Univ., Tashkent (Uzbekistan); Tashkent State Univ., Inst. of Applied Physics, Tashkent (Uzbekistan); Uzbekistan Academy of Sciences, Scientific Association 'Physics-Sun', Tashkent (Uzbekistan); Bukhara Technological Inst., Bukhara (Uzbekistan); 358 p; Aug 1999; p. 126-127; 3. international conference ''Modern problems of nuclear physics''; Bukhara (Uzbekistan); 23-27 Aug 1999; 7 refs.

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Goehmann, Frank, E-mail: frank.goehmann@uni-bayreuth.de

AbstractAbstract

[en] We solve the gl(1 vertical bar 2) generalized model by means of the algebraic Bethe ansatz. The resulting eigenvalue of the transfer matrix and the Bethe ansatz equations depend on three complex functions, called the parameters of the generalized model. Specifying the parameters appropriately, we obtain the Bethe ansatz equations of the supersymmetric t-J model, the Hubbard model, or of Yang's model of electrons with delta interaction. This means that the Bethe ansatz equations of these (and many other) models can be obtained from a common algebraic source, namely from the Yang-Baxter algebra generated by the gl(1 vertical bar 2) invariant R-matrix

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S0550321301004977; Copyright (c) 2002 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: India

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