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e{sup +}e{sup -} Physics Today and Tomorrow: Four Tutorial Lectures Delivered at the Arctic School of Physics 1980

Description: Four tutorial lectures were delivered to provide an introduction to high energy positron-electron annihilation physics, and to serve as a foundation for more advanced lectures. The first lecture discusses three subjects: the parameters of e{sup +}e{sup -} storage rings that are directly relevant to experiments, the physics of e{sup +}e{sup -} one-photon exchange as illustrated by the reaction e{sup +}e{sup -} ..-->.. ..mu..{sup +}..mu..{sup -}, and the naive quark model for the reaction e{sup +}e{sup -} ..-->.. hadrons. The second lecture is devoted to heavy leptons: the status of the tau lepton, and the status of the search for heavier leptons. The third lecture discusses the nonrelativistic quantum mechanics of heavy quark-antiquark systems - the psi/J particle family and the T particle family. As e{sup +}e{sup -} colliding beams machines attain very high energy, E{sub c.m.} greater than or equal to 50 GeV, e{sup +}e{sup -} annihilation will occur through the weak interactions as well as through the electromagnetic interaction; this will allow the study of the weak interactions and the study of any new particle related to, or produced through, the weak interactions. Lecture 4 discusses this physics at an energy corresponding to the mass of the Z{sup 0} intermediate boson, and then discusses the physics at yet higher energy. The lecture concludes with a description of the capabilities and limitations of the e{sup +}e{sup -} colliding beams machines needed to attain this very high energy - both storage rings and colliding linear accelerators. (RWR)
Date: September 1, 1980
Creator: Perl, M.L.
Partner: UNT Libraries Government Documents Department

Determination of very slow. mu. /sup +/ hop rates in Cu by LLF-. mu. SR

Description: Muon spin relaxation in low (weak) longitudinal magnetic field (LLF-..mu..SR) provides a means of independently determining the static dipolar width ..delta.. characterizing the ..mu../sup +/ lattice site and the correlation time tau/sub c/ for ..mu../sup +/ hopping, in a manner that is nearly model-independent for tau/sub c/ and especially accurate in the near-static limit (tau/sub c/ > tau/sub ..mu../). The advantages of this method are illustrated by its application to muon hopping in Cu near the tau/sub c/ maximum around 50/sup 0/K.
Date: January 1, 1986
Creator: Brewer, J.H.; Celio, M.; Harshman, D.R.; Keitel, R.; Kreitzman, S.R.; Luke, G.M. et al.
Partner: UNT Libraries Government Documents Department

Positive muon and the positron as probes of defects

Description: The positive muon and the positron are each being used nowadays to investigate defects in condensed matter. A brief summary of the experimental methods employed with each particle is given in this paper. Similarities and differences between the behavior of the two leptons when implanted in consensed matter are pointed out, and by means of a comparison between muon and positron data in Al it is shown that the combination of muon and positron experiments can serve as a useful new probe of defects in solids.
Date: January 1, 1980
Creator: Lynn, K G
Partner: UNT Libraries Government Documents Department

A study of positrons from Soviet nuclear powered satellites as tracers for magnetospheric research

Description: Two Soviet satellites carrying nuclear reactors operated in circular 790 km orbits (65{degree} inclination) in 1987 and 1988. Positrons generated in the satellites' surfaces by the intense reactor gamma radiation escaped and were trapped for periods of minutes to hours in the geomagnetic field. These positrons have been observed on many occasions by gamma ray sensors on the SMM satellite (in 500 km orbit) which identify the positrons by the 511 keV gamma rays created when they annihilate in the satellite surface. The SMM detector provides a time resolution of 64 milliseconds. It has recorded positron rise-times of less than 0.5 second (corresponding to about 1 positron gyroradius) on many occasions as it encounters the low-L edge of positrons injected by the Soviet satellites as far as half-way around the earth. We are studying the potential of these sharply defined positron shells as magnetospheric tracers and as a means for examining particle diffusion and loss processes. 3 refs., 5 figs.
Date: January 1, 1990
Creator: Hones, E.W. Jr. (Mission Research Corp., Los Alamos, NM (USA))
Partner: UNT Libraries Government Documents Department

Positron ionization mass spectrometry: An organic mass spectrometrist's view

Description: We are currently engaged in a research program to study the ionization of polyatomic molecules by positrons. We refer to the technique herein as positron ionization mass spectrometry which includes all of the possible ionization mechanisms. In the course of this work we will attempt to characterize each of the important ionization mechanisms. Our ultimate objective is to explore the use of positron ionization mass spectrometry for chemical analysis. Several other groups have also begun to pursue aspects of positron ionization in parallel with our efforts although with somewhat different approaches and, perhaps with slightly different emphases. Recently, for example, Passner et al. have acquired mass spectra in a Penning trap resulting from the ionization of several different polyatomic molecules by near thermal kinetics energy positrons. Our research involves studying the different types of ionizing interactions of positrons with organic molecules, as a function of positron kinetic energy. For ionization of polyatomic molecules by positrons, several possible mechanisms are apparent from lifetime and scattering cross-section data. These mechanisms are discussed.
Date: January 1, 1990
Creator: Glish, G.L.; Donohue, D.L.; McLuckey, S.A.; Eckenrode, B.A. & Hulett, L.D. Jr.
Partner: UNT Libraries Government Documents Department

Contribution to the theory of positive muon diffusion in metals at low temperature

Description: We study the temperature dependence of the ..mu../sup +/ diffusion in a metal within the small polaron theory. The geometry of the strain field due to an impurity is shown to strongly influence the ..mu../sup +/ diffusion properties. We reanalyzed part of the Al data.
Date: January 1, 1983
Creator: Yaouanc, A.
Partner: UNT Libraries Government Documents Department

Test beam results from the D0 end electromagnetic calorimeter

Description: Test beam results are presented for the DO end electromagnetic calorimeter. Data were taken with electrons and pions ranging in energy from 5 GeV to 150 GeV. Results from the analysis of the test beam data are presented on energy resolution and linearity, stability and uniformity of response, position resolution and electron-pion separation.
Date: November 1, 1991
Creator: Roe, N.A.
Partner: UNT Libraries Government Documents Department

Resolvability of defect ensembles with positron annihilation studies

Description: Recent advances in the use of positron annihilation to study defect ensembles in and on the surfaces of metals, are pointing the way towards studies where particular positron-electron annihilation modes may be identified and studied in the presence of one another. Although a great deal is understood about the annihilation of positrons in ostensibly defect-free metals, much less is understood when the positron annihilates in complex defect systems such as liquid metals, amorphous solids, or at or near the vacuum-solid interface. In this paper the results of three experiments, all of which demonstrate means by which we can resolve various poistron annihilation channels from one another, are discussed.
Date: November 12, 1984
Creator: Fluss, M.J.; Howell, R.H.; Rosenberg, I.J. & Meyer, P.
Partner: UNT Libraries Government Documents Department

Muon spin relaxation and Knight shift in the heavy-fermion superconductor UPt/sub 3/

Description: Positive muon spin relaxation experiments have been conducted on the heavy-fermion superconductor UPt/sub 3/ in both the normal and superconducting states for zero, transverse, and longitudinally applied magnetic fields. Below 6 K in zero applied field, the ..mu../sup +/ relaxation rate is approximately twice that expected from /sup 195/Pt nuclear dipolar relaxation alone. Transverse- and longitudinal-field measurements show that the observed relaxation rate depends on magnetic field and is quasistatic in origin. It is suggested that the onset of very weak (approx.10/sup -3/ ..mu../sub B//U atom) magnetic ordering below approximately 6 K is responsible for the observed increase in the relaxation rate. ..mu../sup +/ Knight shift measurements in the normal state of UPt/sub 3/ show a temperature dependent shift K/sub ..mu../ which tracks the bulk susceptibility chi. From the K/sub ..mu../ vs chi plot, a ..mu../sup +/ hyperfine field of approximately 100 Oe/..mu../sub B/ is extracted.
Date: January 1, 1986
Creator: Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.; Smith, J.L.; Willis, J.O. et al.
Partner: UNT Libraries Government Documents Department

Cyclotron targetry for production of short-lived positron emitters

Description: The basic concepts of cyclotron target design are presented along with the relevant practical experience gained by workers in this field over the years. Results are presented from several recent studies on the temperature and density distribution inside gas and liquid targets. 5 refs., 3 figs.
Date: January 1, 1989
Creator: Schlyer, D.J.
Partner: UNT Libraries Government Documents Department

Study of the equilibrium vacancy ensemble in aluminum using 1D- and 2D-angular correlation of annihilation radiation

Description: One- and two-dimensional angular correlation of positron-electron annihilation radiation (1D and 2D-ACAR) data have been obtained between 293 and 903 K for single crystals of aluminum. The peak counting rates vs temperature, which were measured using the 1D-ACAR technique, provide a model independent value for the temperature dependence of the positron trapping probability. Using these results it is possible to strip out the Bloch state contribution from the observed 2D-ACAR surfaces and then compare the resulting defect ACAR surfaces to calculated 2D-ACAR surfaces for positrons annihilating from the Bloch, monovacancy, and divacancy-trapped states. The result of this comparison is that the presence of an increasing equilibrium divacancy population is consistent with the observed temperature dependence of ACAR data at high temperature in Al and that the present results when compared to earlier studies on Al indicate that the ratio of the trapping rates at divacancies and monovacancies is of order two.
Date: March 12, 1985
Creator: Fluss, M.J.; Berko, S.; Chakraborty, B.; Hoffmann, K.R.; Lippel, P. & Siegel, R.W.
Partner: UNT Libraries Government Documents Department

Possibility of studying crystal-field levels and excitations by. mu. /sup +/SR spectroscopy

Description: We point out that ..mu../sup +/SR relaxation times T/sub 1/ and T/sub 2/ measured in metallic magnetic materials can sometimes be expressed in terms of the spin-spin correlation functions of the magnetic ions. We calculate these functions in a random phase approximation and notice they can strongly depend on the crystal field levels and excitations of the magnetic ions. The shortcomings of this approximation are discussed.
Date: January 1, 1983
Creator: Yaouanc, A.
Partner: UNT Libraries Government Documents Department

Rare muon processes

Description: The status of rare muon processes as tests of the standard model is reviewed with the emphasis on results that are expected from experiments in the near future.
Date: January 1, 1993
Creator: Cooper, M.D.
Partner: UNT Libraries Government Documents Department

Positron-annihilation spectroscopy of vacancy defects in aluminum

Description: Positron-annihilation characteristics in a monovacancy and a divacancy in aluminium have been calculated self-consistently using a local density functional formalism, into which the many-body enhancement effects have been incorporated. Results for the theoretical two-dimensional angular correlation of annihilation radiation spectra are compared to experimental results obtained from an aluminum single crystal at 20/sup 0/C, where positrons annihilate from a Bloch-state, and at higher temperatures, 500/sup 0/C and 630/sup 0/C, where they annihilate primarily from vacancy-trapped states.
Date: June 1, 1982
Creator: Chakraborty, B.; Berko, S.; Fluss, M.J.; Hoffmann, K.; Lippel, P. & Siegel, R.W.
Partner: UNT Libraries Government Documents Department

Prevacancy effects in metals observed by positron annihilation

Description: The prevacancy effects sometimes observed in high-purity, well-annealed metals, are discussed. It is concluded that these effects are extrinsic and are most likely due to positron trapping in defects. The nature of the defects is discussed, and it is pointed out that the presence of dislocations in the samples could cause prevacancy effects.
Date: March 1, 1982
Creator: Smedskjaer, L.C.
Partner: UNT Libraries Government Documents Department

A correction scheme for the quadrupole misalignment errors in the ANL--APS positron linac

Description: The Argonne Advanced Photon Source (APS) positron linac contains 24 quadrupoles of which 22 are configured as a FODO system and are distributed along the last 7 constant gradient accelerating structures. Errors in quadrupole and waveguide positions deflect the positron beam centroid, contributing to the aperture requirements in the accelerating structures and quadrupoles. A correction scheme using correction dipole magnets is proposed to compensate for the random errors in quadrupoles.
Date: January 1, 1992
Creator: Nassiri, A.
Partner: UNT Libraries Government Documents Department

Electronic structure of disordered CuPd alloys by positron-annihilation 2D-ACAR

Description: We report 2D-ACAR experiments and KKR CPA calculations on alpha-phase single-crystal Cu/sub 1-x/Pd/sub x/ in the range x less than or equal to 0.25. The flattening of the Fermi surface near (110) with increasing x predicted by theory is confirmed by our experimental results. 16 refs., 2 figs.
Date: January 1, 1988
Creator: Smedskjaer, L.C.; Benedek, R.; Siegel, R.W.; Legnini, D.G.; Stahulak, M.D. & Bansil, A.
Partner: UNT Libraries Government Documents Department

Correlations between the production of prompt positrons at low transverse momentum and the associated charged multiplicity

Description: The production of prompt positrons in pp-collisions at ..sqrt..s = 63 GeV and y - 0 has been measured as a function of the associated charged particle multiplicity over the P/sub T/ internal 0.12 < P/sub T/ < 1.0 GeV/c. Preliminary results indicate that the production of positrons is proportional to the square of the mean multiplicity at low P/sub T/ (< 0.4 GeV/c). Such a square dependence is not expected from final state sources such as hadronic bremsstrahlung or hadronic decays. It could however indicate a production mechanism of the soft lepton continuum over an extensive volume during the early stages of the collision.
Date: January 1, 1986
Partner: UNT Libraries Government Documents Department

Search for right-handed currents in muon decay

Description: We report preliminary results of an experiment designed to measure the mass of the right-handed intermediate vector boson. The presence of such a particle in electroweak interactions is predicted by left-right symmetric gauge theories. The experiment measures the momentum spectrum of the positrons from the decay at rest of (1) longitudinally polarized muons produced in the decay at rest of ..pi../sup +/ ..-->.. ..mu../sup +/nu (polarization P/sub ..mu../) and (2) unpolarized muons. The endpoints of these two spectra are used to determine the quantity xi P/sub ..mu../ where xi is a Michel parameter. This product is related to the ratio of the mass of left and right handed W and to the phase between the two helicity states. We measure, at the 90% CL, 1 - delta/rho < 0.0041 and infer the mass M(W/sub R/) > 380 GeV/c/sup 2/.
Date: January 1, 1983
Creator: Gobbi, B.
Partner: UNT Libraries Government Documents Department

Search for the violation of time-reversal invariance in K/sub. mu. 3/ decays

Description: The polarization of the ..mu../sup +/ from the decays K/sup 0//sub L/ ..-->.. ..pi../sup -/..mu../sup +/..nu.. and K/sup +/ ..-->.. ..pi../sup 0/..mu../sup +/..nu.. was measured. The transverse polarization forbidden by time reversal invariance is (1.85 +- 3.60) x 10/sup -3/ based on the final data sample of thirty-four million events. This null result places constraints on certain models of CP-violation through the exchange of Higgs bosons.
Date: August 1, 1981
Creator: Morse, W.M.; Leipuner, L.B.; Larsen, R.C.; Blatt, S.R.; Campbell, M.K.; Adair, R.K. et al.
Partner: UNT Libraries Government Documents Department

Search for right-handed currents in muon decay

Description: We report new limits on right-handed currents, based on precise measurement of the endpoint of the e/sup +/ spectrum from ..mu../sup +/ decay. Highly polarized ..mu../sup +/ from the TRIUMF surface beam were stopped in pure metal foils within either an 1.1-T spin-holding longitudinal field, or a 70-gauss spin-precessing transverse field. Decay e/sup +/ emitted within 200 mrad of the beam direction were momentum-analyzed to +-0.2%. For the spin-held data, decay via (V-A) currents requires the e/sup +/ rate to approach zero in the beam direction at the endpoint. Measurement of this rate sets the 90% confidence limits xi P/sub ..mu../delta/rho > 0.9959 and M(W/sub R/) > 380 GeV, where W/sub R/ is the possible right-handed gauge boson. For the spin-precessed data we independently determine a 90% confidence limit xi P/sub ..mu../delta/rho > 0.9918. 18 references.
Date: April 1, 1983
Creator: Carr, J.; Gidal, G.; Gobbi, B.; Jodidio, A.; Oram, C.J.; Shinsky, K.A. et al.
Partner: UNT Libraries Government Documents Department