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Description: The idea of ''antiparticles'', as is well known, originated with Dirac, who in establishing the relativistic equations for the electron noted that besides the solutions corresponding to ordinary electrons there were also ''unwanted solutions'' corresponding to particles of electronic mass but of charge +e instead of the electronic charge - e. The discovery of the positron by CD Anderson offered a brilliant experimental confirmation of Dirac's prediction and gave the first example of an ''antiparticle.''
Date: April 1, 1958
Creator: Segre, Emilio
Partner: UNT Libraries Government Documents Department


Description: By means of the Mandelstam representation, expressions are obtained for the two-pion-exchange contributions to the higher partial waves of N-N scattering. A set of ten invariant amplitudes is selected, of which each member obeys the Mandelstam representation. Dispersion relations are written for the amplitudes in which the discontinuities are absorptive parts for N-bar-N scattering. By means of the unitarity condition the absorptive parts are expressed as a partial- wave expansion in terms of the pi pi - NN partialwave amplitudes of Frazer and Fulco, except for the contributions of the pole in the pi -N system which are treated exactly in order to ensure better convergence of the partial-wave expansion. The N-N transition amplitudes in the angular-momentum representation are expressed in terms of the invariant amplitudes. (auth)
Date: June 1, 1960
Creator: Cziffra, P.
Partner: UNT Libraries Government Documents Department

Inclusive Lambda_c Production in e+e- Annihilations at sqrt{s}=10.54 GeV and in Upsilon(4S) Decays

Description: We present measurements of the total production rates and momentum distributions of the charmed baryon {Lambda}{sub c}{sup +} in e{sup +}e{sup -} {yields} hadrons at a center-of-mass energy of 10.54 GeV and in {Upsilon}(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e{sup +}e{sup -} {yields} c{bar c} events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for {Lambda}{sub c}{sup +} baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of (x{sub p}) = 0.574 {+-} 0.009 and a total rate of N{sub {Lambda}{sub c}}{sup q{bar q}} = 0.057 {+-} 0.002(exp.) {+-} 0.015(BF) {Lambda}{sub c}{sup +} per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK{sup -} {pi}{sup +}. In {Upsilon}(4S) decays we measure a total rate of N{sub {Lambda}{sub c}}{sup {Upsilon}} = 0.091 {+-} 0.006(exp.) {+-} 0.024(BF) per {Upsilon}(4S) decay, and find a much softer momentum distribution than expected from B decays into a {Lambda}{sub c}{sup +} plus an antinucleon and one to three pions.
Date: September 7, 2006
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Vacuum, matter, antimatter and the problem of cold compression

Description: We discuss the possibility of producing a new kind of nuclear system by putting a few antibaryons inside ordinary nuclei. The structure of such systems is calculated within the relativistic mean-field model assuming that the nucleon and antinucleon potentials are related by the G-parity transformation. The presence of antinucleons leads to decreasing vector potential and increasing scalar potential for the nucleons. As a result, a strongly bound system of high density is formed. Due to the significant reduction of the available phase space the annihilation probability might be strongly suppressed in such systems.
Date: January 1, 2003
Creator: Greiner, Walter, & Buervenich, T. J. (Thomas J.)
Partner: UNT Libraries Government Documents Department

Antinucleus productions at RHIC

Description: Light antinuclei may be formed in relativistic heavy ion collisions via final state coalescence of antinucleons. The yields of antinuclei are sensitive to primordial antinucleon production, the volume of the system at kinetic freeze-out, and space-momentum correlations among antinucleons at freeze-out. We report here preliminary STAR results on {bar d} and {bar {sup 3}He} production in 130A GeV Au+Au collisions. These results are examined in a coalescence framework to elucidate the space-time structure of the antinucleon source.
Date: May 1, 2001
Creator: Hardtke, D. & Collaboration, STAR
Partner: UNT Libraries Government Documents Department

Interactions of Antiprotons in Hydrogen, Beryllium, and Carbon

Description: To determine the nature of the interactions between antinucleons and nucleons, it has been necessary to do an experiment in which the elastic, inelastic, and charge-exchange interactions could be measured. Improvements in the 6-Bev Bevatron have permitted production of a considerably larger flux of antiprotons, than was available in earlier studies. With the use of strong-focusing magnetic quadrupoles, a crossed electric- and magnetic-field spectrometer, and time-of-flight scintillation counters it has been possible to detect approximately 30 antiprotons per minute. By means of a system of 4{pi} solid-angle scintillation counters, it has been possible to measure these cross sections, including the angular distribution of elastic scattering. These cross sections have been measured for antiprotons scattered from hydrogen, beryllium, and carbon in the energy range from 133 to 333 Mev. Ball and Chew have assumed that pion exchange is responsible for the nucleon-nucleon interaction, and have used field theory to calculate the antinucleon-nucleon interaction. They have assumed that the pionic charge of the antinucleon is opposite that of the nucleon; thus, the exchange of an odd number of pions should change the sign of the potential. Outside the hard core, the exchange is assumed to be due to two pions, and the sign of the potential is not reversed for either the nucleon or the antinucleon case.
Date: March 1, 1960
Creator: Cork, Bruce
Partner: UNT Libraries Government Documents Department

The AGS complex as an antiproton filling station

Description: A transportable antiproton storage device to store and transport low energy antiprotons for use away from the production facility has been proposed previously. In this note the AGS complex is examined as a possible filling station for such a device. The production and collection rate of antiprotons is discussed, and a possible scenario is offered for the antiproton collection and deceleration cycle. (LEW)
Date: January 1, 1987
Creator: Lee, Y.Y. & Lowenstein, D.I.
Partner: UNT Libraries Government Documents Department

Looking for new gravitational forces with antiprotons

Description: Quite general arguments based on the principle of equivalence and modern field theory show that it is possible for the gravitational acceleration of antimatter to be different than that for matter. Further, there is no experimental evidence to rule out the possibility. In fact, some evidence indicates there may be unexpected effects. Thus, the planned experiment to measure the gravitational acceleration of antiprotons is of fundamental importance. 20 refs., 3 figs.
Date: January 1, 1987
Creator: Nieto, M.M. & Bonner, B.E.
Partner: UNT Libraries Government Documents Department

Experimental area plans for an advanced hadron facility

Description: A brief overview is presented of the current plans for an experimental area for a new advanced hadron facility for the exploration of nuclear and particle physics. The facility, LAMPF II, is presently visualized as consisting of the LAMPF linac sending 800 MeV protons to a 6 GeV booster ring followed by a 45 GeV main ring. Two experimental areas area planned. The first is intended to provide neutrinos via a pair of pulsed focusing horns. The other is designed to accommodate secondary beams that span the range of useful energies up to GeV/c. Beam specification goals are discussed with respect to source brightness, beam purity, and beam-line acceptance and length. The various beam lines are briefly described. Production cross sections and rates are estimated for antiproton production. Problems of thermal energy deposition in both components and targets and of effectiveness of particle separators are discussed. 9 refs. (LEW)
Date: January 1, 1986
Creator: Hoffman, E.W.; Macek, R.J. & Tschalear, C.
Partner: UNT Libraries Government Documents Department

Experiment to measure the gravitational force on the antiproton

Description: A collaboration has been formed to measure the acceleration of antiprotons in the earth's gravitational field. The technique is to produce, decelerate, and trap quantities of antiprotons, to cool them to untralow energy, and to measure their acceleration in a time-of-flight experiment. Present plans and the results of initial efforts toward this end are presented.
Date: January 1, 1985
Creator: Brown, R.E.
Partner: UNT Libraries Government Documents Department

Baryon production at PEP

Description: Measurements of inclusive ..lambda.. + anti ..lambda.. production for 1.0 less than or equal to p less than or equal to 10.0 GeV/c and p + anti p production for 0.4 less than or equal to p less than or equal to 2.0 GeV/c show significant baryon production in e/sup +/e/sup -/ annihilation at E/sub cm/ = 29 GeV. ..lambda.. + anti ..lambda.. production represents 0.2 ..lambda..'s or anti ..lambda..'s per PEP event while the observed p + anti p production implies all baryon-antibaryon pair production is occurring at least as often as 0.6 per event, depending on the yet to be measured p + anti p production at high momentum. Comparisons are made with the first theoretical attempts to account for baryon production at these energies.
Date: September 1, 1981
Creator: Goldhaber, G. & Weiss, J.M.
Partner: UNT Libraries Government Documents Department

Wake-riding electrons emitted by antiprotons traversing solid targets

Description: The dielectric response of the medium to a swift ion induces collective charge-density fluctuations which result in an oscillatory polarization potential trailing the ion ( wake''). The concept of such a wake'' dates back to Bohr. Meanwhile, a large number of investigations implementing approximations at various levels of sophistication have been performed. The plasmon-pole approximation is one of the simplest approximation which still accounts qualitatively for most of the features of the wake. Clearly, more subtle effects like bow waves and other dispersion effects are neglected. We will restrict ourselves in this paper to the plasmon-pole approximation including a phenomenological damping. We will neglect the effects of the self-wake which can affect the shape of the wake potential. 21 refs., 8 figs.
Date: January 1, 1989
Creator: Burgdorfer, J.; Wang, J. & Mueller, J. (Tennessee Univ., Knoxville, TN (USA). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Portable Pbars, traps that travel

Description: The advent of antiproton research utilizing relatively small scale storage devices for very large numbers of these particles opens the possibility of transporting these devices to a research site removed from the accelerator center that produced the antiprotons. Such a portable source of antiprotons could open many new areas of research and make antiprotons available to a new research community. At present antiprotons are available at energies down to 1 MeV. From a portable source these particles can be made available at energies ranging from several tens of kilovolts down to a few millielectron volts. These low energies are in the domain of interest to the atomic and condensed matter physicist. In addition such a source can be used as an injector for an accelerator which could increase the energy domain even further. Moreover, the availability of such a source at a university will open research with antiprotons to a broader range of students than possible at a centralized research facility. This report focuses on the use of ion traps, in particular cylindrical traps, for the antiproton storage device. These devices store the charged antiprotons in a combination of electric and magnet fields. At high enough density and low enough temperature the charged cloud will be susceptible to plasma instabilities. Present day ion trap work is just starting to explore this domain. Our assessment of feasibility is based on what could be done with present day technology and what future technology could achieve. We conclude our report with a radiation safety study that shows that about 10/sup 11/ antiprotons can be transported safely, however the federal guidelines for this transport must be reviewed in detail. More antiprotons than this will require special transportation arrangements. 28 refs., 8 figs.
Date: October 1, 1987
Creator: Howe, S.D.; Hynes, M.V. & Picklesimer, A.
Partner: UNT Libraries Government Documents Department

Early work at the Bevatron: a personal account

Description: Personal reminiscences of the author's work at the Bevatron in the 1950's are given. Setting up photographic emulsions and startup of the Bevatron are recalled. A brief account is given of the physics prior to the Bevatron, followed by the development of the machine and its use to study K mesons, theta and tau particles. The search for the antiproton is remembered. 16 refs., 6 figs. (LEW)
Date: December 1, 1985
Creator: Goldhaber, G.
Partner: UNT Libraries Government Documents Department

Particle production and targeting experience at the Brookhaven AGS

Description: Experience in production of secondary pions (neutrinos), kaons and antiprotons by 28.5 GeV/c protons incident on various target materials is given. The problems associated with various target materials with respect to target heating, physical degradation and in some cases, disintegration, are discussed. The effect of target length and production angle on secondary beam flux and optical quality will be illustrated by some incomplete but nonetheless informative data.
Date: January 1, 1986
Creator: Lazarus, D.M.
Partner: UNT Libraries Government Documents Department

Antimatter clusters from hadronizing quark-gluon plasma

Description: A realistic model is used for the phase transition between the color deconfining quark-gluon plasma phase and the color confining hadronic gas phase of nuclear matter to discuss the question how quarks and antiquarks hadronize in an expanding quark-gluon plasma. Particular attention is given to the problem associated with the latent heat and latent entropy set free in the hadronization process. Assuming a specific space-time scenario for the phase transition, relative abundances are computed for different hadronic particles and resonances produced during hadronization, showing that in particular antinucleons and light antinuclei are enhanced above their equilibrium abundances in a hadron gas of similar density and temperature. This enhancement is interpreted as a possible signature for the existence of a transient quark-gluon plasma phase in relativistic heavy-ion collisions which can complement the widely discussed strangeness signal. However, detailed dynamical studies of the hadronization process are necessary in order to definitevely settle questions about the quantitative yields. 21 refs., 8 figs.
Date: January 1, 1986
Creator: Heinz, U.
Partner: UNT Libraries Government Documents Department

Polarization of antiprotons by antiproton decay

Description: The production of polarized antiproton beams at Fermilab is briefly reviewed. Two types of high-energy anti p polarimeters are described - the Coulomb-nuclear polarimeter and the Primakoff-effect polarimeter. The production of 8.9 GeV/c polarized antiprotons before entering the Fermilab accumulator ring is then discussed. 5 refs., 6 figs. (LEW)
Date: January 1, 1985
Creator: Yokosawa, A.
Partner: UNT Libraries Government Documents Department

High energy polarized beams from hyperon decays

Description: The use of various ways to utilize lambda decays to obtain polarized beams of protons and antiprotons is emphasized. Examples described are the Fermilab polarized beam, now under construction, and the use of similar techniques at other energies. Beam transport, spin precession and reversal systems, and polarimeters are also discussed. 8 refs., 4 figs.
Date: January 1, 1986
Creator: Underwood, D.G.
Partner: UNT Libraries Government Documents Department