88 Matching Results

Search Results

Advanced search parameters have been applied.


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

Antimatter gravity experiment

Description: An experiment is being developed to measure the acceleration of the antiproton in the gravitational field of the earth. Antiprotons of a few MeV from the LEAR facility at CERN will be slowed, captured, cooled to a temperature of about 10 K, and subsequently launched a few at a time into a drift tube where the effect of gravity on their motion will be determined by a time-of-flight method. Development of the experiment is proceeding at Los Alamos using normal matter. The fabrication of a drift tube that will produce a region of space in which gravity is the dominant force on moving ions is of major difficulty. This involves a study of methods of minimizing the electric fields produced by spatially varying work functions on conducting surfaces. Progress in a number of areas is described, with stress on the drift-tube development.
Date: January 1, 1990
Creator: Brown, R.E.; Camp, J.B. & Darling, T.W.
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

Gordon Conference on Nuclear Research

Description: Session topics were: quarks and nuclear physics; anomalons and anti-protons; the independent particle structure of nuclei; relativistic descriptions of nuclear structure and scattering; nuclear structure at high excitation; advances in nuclear astrophysics; properties of nuclear material; the earliest moments of the universe; and pions and spin excitations in nuclei.
Date: September 1, 1983
Creator: Austin, S.M.
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

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

Microwave stability limits for the main ring and growth across transition

Description: The purpose of this paper is to estimate the phase space blowup across transition and give critical absolute value of Z/n limits at each stage of performance. It turns out that the most stringent limit is absolute value of Z/n approx.1.3 ..cap omega.. which occurs during the RF manipulation of the proton bunches at 120 GeV in preparation of anti p production.
Date: January 1, 1986
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Raising the acceptance of the AP2-line

Description: The 120 GeV Main Ring proton beam collides with the target at the end of the AP-1 line and creates antiprotons and other secondary particles. The AP-2 line transfers the negative particles from the target to the Debuncher. To provide a bigger antiproton stack size in the Accumulator, both the Debuncher as well as the AP-2 line acceptance have to be raised. This is a proposal for the improvement of the AP-2 line acceptance. The first part of the memo presents an acceptance examination of the existing AP-2 line by computer simulation, while the second presents a short proposal for aperture corrections. The computer program TURTLE was used to trace antiprotons through the AP-2 line without taking into account other negative charged particles. Betatron functions were obtained from the output of the SYNCH computer program. The SYNCH program was also used to check the dispersion match between the AP-2 line and the Debuncher. 3 refs., 6 figs., 5 tabs.
Date: April 5, 1989
Creator: Trbojevic, D.
Partner: UNT Libraries Government Documents Department

Accelerator Technology Program. Status report, April-September 1985

Description: This report presents highlights of major projects in the Accelerator Technology (AT) Division of the Los Alamos National Laboratory. Radio-frequency and microwave technology are dealt with. The p-bar gravity experiment, accelerator theory and simulation activities, the Proton Storage Ring, and the Fusion Materials Irradiation Test accelerator are discussed. Activities on the proposed LAMPF II accelerator, the BEAR (Beam Experiment Aboard Rocket) project, beam dynamics, the National Bureau of Standards racetrack microtron, and the University of Illinois racetrack microtron are covered. Papers published by AT-Division personnel during this reporting period are listed.
Date: September 1, 1986
Creator: Jameson, R.A. & Schriber, S.O. (comps.)
Partner: UNT Libraries Government Documents Department