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Heavy quark symmetries and the decays baryon antibaryon

Description: We enumerate the form factors necessary to describe the two-body baryonic decays of B mesons.We use the symmetries of the heavy quark effective theory to arrive at some relations among these form factors, when at least one of the daughter baryons is heavy.
Date: October 1, 1991
Creator: Roberts, Winston; Roberts, Winston & Ryzak, Z.
Partner: UNT Libraries Government Documents Department

Antibaryon production in AU+AU collisions at the AGS.

Description: Experiment E917 at the Brookhaven AGS has made a measurement of near-mid-rapidity antibaryon production in both the antiproton and antilambda channel. Results on dN/dy and inverse slope parameters are shown. A preliminary measurement of the ratio {bar {Lambda}}/{bar p} is also presented.
Date: July 2, 1999
Creator: Back, B. B.; Betts, R. R.; Chang, J.; Chang, W. C.; Chi, C. Y.; Collaboration, E917 et al.
Partner: UNT Libraries Government Documents Department

Results from experiment E917 for Au + Au collisions at the AGS.

Description: The effects of baryon stopping and its resulting energy deposition on the dynamics of Au + Au collisions at 6, 8 and 10.8 GeV/nucleon are explored with recent results from the AGS experiment E917. Current analyses of stopping, collective flow signals and HBT parameters are presented. Strangeness and anti-baryon production is examined using the yields of anti-lambdas and anti-protons.
Date: August 4, 1999
Creator: Back, B. B.; Betts, R. R.; Chang, J.; Chang, W. C.; Collaboration, E917; Gillitzer, A. et al.
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

Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR

Description: Identified charged particle spectra of {pi}{sup {+-}}, K{sup {+-}}, p and {bar p} at mid-rapidity (|y| < 0.1) measured by the dE/dx method in the STAR-TPC are reported for pp and d + Au collisions at {radical}s{sub NN} = 200 GeV and for Au + Au collisions at 62.4 GeV, 130 GeV, and 200 GeV. Average transverse momenta, total particle production, particle yield ratios, strangeness and baryon production rates are investigated as a function of the collision system and centrality. The transverse momentum spectra are found to be flatter for heavy particles than for light particles in all collision systems; the effect is more prominent for more central collisions. The extracted average transverse momentum of each particle species follows a trend determined by the total charged particle multiplicity density. The Bjorken energy density estimate is at least several GeV/fm{sub 3} for a formation time less than 1 fm/c. A significantly larger net-baryon density and a stronger increase of the net-baryon density with centrality are found in Au + Au collisions at 62.4 GeV than at the two higher energies. Antibaryon production relative to total particle multiplicity is found to be constant over centrality, but increases with the collision energy. Strangeness production relative to total particle multiplicity is similar at the three measured RHIC energies. Relative strangeness production increases quickly with centrality in peripheral Au + Au collisions, to a value about 50% above the pp value, and remains rather constant in more central collisions. Bulk freeze-out properties are extracted from thermal equilibrium model and hydrodynamics-motivated blast-wave model fits to the data. Resonance decays are found to have little effect on the extracted kinetic freeze-out parameters due to the transverse momentum range of our measurements. The extracted chemical freeze-out temperature is constant, independent of collision system or centrality; its value is ...
Date: April 11, 2009
Creator: Coll, STAR
Partner: UNT Libraries Government Documents Department

Measurement of Branching Fractions and CP-ViolatingCharge Asymmetries for B Meson Decays to D(*)D(*), and Implications for the CKMAngle gamma

Description: In summary, the authors have measured branching fractions, upper limits, and charge asymmetries for all B meson decays to D{sup (*)} {bar D}{sup (*)}.
Date: July 6, 2006
Creator: Aubert, B.; Barate, R.; Bona, M.; Boutigny, D.; Couderc, F.; Karyotakis, Y. et al.
Partner: UNT Libraries Government Documents Department

Study of B-Meson Decays to Final States with a Single Charm Baryon

Description: A study of B-meson decays to final states with a single charm baryon is presented based on data recorded by the BABAR detector at the Stanford Linear Accelerator Center. Although the B meson is the lightest bottom-flavored meson, it is heavy enough to decay to a baryon made of three quarks and an antibaryon made of three antiquarks. By studying the baryonic weak decays of the B meson, we can investigate baryon production mechanisms in heavy meson decays. In particular, we measure the rates of the decays B{sup -} {yields} {Lambda}{sub c}{sup +}{bar p}{pi}{sup -} and {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +}{bar p}. Comparing these rates, we confirm an observed trend in baryonic B decays that the decay with the lower energy release, B{sup -} {yields} {Lambda}{sub c}{sup +}{bar p}{pi}{sup -}, is favored over {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +}{bar p}. The dynamics of the baryon-antibaryon ({Lambda}{sub c}{sup +}{bar p}) system in the three-body decay also provide insight into baryon-antibaryon production mechanisms. The B{sup -} {yields} {Lambda}{sub c}{sup +}{bar p}{pi}{sup -} system is a laboratory for searches for excited {Sigma}{sub c} baryon states; we observe the resonant decays B{sup -} {yields} {Sigma}{sub c}(2455){sup 0}{bar p} and B{sup -} {yields} {Sigma}{sub c}(2800){sup 0}{bar p}. This is the first observation of the decay B{sup -} {yields} {Sigma}{sub c}(2800){sup 0}{bar p}; however, the mass of the observed {Sigma}{sub c}(2800){sup 0} state is inconsistent with previous measurements. Finally, we examine the angular distribution of the B{sup -} {yields} {Sigma}{sub c}(2455){sup 0}{bar p} decays and measure the spin of the {Sigma}{sub c}(2455){sup 0} baryon to be J = 1/2, as predicted by the quark model.
Date: June 2, 2009
Creator: Majewski, Stephanie A.
Partner: UNT Libraries Government Documents Department

Can antibaryons signal the formation of a quark-gluon plasma

Description: We report on recent work which indicates that an enhancement of antibaryons produced in the hadronization phase transition can signal the existence of a transient quark-gluon plasma phase formed in a heavy-ion collision. The basis of the enhancement mechanism is the realization that antiquark densities are typically a factor 3 higher in the quark-gluon plasma phase than in hadronic matter at the same temperature and baryon density. The signal is improved by studying larger clusters of antimatter, i.e., light antinuclei like anti ..cap alpha.., in the central rapidity region. The effects of the transition dynamics and of the first order nature of the phase transition on the hadronization process are discussed.
Date: January 1, 1985
Creator: Heinz, U.; Subramanian, P.R. & Greiner, W.
Partner: UNT Libraries Government Documents Department

Search for. lambda. anti. lambda. heavy states at ISA

Description: The possibility of observing ..lambda..anti..lambda.. heavy states using the Isabelle storage rings is discussed. Not many particles are known to date to decay into ..lambda..anti..lambda... The J/psi is a notable exception, with a branching ratio of about 0.2% (vs. 7% into e/sup +/e/sup -/ and ..mu../sup +/..mu../sup -/). However, it is not inconceivable that higher mass states, produced at Isabelle energies, will have substantial branching fractions into ..lambda..anti..lambda... If this will indeed be the case, then one may think of getting additional information on the properties of the new states by taking advantage of the parity-violating ..lambda.. and anti..lambda.. decays. Detectors, rate and background considerations, and methods of particle detection are discussed.
Date: January 1, 1977
Creator: Flaminio, V.; Lesnik, A. & Rehak, P.
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

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

Phase transitions in nuclear matter

Description: The rather general circumstances under which a phase transition in hadronic matter at finite temperature to an abnormal phase in which baryon effective masses become small and in which copious baryon-antibaryon pairs appear is emphasized. A preview is also given of a soliton model of dense matter, in which at a density of about seven times nuclear density, matter ceases to be a color insulator and becomes increasingly color conducting. 22 references.
Date: November 1, 1984
Creator: Glendenning, N.K.
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 1983
Creator: Austin, S. M.
Partner: UNT Libraries Government Documents Department

Threshold effects and oscillations in models with t-channel factorization

Description: From meeting of the division of particles and fields; Berkeley, California USA (13 Aug 1973). Threshold effects and oscillating cross sections are reviewed in the context of models (such as the multiperipheral) which employ factorization and indefinite repetition in the t-channel. The origin of logarithmic energy thresholds is illustrated by the ABFST model and applied to antibaryon production and rising cross sections at high energy. Then one discusses large-mass diffraction dissociation and it is argued that this process is not responsible for the increase in the p-p total cross section at ISR energies. (auth)
Date: September 26, 1973
Creator: Koplik, J.
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