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Operator analysis of L=1 baryon masses in large N{sub c} QCD

Description: The authors consider in detail the mass operator analysis for the nonstrange L=1 excited baryons in large N{sub c} QCD. They present a straightforward procedure for constructing the large N{sub c} baryon wavefunctions, and provide complete analytic expressions for the matrix elements of all the independent isosinglet mass operators. They discuss the relationship between the old-fashioned operator analyses based on nonrelativistic SU(6) symmetry and the modern large N{sub c} approach, which has a firmer theoretical foundation. They then suggest a possible dynamical interpretation for the subset of operators preferred strongly by the data.
Date: December 1, 1998
Creator: Carlson, Carl E.; Carone, Christopher D.; Goity, Jose L. & Lebed, Richard F.
Partner: UNT Libraries Government Documents Department

Phases of resonant amplitudes: {pi}N {Yields} {pi}{delta}

Description: The phases of resonant amplitudes in pi N yields pi DELTA are studied in a modified version of SU(6)w in which amplitudes involving different relative orbital angular momenta l are uncoupled from one another. This form of SU(6)/sub W/ is equivalent to one studied recently by Melosh, in which the set of selection rules for decays is extended to allow for more types of transition than in the original version of this symmetry. The predictions are compared with a recent preliminary analysis by Herndon et al. Even the extended (''l-broken'') version of SU(6)/sub W/ is found to disagree with the present experimental solution. If this solution persists, it constitutes the strongest present evidence against such a symmetry. (auth)
Date: May 23, 1973
Creator: Faiman, D. & Rosner, J.
Partner: UNT Libraries Government Documents Department

A meson exchange model for the YN interaction

Description: We present a new model for the hyperon-nucleon (Lambda N, Sigma N) interaction, derived within the meson exchange framework. The model incorporates the standard one boson exchange contributions of the lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) symmetry relations. In addition - as the main feature of the new model - the exchange of two correlated pions or kaons, both in the scalar-isoscalar (sigma) and vector-isovector (rho) channels, is included.
Date: September 1, 2001
Creator: Haidenbauer, J.; Melnitchouk, W. & Speth, J.
Partner: UNT Libraries Government Documents Department

Current quarks, constituent quarks, and symmetries of resonance decays

Description: The transformation between ''current'' quarks and ''constituent'' quarks recently suggested by Melosh is examined with respect to its predictions for pionic decays of resonances. It implies the use of SU(6)/sub W/ for classifying particle states but not for describing decay processes. lnstead, pion emission proceeds via DELTA L/sub z/ = 0, plus or minus 1, where L is the internal (''quark'') orbital angular momentum. This decay symmetry is called SU(6)/sub W/ (DELTA L/sub z/ = 0, plus or minus 1). It is proven equivalent for any decay A yields B + pi (where A, B are arbitrary qq-bar or qqq hadrons) to the /sup 3/P/sub 0/ quark-pair creation model for such decays, as formulated by Micu, Colglazier, Petersen and Rosner. The roles of final orbital angular momenta l and of SU(3) x SU(3) subgroups of SU(6)w are also discussed, and some new predictions are made for decays of meson resonances below 1700 MeV. (auth)
Date: April 18, 1973
Creator: Hey, A.J.G.; Rosner, J.L. & Weyers, J.
Partner: UNT Libraries Government Documents Department

Resonances in high-energy colliding lepton beams

Description: The search for the correct higher symmetry of decay vertices is discussed. It is noted that something higher than SU(3) is certainly valid and colliding lepton beams can help find what it is. SU(6(/sub W/ and its limitations, L = 1, 2 mesons, and the two-photon processes e/sup +/ + e/sup -/ yields e/sup +/ + e/sup -/ + hadrons, and e/sup -/ + e/sup -/ yields e/sup -/ + e/sup -/ + hadrons are considered. (JFP)
Date: March 13, 1973
Creator: Rosner, J.L.
Partner: UNT Libraries Government Documents Department

Old and new physics in nucleon spin structure

Description: EMC implies quarks carry very little of the proton spin. (G{sub A}/G{sub V}){sub n{yields}p} implies that valence quarks carry 70% of the spin, but disagrees with SU(6). (G{sub A}/G{sub V}){sub {Sigma}{minus}{yields}n} agrees strinkingly with SU(6). All semileptonic decay data can be fit by SU(3), but no model fits the data by breaking SU(6) without also breaking SU(3). Considerable data on hadron masses and magnetic moments are fit by a simple constituent quark model with only constituent quarks. A toy model for the proton with valence quarks and sea fits nearly everything.
Date: December 31, 1991
Creator: Lipkin, H. J.
Partner: UNT Libraries Government Documents Department

Old and new physics in nucleon spin structure

Description: EMC implies quarks carry very little of the proton spin. (G{sub A}/G{sub V}){sub n{yields}p} implies that valence quarks carry 70% of the spin, but disagrees with SU(6). (G{sub A}/G{sub V}){sub {Sigma}{minus}{yields}n} agrees strinkingly with SU(6). All semileptonic decay data can be fit by SU(3), but no model fits the data by breaking SU(6) without also breaking SU(3). Considerable data on hadron masses and magnetic moments are fit by a simple constituent quark model with only constituent quarks. A toy model for the proton with valence quarks and sea fits nearly everything.
Date: January 1, 1991
Creator: Lipkin, H.J. (Weizmann Inst. of Science, Rehovoth (Israel). Dept of Physics Washington Univ., Seattle, WA (United States). Inst. for Nuclear Theory)
Partner: UNT Libraries Government Documents Department

Group representation matrix and scattering from nuclei

Description: It is shown that the transition matrix for elastic and inelastic medium energy protons scattered from nuclei described by the interacting boson model is the SU/sub 6/ group representation matrix. Closed form expressions for this transition matrix are derived for the special cases of a vibrational nucleus, a ..gamma..-unstable rotor nucleus, and an axially symmetric rotor nucleus.
Date: January 1, 1985
Creator: Ginocchio, J.N.
Partner: UNT Libraries Government Documents Department

Basis for calculations in the topological expansion

Description: Investigations aimed at putting the topological theory of particles on a more quantitative basis are described. First, the incorporation of spin into the topological structure is discussed and shown to successfully reproduce the observed lowest mass hadron spectrum. The absence of parity-doubled states represents a significant improvement over previous efforts in similar directions. This theory is applied to the lowest order calculation of elementary hadron coupling constant ratios. SU(6)/sub W/ symmetry is maintained and extended via the notions of topological supersymmetry and universality. Finally, efforts to discover a perturbative basis for the topological expansion are described. This has led to the formulation of off-shell Feynman-like rules which provide a calculational scheme for the strong interaction components of the topological expansion once the zero-entropy connected parts are known. These rules are shown to imply a topological asymptotic freedom. Even though the nonlinear zero-entropy problem cannot itself be treated perturbatively, plausible general assumptions about zero-entropy amplitudes allow immediate qualitative inferences concerning physical hadrons. In particular, scenarios for mass splittings beyond the supersymmetric level are described.
Date: December 1, 1982
Creator: Levinson, M.A.
Partner: UNT Libraries Government Documents Department

Summary of the 8th international symposium on high energy spin physics

Description: The series of conferences on high energy spin physics dates back to Argonne, 1974, and the first use of the polarized proton beam at the ZGS. This conference is unique in that it is concerned both with the technology of spin and with particle physics: particle physicists need to know what experiments might be possible and target/beam/source physicists want to know what their work will lead to, and get new ideas. In many cases, and I believe that this is central to the success of spin physics and of this conference series, these are the same people. This summary will have three basic parts: where we are now relative to Argonne in 1974; a discussion of new experiments and theory---there were many new and intriguing results presented here; and new ideas for polarized sources, beams, and targets which point toward an exciting future program of particle physics. 13 refs., 2 figs., 4 tabs.
Date: January 1, 1988
Creator: Bunce, G.
Partner: UNT Libraries Government Documents Department

Spin models of the proton

Description: We have constructed a model of the proton spin based on a broken SU(6) parameterization for the spin-weighted valence quark distributions in a longitudinally polarized proton. The polarized sea and gluon distributions are assumed to have simple relations to the corresponding unpolarized structure functions. The sum rules, which involve the non-singlet components of the structure function xg/sub 1/, imply that the valence quarks carry about 78% of the proton spin, while the spin carried by sea quarks is negative. Recent EMC data suggest a model in which the sea quarks carry a large negative polarization, whereas certain theoretical arguments favor a model with a smaller negatively polarized sea. These models are discussed with reference to the sum rules. Experiments are suggested which will discriminate between these models. 24 refs., 4 figs.
Date: October 20, 1988
Creator: Ramsey, G.P.
Partner: UNT Libraries Government Documents Department

Skyrmions and vector mesons: a symmetric approach

Description: We propose an extension of the effective, low-energy chiral Lagrangian known as the Skyrme model, to one formulated by a non-linear sigma model generalized to include vector mesons in a symmetric way. The model is based on chiral SU(6) x SU(6) symmetry spontaneously broken to static SU(6). The rho and other vector mesons are dormant Goldstone bosons since they are in the same SU(6) multiplet as the pion and other pseudoscalars. Hence the manifold of our generalized non-linear sigma model is the coset space (SU(6) x SU(6))/Su(6). Relativistic effects, via a spin-dependent mass term, break the static SU(6) and give the vectors a mass. The model can then be fully relativistic and covariant. The lowest-lying Skyrmion in this model is the whole baryonic 56-plet, which splits into the octet and decuplet in the presence of relativistic SU(6)-breaking. Due to the built-in SU(6) and the presence of vector mesons, the model is expected to have better phenomenological results, as well as providing a conceptually more unified picture of mesons and baryons. 29 references.
Date: January 1, 1984
Creator: Caldi, D.G.
Partner: UNT Libraries Government Documents Department

High energy physics studies progress report. Part I. Experimental program. [Summaries of research activities at Ohio State University]

Description: The experimental program of research, including Assembly of an experiment at Fermilab E-351 to measure decay lifetimes, with tagged emulsion, of charmed particles produced by high energy neutrinos will continue. A data-taking run will take place in the coming fiscal year. Participation in the neutrino experiment E-310, Fermilab-Harvard-Pennsylvania-Rutgers-Wisconsin, will also continue. Data analysis from several experiments performed in the recent past at the ZGS ANL is in progress and will be pursued. These experiments are, E-397, E-420 and E-428 performed with the Charged and Neutral Spectrometer, and E-347 with the ..sigma../sub ..beta../ Spectrometer. Plans are in the making to collaborate with a polarized proton experiment at the ZGS. New approaches to ''third generation'' neutrino experiments at Fermilab are being discussed by the whole high energy group. Ideas of pursuing experiments at the AGS-BNL with the ..sigma../sub ..beta../ Spectrometer are explored. The theoretical research program covers topics of current interest in particle theory which will be investigated in the coming year; namely, the role of instantons in quantum chromodynamics, Higgs Lagrangian involving scalar fields, phenomenology of neutrino physics and in particular the nature of trimuon production, higher order symmetries like SU(3) x U(1) SU(5) and SU(6), dynamics of high energy diffractive scattering, classical solutions to the gauge field theories.
Date: January 1, 1977
Partner: UNT Libraries Government Documents Department

Pion-nucleon scattering and pion production in nucleon-nucleon and nucleus-nucleus collisions

Description: Lecture notes are presented on the following: (1) basic aspects of ..pi..N interactions (properties of pions and nucleons, SU(3) and SU(6) classification phenomenology of ..pi..N scattering ((3.3) resonance; phase shift analysis, and bag model approach to ..pi..N); (2) pion production and absorption in the two nucleon system (NN ..-->.. NN..pi.. (isobar model) and ..pi..d reversible NN (existence of dibaryon resonances)); (3) pion absorption in complex nuclei (multiparticle aspects and cascade calculations); and (4) pion production with nuclear targets including (a) nucleon-nucleus, (b) nucleus-nucleus (Fermi-averaged 2-body vs thermodynamic models), and (c) ..pi pi.. interoferometry.
Date: January 1, 1982
Creator: Dover, C.B.
Partner: UNT Libraries Government Documents Department