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Quark confinement and surface critical phenomena

Description: Surface critical phenomena and the related onset of Goldstone modes probe the fundamental properties of the confining flux in Quantum Chromodynamics. New ideas on surface roughening and their implications for lattice studies of quark confinement are presented. Problems with the oversimplified string description of the Wilson flux sheet are discussed.
Date: October 20, 1999
Creator: K.J. Juge, J. Kuti and C.J. Morningstar
Partner: UNT Libraries Government Documents Department

Crossover transition in bag-like models

Description: We formulate a simple model for a gas of extended hadrons at zero chemical potential by taking inspiration from the compressible bag model. We show that a crossover transition qualitatively similar to lattice QCD can be reproduced by such a system by including some appropriate additional dynamics. Under certain conditions, at high temperature, the system consist of a finite number of infinitely extended bags,which occupy the entire space. In this situation the system behaves as an ideal gas of quarks and gluons.
Date: March 13, 2009
Creator: Ferroni, Lorenzo & Koch, Volker
Partner: UNT Libraries Government Documents Department

Evidence for light scalar resonances in charm meson decays from Fermilab E791

Description: From Dalitz-plot analyses of D{sup +} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup +} and D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +} decays, we find evidence for light and broad scalar resonances {sigma}(500) and {kappa}(800). From a Dalitz-plot analysis of D{sub s}{sup +} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup +} decays, they measure the masses and decay widths of the scalar resonances f{sub 0}(980) and f{sub 0}(1370).
Date: January 24, 2003
Creator: Schwartz, Alan J.
Partner: UNT Libraries Government Documents Department

Search for eta b at CDF

Description: The {eta}{sub b} (1S) is the J{sup PC} = 0{sup {-+}} b{bar b} ground state, and has not yet been experimentally observed. Theorists have recently suggested that it could be observed at the Fermilab Tevatron through its decay to J/{psi}J/{psi}, if not in the 1992-96 (''Run 1'') dataset, then in Run 2. This article describes a search for this particle at CDF in Run 1 using this decay channel. A small cluster is seen, with 7 events where 1.8 events are expected from background. The statistical significance is estimated to be 2.2{sigma}, and an upper limit is set on the product of cross section and branching fractions.
Date: January 2, 2003
Creator: Tseng, J.
Partner: UNT Libraries Government Documents Department

Are partons confined tachyons?

Description: The author notes that if hadrons are gravitationally stabilized ``black holes``, as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v{sup 2} > c{sup 2}, without conflict with the observational fact that neither quarks nor tachyons have appeared as ``free particles``. Some consequences of this model are explored.
Date: March 1, 1996
Creator: Noyes, H.P.
Partner: UNT Libraries Government Documents Department

Thermal rho`s in the quark-gluon plasma

Description: I discuss different models which predict changes in the mass of the thermal {rho} field. I emphasize that while the predictions are strongly model dependent, nevertheless substantial shifts in the thermal {rho} mass are expected to occur at the point of phase transition. As long as the thermal {rho} peak does not become too broad, this should provide a striking signature of the existence of a phase transition.
Date: March 1, 1995
Creator: Pisarski, R.D.
Partner: UNT Libraries Government Documents Department

Mapping Quark Confinement by Exotic Particles

Description: According to our increasing understanding of quark physics, more kinds of particles should exist than are presently known. New experiments at the Jefferson Laboratory are setting out to search for these particles.
Date: September 1, 2000
Creator: Dzierba, Alex & Isgur, Nathan
Partner: UNT Libraries Government Documents Department

Confinement through a relativistic generalization of the linear interaction

Description: Generalizing a covariant framework previously developed, it is shown that confinement insures that meson {r_arrow} q + {anti q} decay amplitudes vanish when both quarks are on-shell. Regularization of singularities in a covariant linear potential associated with nonzero energy transfers (i.e. q{sup 2}=0, q{sup {mu}} {ne} 0) is improved.
Date: June 1, 1998
Creator: Savkli, Cetin & Gross, Franz
Partner: UNT Libraries Government Documents Department

Physics Prospects with the JLab 12-GeV upgrade

Description: Increasing the beam energy of the CEBAF accelerator to 12 GeV will greatly expand the physics opportunities to explore the nature of strongly interacting matter. The primary thrusts of the experimental program will include the study of quark confinement and the direct exploration of the quark-gluon structure of hadrons and nuclei in the valence-quark region.
Date: October 1, 2002
Creator: Smith, Elton
Partner: UNT Libraries Government Documents Department

Measurements of b to s gamma Decays at BaBar

Description: We present measurements of the Branching Fraction and photon energy spectrum in B {yields} X{sub S}{gamma} decays in a sample of 89 million B{bar B} pairs collected at the BABAR detector at Stanford Linear Accelerator Center's PEP-II asymmetric B-factory. Results from a fully-inclusive and a sum of 38 exclusive final states techniques are presented and found to be consistent with the Standard Model calculations, as well as experimental results obtained from semileptonic B {yields} X{sub c}lv decays.
Date: July 5, 2007
Creator: Piatenko, T. & /Caltech
Partner: UNT Libraries Government Documents Department

Charmonium correlators and spectral functions at finite temperature

Description: We present an operational approach to address the in-medium behavior of charmonium and analyze the reliability of maximum entropy method (MEM). We study the dependences of the ratio of correlators to the reconstructed one and the free one on the resonance's width and the continuum's threshold. Furthermore, we discuss the issue of the default model dependence of the spectral function obtained from MEM.
Date: September 1, 2008
Creator: Ding,H.T.; Kaczmarek, O.; Karsch, F. & Satz, H.
Partner: UNT Libraries Government Documents Department

The transverse momentum dependent distribution functions in the bag model

Description: Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.
Date: January 29, 2010
Creator: Avakian, Harut; Efremov, Anatoly; Schweitzer, Peter & Yuan, Feng
Partner: UNT Libraries Government Documents Department

Deconfinement and hadron properties at extremes of temperature and density

Description: After introducing essential, qualitative concepts and results, the authors discuss the application of Dyson-Schwinger equations to QCD at finite T and {mu}. They summarize the calculation of the critical exponents of two-light-flavor QCD using the chiral and thermal susceptibilities; and an algebraic model that elucidates the origin of an anticorrelation between the {mu}- and T-dependence of a range of meson properties. That model also provides an algebraic understanding of why the finite-T behavior of bulk thermodynamic properties is mirrored in their {mu}-dependence, and why meson masses decrease with {mu} even though f{sub {pi}} and {minus}<{anti q}q> increase. The possibility of diquark condensation is canvassed. Its realization is uncertain because it is contingent upon an assumption abut the quark-quark scattering kernel that is demonstrably false in some applications; e.g., it predicts the existence of colored diquarks in the strong interaction spectrum, which are not observed.
Date: August 1, 1998
Creator: Blaschke, D. & Roberts, C.D.
Partner: UNT Libraries Government Documents Department

Spin-orbit inversion of excited heavy quark mesons

Description: The mesonic heavy quark spin multiplets with s{sub l}{sup {pi}{sub l}}=(1/2){sup +} and (3/2){sup +} are expected to be the lowest-lying excitations about the pseudoscalar and vector ground states with s{sub l}{sup {pi}{sub l}}=(1/2){sup {minus}}. The author shows that for charm and bottom these multiplets are probably inverted, with the 2{sup +} and 1{sup +} states with s{sub l}{sup {pi}{sup l}}=(3/2){sup +} about 150 MeV below the 1{sup +} and 0{sup +} states with s{sub l}{sup {pi}{sub l}}=(1/2){sup +}. If verified, such an inversion would both support the expectation that confinement has no dynamical spin-dependence and indicate that heavy and light quark systems may be characterized by the same effective low-energy degrees of freedom. As an important byproduct, this work establishes the dynamics of the strange quark as a critical link between heavy- and light-quark hadrons, justifying efforts toward a much more complete experimental and theoretical understanding of strange mesons and baryons and of strangeonia.
Date: June 1, 1997
Creator: Isgur, Nathan
Partner: UNT Libraries Government Documents Department

Temperature, chemical potential and the {rho}-meson

Description: Models of QCD must confront nonperturbative phenomena such as confinement, dynamical chiral symmetry breaking (DCSB) and the formation of bound states. In addition, a unified approach should describe the deconfinement and chiral symmetry restoring phase transition exhibited by strongly-interacting matter under extreme conditions of temperature and density. Nonperturbative Dyson-Schwinger equation (DSE) models provide insight into a wide range of zero temperature hadronic phenomena; e.g., non-hadronic electroweak interactions of light- and heavy-mesons, and diverse meson-meson and meson-nucleon form factors. This is the foundation for their application at nonzero-(T, {mu}). Herein the authors describe the calculation of the reconfinement and chiral symmetry restoring phase boundary, and the medium dependence of {rho}-meson properties. They also introduce an extension to describe the time-evolution in the plasma of the quark's scalar and vector self energies based on a Vlasov equation.
Date: February 17, 2000
Creator: Roberts, C. D. & Schmidt, S. M.
Partner: UNT Libraries Government Documents Department

From surface roughening to QCD string theory

Description: Surface critical phenomena and the related onset of Goldstone modes represent fundamental properties of the confining flux in Quantum Chromodynamics. New ideas on surface roughening and their implications for lattice studies of quark confinement and string formation are presented. Problems with a simple string description of the large Wilson surface are discussed.
Date: May 23, 2001
Creator: al., Keisuke Jimmy Juge et
Partner: UNT Libraries Government Documents Department


Description: The authors discuss transverse polarization distribution and fragmentation functions, in particular, T-odd functions with transverse momentum dependence, which might be relevant for the description of single transverse spin asymmetries. The role of intrinsic transverse momentum in the expansion in inverse powers of the hard scale is elaborated upon. The sin {phi} single spin asymmetry in the process e {rvec p} {r_arrow} e{prime} {pi}{sup +} X as recently reported by the HERMES Collaboration is investigated, in particular, by using the bag model.
Date: April 11, 2000
Creator: BOER,D.
Partner: UNT Libraries Government Documents Department

Nonperturbative QCD with modern tools

Description: In these lectures the author introduces and explores a range of topics of contemporary interest in hadronic physics: from what drives the formation of a nonzero quark condensate to the effect that mechanism has on light and heavy meson form factors and the properties of the quark-gluon plasma. The trail leads naturally through a discussion of confinement, dynamical chiral symmetry breaking and bound state structure: phenomena that require nonperturbative methods for their explanation. In all of this, the necessary and necessarily momentum-dependent modification of the quark and gluon propagators plays a significant role.
Date: July 1, 1998
Creator: Roberts, C.D.
Partner: UNT Libraries Government Documents Department

The nucleon-nucleon potential in the chromodielectric soliton model

Description: The short- and medium-range parts of the nucleon-nucleon interaction are being studied in the framework of the chromodielectric soliton model. The model consists of current quarks, gluons in the abelian approximation, and a scalar {sigma} field which simulates the nonabelian interactions of the gluons and governs the medium through the dielectric function {kappa}({sigma}). Absolute color confinement is effected by the vanishing of the dielectric in vacuum; this also removes the troublesome van der Waals problem. The authors distinguish between spatial confinement, which arises from the self energy of the quarks in medium (excluding MFA contributions), and color confinement which is effected through OGE in the MFA (including the corresponding self energy contributions). The static (adiabatic) energies are computed as a function of deformation (generalized bag separation) in a constrained MFA. Six quark molecular-type wave functions in all important space-spin-isospin-color configurations are included. The gluon propagator is solved in the deformed dielectric medium. The resultant Hamiltonian matrix is diagonalized. Dynamics are handled in the Generator Coordinate Method, which leads to the Hill-Wheeler integral equation. In the present case, this yields a set of coupled equations corresponding to the various configurations. Although this can be approximated by a set of differential equations, they propose to solve the integral equations with some regularization scheme.
Date: December 31, 1993
Creator: Koepf, W.; Wilets, L.; Pepin, S. & Stancu, F.
Partner: UNT Libraries Government Documents Department

Upgrading CEBAF to 12 GeV

Description: The Thomas Jefferson National Accelerator Facility (TJNAF) is proposing to upgrade its {approx}6 GeV cw electron accelerator (CEBAF) to 12 GeV with the purpose of extending its reach in exploring the nature hadronic matter, including the explanation for quark confinement. A plan has been developed that carefully balances cost and risk. TJNAF plans to do the upgrade without change to most of the accelerator components. The core of the upgrade is the addition of ten new 100 MV cryomodules and their supporting rf and cryogenics systems. A new experimental hall, devoted to the quark confinement investigation, will be placed so that the beam transits one of the linacs 6 times (vs 5 times for the other linac). Upgrades to the beam transport system will be required. No new developments in beam diagnostics appear to be required. Beam emittances are degraded by synchrotron radiation but meet the needs of the research program. This paper discusses the issues listed above plus requirements for all systems and developmental opportunities presented by the project.
Date: August 1, 2002
Creator: Harwood, Leigh
Partner: UNT Libraries Government Documents Department