13 research outputs found

    Higher Twist Effects in Deep Inelastic Scattering on Nuclei

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    Particle production in deep inelastic scattering on nuclei is reduced due to absorption of the produced particles in the nucleus. The photon ejects a quark from a bound nucleon which propagates through the nucleus forming a prehadron before turning into a hadron. We calculate the higher twist effect in hadronization which dominates the z1z \to 1 region of fragmentation.Comment: Based on a talk given by H.J. Pirner at the Fifth International Conference on Perspectives in Hadronic Physics, Trieste, May 200

    Vacuum Expectation Value of a Wegner-Wilson Loop near the Light Cone

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    Vacuum expectation values for one Wegner-Wilson loop representing a moving quark-antiquark pair are calculated in four-dimensional Euclidean and Minkowski space-time. The calculation uses gluon field strength correlators with perturbative gluon exchange and non-perturbative correlations from the stochastic vacuum model. The expectation value of a Wegner-Wilson loop forming a hyperbolic angle in Minkowski space-time is connected by an analytical continuation to the expectation value of the Wegner-Wilson loop in Euclidean four-space. The obtained result shows how confinement enters into the light-cone Hamiltonian for valence quarks independently of the chosen model.Comment: 12 pages, 2 figures, sections 2 and 3 shortened, more details added in section

    Linking the Quark Meson Model with QCD at High Temperature

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    We model the transition of a system of quarks and gluons at high energies to a system of quarks and mesons at low energies in a consistent renormalization group approach. Flow equations interpolate between the physics of the high-temperature degrees of freedom and the low-temperature dynamics at a scale of 1 GeV. We also discuss the dependence of the equation of state on baryon density and compare our results with recent lattice gauge simulations.Comment: 11 pages, 4 figures additional discussion of the second order phase transitio

    Critical Correlations of Wilson Lines in SU(3) and the High Energy γp\gamma^*p Cross Section

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    We discuss deep inelastic scattering at high energies as a critical phenomenon in 2+1 space - time dimensions. In the limit of Bjorken x0x \to 0, QCDQCD SU(3) with quark fields becomes a critical theory with a diverging correlation length ξ(x)x12λ2\xi(x) \propto x^{-\frac{1}{2 \lambda_2}} where the exponent λ2=2.52\lambda_2=2.52 is obtained from the center group Z(3) of SU(3). We conjecture that the dipole wave function of the virtual photon for transverse sizes 1/Q<x<ξ1/Q<x_{\bot}<\xi obeys correlation scaling Ψ(x)(1+n)\Psi \propto (x_{\bot})^{-(1+n)} before exponentially decaying for distances larger than the correlation length. Using this behavior combined with different xx -independent dipole proton cross sections we calculate the proton structure function and compare with the experimental data. We take the good agreement with the measured proton structure function F2(x,Q2)_2(x,Q^2) as an indication that at high energies dimensional reduction to an effective three dimensional theory with a critical point occurs.Comment: 21 pages, 3 figure

    The Spectrum of the Dirac Operator in the Linear Sigma Model with Quarks

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    We derive the spectrum of the Dirac operator for the linear sigma-model with quarks in the large N_c approximation using renormalization group flow equations. For small eigenvalues, the Banks-Casher relation and the vanishing linear term are recovered. We calculate the coefficient of the next to leading term and investigate the spectrum beyond the low energy regime.Comment: 15 pages, 6 figures, to appear in Phys. Rev.
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