Towards the Theory of Diffractive DIS

The large rapidity gap events, observed at HERA, have changed considerably our physical picture of deep inelastic scattering during the past years. We review the present theoretical understanding of diffractive DIS with emphasis on the close relation to inclusive DIS. This includes success and limitations of the leading twist description, the connection between diffractive and inclusive parton distributions in the semiclassical approach, the colour structure of the proton and comparison with data. The progress report concludes with a list of open questions.Comment: 19 pages, 8 figures; presented at `New Trends in HERA Physics', Ringberg Workshop, June 199

Combined analysis of diffractive and inclusive structure functions in the semiclassical framework

Small-x DIS is described as the scattering of a partonic fluctuation of the photon off a superposition of target color fields. Diffraction occurs if the emerging partonic state is in a color singlet. Introducing a specific model for the averaging over all relevant color field configurations, both diffractive and inclusive parton distributions at some low scale Q_0^2 can be calculated. A conventional DGLAP analysis results in a good description of diffractive and inclusive structure functions at higher values of Q^2.Comment: 3 pages LaTeX, 3 figures, talk presented at the 7th International Workshop on Deep Inelastic Scattering and QCD (DIS99), Zeuthen, Germany, April 19-23, 199

Quark Lepton Mass Hierarchies and the Baryon Asymmetry

The mass hierarchies of quarks and charged leptons as well as a large \n_\m-\n_\t mixing angle are naturally explained by the Frogatt-Nielsen mechanism with a nonparallel family structure of chiral charges. We extend this mechanism to right-handed neutrinos. Their out-of-equilibrium decay generates a cosmological baryon asymmetry whose size is quantized in powers of the hierarchy parameter \e^2. For the simplest hierarchy pattern the neutrino mass \bar{m}_\n= (m_{\n_\m}m_{\n_\t})^{1/2} \sim 10^{-2} eV, which is inferred from present indications for neutrino oscillations, implies a baryon asymmetry $n_B/s \sim 10^{-10}$. The corresponding baryogenesis temperature is $T_B \sim 10^{10}$ GeV.Comment: 7 page

Neutrino masses and the baryon asymmetry

Due to sphaleron processes in the high-temperature symmetric phase of the standard model the cosmological baryon asymmetry is related to neutrino properties. For hierarchical neutrino masses, with $B-L$ broken at the unification scale $\Lambda_{GUT}\sim 10^{16}$GeV, the observed baryon asymmetry $n_B/s \sim 10^{-10}$ can be naturally explained by the decay of heavy Majorana neutrinos. We illustrate this mechanism with two models of neutrino masses, consistent with the solar and atmospheric neutrino anomalies, which are based on the two symmetry groups $SU(5)\times U(1)_F$ and $SU(3)_c\times SU(3)_L\times SU(3)_R\times U(1)_F$. We also review related cosmological bounds on Majorana neutrino masses and the use of Boltzmann equations.Comment: 45 pages, 12 figure

High-p⊥p_\perp Jets in Diffractive Electroproduction

The diffractive production of high-$p_{\perp}$ jets in deep-inelastic scattering is studied in the semiclassical approach. The $p_{\perp}$-spectra of $q {\bar q}$ and $q {\bar q} g$ diffractive final states are found to be qualitatively different. For $q {\bar q}$ final states, which are produced by `hard' colour-singlet exchange, the $p_{\perp}$-spectrum is much softer than for $q {\bar q} g$ final states, where the colour neutralization is `soft'. Furthermore, the two different final states can be clearly distinguished by their diffractive mass distributions.Comment: 9 pages, latex, 5 figure

Quantum mechanics of baryogenesis

The cosmological baryon asymmetry can be explained as remnant of heavy Majorana neutrino decays in the early universe. We study this out-of-equilibrium process by means of Kadanoff-Baym equations which are solved in a perturbative expansion. To leading order the problem is reduced to solving a set of Boltzmann equations for distribution functions.Comment: 12 pages, 2 figures, typos corrected. To be published in Physics Letter