The Neutrinoless Double Beta Decay, Physics beyond the Standard Model and the Neutrino Mass

The Neutrinoless double beta Decay allows to determine the effectice Majorana electron neutrino mass. For this the following conditions have to be satisfied: (i) The neutrino must be a Majorana particle, i. e. identical to the antiparticle. (ii) The half life has to be measured. (iii)The transition matrix element must be reliably calculated. (iv) The leading mechanism must be the light Majorana neutrino exchange. The present contribution studies the accuracy with which one can calculate by different methods: (1) Quasi-Particle Random Phase Approach (QRPA), (2) the Shell Model (SM), (3) the (before the variation) angular momentum projected Hartree-Fock-Bogoliubov method (PHFB)and the (4) Interacting Boson Approach (IBA). In the second part we investigate how to determine experimentally the leading mechanism for the Neutrinoless Double Beta Decay. Is it (a) the light Majorana neutrino exchange as one assumes to determine the effective Majorana neutrino mass, ist it the heavy left (b) or right handed (c) Majorana neutrino exchange allowed by left-right symmetric Grand Unified Theories (GUT's). Is it a mechanism due to Supersymmetry e.g. with gluino exchange and R-parity and lepton number violating terms. At the end we assume, that Klapdor et al. have indeed measured the Neutrinoless Double Beta Decay(, although contested,)and that the light Majorana neutrino exchange is the leading mechanism. With our matrix elements we obtain then an effective Majorana neutrino mass of: = 0.24 [eV], exp (pm) 0.02; theor. (pm) 0.01 [eV]Comment: 13 pages, 5 figure

Perspectives of Nuclear Physics

The organizers of this meeting have asked me to present perspectives of nuclear physics. This means to identify the areas where nuclear physics will be expanding in the next future. In six chapters a short overview of these areas will be given, where I expect that nuclear physics willdevelop quite fast: A. Quantum Chromodynamics and effective field theories in the confinement region; B. Nuclear structure at the limits; C. High energy heavy ion collisions; D. Nuclear astrophysics; E. Neutrino physics; F. Test of physics beyond the standard model by rare processes. After a survey over these six points I will pick out a few topics where I will go more in details. There is no time to give for all six points detailed examples. I shall discuss the following examples of the six topics mentionned above: 1. The perturbative chiral quark model and the nucleon $\Sigma$-term, 2. VAMPIR (Variation After Mean field Projection In Realistic model spaces and with realistic forces) as an example of the nuclear structure renaissance, 3. Measurement of important astrophysical nuclear reactions in the Gamow peak, 4. The solar neutrino problem. As examples for testing new physics beyond the standard model by rare processes I had prepared to speak about the measurement of the electric neutron dipole moment and of the neutrinoless double beta decay. But the time is limited and so I have to skip these points, although they are extremely interesting.Comment: 27 pages. Invited talk given at the ``IX Cortona meeting on problems in theoretical nuclear physics", Cortona, Italy, October 9-12, 200

K^+ production in p-C-collisions at a beam energy 1.2 GeV

The isobar model and the resonance model are applied for the first analysis of the subthreshold $K^+$-meson production in proton-carbon collisions, which was perfomed at GSI at an emission angle of 40 degrees and a bombarding energy of 1.2 GeV. In this study, we focus on the role of the secondary processes $\pi N \to K^+ Y$ in normal nuclear matter density. It turns out that the present approach can reproduce very well both the $\pi^+$- and $K^+$- meson spectra. It is also demonstrated that the different kinds of descriptions for the $\pi N \to K^+ \Lambda$ reactions substantially differentiate the calculated results for the $p A \to K^+ X$ differential cross sections.Comment: Latex 6 pages with 4 figures (eps file

Delta excitation in antiproton-deutron annihilation

The $\Delta$-excitation in $\overline{p}d$ annihilation at rest was studied. The annihilation amplitude from the statistical model and the $\pi N$ amplitude from the resonance model were adopted in our calculations. We analyze the invariant mass of the $\pi^+p$ and $\pi^-p$ systems selecting the protons with momenta above 400 MeV/c and with respect to the different final reaction channels. Our model reproduces reasonably the experimental data.Comment: 13 pages including 7 figures. Latex file. The uuencoded ps files for the figures are added. To be published in Z. Phys.