Effective Field Theory for Neutron-Deuteron Scattering: Higher Partial Waves

The phase shifts for the higher partial waves in the spin quartet and doublet channel of nd scattering are presented at next-to-leading and next-to-next-to-leading order in an effective field theory in which pions are integrated out. The results agree with both phase shift analyses and potential model calculations.Comment: 2 LaTeX2 pages with 8 eps figures, uses sprocl.sty (included), graphicx and epsfig. Abstract of a talk held at the Workshop "Chiral Dynamics 2000: Theory and Experiment," TJNAF (Newport News, USA), July 17-22, 2000; to be published in the Proceeding

Encoding and processing of sensory information in neuronal spike trains

Recently, a statistical signal-processing technique has allowed the information carried by single spike trains of sensory neurons on time-varying stimuli to be characterized quantitatively in a variety of preparations. In weakly electric fish, its application to first-order sensory neurons encoding electric field amplitude (P-receptor afferents) showed that they convey accurate information on temporal modulations in a behaviorally relevant frequency range (<80 Hz). At the next stage of the electrosensory pathway (the electrosensory lateral line lobe, ELL), the information sampled by first-order neurons is used to extract upstrokes and downstrokes in the amplitude modulation waveform. By using signal-detection techniques, we determined that these temporal features are explicitly represented by short spike bursts of second-order neurons (ELL pyramidal cells). Our results suggest that the biophysical mechanism underlying this computation is of dendritic origin. We also investigated the accuracy with which upstrokes and downstrokes are encoded across two of the three somatotopic body maps of the ELL (centromedial and lateral). Pyramidal cells of the centromedial map, in particular I-cells, encode up- and downstrokes more reliably than those of the lateral map. This result correlates well with the significance of these temporal features for a particular behavior (the jamming avoidance response) as assessed by lesion experiments of the centromedial map

Lepton Flavour Violating Z Decays in the MSSM

The possibility to observe lepton flavour violating Z decays in the GigaZ option of DESY's TESLA project consistently with present bounds from other processes is analyzed in the context of the minimal supersymmetric standard model. In particular, constraints on the slepton mass matrices from radiative lepton decays are updated and taken into account. Their correlation to the present measurement of the muon anomalous dipole moment is briefly discussed.Comment: 5 pages, 3 figures. Talk presented at the 6th International Symposium on Radiative Corrections RADCOR 2002, and the 6th Zeuthen Workshop on Elementary Particle Theory, Loops and Legs in Quantum Field Theory, Kloster Banz, Germany, 8-13 September, 2002. To appear in the proceeding

Bi-Maximal Neutrino Mixing in the MSSM with a Single Right-Handed Neutrino

We discuss neutrino masses in the framework of a minimal extension of the minimal supersymmetric standard model (MSSM) consisting of an additional single right-handed neutrino superfield $N$ with a heavy Majorana mass $M$, which induces a single light see-saw mass $m_{\nu_3}$ leaving two neutrinos massless at tree-level. This trivial extension to the MSSM may account for the atomospheric neutrino data via $\nu_{\mu}\to \nu_{\tau}$ oscillations by assuming a near maximal mixing angle $\theta_{23}\sim \pi/4$ and taking $\Delta m_{23}^2 \sim m_{\nu_3}^2 \sim 2.5\times 10^{-3} eV^2$. In order to account for the solar neutrino data we appeal to one-loop radiative corrections involving internal loops of SUSY particles, which we show can naturally generate an additional light neutrino mass $m_{\nu_{2}}\sim 10^{-5} eV$ again with near maximal mixing angle $\theta_{12}\sim \pi/4$. The resulting scheme corresponds to so-called ``bi-maximal'' neutrino mixing involving ``just-so'' solar oscillations.Comment: 18 pages, Latex. References to bi-maximal mixing fixe