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Search Results: 1 - 10 of 84434 matches for " W. Tornow "
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Brief Note on a Scalar Quantum Field with Finite Lifetime in a Lorentz Invariant Non-Rectangular Euclidean Space  [PDF]
Carmen Tornow
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.514135

A not necessary rectangular Euclidean space (NoNRES) is constructed, in which one obtains a generally Lorentz invariant scalar product for the low energy sector (LES). This sector is defined for energies below the Planckian limit. If the energy is zero, the NoNRES becomes rectangular and due to the Lorentz invariance, it is applicable for the complete LES of the theory. In contrast to the usual Minkowski space the metric of the NoNRES depends on the kinetic energy of the observed quantum particles. It is assumed that this metric may be useful to derive the scattering cross-section of the corresponding quantum field theory. This assumption is related to the occurrence of divergent loop momentum integrals caused by including the infinite energy range above the Planckian limit (high energy sector or HES). Due to its energy dependence, the metric in both energy sectors differs. In the HES, it depends on the effective dimension of the NoNRES. This dependency results from fluctuations of the space-time above the Planckian limit. Even if they are not part of the theory (as they would be in quantum gravity), these fluctuations should not be ignored. The effective dimension decreases if the energy of the considered particle increases. Since this is true for the HES only, the ultraviolet divergences of loop integrals seem to vanish without distorting the results of the LES. The mechanism is illustrated by calculating the tadpole integral occurring for a simple self-interacting scalar quantum field (with the Higgs mass as example). One obtains a finite contribution for the integral and consequently for the lifetime of the scalar particle.

Hardware Approach for Real Time Machine Stereo Vision
Michael Tornow,Jens Kaszubiak,Thomas Schindler,Robert W. Kuhn
Journal of Systemics, Cybernetics and Informatics , 2006,
Abstract: Image processing is an effective tool for the analysis of optical sensor information for driver assistance systems and controlling of autonomous robots. Algorithms for image processing are often very complex and costly in terms of computation. In robotics and driver assistance systems, real-time processing is necessary. Signal processing algorithms must often be drastically modified so they can be implemented in the hardware. This task is especially difficult for continuous real-time processing at high speeds. This article describes a hardware-software co-design for a multi-object position sensor based on a stereophotogrammetric measuring method. In order to cover a large measuring area, an optimized algorithm based on an image pyramid is implemented in an FPGA as a parallel hardware solution for depth map calculation. Object recognition and tracking are then executed in real-time in a processor with help of software. For this task a statistical cluster method is used. Stabilization of the tracking is realized through use of a Kalman filter. Keywords: stereophotogrammetry, hardware-software co-design, FPGA, 3-d image analysis, real-time, clustering and tracking.
Intrinsic Regularization in a Lorentz invariant non-orthogonal Euclidean Space
Carmen Tornow
Physics , 2006,
Abstract: It is shown that the Lorentz transformations can be derived for a non-orthogonal Euclidean space. In this geometry one finds the same relations of special relativity as the ones known from the orthogonal Minkowski space. In order to illustrate the advantage of a non-orthogonal Euclidean metric the two-point Green's function at x = 0 for a self-interacting scalar field is calculated. In contrast to the Minkowski space the one loop mass correction derived from this function gives a convergent result due to an intrinsic regularization parameter called effective dimension. This parameter is an entropy related measure for the information loss caused by quantum fluctuations of the metric at energies higher than the Planckian limit.
Search for Neutrinoless Double-Beta Decay
Werner Tornow
Physics , 2014,
Abstract: After the pioneering work of the Heidelberg-Moscow (HDM) and International Germanium Experiment (IGEX) groups, the second round of neutrinoless double-$\beta$ decay searches currently underway has or will improve the life-time limits of double-$\beta$ decay candidates by a factor of two to three, reaching in the near future the $T_{1/2} = 3 \times 10^{25}$ yr level. This talk will focus on the large-scale experiments GERDA, EXO-200, and KamLAND-Zen, which have reported already lower half-life time limits in excess of $10^{25}$ yr. Special emphasis is given to KamLAND-Zen, which is expected to approach the inverted hierarchy regime before future 1-ton experiments probe completely this life-time or effective neutrino-mass regime, which starts at $\approx 2 \times 10^{26}$ yr or $\approx 50$ meV.
Effects of the magnetic moment interaction between nucleons on observables in the 3N continuum
H. Witala,J. Golak,R. Skibinski,C. R. Howell,W. Tornow
Physics , 2003, DOI: 10.1103/PhysRevC.67.064002
Abstract: The influence of the magnetic moment interaction of nucleons on nucleon-deuteron elastic scattering and breakup cross sections and on elastic scattering polarization observables has been studied. Among the numerous elastic scattering observables only the vector analyzing powers were found to show a significant effect, and of opposite sign for the proton-deuteron and neutron-deuteron systems. This finding results in an even larger discrepancy than the one previously established between neutron-deuteron data and theoretical calculations. For the breakup reaction the largest effect was found for the final-state-interaction cross sections. The consequences of this observation on previous determinations of the ^1S_0 scattering lengths from breakup data are discussed.
Measurement of the elastic scattering cross section of neutrons from argon and neon
S. MacMullin,M. Kidd,R. Henning,W. Tornow,C. R. Howell,M. Brown
Physics , 2012, DOI: 10.1103/PhysRevC.87.054613
Abstract: Background: The most significant source of background in direct dark matter searches are neutrons that scatter elastically from nuclei in the detector's sensitive volume. Experimental data for the elastic scattering cross section of neutrons from argon and neon, which are target materials of interest to the dark matter community, were previously unavailable. Purpose: Measure the differential cross section for elastic scattering of neutrons from argon and neon in the energy range relevant to backgrounds from (alpha,n) reactions in direct dark matter searches. Method: Cross-section data were taken at the Triangle Universities Nuclear Laboratory (TUNL) using the neutron time-of-flight technique. These data were fit using the spherical optical model. Results: The differential cross section for elastic scatting of neutrons from neon at 5.0 and 8.0 MeV and argon at 6.0 MeV was measured. Optical-model parameters for the elastic scattering reactions were determined from the best fit to these data. The total elastic scattering cross section for neon was found to differ by 6% at 5.0 MeV and 13% at 8.0 MeV from global optical-model predictions. Compared to a local optical-model for 40Ar, the elastic scattering cross section was found to differ from the data by 8% at 6.0 MeV. Conclusions: These new data are important for improving Monte-Carlo simulations and background estimates for direct dark matter searches and for benchmarking optical models of neutron elastic scattering from these nuclei.
Two-neutrino double-beta decay of $^{150}$Nd to excited final states in $^{150}$Sm
Mary F. Kidd,James H. Esterline,Sean W. Finch,Werner Tornow
Statistics , 2014, DOI: 10.1103/PhysRevC.90.055501
Abstract: Double-beta decay is a rare nuclear process in which two neutrons in the nucleus are converted to two protons with the emission of two electrons and two electron anti-neutrinos. We measured the half life of the two-neutrino double-beta decay of $^{150}$Nd to excited final states of $^{150}$Sm by detecting the de-excitation gamma rays of the daughter nucleus. This study yields the first detection of the coincidence gamma rays from the 0$^+_1$ excited state of $^{150}$Sm. These gamma rays have energies of 333.97 keV and 406.52 keV, and are emitted in coincidence through a 0$^+_1\rightarrow$2$^+_1\rightarrow$0$^+_{gs}$ transition. The enriched Nd$_2$O$_3$ sample consisted of 40.13 g $^{150}$Nd and was observed for 642.8 days at the Kimballton Underground Research Facility, producing 21.6 net events in the region of interest. This count rate gives a half life of $T_{1/2}=(1.07^{+0.45}_{-0.25}(stat)\pm0.07(syst.))\times 10^{20}$ years. The effective nuclear matrix element was found to be 0.0465$^{+0.0098}_{-0.0054}$. Finally, lower limits were obtained for decays to higher excited final states. Our half-life measurement agrees within uncertainties with another recent measurement in which no coincidence was employed. Our nuclear matrix element calculation may have an impact on a recent neutrinoless double-beta decay nuclear matrix element calculation which implies the decay to the first excited state in $^{150}$Sm is favored over that to the ground state.
New Results for Double-Beta Decay of Mo-100 to Excited Final States of Ru-100 Using the TUNL-ITEP Apparatus
M. F. Kidd,J. H. Esterline,W. Tornow,A. S. Barabash,V. I. Umatov
Statistics , 2009, DOI: 10.1016/j.nuclphysa.2009.01.082
Abstract: The coincidence detection efficiency of the TUNL--ITEP apparatus designed for measuring half-life times of two-neutrino double-beta decay transitions to excited final states in daughter nuclei has been measured with a factor of 2.4 improved accuracy. In addition, the previous measuring time of 455 days for the study of the Mo-100 two-neutrino double-beta decay to the first excited 0+ state in Ru-100 has been increased by 450 days, and a new result (combined with the previous measurement obtained with the same apparatus) for this transition is presented: T_(1/2) = [5.5 (+1.2/-0.8) (stat) +/- 0.3 (syst)] x 10^20 y. Measured two-neutrino double-beta decay half-life times to excited states can be used to test the reliability of nuclear matrix element calculations needed for determining the effective neutrino mass from zero-neutrino double-beta decay data. We also present new limits for transitions to higher excited states in Ru-100 which, if improved, may be of interest for more exotic conjectures, like a bosonic component to neutrino statistics.
Measurements at low energies of the polarization-transfer coefficient Kyy' for the reaction 3H(p,n)3He at 0 degrees
W. S. Wilburn,C. R. Gould,G. M. Hale,P. R. Huffman,C. D. Keith,N. R. Roberson,W. Tornow
Physics , 1997, DOI: 10.1007/s006010050074
Abstract: Measurements of the transverse polarization coefficient Kyy' for the reaction 3H(p,n)3He are reported for outgoing neutron energies of 1.94, 5.21, and 5.81 MeV. This reaction is important both as a source of polarized neutrons for nuclear physics experiments, and as a test of theoretical descriptions of the nuclear four-body system. Comparison is made to previous measurements, confirming the 3H(p,n)3He reaction can be used as a polarized neutron source with the polarization known to an accuracy of approximately 5%. Comparison to R-matrix theory suggests that the sign of the 3F3 phase-shift parameter is incorrect. Changing the sign of this parameter dramatically improves the agreement between theory and experiment.
Conductance Through a Redox System in the Coulomb Blockade Regime: Many-Particle Effects and Influence of Electronic Correlations
Sabine Tornow,Gertrud Zwicknagl
Physics , 2009, DOI: 10.1002/pssr.200903402
Abstract: We investigate the transport characteristics of a redox system weakly coupled to leads in the Coulomb blockade regime. The redox system comprises a donor and acceptor separated by an insulating bridge in a solution. It is modeled by a two-site extended Hubbard model which includes on-site and inter-site Coulomb interactions and the coupling to a bosonic bath. The current voltage characteristics is calculated at high temperatures using a rate equation approach. For high voltages exceeding the Coulomb repulsion at the donor site the calculated transport characteristics exhibit pronounced deviations from the behavior expected from single-electron transport. Depending on the relative sizes of the effective on-site and inter-site Coulomb interactions on one side and the reorganization energy on the other side we find negative differential resistance or current enhancement.
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