120855950
Pionic and electromagnetic excitation of A* resonances
The nuclear excitation spectrum in the Delta (3,3) energy range is studied by comparing elastic pion scattering with coherent neutral pion photoproduction. The corresponding multipole excitation strength distributions are found to be quite different. This emphasises the role of the electromagnetic excitations of nuclei for the investigation of the A* resonances which is complementary to their mesonic excitation. Results are presented for 12C( gamma , pi 0) 12C(GS); they are compared with those of the phenomenological isobar doorway model and of DWIA calculations.
117571760
On the possible existence of narrow (N *N)‐resonances
Due to the coupling of N*N configurations with the real pion continuum energy‐shifts and modifications of the widths of the corresponding dibaryonic molecules are expected. For configurations, which cannot couple to the absorptive channels this mechanism may lead to a narrowing of specific resonances. Results of model calculations are applied to elastic pion deuteron scattering.
125549487
Light mesons and mesonic states
123084597
Universal relationship connecting various two-body effective residual interactions
Starting from a momentum space analysis of the two-body matrix elements, a relation has been established between the size of the model space actually used in a specific calculation and the relevant properties of the effective residual interaction. It turns out that the two-body transition density acts like a filter function on the Fourier transform of the force; it exhibits a distinct structure which clearly reflects the size and the detailed properties of the configuration space actually used. From an investigation of this filter function an equivalence criterion for different effective residual two-body interactions has been established both for closed and open shell nuclei. This result can be used to construct simple although realistic effective forces. As an example, a model for a separable residual interaction is proposed in which the corresponding parameters are being clearly related to the nuclear radius (i.e., the mass number), to the quantum numbers (i.e., the angular momentum) of the state under consideration and to the size of the configuration space used. For a number of examples this force has been applied successfully for the description of low energy properties of both closed and open shell nuclei. (AIP)
13703277
COLLECTIVE TREATMENT OF THE GIANT RESONANCES IN SPHERICAL NUCLEI.
In a collective treatment the energies of the giant resonances are given by the boundary conditions at the nuclear surface, which is subject to vibration in spherical nuclei. The general form of the coupling between these two collective motions is given by angular-momentum and parity conservation. The coupling constants are completely determined within the hydrodynamical model. In the present treatment the influence of the surface vibrations on the total photon-absorption cross section is calculated. It turns out that in most of the spherical nuclei this interaction leads to a pronounced structure in the cross section. The agreement with the experiments in medium-heavy nuclei is striking; many of the experimental characteristics are reproduced by the present calculations. In some nuclei, however, there seem to be indications of single-particle excitations which are not yet contained in this work.
19234257
Experimental realization of decoherence-free subspace in neutron interferometry.
A decoherence-free subspace (DFS) is an important class of quantum-error-correcting (QEC) codes that have been proposed for fault-tolerant quantum computation. The applications of QEC techniques, however, are not limited to quantum-information processing (QIP). Here we demonstrate how QEC codes may be used to improve experimental designs of quantum devices to achieve noise suppression. In particular, neutron interferometry is used as a test bed to show the potential for adding quantum error correction to quantum measurements. We built a five-blade neutron interferometer that incorporates both a standard Mach-Zender configuration and a configuration based on a DFS. Experiments verify that the DFS interferometer is protected against low-frequency mechanical vibrations. We anticipate these improvements will increase the range of applications for matter-wave interferometry.
119208185
Going beyond the propagators of Landau gauge Yang-Mills theory
We present results for the propagators and the ghost-gluon vertex of Landau gauge Yang-Mills theory obtained from Dyson-Schwinger equations. Solving these three quantities simultaneously constitutes a new step in truncating these equations. We also introduce a new model for the three-gluon vertex that is motivated by lattice results. It features a zero crossing which is confirmed a posteriori by a Dyson-Schwinger calculation. Within our setup we can reproduce lattice data very well. We establish that also for the ghost-gluon vertex a difference between decoupling and scaling solutions is present. For the scaling solution we discuss the possibility of modifying the infrared exponents via an angle dependence of the ghost-gluon vertex. However, no such dependence is found in our calculations. Finally, we calculate the Schwinger function for the gluon propagator.
14499726
Analysis of the low-energy electron-recoil spectrum of the CDMS experiment
We report on the analysis of the low-energy electron-recoil spectrum from the CDMS II experiment using data with an exposure of 443.2 kg-days. The analysis provides details on the observed counting rate and possible background sources in the energy range of 2–8.5 keV. We find no significant excess of a peaked contribution to the total counting rate above the background model, and compare this observation to the recent DAMA results. In the framework of a conversion of a dark matter particle into electromagnetic energy, our 90% confidence level upper limit of 0.246  events/kg/day at 3.15 keV is lower than the total rate above background observed by DAMA. In absence of any specific particle physics model to provide the scaling in cross section between NaI and Ge, we assume a Z2 scaling. With this assumption the observed rate in DAMA remains higher than the upper limit in CDMS. Under the conservative assumption that the modulation amplitude is 6% of the total rate we obtain upper limits on the modulation amplitude a factor of ~2 lower than observed by DAMA, constraining some possible interpretations of this modulation.
6090781
Search for axions with the CDMS experiment.
We report on the first axion search results from the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory. An energy threshold of 2 keV for electron-recoil events allows a search for possible solar axion conversion into photons or local galactic axion conversion into electrons in the germanium crystal detectors. The solar axion search sets an upper limit on the Primakov coupling g(agammagamma) of 2.4x10(-9) GeV-1 at the 95% confidence level for an axion mass less than 0.1 keV/c2. This limit benefits from the first precise measurement of the absolute crystal plane orientations in this type of experiment. The galactic axion search analysis sets a world-leading experimental upper limit on the axioelectric coupling g(aee) of 1.4x10(-12) at the 90% confidence level for an axion mass of 2.5 keV/c2.
6499072
Present results and future goals of the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) uses Ge and Si detectors to search for Weakly Interacting Massive Particles (WIMPs) via their elastic-scattering interaction with atomic nuclei. The present results from CDMS give limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude previously unexplored parameter space above 10 GeV/c2. The second phase of the CDMS experiment, scheduled to start in January 2002, is expected to improve on the present sensitivity by more than two orders of magnitude.
122949791
Deployment of the first CDMS II ZIP Detectors at the Stanford Underground Facility
Abstract The CDMS II experiment deployed the first set of ZIP (Z-dependent Ionization and Phonon) detectors at the Stanford Underground Facility (SUF) shallow depth site in the spring of 2000. With a payload consisting of 3 Ge (250g ea.) and 3 Si (100g ea.) ZIPs, the run was the first demostration of multiple ZIPs operating simltaneously. Good discrimination between electron and nuclear recoil events of 99.8% was established, down to recoil energies of 10 keV. A measurement of the γ, β, and neutron backgrounds was made.