arXiv subjects

H. L. Harney

Publications and source records attributed to H. L. Harney.

27 records · Page 2Linked to original sources

arXiv2002

Evidence for Neutrinoless Double Beta Decay

The data of the Heidelberg-Moscow double beta decay experiment for the measuring period August 1990 - May 2000 (54.9813 kg y or 723.44 molyears), published recently, are analyzed using the potential of the Bayesian method for low counting rates. First evidence for neutrinoless double beta decay is observed giving first evidence for lepton number violation. The evidence for this decay mode is 97% (2.2σ) with the Bayesian method, and 99.8% c.l. (3.1σ) with the method recommended by the Particle Data Group. The half-life of the process is found with the Bayesian method to be T_{1/2}^{0ν} = (0.8 - 18.3) x 10^{25} y (95% c.l.) with a best value of 1.5 x 10^{25} y. The deduced value of the effective neutrino mass is, with the nuclear matrix elements from [Sta90,Tom91] < m >= (0.11 - 0.56) eV (95% c.l.), with a best value of 0.39 eV. Uncertainties in the nuclear matrix elements may widen the range given for the effective neutrino mass by at most a factor 2. Our observation which at the same time means evidence that the neutrino is a Majorana particle, will be of fundamental importance for neutrino physics. PACS. 14.69.Pq Neutrino mass and mixing; 23.40.Bw Weak-interaction and lepton (including neutrino) aspects 23.40.-s Beta decay; double beta decay; electron and muon capture.

hep-ph↗

arXiv2000

The Chirality of Exceptional Points

Exceptional points are singularities of the spectrum and wave functions which occur in connection with level repulsion. They are accessible in experiments using dissipative systems. It is shown that the wave function at an exceptional point is one specific superposition of two wave functions which are themselves specified by the exceptional point. The phase relation of this superposition brings about a chirality which should be detectable in an experiment.

quant-ph↗

arXiv1999

The Impact of Isospin Breaking on the Distribution of Transition Probabilities

In the present paper we investigate the effect of symmetry breaking in the statistical distributions of reduced transition amplitudes and reduced transition probabilities. These quantities are easier to access experimentally than the components of the eigenvectors and were measured by Adams et al. for the electromagnetic transitions in ^{26}Al. We focus on isospin symmetry breaking described by a matrix model where both, the Hamiltonian and the electromagnetic operator, break the symmetry. The results show that for partial isospin conservation, the statistical distribution of the reduced transition probability can considerably deviate from the Porter-Thomas distribution.

nucl-th↗

arXiv1999

Analyzing symmetry breaking within a chaotic quantum system via Bayesian inference

Bayesian inference is applied to the level fluctuations of two coupled microwave billiards in order to extract the coupling strength. The coupled resonators provide a model of a chaotic quantum system containing two coupled symmetry classes of levels. The number variance is used to quantify the level fluctuations as a function of the coupling and to construct the conditional probability distribution of the data. The prior distribution of the coupling parameter is obtained from an invariance argument on the entropy of the posterior distribution.

physics.data-an↗

arXiv1998

Coupled Microwave Billiards as a Model for Symmetry Breaking

Two superconducting microwave billiards have been electromagnetically coupled in a variable way. The spectrum of the entire system has been measured and the spectral statistics analyzed as a function of the coupling strength. It is shown that the results can be understood in terms of a random matrix model of quantum mechanical symmetry breaking -- as e.g. the violation of parity or isospin in nuclear physics.

chao-dyn↗

arXiv1997

Objective Bayesian Statistics

Bayesian inference --- although becoming popular in physics and chemistry --- is hampered up to now by the vagueness of its notion of prior probability. Some of its supporters argue that this vagueness is the unavoidable consequence of the subjectivity of judgements --- even scientific ones. We argue that priors can be defined uniquely if the statistical model at hand possesses a symmetry and if the ensuing confidence intervals are subjected to a frequentist criterion. Moreover, it is shown via an example taken from recent experimental nuclear physics, that this procedure can be extended to models with broken symmetry.

physics.data-an↗

arXiv1997

Correlation-Hole Method for Spectra of Superconducting Microwave Billiards

The spectral fluctuation properties of various two- and three-dimensional superconducting billiard systems are investigated by employing the correlation-hole method. It rests on the sensitivity of the spectral Fourier transform to long range correlations and is thus an alternative technique to study chaotic dynamics. First, we apply the method to the eigenfrequencies which are extracted from the measured resonances. Second, we analyze the unfolded raw spectra, including the shape of the resonances. The merit of the method lies in a clear separation of the statistics due to the positions and due to the shape of the resonances. However, we show that statistical fluctuations of the intensities of the resonances have a strong impact on the observable. Therefore, the visibility of the correlation hole is studied as a function of the number of independent statistical variables entering into the intensities. The visibility improves if independent spectra are superimposed.

chao-dyn↗

arXiv1995

Decay of Classical Chaotic Systems - the Case of the Bunimovich Stadium

The escape of an ensemble of particles from the Bunimovich stadium via a small hole has been studied numerically. The decay probability starts out exponentially but has an algebraic tail. The weight of the algebraic decay tends to zero for vanishing hole size. This behaviour is explained by the slow transport of the particles close to the marginally stable bouncing ball orbits. It is contrasted with the decay function of the corresponding quantum system.

chao-dyn↗

arXiv1995

Propagation of a $K$-body force into $A$-body space

The calculation of the spreading width of a compound nuclear reaction caused by a symmetry breaking $K$-body force acting in an $A$-body system ($K << A$, usually $K=2$) involves the determination of the local average square matrix element in $A$-body space. This problem is reduced to finding the global mean square matrix element $v^2$ in $K$-body space. The result is a compact formula for the spreading width which contains $v^2$ as an input. Our method is based on the dilute gas approximation for excitons close to the Fermi edge. The relative strength of the contributions of operators with different exciton rank as well as the connection between the energy dependence of the spreading width and the body rank of the underlying interaction are established.

nucl-th↗