20578469
A Generic Surface Sampler for Monte Carlo Simulations
We present a Monte Carlo algorithm that generates points randomly and uniformly on a set of arbitrary surfaces. The algorithm is completely general and only requires the geometry modeling software to provide the intersection points of an arbitrary line with the surface being sampled. We demonstrate the algorithm using the Geant4 Monte Carlo simulation toolkit. The efficiency of the sampling algorithm is discussed, along with various options in the implementation and example applications.
121657706
A Pulse Shape Analysis Technique for the MAJORANA Experiment
Abstract In order to achieve background count rates sufficiently low so as to allow the observation of rare events such as neutrinoless double beta (0νββ) decay, background suppression techniques are routinely employed. In this paper we present details of a novel Pulse Shape Analysis algorithm, which allows single-site events such as 0νββ decay to be distinguished from multi-site background events in germanium detectors. The algorithm, which is based on the event-by-event χ 2 fitting of experimental signals to a basis data set of unique single-site pulse shapes, has been developed through simulation studies and tested experimentally using a Broad Energy Germanium detector. It is found experimentally that the technique is able to successfully identify and reject 99% of multi-site events in the single escape peak associated with the gamma decay of 208 Tl, whilst maintaining a survival probability of 98% for neutrinoless double-beta-decay-like double escape peak events.
7696495
Search for an annual modulation in a p-type Point Contact germanium dark matter detector.
Fifteen months of cumulative CoGeNT data are examined for indications of an annual modulation, a predicted signature of weakly interacting massive particle (WIMP) interactions. Presently available data support the presence of a modulated component of unknown origin, with parameters prima facie compatible with a galactic halo composed of light-mass WIMPs. Unoptimized estimators yield a statistical significance for a modulation of ∼2.8σ, limited by the short exposure.
16108826
Validation of spallation neutron production and propagation within Geant4
Using simulations to understand backgrounds from muon-induced neutrons is important in designing next-generation low-background underground experiments. Validation of relevant physics within the Geant4 simulation package has been completed by comparing to data from two recent experiments. Verification focused on the production and propagation of neutrons at energies important to underground experiments. Discrepancies were observed between experimental data and the simulation. Techniques were explored to correct for these discrepancies.
22349078
Development of a data acquisition system for the MALBEK Low-Background BEGe detector
The Majorana collaboration is currently building the Majorana Demonstrator, an array of natural and en­riched high purity germanium (HPGe) detectors that will search for the neutrinoless double-beta decay of the 76Ge isotope. As part of the Demonstrator research and development effort we have deployed a prototype 450 g modified broad energy germanium (BEGe) detector at the Kimballton Underground Research Facility (KURF) in Ripplemeade, VA. This detector, the Majorana Low-Background BEGe Detector at KURF (MAL-BEK), will examine detector performance and background in the double-beta decay region of interest as well as explore the sub-keV energy spectrum in a search for light weakly interacting massive particles (WIMPs). In order to achieve this goal we have implemented a modular and highly automated data acquisition system (DAQ) capable of digitizing sub-keV signals and running autonomously in an underground environment. The DAQ is built using the Object-oriented Real-time Control and Acquisition (ORCA) application. ORCA enables the remote monitoring and control of all DAQ electronics, hardware, and slow control systems. A built in scripting language, ORCAScript, allows for the automation of run-time experimental parameters, real-time event building and data filtering, and system monitoring with email notification and alarms. The implemented MALBEK DAQ is currently operating at KURF in a production data taking mode.
35493425
A magnetically shielded room with ultra low residual field and gradient.
A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.
10123734
A topological lagrangian for monopoles on four-manifolds
Abstract We present a topological quantum field theory which corresponds to the moduli problem associated to Witten's monopole equations for four-manifolds. The construction of the theory is carried out in purely geometrical terms using the Mathai-Quillen formalism, and the corresponding observables are described. These provide a rich set of new topological quantities.
7030705
Counting BPS States on the Enriques Calabi-Yau
We study topological string amplitudes for the FHSV model using various techniques. This model has a type II realization involving a Calabi-Yau threefold with Enriques fibres, which we call the Enriques Calabi-Yau. By applying heterotic/type IIA duality, we compute the topological amplitudes in the fibre to all genera. It turns out that there are two different ways to do the computation that lead to topological couplings with different BPS content. One of them gives the standard D0-D2 counting amplitudes, and from the other one we obtain information about bound states of D0-D4-D2 branes on the Enriques fibre. We also study the model using mirror symmetry and the holomorphic anomaly equations. We verify in this way the heterotic results for the D0-D2 generating functional for low genera and find closed expressions for the topological amplitudes on the total space in terms of modular forms, and up to genus three. This model turns out to be much simpler than the generic B-model and might be exactly solvable.
119725893
Knots, links and branes at large N
We consider Wilson loop observables for Chern-Simons theory at large N and its topological string dual and extend the previous checks for this duality to the case of links. We find an interesting structure involving representation/spin degeneracy of branes ending on branes which features in the large-N dual description of Chern-Simons theory. This leads to a refinement of the integer invariants for links and knots. We illustrate our results with explicit computations on the Chern-Simons side.
15514221
Framed Knots at Large N
We study the framing dependence of the Wilson loop observable of U(N) ChernSimons gauge theory at large N. Using proposed geometrical large N dual, this leads to a direct computation of certain topological string amplitudes in a closed form. This yields new formulae for intersection numbers of cohomology classes on moduli of Riemann surfaces with punctures (including all the amplitudes of pure topological gravity in two dimensions). The reinterpretation of these computations in terms of BPS degeneracies of domain walls leads to novel integrality predictions for these amplitudes. Moreover we find evidence that large N dualities are more naturally formulated in the context of U(N) gauge theories rather than SU(N).
119151466
BPS states and algebras from quivers
We discuss several aspects of D-brane moduli spaces and BPS spectra near orbifold points. We give a procedure to determine the decay products on a line of marginal stability, and we define the algebra of BPS states in terms of quivers. These issues are illustrated in detail in the case of type-IIA theory on 2/N. We also show that many of these results can be extended to arbitrary points in the compactification moduli space using Π-stability.