Search results for "Free parameter"
showing 10 items of 49 documents
ComPWA: A common amplitude analysis framework for PANDA
2014
A large part of the physics program of the PANDA experiment at FAIR deals with the search for new conventional and exotic hadronic states like e.g. hybrids and glueballs. For many analyses PANDA will need an amplitude analysis, e.g. a partial wave analysis (PWA), to identify possible candidates and for the classification of known states. Therefore, a new, agile and efficient amplitude analysis framework ComPWA is under development. It is modularized to provide easy extension with models and formalisms as well as fitting of multiple datasets, even from different experiments. Experience from existing PWA programs was used to fix the requirements of the framework and to prevent it from restric…
Born-Infeld Gravity: Constraints from Light-by-Light Scattering and an Effective Field Theory Perspective
2021
By using a novel technique that establishes a correspondence between general relativity and metric-affine theories based on the Ricci tensor, we are able to set stringent constraints on the free parameter of Born-Infeld gravity from the ones recently obtained for Born-Infeld electrodynamics by using light-by-light scattering data from ATLAS. We also discuss how these gravity theories plus matter fit within an effective field theory framework.
A dispersion theoretical approach to the threshold amplitudes of pion photoproduction
1996
We give predictions for the partial wave amplitudes of pion photoproduction near threshold by means of dispersion relations at fixed t. The free parameters of this approach are determined by a fit to experimental data in the energy range 160 MeV $\le E_{\gamma} \le$ 420 MeV. The observables near threshold are found to be rather sensitive to the amplitudes in the resonance region, in particular to the $\Delta$ (1232) and $N^*$ (1440). We obtain a good agreement with the existing threshold data for both charged and neutral pion production. Our predictions also agree well with the results of chiral perturbation theory, except for neutral pion production off the neutron.
Coarse-grained models of double-stranded DNA based on experimentally determined knotting probabilities
2018
Abstract To accurately model double-stranded DNA in a manner that is computationally efficient, coarse-grained models of DNA are introduced, where model parameters are selected by fitting the spectrum of observable DNA knots: We develop a general method to fit free parameters of coarse-grained chain models by comparing experimentally obtained knotting probabilities of short DNA chains to knotting probabilities that are computed in Monte Carlo simulations, resulting in coarse-grained DNA models which are tailored to reflect DNA topology in the best possible way. The method is exemplified by fitting ideal chain models as well as a bead-spring model with excluded volume interactions, to model …
StalAge – An algorithm designed for construction of speleothem age models
2011
Abstract Here we present a new algorithm ( StalAge ), which is designed to construct speleothem age models. The algorithm uses U-series ages and their corresponding age uncertainty for modelling and also includes stratigraphic information in order to further constrain and improve the age model. StalAge is applicable to problematic datasets that include outliers, age inversions, hiatuses and large changes in growth rate. Manual selection of potentially inaccurate ages prior to application is not required. StalAge can be applied by the general, non-expert user and has no adjustable free parameters. This offers the highest degree of reproducibility and comparability of speleothem records from …
EXTRACTION OF THE Λ(1405) POLES FROM π0Σ0 PHOTOPRODUCTION DATA
2014
In this contribution we review a work where we showed how to extract the position of the two Λ(1405) poles from experimental photoproduction data which have been measured recently in the γp → K+π0Σ0 reaction at Jefferson Lab. Using a potential motivated by chiral dynamics but with free parameters, we solve the Bethe Salpeter equation in the coupled channels [Formula: see text] and πΣ in isospin I=0 and parameterize the amplitude for the photonuclear reaction in terms of a linear combination of the πΣ → πΣ and [Formula: see text] scattering amplitudes in I=0, with a different linear combination for each energy. Good fits to the data are obtained which lead to two poles at 1385 - 68i MeV and…
Folding description of the fine structure of α decay to2+vibrational and transitional states
2007
We analyze \ensuremath{\alpha}-decays to ground and ${2}^{+}$ vibrational states in even-even nuclei by using a coupled channels formalism. The \ensuremath{\alpha}-nucleus interaction is simulated by a double folding procedure using M3Y plus Coulomb two-body forces. Collective excitations are described by vibrations of the nuclear surface. We use a repulsive potential, with one independent parameter, in order to simulate Pauli principle and to adjust the energy of the resonant state to the experimental $Q$-value. The decaying state is identified with the zero nodes resonance inside the resulting pocket-like potential. We have found that the fine structure is very sensitive to the strength o…
Search for Electron Antineutrino Appearance in a Long-baseline Muon Antineutrino Beam
2020
Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40 σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and a…
Multiscale modelling of structure formation of C$_{60}$ on insulating CaF$_2$ substrates
2021
Morphologies of adsorbed molecular films are of interest in a wide range of applications. To study the epitaxial growth of these systems in computer simulations requires access to long time and length scales, and one typically resorts to kinetic Monte Carlo (KMC) simulations. However, KMC simulations require as input transition rates and their dependence on external parameters (such as temperature). Experimental data allow only limited and indirect access to these rates, and models are often oversimplified. Here, we follow a bottom-up approach and aim at systematically constructing all relevant rates for an example system that has shown interesting properties in experiments, buckminsterfull…
A predictive model for the electronic stopping force for molecular dynamic simulation (I)
2010
Abstract We have examined a predictive model for the electronic stopping force (dE/dx)e to be used in the classical molecular dynamic (MD) simulation. The essential term (dE/dx)proton of (dE/dx)e is based on the Lindhard–Winther theory, while the effective charge follows the Brandt–Kitagawa model. The (dE/dx)proton term is expressed by the electron local density ρ(r) defined by the Muffin-tin model and the Hartree–Fock–Slater approximation. This model had been proposed to explain the impact-parameter dependence of (dE/dx)e for channeling ions passing through a semiconductor. Here the energy dependence of the averaged 〈dE/dx〉e after thin-film transmission was examined, where the electron–pho…