Mon·Mar 5, 2018Monday·March 5, 2018

1. 01*

   Study of the $\gamma p\to {\pi }^0\eta p$ reaction with the A2 setup at MAMI

   V.Sokhoyan · S.Prakhov · A.Fix · S.Abt · P.Achenbach · P.Adlarson · F.Afzal · P.Aguar-Bartolomé · Z.Ahmed · J.Ahrens · J.R.M.Annand · H.J.Arends and 90 other authors

   The data available from the A2 Collaboration at MAMI were analyzed to select the $\gamma p\to {\pi }^0\eta p$ reaction on an event-by-event basis, which allows for partial-wave analyses of three-body final states to obtain more reliable results, compared to fits to measured distributions. These data provide the world's best statistical accuracy in the energy range from threshold to $E_{\gamma }=1.45$ GeV, allowing a finer energy binning in the measurement of all observables needed for understanding the reaction dynamics. The results obtained for the measured observables are compared to existing models, and the impact from the new data is checked by the fit with the revised Mainz model.

   nucl-exPRC(2018)·26 citations
2. 02*

   Measurement of the neutron flux at spallation sources using multi-foil activation

   Davide Chiesa🇮🇹 · Massimiliano Nastasi🇮🇹 · Carlo Cazzaniga · Marica Rebai · Laura Arcidiacono · Ezio Previtali🇮🇹 · Giuseppe Gorini · Christopher D. Frost

   Activation analysis is used in this work to measure the flux of a fast neutron beamline at a spallation source over a wide energy spectrum, extending from thermal to hundreds of MeV. The experimental method is based on the irradiation of multiple elements and measurements of activation {\gamma}-lines using a High Purity Germanium detector. The method for data analysis is then described in detail, with particular attention to the evaluation of uncertainties. The reactions have been chosen so to cover the whole energy range, using mainly (n,{\gamma}) for thermal and epithermal neutrons, and threshold reactions for the fast region. The variety of these reactions allowed for the unfolding of the neutron spectrum, using an algorithm based on a Bayesian statistical model, and limited correlations have been found between the energy groups.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·14 citations
3. 03*

   Distribution of Magnetic Dipole Strength -Binning

   Arun Kingan · Mingyang Ma · Larry Zamick

   In previous works we examined the systematics of magnetic dipole transitions in a single j shell. We here extend the study to large space calculations. We consider Ti and Cr isotopes.. In this work we focus on the B(M1) strength as a function of excitation of energy. The initial state is the lowest J= state. T=1 state in a specified nucleus. The final states are J=0 T=2 , all in one plot, and J=2 T=2 in another. The initial figures have points all over the map although there is a suggestion of an exponential trend. To reduce clutter we perform binning operations in which the summed strength in a given energy interval is represented by a single point. The new binning curves show more clearly the exponential fall of B(M1)'s with energy.

   ↳ nucl-thnucl-exIJMPE(2020)·5 citations
4. 04*

   Inclusive electron-nucleus cross section within the Self Consistent Green's Function approach

   N. Rocco🇬🇧 · C. Barbieri🇬🇧

   We compute inclusive electron-nucleus cross sections using ab initio spectral functions of ${}^4$He and ${}^{16}$O obtained within the Self Consistent Green's Function approach. The formalism adopted is based on the factorization of the spectral function and the nuclear transition matrix elements. This allows to provide an accurate description of nuclear dynamics and to account for relativistic effects in the interaction vertex. Our calculations use a saturating chiral Hamiltonian in order reproduce the correct nuclear sizes. When final state interactions for the struck particle are accounted for, we find nice agreement between the data and the theory for the inclusive electron-${}^{16}$O cross section. The results lay the foundations for future applications of the Self Consistent Green's Function method, in both closed and open shell nuclei, to neutrino data analysis. This work also presents results for the point-proton, charge and single-nucleon momentum distribution of the same two nuclei. The center of mass can affect these quantities for light nuclei and cannot be separated cleanly in most ab initio post-Hartree-Fock methods. In order to address this, we developed a Metropolis Monte Carlo calculation in which the center of mass coordinate can be subtracted exactly from the trial wave function and the expectation values. We gauged this effect for ${}^4$He by removing the center of mass effect from the Optimal Reference State wave function that is generated during the Self Consistent Green's Function calculations. Our findings clearly indicate that the residual center of mass contribution strongly modifies calculated matter distributions with respect to those obtained in the intrinsic frame. Hence, its subtraction is crucial for a correct description of light nuclei.

   ↳ nucl-thhep-exnucl-exPRC(2018)·33 citations
5. 05*

   Fitting and Analysis Technique for Inconsistent Nuclear Data

   Georg Schnabel🇫🇷

   Consistent experiment data are crucial to adjust parameters of physics models and to determine best estimates of observables. However, often experiment data are not consistent due to unrecognized systematic errors. Standard methods of statistics such as ${\chi }^2$-fitting cannot deal with this case. Their predictions become doubtful and associated uncertainties too small. A human has then to figure out the problem, apply corrections to the data, and repeat the fitting procedure. This takes time and potentially costs money. Therefore, a Bayesian method is introduced to fit and analyze inconsistent experiment data. It automatically detects and resolves inconsistencies. Furthermore, it allows to extract consistent subsets from the data. Finally, it provides an overall prediction with associated uncertainties and correlations less prone to the common problem of too small uncertainties. The method is foreseen to function with a large corpus of data and hence may be used in nuclear databases to deal with inconsistencies in an automated fashion.

   ↳ nucl-thnucl-exphysics.data-an8 citations
6. 06*

   MultiSIMNRA: a computational tool for self-consistent ion beam analysis using SIMNRA

   Tiago F. Silva · Matej Mayer🇺🇸 · Cleber L. Rodrigues · Marcos V. Moro · Gustavo F. Trindade · Fernando R. Aguirre · Nemitala Added · Márcia A. Rizzutto · Manfredo H. Tabacniks

   SIMNRA is widely adopted by the scientific community of ion beam analysis for interpretation of nuclear scattering analysis. Taking advantage of its recognized reliability and quality of the simulations, we developed a computer program that use parallel sessions of SIMNRA to perform self-consistent analysis for energy spectra of a given sample obtained using different techniques or experimental setups. In this paper, we present a result using MultiSIMNRA on self-consistent analysis for a multielemental thin film produced by magnetron sputtering. The results demonstrate the potentialities of the self-consistent analysis and its feasibility when using MultiSIMNRA.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.B(2016)·7 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.