arXiv subjects

R. Navarro Perez

Publications and source records attributed to R. Navarro Perez.

29 records · Page 2Linked to original sources

arXiv2014

Statistical Error analysis of Nucleon-Nucleon phenomenological potentials

Nucleon-Nucleon potentials are commonplace in nuclear physics and are determined from a finite number of experimental data with limited precision sampling the scattering process. We study the statistical assumptions implicit in the standard least squares fitting procedure and apply, along with more conventional tests, a tail sensitive quantile-quantile test as a simple and confident tool to verify the normality of residuals. We show that the fulfilment of normality tests is linked to a judicious and consistent selection of a nucleon-nucleon database. These considerations prove crucial to a proper statistical error analysis and uncertainty propagation. We illustrate these issues by analyzing about 8000 proton-proton and neutron-proton scattering published data. This enables the construction of potentials meeting all statistical requirements necessary for statistical uncertainty estimates in nuclear structure calculations.

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arXiv2014

Coarse grained NN potential with Chiral Two Pion Exchange

We determine the chiral constants of the Nucleon-Nucleon Two Pion Exchange potential deduced from Chiral Perturbation Theory. By using a coarse grained representation of the short distance interactions with 30 parameters, the Partial Wave Analysis fit gives chi^2/dof = 1.1 to a mutually consistent set of 6713 data previously built from all published proton-proton and neutron proton scattering data from 1950 till 2013 with LAB energy below 350 MeV. We obtain (c1, c3, c4)=(-0.41+- 1.08,-4.66+- 0.60, 4.31+- 0.17)/GeV with an almost 100% anti-correlation between c1 and c3. We also provide the errors in the short distance parameters and propagate them to the deuteron properties and low partial waves phase shifts.

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arXiv2013

Partial Wave Analysis of Chiral NN Interactions

We analyze chiral interactions to N2LO on the light of proton-proton and neutron-proton scattering data published from 1950 till 2013 and discuss conditions under which the chiral coefficients can be extracted

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arXiv2013

Error Analysis of Nuclear Matrix Elements

We estimate the expected errors of nuclear matrix elements coming from the uncertainty on the NN interaction. We use a coarse grained (GR) interaction fitted to NN scattering data, with several prescriptions for the long-part of the interaction, including one pion exchange and chiral two-pion exchange interactions.

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arXiv2013

Coarse grained Potential analysis of neutron-proton and proton-proton scattering below pion production threshold

Using the delta-shell representation we present a successful fit to neutron-proton and proton-proton scattering data below pion production threshold. A detailed overview of the theory necessary to calculate observables with this potential is presented. A new data selection process is used to obtain the largest mutually consistent data base. The analysis includes data within the years 1950 to 2013. Using 46 parameters we obtain chi^2/Ndata = 1.04 with Ndata = 6713 including normalization data. Phase shifts with error bars are provided.

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arXiv2013

Partial Wave Analysis of Nucleon-Nucleon Scattering below pion production threshold

We undertake a simultaneous partial wave analysis to proton-proton and neutron-proton scattering data below pion production threshold up to LAB energies of 350MeV. We represent the interaction as a sum of delta-shells in configuration space below 3fm and a charge dependent one pion exchange potential above 3fm together with electromagnetic effects. We obtain chi^2 = 2813|pp + 3985|np with a total of N = 2747|pp + 3691|np data obtained till 2013 and a total number of 46 fitting parameters yielding chi^2 /d.o.f = 1.06. Special attention is paid to estimate the errors of the phenomenological interaction as well as the derived effects on the phase-shifts and scattering amplitudes.

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arXiv2012

Effective interactions in the delta-shells potential

We determine two-body Skyrme force parameters from a Nucleon-Nucleon interaction as a function of the maximal momentum fitting NN scattering data. We find general agreement with Vlowk interactions based on high quality potentials.

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arXiv2012

Nuclear Binding Energies and NN uncertainties

There is an increasing interest in quantifying the predictive power in nuclear structure calculations. We discuss how both experimental and systematic errors at the NN-level can be used to estimate the theoretical uncertainties by rather simple means and without solving the full nuclear many body problem. We emphasize the role of effective interactions defined by coarse graining the NN potential to length scales of the order of the minimal de Broglie wavelength probed between nucleons in nuclei. We find an a priori error of \DeltaB/A \sim 0.1 - 0.4MeV for the binding energy per particle throughout the periodic table for 2 \leq A \leq 208, and a linear growth of the error with density for nuclear matter \DeltaB/A \sim 3.75ρn.m. and neutron matter \DeltaB/N \sim 3.5ρn.. This suggests to limit the computational effort in solving the Nuclear Many Body Problem to such an accuracy.

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arXiv2012

Phenomenological High Precision Neutron-Proton Delta-Shell Potential

We provide a successful fit for proton-neutron scattering below pion production threshold up to LAB energies of 350 MeV. We use seven high-quality fits based on potentials with different forms as a measure of the systematic uncertainty. We represent the interaction as a sum of delta-shells in configuration space below the 3fm and a charge dependent one pion exchange potential above 3fm together with magnetic and vacuum polarization effects. Special attention is paid to estimate the errors of the phenomenological interaction.

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arXiv2012

Error estimates on Nuclear Binding Energies from Nucleon-Nucleon uncertainties

Despite great theoretical efforts the NN interaction can only be determined with a finite precision, implying an error upper bound for nuclear masses. We analyze for the first time the problem of estimating the systematic errors related to the form of the potential and their impact on nuclear binding. To this end we exploit the concept of coarse grained interactions to typical nuclear wavelengths. Our estimate gives an error of 0.1-0.4 MeV for the binding energy per particle and paves the way for ab initio calculations tailored to such a precision.

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arXiv2011

Coarse graining Nuclear Interactions

We consider a coarse graining of NN interactions in coordinate space very much in the spirit of the well known Vlowk approach. To this end we sample the interaction at about the minimal de Broglie wavelength probed by NN scattering below pion production threshold. This amounts to provide a simple delta-shell potential plus the standard OPE potential above 2 fm. The possible simplifications in the Nuclear many body problem are discussed.

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