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Carl R. Brune

Publications and source records attributed to Carl R. Brune.

15 recordsLinked to original sources
arXiv2025

Connecting ground-state properties of ${}^6$Li to each other and to scattering data

We examine the relationship between the Asymptotic Normalization Coefficient (ANC) of $^6$Li and other low-energy observables in the $α$-deuteron system. Our analysis uses a set of calculations carried out within the {\it ab initio} No Core Shell Model with Continuum (NCSMC) using a variety of inter-nucleon interactions and basis sizes, and yielding ${}^6$Li deuteron separation energies between 1.3 and 1.8 MeV [Phys. Rev. Lett. 129, 042503 (2022)]. These NCSMC calculations show that the square of the ANC is strongly correlated with the separation energy over this range. In this work, we investigate the origin of this correlation using the phenomenological $R$-matrix, a single-channel potential and a perturbative approach. We show that this correlation occurs because the depth of the $α$-deuteron central potential changes by only a small relative amount as the separation energy varies. We then investigate if the ANC can be accurately extracted from $α$-deuteron phase shifts in an ideal case in which low-energy data are available and there are no experimental errors. We find that both $R$-matrix and Coulomb-modified effective-range theory (CM-ERE) yield extracted ANCs close to, although not exactly equal to, the true value, provided the extrapolation is constrained by the known position of the bound-state pole and at least three terms are included in the fit function. The $R$-matrix approach converges faster than the CM-ERE as the number of parameters increases and is also more robust against the inclusion of low-energy and high-energy phase shift data. Finally, our study also shows that a naive quantification of uncertainties by comparing different truncations used in both theories is not accurate, and suggests the accuracy of ANCs extracted from phase shift data needs further investigation.

nucl-th↗
arXiv2023

Performing Bayesian analyses with AZURE2 using BRICK: an application to the ${}^7$Be system

Phenomenological $R$-matrix has been a standard framework for the evaluation of resolved resonance cross section data in nuclear physics for many years. It is a powerful method for comparing different types of experimental nuclear data and combining the results of many different experimental measurements in order to gain a better estimation of the true underlying cross sections. Yet a practical challenge has always been the estimation of the uncertainty on both the cross sections at the energies of interest and the fit parameters, which can take the form of standard level parameters. Frequentist ($χ^2$-based) estimation has been the norm. In this work, a Markov Chain Monte Carlo sampler, \texttt{emcee}, has been implemented for the $R$-matrix code \texttt{AZURE2}, creating the Bayesian $R$-matrix Inference Code Kit (\texttt{BRICK}). Bayesian uncertainty estimation has then been carried out for a simultaneous $R$-matrix fit of the $^3$He$(α,γ)^7$Be and $^3$He$(α,α)^3$He reactions in order to gain further insight into the fitting of capture and scattering data. Both data sets constrain the values of the bound state $α$-particle asymptotic normalization coefficients in $^7$Be. The analysis highlights the need for low-energy scattering data with well-documented uncertainty information and shows how misleading results can be obtained in its absence.

nucl-th↗
arXiv2022

Measurements of the $^{96}$Zr($α$,n)$^{99}$Mo cross section for astrophysics and applications

The reaction $^{96}$Zr($α$,n)$^{99}$Mo plays an important role in $ν$-driven wind nucleosynthesis in core-collapse supernovae and is a possible avenue for medical isotope production. Cross section measurements were performed using the activation technique at the Edwards Accelerator Laboratory. Results were analyzed along with world data on the $^{96}{\rm Zr}(α,n)$ cross section and $^{96}{\rm Zr}(α,α)$ differential cross section using large-scale Hauser-Feshbach calculations. We compare our data, previous measurements, and a statistical description of the reaction. We find a larger cross section at low energies compared to prior experimental results, allowing for a larger astrophysical reaction rate. This may impact results of core-collapse supernova $ν$-driven wind nucleosynthesis calculations, but does not significantly alter prior conclusions about $^{99}{\rm Mo}$ production for medical physics applications. The results from our large-scale Hauser-Feshbach calculations demonstrate that phenomenological optical potentials may yet be adequate to describe $(α,n)$ reactions of interest for $ν$-driven wind nucleosynthesis, albeit with regionally-adjusted model parameters.

nucl-ex↗
arXiv2020

Spectroscopic factors, overlaps, and isospin symmetry from an $R$-matrix point of view

Background: Spectroscopic factors, overlaps, and isospin symmetry are often used in conjunction with single-particle wave functions for the phenomenological analysis of nuclear structure and reactions. Many differing prescriptions for connecting these quantities to physically relevant asymptotic normalization constants or widths are available in the literature, but their relationship and degree of validity are not always clear. Purpose: This paper derives relationships among the above quantities of interest using well-defined methodology and starting assumptions. Method: $R$-matrix theory is used as the primary tool to interoperate between the quantities of interest to this work. Particular attention is paid to effects arising from beyond the nuclear surface, where isospin symmetry is strongly violated. Results: Relationships among the quantities of interest are derived. Example applications of these methods to mirror levels in nucleon+${}^{12}{\rm C}$, nucleon+${}^{16}{\rm O}$, and nucleon+${}^{26}{\rm Al}$ are presented. A new approach to multi-level mirror symmetry is derived and applied to the first three $2^+$ states of ${}^{18}{\rm O}$ and ${}^{18}{\rm Ne}$. Conclusions: The relationship between the quantities of interest is clarified and certain procedures are recommended. It is found that the asymptotic normalization constant of the second $2^+$ state in ${}^{18}{\rm Ne}$ deduced from the mirror state in ${}^{18}{\rm O}$ is significantly larger than found in previous work. This finding has the effect of increasing the ${}^{17}{\rm F}(p,γ){}^{18}{\rm Ne}$ reaction rate in novae.

nucl-th↗
arXiv2020

Secondary $γ$-ray decays from the partial-wave $T$ matrix with an $R$-matrix application to ${}^{15}{\rm N}(p,α_1γ){}^{12}{\rm C}$

The secondary $γ$ rays emitted following a nuclear reaction are often relatively straightforward to detect experimentally. Despite the large volume of such data, a practical formalism for describing these $γ$ rays in terms of partial-wave $T$-matrix elements has never been given. The partial-wave formalism is applicable when $R$-matrix methods are used to describe the reaction in question. This paper supplies the needed framework, and it is demonstrated by the application to the ${}^{15}{\rm N}(p,α_1γ){}^{12}{\rm C}$ reaction.

nucl-th↗
arXiv2018

Derivative Corrections to the Trapezoidal Rule

Extensions to the trapezoidal rule using derivative information are studied for periodic integrands and integrals along the entire real line. Integrands which are analytic within a half plane or within a strip containing the path of integration are considered. Derivative-free error bounds are obtained. Alternative approaches to including derivative information are discussed.

math.NA↗
arXiv2018

Proton Radiation Damage Experiment on a Hybrid CMOS Detector

We report on the initial results of an experiment to determine the effects of proton radiation damage on an X-ray hybrid CMOS detector (HCD). The device was irradiated at the Edwards Accelerator Lab at Ohio University with 8 MeV protons, up to a total absorbed dose of 3 krad(Si) (4.5 $\times$ 10$^9$ protons/cm$^2$). The effects of this radiation on read noise, dark current, gain, and energy resolution are then analyzed. This exposure is the first of several which will be used for characterizing detector performance at absorbed dose levels that are relevant for imaging devices operating in a deep-space environment.

physics.ins-det↗
arXiv2018

Monotonic properties of the shift and penetration factors

We study derivatives of the shift and penetration factors of collision theory with respect to energy, angular momentum, and charge. Definitive results for the signs of these derivatives are found for the repulsive Coulomb case. In particular, we find that the derivative of the shift factor with respect to energy is positive for the repulsive Coulomb case, a long anticipated but heretofore unproven result. These results are closely connected to the properties of the sum of squares of the regular and irregular Coulomb functions; we also present investigations of this quantity.

quant-ph↗
arXiv2016

White Paper on Nuclear Astrophysics

This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town meeting of the nuclear astrophysics community organized by the Joint Institute for Nuclear Astrophysics (JINA) on October 9- 10, 2012 Detroit, Michigan, with the purpose of developing a vision for nuclear astrophysics in light of the recent NRC decadal surveys in nuclear physics (NP2010) and astronomy (ASTRO2010). The white paper is furthermore informed by the town meeting of the Association of Research at University Nuclear Accelerators (ARUNA) that took place at the University of Notre Dame on June 12-13, 2014. In summary we find that nuclear astrophysics is a modern and vibrant field addressing fundamental science questions at the intersection of nuclear physics and astrophysics. These questions relate to the origin of the elements, the nuclear engines that drive life and death of stars, and the properties of dense matter. A broad range of nuclear accelerator facilities, astronomical observatories, theory efforts, and computational capabilities are needed. With the developments outlined in this white paper, answers to long standing key questions are well within reach in the coming decade.

astro-ph.SR↗
arXiv2010

New Nuclear Physics for Big Bang Nucleosynthesis

We discuss nuclear reactions which could play a role in Big Bang Nucleosynthesis (BBN). Most of these reactions involve lithium and beryllium isotopes and the rates for some of these have not previously been included in BBN calculations. Few of these reactions are well studied in the laboratory. We also discuss novel effects in these reactions, including thermal population of nuclear target states, resonant enhancement, and non-thermal neutron reaction products. We perform sensitivity studies which show that even given considerable nuclear physics uncertainties, most of these nuclear reactions have minimal leverage on the standard BBN abundance yields of 6Li and 7Li. Although a few have the potential to alter the yields significantly, we argue that this is unlikely.

astro-ph.CO↗
arXiv2010

R-matrix Methods with an application to 12C(alpha,gamma)16O

We review some aspects of R-matrix theory and its application to the semi-empirical analysis of nuclear reactions. Important applications for nuclear astrophysics and recent results for the ${}^{12}{\rm C}(α,γ){}^{16}{\rm O}$ reaction are emphasized.

nucl-th↗
arXiv2005

Nuclear Astrophysics

Nuclear physics has a long and productive history of application to astrophysics which continues today. Advances in the accuracy and breadth of astrophysical data and theory drive the need for better experimental and theoretical understanding of the underlying nuclear physics. This paper will review some of the scenarios where nuclear physics plays an important role, including Big Bang Nucleosynthesis, neutrino production by our sun, nucleosynthesis in novae, the creation of elements heavier than iron, and neutron stars. Big-bang nucleosynthesis is concerned with the formation of elements with A <= 7 in the early Universe; the primary nuclear physics inputs required are few-nucleon reaction cross sections. The nucleosynthesis of heavier elements involves a variety of proton-, alpha-, neutron-, and photon-induced reactions, coupled with radioactive decay. The advent of radioactive ion beam facilities has opened an important new avenue for studying these processes, as many involve radioactive species. Nuclear physics also plays an important role in neutron stars: both the nuclear equation of state and cooling processes involving neutrino emission play a very important role. Recent developments and also the interplay between nuclear physics and astrophysics will be highlighted.

astro-ph↗
arXiv2002

An Alternative Parameterization of R-matrix Theory

An alternative parameterization of R-matrix theory is presented which is mathematically equivalent to the standard approach, but possesses features which simplify the fitting of experimental data. In particular there are no level shifts and no boundary-condition constants which allows the positions and partial widths of an arbitrary number levels to be easily fixed in an analysis. These alternative parameters can be converted to standard R-matrix parameters by a straightforward matrix diagonalization procedure. In addition it is possible to express the collision matrix directly in terms of the alternative parameters.

nucl-th↗