49 research outputs found
Inclusive deuteron-induced reactions and final neutron states
We present in this paper a formalism for deuteron-induced inclusive
reactions. We disentangle direct elastic breakup contributions from other
processes (which we generically call non-elastic breakup) implying a capture of
the neutron both above and below the neutron emission threshold. The reaction
is described as a two step process, namely the breakup of the deuteron followed
by the propagation of the neutron-target system driven by an optical potential.
The final state interaction between the neutron and the target can eventually
form an excited compound nucleus. Within this context, the direct neutron
transfer to a sharp bound state is a limiting case of the present formalism.Comment: To appear in the proceedings of the 14th International Conference on
Nuclear Reaction Mechanisms, Varenna, Ital
The complete quantification of parametric uncertainties in (d,p) transfer reactions
Previous work quantified the uncertainty associated with the optical
potentials between the nucleons and the target. In this study, we extend that
work by also including the parameters of the mean field associated with the
overlap function of the final bound state, thus obtaining the full parametric
uncertainty on transfer observables. We use Bayesian Markov Chain Monte Carlo
simulations to obtain parameter posterior distributions. We use
elastic-scattering cross sections to constrain the optical potential parameters
and use the asymptotic normalization coefficient of the final state to
constrain the bound state interaction. We then propagate these posteriors to
the transfer angular distributions and obtain confidence intervals for this
observable. We study (d,p) reactions on 14C, 16O, and 48Ca at energies in the
range E=10-24 MeV. Our results show a strong reduction in uncertainty by using
the asymptotic normalization coefficient as a constraint, particularly for
those reactions most sensitive to ambiguities in the mean-field. For those
reactions, the importance of constraining the bound state interaction is equal
to that of constrain the optical potentials. The case of 14C is an outlier
because it populates a halo state, and the observable is less sensitive to the
nuclear interior. We conclude that when minimal constraints are used on the
parameters of the nucleon-target interaction, the 68% confidence interval
uncertainties on the differential cross sections are very large (~ 140-185%).
However, if elastic-scattering data and the asymptotic normalization
coefficient are used in the analysis, with an error of 10% (5%), this
uncertainty reduces to ~30% (~15%)
Study of Cluster Structures in Nuclei through the Ratio Method. A Tribute to Mahir Hussein
For one-neutron halo nuclei, the cross section for elastic scattering and
breakup at intermediate energy exhibit similar angular dependences. The Recoil
Excitation and Breakup (REB) model of reactions elegantly explains this
feature. It also leads to the idea of a new reaction observable to study the
structure of loosely-bound nuclear systems: the Ratio. This observable consists
of the ratio of angular distributions for different reaction channels, viz.
elastic scattering and breakup, which cancels most of the dependence on the
reaction mechanism; in particular it is insensitive to the choice of optical
potentials that simulate the projectile-target interaction. This new observable
is very sensitive to the structure of the projectile. In this article, we
review the Ratio Method and its extension to low beam energies and proton-halo
nuclei.Comment: Submitted to the European Physical Journal A as a contribution to the
Special Issue on "Cluster structure and dynamics of nuclei" dedicated to the
memory of Mahir S. Hussein (1944-2019). 12 pages, 7 figure
New perspectives on spectroscopic factor quenching from reactions
The evolution of single-particle strengths as the neutron-to-proton asymmetry
changes informs us of the importance of short- and long-range correlations in
nuclei and has therefore been extensively studied for the last two decades.
Surprisingly, the strong asymmetry dependence of these strengths and their
extreme values for highly-asymmetric nuclei inferred from knockout reaction
measurements on a target nucleus are not consistent with what is extracted from
electron-induced, transfer, and quasi-free reaction data, constituting a
two-decade old puzzle. This work presents the first consistent analysis of
one-nucleon transfer and one-nucleon knockout data, in which theoretical
uncertainties associated with the nucleon-nucleus effective interactions
considered in the reaction models are quantified using a Bayesian analysis. Our
results demonstrate that, taking into account these uncertainties, the
spectroscopic strengths of loosely-bound nucleons extracted from both probes
agree with each other and, although there are still discrepancies for
deeply-bound nucleons, the slope of the asymmetry dependence of the
single-particle strengths inferred from transfer and knockout reactions are
consistent within . Both probes are consistent with a small asymmetry
dependence of these strengths. The uncertainties obtained in this work
represent a lower bound and are already significantly larger than the original
estimates.Comment: 14 pages: 7 pages of the main text (including one and a half of
reference) and 7 pages of supplemental material. Accepted for publication in
Phys. Rev. Let
Uncertainty Quantification in Breakup Reactions
Breakup reactions are one of the favored probes to study loosely bound
nuclei, particularly those in the limit of stability forming a halo. In order
to interpret such breakup experiments, the continuum discretized coupled
channel method is typically used. In this study, the first Bayesian analysis of
a breakup reaction model is performed. We use a combination of statistical
methods together with a three-body reaction model (the continuum discretized
coupled channel method) to quantify the uncertainties on the breakup
observables due to the parameters in the effective potential describing the
loosely bound projectile of interest. The combination of tools we develop opens
the path for a Bayesian analysis of not only breakup processes, but also a wide
array of complex processes that require computationally intensive reaction
models
Theory of (d,p) and (p,d) reactions including breakup: Comparison of methods
There is an increasing interest in studying transfer reactions to probe the nuclear structure of exotic nuclei. For these loosely bound systems, the role of the continuum needs to be well understood. In this study, we concentrate on (p,d) and (d,p) reactions and compare two formulations for the transfer process that take into account breakup states. Applications to 11Be(p,d)10Be at Elab=38.4 MeV/nucleon and 10Be(d,p)11Be at Elab=12.5 MeV/nucleon are presented, as is a detailed discussion of convergence rates.Ministerio de Ciencia e Innovación FPA2006-13807-c02-01Programa Consolider- Ingenio 2010 CSD2007-0004
Quantifying uncertainties due to optical potentials in one-neutron knockout reactions
One-neutron knockout reactions have been widely used to extract information
about the single-particle structure of nuclei from the valley of stability to
the driplines. The interpretation of knockout data relies on reaction models,
where the uncertainties are typically not accounted for. In this work we
quantify uncertainties of optical potentials used in these reaction models and
propagate them, for the first time, to knockout observables using a Bayesian
analysis. We study two reactions in the present paper, the first of which
involves a loosely-bound halo projectile, Be, and the second a
tightly-bound projectile, C. We first quantify the parametric
uncertainties associated with phenomenological optical potentials.
Complementing to this approach, we also quantify the model uncertainties
associated with the chiral forces that can be used to construct microscopic
optical potentials. For the phenomenological study, we investigate the impact
of the imaginary terms of the optical potential on the breakup and stripping
components of the knockout cross sections as well as the impact of the angular
range. For the Be case, the theoretical uncertainty from the
phenomenological method is on the order of the experiment uncertainty on the
knockout observables; however, for the C case, the theoretical
uncertainty is significantly larger. The widths of the confidence intervals for
the knockout observables obtained for the microscopic study and the
phenomenological approach are of similar order of magnitude. Based on this work
we conclude that structure information inferred from the ratio of the knockout
cross sections, will carry a theoretical uncertainty of at least for
halo nuclei and at least for tightly-bound nuclei.Comment: 12 pages (including 2 of supplemental material and 1 of reference), 5
figures, 2 table
Biocompounds recovery from Spirulina by conventional and ohmic heating methodologies: chemical and biological properties
Extracting the totality of bio-compounds with industrial interest from Cyanobacterium is often prevented by
the intrinsic rigidity of its cell wall. In this sense, the present study focuses on evaluating the influence thermal
batch extraction (conventional extraction technologies) and ohmic heating (OH) assisted extraction
(considered a greener alternative technology) in blue green microalgae Arthrospira platensis (Spirulina) cell
disruption for bioactive fractions recovery.
The proximal composition of Spirulina was initially determined. The maximum protein content (i.e., CPhycocyanin),
total carbohydrates (TC) and total phenolic compounds (TPC) extracted in water at different
times (30-120 min) and temperatures (30-51 ºC) was quantified after the conventional and OH- assisted
extraction. The freeze-thawing process was used as control. The antioxidant activity (i.e., FRAP and DPPH
assays) of the obtained extracts was assessed.
Results showed that with the freeze-thawing process, traditionally used for the recovery of bio- compounds
from Spirulina, the concentration of C-phycocyanin was approx. 42 mg/g of Spirulina, 26 mgGlcE/g Spirulina
of TC and 9 mgGAE/g Spirulina of TPC. Using OH-assisted extraction, the maximum of C-Phycocyanin
content obtained was 45 mg/g of Spirulina (obtained at 37 ºC, 30 min), the maximum carbohydrates content
was 40 mgGlcE/g Spirulina and the maximum TPC was 10 mgGAE/g Spirulina. On the other hand, using
conventional thermal treatment it can be observed that, under the same conditions, the bioactive compounds
recovery decreased to 35 mg/g, 20 mgGlcE/g Spirulina for C-phycocyanin concentration and TC (p<0.05),
respectively. The concentration in phenolic compounds is not so affected, but even so the ohmic heating
potentiates the extraction of these secondary metabolites.
The antioxidant activity of the extracts there was not different between conventional treatments andOH.
Thus, the results indicated that OH is a good alternative to conventional methods aiming at the extraction of
intracellular components with a decrease in processing time and energy costs associated with the extraction
process, which together with an easy upscale make OH an interesting methodology for use in the industrial
production of microalgae colorants and bioactive supplements.info:eu-repo/semantics/publishedVersio