Nuclear Theory·nucl-th

Wednesday·February 12, 2020

8 papers—3 primary·5 cross-listed

01
Statistical aspects of nuclear mass models
Vojtech Kejzlar · Léo Neufcourt · Witold Nazarewicz · Paul-Gerhard Reinhard
We study the information content of nuclear masses from the perspective of global models of nuclear binding energies. To this end, we employ a number of statistical methods and diagnostic tools, including Bayesian calibration, Bayesian model averaging, chi-square correlation analysis, principal component analysis, and empirical coverage probability. Using a Bayesian framework, we investigate the structure of the 4-parameter Liquid Drop Model by considering discrepant mass domains for calibration. We then use the chi-square correlation framework to analyze the 14-parameter Skyrme energy density functional calibrated using homogeneous and heterogeneous datasets. We show that a quite dramatic parameter reduction can be achieved in both cases. The advantage of Bayesian model averaging for improving uncertainty quantification is demonstrated. The statistical approaches used are pedagogically described; in this context this work can serve as a guide for future applications.
nucl-thstat.APstat.MLJ.Phys.G(2020)·42 citations
02
Asymptotic of the electric structure function and the deuteron wave function
V.I. Zhaba
The main features of obtaining the asymptotic behaviour of the electric structure function A(p) at large values of the transmitted momentum are analysed. The asymptotic behaviour of the structure function A(p) was determined to take into account the asymptotic behaviour of the deuteron form factors and the original dipole approximation for the nucleon form factors. Asymptotic values of A(p) were obtained for the nucleon-nucleon potential Reid93 and compared with the calculations for different nucleon form factors models and their approximations. In the broad momentum range up to 12.5 fm^(-1), the basic forms of the asymptotic behaviour of the electric structure function are demonstrated and compared with the experimental data of the modern collaborations. As the analysis shows in most cases considered, the asymptotic for A(p) is represented in the form of the power function p^(-n).
nucl-thMod.Phys.Lett.A(2020)·1 citation
03
Quantum expression for the electrical conductivity of massless quark matter and of the hadron resonance gas in the presence of a magnetic field
Jayanta Dey🇮🇳 · Subhasis Samanta🇵🇱 · Sabyasachi Ghosh🇮🇳 · Sarthak Satapathy🇮🇳
We have studied the classical and quantum expressions of electrical conductivity and their numerical estimation in the presence of a magnetic field for hadron resonance gas (HRG) and massless quark matter. Classical results of transport coefficients of HRG matter in the presence of a magnetic field were studied previously by Dash et al. [Phys. Rev. D 102, 016016 (2020)] using the standard relaxation time approximation in the Boltzmann equation. In the same reference, the transition from isotropic transport coefficients to anisotropic coefficients in the presence of a magnetic field was also estimated for massless and HRG matter. This led to an upper limit or Stefan-Boltzmann (SB) type limit to the nonperturbative domain transition of transport coefficients. In a similar context, the present work has concentrated on the classical to quantum transition of HRG transport from the domain of high temperature and low magnetic field to that of low temperature and high magnetic field. We have also compared the quantum modification of HRG results with that of massless quark matter, where we observed an opposite trend. A similar kind of quantum effect is also noticed between mesons and baryons due to their different particle distribution functions. Despite the fact that HRG contains both mesons and baryons, Landau quantization of its net magnetothermodynamic phase space reveals meson- or boson-dominated quantum modification. That is why the quantum modification of HRG results reveals the opposite trend from that of massless quark matter, which faces fermionic quantum modification.
nucl-thhep-phhep-thPRC(2022)·31 citations
04
Quarkonium Production in Heavy Ion Collisions: From Open Quantum System to Transport Equation
Xiaojun Yao🇺🇸 · Weiyao Ke🇺🇸 · Yingru Xu🇺🇸 · Steffen A. Bass🇺🇸 · Thomas Mehen🇺🇸 · Berndt Müller🇺🇸
Using the open quantum system formalism and effective field theory of QCD, we derive the Boltzmann transport equation of quarkonium inside the quark-gluon plasma. Our derivation illuminates that the success of transport equations in quarkonium phenomenology is closely related to the separation of scales in the problem.
↳ hep-phnucl-thNPA(2021)·11 citations
05
Nucleon and $Δ$ resonances in $γ p \to K^{+} Σ^{0} (1385)$ photoproduction
Ai-Chao Wang🇨🇳 · Wen-Ling Wang🇨🇳 · Fei Huang🇨🇳
The photoproduction of $γ p \to K^{+} Σ^{0} (1385)$ is investigated based on an effective Lagrangian approach using the tree-level Born approximation, with the purpose of understanding the reaction mechanisms and resonance contents and their associated parameters in this reaction. In addition to the $t$ -channel $K$ and $K^{*} (892)$ exchanges, $s$ -channel nucleon ( $N$ ) exchange, $u$ -channel $Λ$ exchange, and generalized contact term, the exchanges of a minimum number of $N$ and $Δ$ resonances in the $s$ channel are taken into account in constructing the reaction amplitudes to describe the experimental data. It is found that the most recent differential cross-section data from the CLAS Collaboration can be well reproduced by including one of the $N (1895) 1/2^{-}$ , $Δ (1900) 1/2^{-}$ , and $Δ (1930) 5/2^{-}$ resonances. The reaction mechanisms of $γ p \to K^{+} Σ^{0} (1385)$ are discussed in detail, and the predictions of the beam and target asymmetries for this reaction are given. The cross sections of $γ p \to K^{0} Σ^{+} (1385)$ are shown to be able to further constrain the theoretical models and pin down the resonance contents for $γ p \to K^{+} Σ^{0} (1385)$ .
↳ hep-phnucl-thPRD(2020)·15 citations
06
Detection prospects for the second-order weak decays of $^{124}$ Xe in multi-tonne xenon time projection chambers
Christian Wittweg🇩🇪 · Brian Lenardo🇺🇸 · Alexander Fieguth🇺🇸 · Christian Weinheimer🇩🇪
We investigate the detection prospects for two-neutrino and neutrinoless second order weak decays of $^{124}$ Xe -- double electron capture ( $0/2 ν ECEC$ ), electron capture with positron emission ( $0/2 ν EC β^{+}$ ) and double-positron emission ( $0/2 ν β^{+} β^{+}$ ) -- in multi-tonne xenon time projection chambers. We simulate the decays in a liquid xenon medium and develop a reconstruction algorithm which uses the multi-particle coincidence in these decays to separate signal from background. This is used to compute the expected detection efficiencies as a function of position resolution and energy threshold for planned experiments. In addition, we consider an exhaustive list of possible background sources and find that they are either negligible in rate or can be greatly reduced using our topological reconstruction criteria. In particular, we draw two conclusions: First, with a half-life of $T_{1/2}^{2 ν EC β^{+}} = (1.7 \pm 0.6) \cdot 1 0^{23} yr$ , the $2 ν EC β^{+}$ decay of $^{124}$ Xe will likely be detected in upcoming Dark Matter experiments (e.g. XENONnT or LZ), and their major background will be from gamma rays in the detector construction materials. Second, searches for the $0 ν EC β^{+}$ decay mode are likely to be background-free, and new parameter space may be within the reach. To this end we investigate three different scenarios of existing experimental constraints on the effective neutrino mass. The necessary 500 kg-year exposure of $^{124}$ Xe could be achieved by the baseline design of the DARWIN observatory, or by extracting and using the $^{124}$ Xe from the tailings of the nEXO experiment. We demonstrate how a combination of $^{124}$ Xe results with those from $0 ν β^{-} β^{-}$ searches in $^{136}$ Xe could help to identify the neutrinoless decay mechanism.
↳ nucl-exhep-exnucl-thEPJC(2020)·19 citations
07
A method to test the coupling strength of the linear and nonlinear contributions to higher-order flow harmonics via Event Shape Engineering
Niseem Magdy🇺🇸 · Olga Evdokimov🇺🇸 · Roy A. Lacey🇺🇸
A Multi-Phase Transport (AMPT) model is used to study the efficacy of shape-engineered events to delineate the degree of coupling between the linear and nonlinear contributions to the higher-order flow harmonics $v_{4}$ and $v_{5}$ . The study shows that the nonlinear contributions are strongly shape-dependent while the linear contributions are shape-independent, indicating little if any, coupling between the linear and nonlinear flow coefficients. The experimental verification of such patterns could be an invaluable tool for robust extraction of the linear and mode-coupled flow coefficients, especially for beam energies where the charged particle multiplicity and the event statistics precludes the use of current methods to establish the coupling strength.
↳ nucl-exnucl-thJ.Phys.G(2020)·24 citations
08
An Integral Experiment on Polyethylene Using Radiative Capture in Indium Foils in a High Flux D-D Neutron Generator
Nnaemeka Nnamani · Karl van Bibber · Lee A Bernstein · Jasmina L Vujic · Jonathan T. Morrell
The Department of Nuclear Engineering, University of California Berkeley built a D-D neutron generator called the High Flux Neutron Generator (HFNG). It operates in the range of 100-125 keV of accelerating voltage. The generator produces neutron current of about 10^8 per second. These neutrons have energies between 2.2-2.8 MeV. We report here the results of a measurement of the scattered vs unscattered neutron fluence on polyethylene determined via neutron activation of multiple natural indium foils from a D-D neutron generator. Both the angle-integrated spectrum and the angle differential results are consistent with the predictions of the Monte Carlo N-Particle Transport (MCNP) code, using the ENDF/B-VII.1. This supports shielding calculations in the fast energy region with high density polyethylene (HDPE). To the best of our knowledge no integral benchmark experiment has been performed on polyethylene using D(D,n)alpha neutron spectrum.
↳ nucl-exnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE