Nuclear Theory·nucl-th

Tuesday·June 18, 2019

10 papers—6 primary·4 cross-listed

01
[Submitted on 14 Jun 2019]
Interpretable deep learning for nuclear deformation in heavy ion collisions
Long-Gang Pang🇺🇸 · Kai Zhou🇩🇪 · Xin-Nian Wang🇺🇸
The structure of heavy nuclei is difficult to disentangle in high-energy heavy-ion collisions. The deep convolution neural network (DCNN) might be helpful in mapping the complex final states of heavy-ion collisions to the nuclear structure in the initial state. Using DCNN for supervised regression, we successfully extracted the magnitude of the nuclear deformation from event-by-event correlation between the momentum anisotropy or elliptic flow ( $v_{2}$ ) and total number of charged hadrons ( $d N_{ch} / d η$ ) within a Monte Carlo model. Furthermore, a degeneracy is found in the correlation between collisions of prolate-prolate and oblate-oblate nuclei. Using the Regression Attention Mask algorithm which is designed to interpret what has been learned by DCNN, we discovered that the correlation in total-overlapped collisions is sensitive to only large nuclear deformation, while the correlation in semi-overlapped collisions is discriminative for all magnitudes of nuclear deformation. The method developed in this study can pave a way for exploration of other aspects of nuclear structure in heavy-ion collisions.
Comments:
8 pages, 2 figures, AI + X research
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1906.06429 [pdf]
23 citations
02
[Submitted on 15 Jun 2019]
High-K isomer and the rotational properties in the odd-Z neutron-rich nucleus $^{163}$ Eu
Xiao-Tao He · Ze-Long Chen
The newly observed isomer and ground-state band in the odd-Z neutron-rich rare-earth nucleus $^{163}$ Eu are investigated by using the cranked shell model (CSM) with pairing treated by the particle-number conserving (PNC) method. This is the first time detailed theoretical investigations are performed of the observed $964 (1)$ keV isomer and ground-state rotational band in $^{163}$ Eu. The experimental data are reproduced very well by the theoretical results. The configuration of the $964 (1)$ keV isomer is assigned as the three-particle state $\frac{13}{2}^{-} (ν \frac{7}{2}^{+} [633] \otimes ν \frac{1}{2}^{-} [521] \otimes π \frac{5}{2}^{+} [413]$ ). More low-lying multi-particle states are predicted in $^{163}$ Eu. Due to its significant effect on the nuclear mean field, the high-order $ε_{6}$ deformation plays an important role in the energy and configuration assignment of the multi-particle states. Compared to its neighboring even-even nuclei $^{162}$ Sm and $^{164}$ Gd, there is a $10% \sim 15%$ increase of $J^{(1)}$ of the one-particle ground-state band in $^{163}$ Eu. This is explained by the pairing reduction due to the blocking of the nucleon on the proton $π \frac{5}{2}^{+}$ [413] orbital in $^{163}$ Eu.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1906.06473 [pdf]
CPC(2019)·4 citations
03
[Submitted on 15 Jun 2019]
A machine learning study to identify spinodal clumping in high energy nuclear collisions
Jan Steinheimer🇩🇪 · LongGang Pang🇺🇸 · Kai Zhou🇩🇪 · Volker Koch🇺🇸 · Jørgen Randrup🇺🇸 · Horst Stoecker🇩🇪
The coordinate and momentum space configurations of the net baryon number in heavy ion collisions that undergo spinodal decomposition, due to a first-order phase transition, are investigated using state-of-the-art machine-learning methods. Coordinate space clumping, which appears in the spinodal decomposition, leaves strong characteristic imprints on the spatial net density distribution in nearly every event which can be detected by modern machine learning techniques. On the other hand, the corresponding features in the momentum distributions cannot clearly be detected, by the same machine learning methods, in individual events. Only a small subset of events can be systematically differentiated if only the momentum space information is available. This is due to the strong similarity of the two event classes, with and without spinodal decomposition. In such scenarios, conventional event-averaged observables like the baryon number cumulants signal a spinodal non-equilibrium phase transition. Indeed the third-order cumulant, the skewness, does exhibit a peak at the beam energy ( $E_{lab} = 3 - 4$ A GeV), where the transient hot and dense system created in the heavy ion collision reaches the first-order phase transition.
Comments:
24 pages, 14 figures, accepted for publication by JHEP
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1906.06562 [pdf]
JHEP(2019)·65 citations
04
[Submitted on 16 Jun 2019]
Comparison between Variational Monte Carlo and Shell Model Calculations of Neutrinoless Double Beta Decay Matrix Elements in Light Nuclei
X.B. Wang🇨🇳 · A.C. Hayes🇺🇸 · J. Carlson🇺🇸 · G.X. Dong🇨🇳 · E. Mereghetti🇺🇸 · S. Pastore🇺🇸 · R.B. Wiringa🇺🇸
Benchmark comparisons between many-body methods are performed to assess the ingredients necessary for an accurate calculation of neutrinoless double beta decay matrix elements. Shell model and variational Monte Carlo (VMC) calculations are carried out for $A = 10$ and $12$ nuclei. Different variational wavefunctions are used to evaluate the uncertainties in the {\it ab initio} calculations, finding fairly small differences between the VMC double beta decay matrix elements. For shell model calculations, the role of model space truncation, radial wavefunction choices, and short-range correlation are investigated and all found to be important. Based on the detailed comparisons between the VMC and shell model approaches, we conclude that accurate descriptions of neutrinoless double beta decay matrix elements require a proper treatment of both long-range and short-range correlations.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1906.06662 [pdf]
PLB(2019)·32 citations
05
[Submitted on 16 Jun 2019]
Fusion hindrance effects in laser-induced non-neutral plasmas
Salvatore Simone Perrotta (1, 2 3, and 4) · Aldo Bonasera (2 and 4) ((1) Dipartimento di Fisica e Astronomia, Università degli studi di Catania, (2) Scuola Superiore di Catania, Università degli studi di Catania, (3) Cyclotron Insitute, Texas A&M University, (4) Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare)
Inertial confinement fusion hotspots and cluster Coulomb explosion plasmas may develop a positive net electric charge. The Coulomb barrier penetrability and the rate of nuclear fusion reactions at ultra-low energies ( $≲ 10$ keV) are altered by such an environment. These effects are here studied via the screening potential approach. Approximate analytical results are developed by evaluating the average screening potential for some scenarios of interest. It is found that fusion is hindered for reactions between thermal fuel nuclei, while an enhancement is expected for secondary and "beam-target" reactions. Depending on the plasma conditions, the variations can be relevant even for relatively small net charges (several % difference or more in the fusion rate for an average net charge per nucleus of $1 0^{- 5}$ proton charges).
Comments:
19 pages, 6 figures. Accepted by Nuclear Physics A (in press)
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph)
arXiv:
1906.06724 [pdf]
NPA(2019)·3 citations
06
[Submitted on 17 Jun 2019]
B $_{Λ}$ ( $_{Λ}^{5}$ He) from short range effective field theory
Lorenzo Contessi🇮🇱 · Nir Barnea🇮🇱 · Avraham Gal🇮🇱
We present an effective field theory (EFT) at leading order to describe light single- $Λ$ hypernuclei. Owing to the weak $Λ$ binding and to the $Λ N$ short interaction range, meson exchange forces are approximated by contact interactions within a pionless EFT where the only degrees of freedom are baryons. At leading order, the $Λ$ -nuclear interaction contains two 2-body (singlet and triplet) and three 3-body interaction terms, a total of 5 terms associated with 5 coupling strengths or low energy constants (LECs). We adopt the 2-body LECs from hyperon-nucleon scattering data and interaction models that constrain the $Λ N$ scattering lengths, while the 3-body LECs are adjusted using both 3-body and 4-body hypernuclear binding energies. To calculate the binding energies for A-body systems with A $>$ 2, we expand the wavefunctions using a correlated Gaussian basis. The stochastic variational method is employed to select the non-linear parameters. The resulting \nopieft~is then applied to calculate the $Λ$ separation energy in $_{Λ}^{5}$ He, where the adjusted 3-body interactions largely resolve the known overbinding problem of $_{Λ}^{5}$ He.
Comments:
HYP2018 conference proceeding
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1906.06958 [pdf]
AIP Conf.Proc.(2019)·6 citations
07
[Submitted on 15 Jun 2019] (cross-list from hep-ph)
Heavy hadron molecules in effective field theory: the emergence of exotic nuclear landscapes
Manuel Pavon Valderrama🇨🇳
Heavy hadron molecules were first theorized from a crude analogy with the deuteron and the nuclear forces binding it, a conjecture which was proven to be on the right track after the discovery of the $X (3872)$ . However, this analogy with nuclear physics has not been seriously exploited beyond a few calculations in the two- and three-body sectors, leaving a great number of possible theoretical consequences unexplored. Here we show that nuclear and heavy hadron effective field theories are formally identical: using a suitable notation, there is no formal difference between these two effective field theories. For this, instead of using the standard heavy superfield notation, we have written the heavy hadron interactions directly in terms of the light quark degrees of freedom. We give a few examples of how to exploit this analogy, e.g. the calculation of the two-pion exchange diagrams. Yet the most relevant application of the present idea is the conjecture of exotic nuclear landscapes, i.e. the possibility of few heavy hadron bound states with characteristics similar to those of the standard nuclei.
Comments:
Prepared for the special issue of "The tower of effective (field) theories and the emergence of nuclear phenomena"; 14 pages, 3 tables and 2 figures; corresponds with published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1906.06491 [pdf]
EPJA(2020)·18 citations
08
[Submitted on 17 Jun 2019] (cross-list from astro-ph.HE)
Presupernova neutrino signals as potential probes of neutrino mass hierarchy
Gang Guo🇩🇪 · Yong-Zhong Qian🇺🇸 · Alexander Heger🇦🇺
We assess the potential of using presupernova neutrino signals at the Jiangmen Underground Neutrino Observatory (JUNO) to probe the yet-unknown neutrino mass hierarchy. Using models for stars of 12, 15, 20, and 25 solar masses, we find that if the electron antineutrino signals from such a star can be predicted precisely and the star is within ~440-880 pc, the number of events of electron antineutrino captures on protons detected within one day of its explosion allows to determine the hierarchy at the > ~95% confidence level. For determination at this level using such signals from Betelgeuse, which is at a distance of ~222 pc, the uncertainty in the predicted number of signals needs to be < ~14-30%. In view of more realistic uncertainties, we discuss and advocate a model-independent determination using both electron neutrino and antineutrino signals from Betelgeuse. This method is feasible if the cosmogenic background for neutrino-electron scattering events can be reduced by a factor of ~2.5-10 from the current estimate. Such reduction might be achieved by using coincidence of the background events, the exploration of which for JUNO is highly desirable.
Comments:
5 pages, 4 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1906.06839 [pdf]
PLB(2019)·14 citations
09
[Submitted on 17 Jun 2019] (cross-list from astro-ph.HE)
Astrophysical implications of double-layer torsional oscillations in a neutron star crust as a lasagna sandwich
Hajime Sotani · Kei Iida · Kazuhiro Oyamatsu
In the crust of a neutron star, global torsional oscillations could occur in two elastic layers. The outer and inner layers are composed of spherical and cylindrical nuclei and of cylindrical holes (tubes) and spherical holes (bubbles), respectively, while between these two layers, a phase of slab-like (lasagna) nuclei with vanishingly small elasticity is sandwiched. In this work, we update systematic calculations of the eigenfrequencies of the fundamental oscillations in the inner layer by newly allowing for the presence of tubes. We find that the frequencies still depend strongly on the slope parameter of the nuclear symmetry energy, $L$ , while being almost independent of the incompressibility of symmetric nuclear matter. We also find that the fundamental frequencies in the inner layer can become smaller than those in the outer layer because the tube phase has a relatively small shear modulus and at the same time dominates the inner layer in thickness. As a result, we can successfully explain not only the quasi-periodic oscillations originally discovered in the observed X-ray afterglow of the giant flare of SGR 1806--20 but also many others recently found by a Bayesian procedure.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1906.06999 [pdf]
MNRAS(2019)·50 citations
10
[Submitted on 17 Jun 2019] (cross-list from hep-ph)
Weak production of strange $Ξ$ baryons off the nucleon
M. Rafi Alam🇮🇳 · I. Ruiz Simo🇪🇸
The charged current Cabibbo-supressed associated $K Ξ$ production off the nucleon induced by anti-neutrinos is studied at low and intermediate energies. The non-resonant terms are obtained using a microscopical model based on the SU(3) chiral Lagrangian. The basic parameters of the model are $f_{π}$ , the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider $Σ^{*} (1385)$ resonance, which can decay in $K Ξ$ final state when this channel is open. The studied mechanism is the prime source of $Ξ$ production at anti-neutrino energies around $2$ GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.
Comments:
10 pages, 4 figures, 3 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1906.07049 [pdf]
PRD(2019)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE