Nuclear Theory·nucl-th

Tuesday·July 3, 2018

11 papers—6 primary·5 cross-listed

01
Domains and defects in nuclear "pasta"
Andre da Silva Schneider🇺🇸 · Matt E. Caplan🇨🇦 · Don K. Berry🇺🇸 · Charles J. Horowitz🇺🇸
Nuclear pasta topology is an essential ingredient to determine transport properties in the inner crust of neutron stars. We perform semi-classical molecular dynamics simulations of nuclear pasta for proton fractions $Y_{p} = 0.30$ and $Y_{p} = 0.40$ near one third of nuclear saturation density, $n = 0.05 fm^{- 3}$ , at a temperature $T = 1.0 MeV$ . Our simulations are, to our knowledge, the largest nuclear pasta simulations to date and contain up to $3276800$ nucleons in the $Y_{p} = 0.30$ and $819200$ nucleons in the $Y_{p} = 0.40$ case. An algorithm to determine which nucleons are part of a given sub-domain in the system is presented. By comparing runs of different sizes we study finite size effects, equilibration time, the formation of multiple domains and defects in the pasta structures, as well as the structure factor dependence on simulation size. Although we find qualitative agreement between the topological structure and the structure factors of runs with $51200$ nucleons and those with $819200$ nucleons or more, we show that simulations with hundreds of thousands of nucleons may be necessary to accurately predict pasta transport properties.
nucl-thPRC(2018)·32 citations
02
Jost-matrix analysis of the resonance 5He*(3/2+) near the dt-threshold
S.A. Rakityansky🇿🇦 · S.N. Ershov🇷🇺
Experimental data on the n-alpha and dt collisions in the quantum state J^pi=3/2+ near the dt-threshold are fitted using the semi-analytic multi-channel Jost matrix with proper analytic structure and some adjustable parameters. Then the spectral points are sought as zeros of the Jost matrix determinant (which correspond to the S-matrix poles) at complex energies. The correct analytic structure makes it possible to calculate the fitted Jost matrix on any sheet of the Riemann surface whose topology involves not only the square-root but also the logarithmic branching caused by the Coulomb interaction. Within a distance of 100,keV above the dt-threshold, three 3/2+ resonances are found on the non-physical sheet of the Riemann surface. Several S-matrix (shadow) poles on the other sheets of this surface are located as well.
nucl-thnucl-exIJMPE(2019)·7 citations
03
Cluster Radioactivity in Super Heavy Nuclei
M. Warda🇵🇱 · A. Zdeb🇵🇱 · L.M. Robledo🇪🇸
Cluster radioactivity is an exotic nuclear decay observed in actinides where a light nucleus is emitted while the remaining heavy mass residue is the doubly magic $^{208}$ Pb or a nucleus in its neighborhood. We have investigated this type of decay in heavier nuclei up to Lv $(Z = 116)$ within a microscopic theory. It has been found that super asymmetric fission with $^{208}$ Pb as heavy fragment may be dominant decay channel in some super heavy nuclei. This reaction is closely related with cluster radioactivity.
nucl-thPRC(2018)·64 citations
04
Microscopic predictions of the nuclear matter liquid-gas phase transition
Arianna Carbone · Artur Polls · Arnau Rios
We present first-principle predictions for the liquid-gas phase transition in symmetric nuclear matter employing both two- and three-nucleon chiral interactions. Our discussion focuses on the sources of systematic errors in microscopic quantum many body predictions. On the one hand, we test uncertainties of our results arising from changes in the construction of chiral Hamiltonians. We use five different chiral forces with consistently derived three-nucleon interactions. On the other hand, we compare the ladder resummation in the self-consistent Green's functions approach to finite temperature Brueckner--Hartree--Fock calculations. We find that systematics due to Hamiltonians dominate over many-body uncertainties. Based on this wide pool of calculations, we estimate that the critical temperature is $T_{c} = 16 \pm 2$ MeV, in reasonable agreement with experimental results. We also find that there is a strong correlation between the critical temperature and the saturation energy in microscopic many-body simulations.
nucl-thnucl-exPRC(2018)·45 citations
05
A systematic study of alpha and cluster decay in Platinum isotopes
Nithu Ashok🇮🇳 · Antony Joseph🇮🇳
The feasibility of alpha and cluster decay from Pt isotopes has been investigated within the framework of Skyrme Hartree-Fock-Bogoliubov theory. Calculation has been carried out for various Skyrme forces. Harmonic oscillator and transformed harmonic oscillator basis are used to solve HFB equations. The role played by shell closure is withal analysed. Half-lives are estimated with the help of Universal Decay Law (UDL). Geiger-Nuttel plots are also plotted and successfully preserves its linear nature.
nucl-thIJMPE(2019)·5 citations
06
Irreducible nonlocality of optical model potentials based on realistic NN interactions
H. F. Arellano🇨🇱 · G. Blanchon🇫🇷
We investigate the nonlocal structure of optical model potentials for nucleon-nucleus scattering based on microscopic approaches. To this purpose, \emph{in-medium} folding optical potentials are calculated in momentum space and their corresponding coordinate-space counterpart are examined, paying special attention to their nonlocal shape. The nucleon-nucleon effective interaction consists of the actual full off-shell $g$ matrix in Brueckner-Hartree-Fock approximation. The nonlocality of effective interactions is preserved throughout all stages in the the calculation. Argonne $v_{18}$ bare potential and chiral next-to-next-to-next-to-leading order bare interaction are used as starting point. The study is focused on proton elastic scattering off $^{40}$ Ca at beam energies between 30 and 800 MeV. We find that the gradual suppression of high-momentum contributions of the optical potential results in quite different-looking coordinate-space counterparts. Despite this non-uniqueness in their nonlocal structure, the implied scattering observables remain unchanged for momentum cutoff above a critical one, which depends on incident energy of the projectile. We find that coordinate-space potentials with momentum cutoffs at the critical value yield the least structured nonlocal behavior. Implications of these findings are discussed.
nucl-thPRC(2018)·16 citations
07
Transversity parton distribution functions from lattice QCD
Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Karl Jansen🇩🇪 · Aurora Scapellato🇨🇾 · Fernanda Steffens🇩🇪
We present the first direct calculation of the transversity parton distribution function within the nucleon from lattice QCD. The calculation is performed using simulations with the light quark mass fixed to its physical value and at one value of the lattice spacing. Novel elements of the calculations are non-perturbative renormalization and extraction of a formula for the matching to light-cone PDFs. Final results are presented in the $MS$ scheme at a scale of $2$ GeV.
↳ hep-lathep-exhep-phnucl-ex+1PRD(2018)·163 citations
08
Holographic Magnetized Chiral Density Wave
Yanyan Bu🇨🇳 · Shu Lin🇨🇳
We explore the end point of the helical instability in finite density, finite magnetic field background discussed by Kharzeev and Yee [1]. The nonlinear solution is obtained and identified with the (magnetized) chiral density wave phase in literature. We find there are two branches of solutions, which match with the two unstable modes in [1]. At large chemical potential and magnetic field, the magnetized chiral density wave can be thermodynamically preferred over chirally symmetric phase and chiral symmetry breaking phase. Interestingly, we find an exotic state with vanishing chemical potential at large magnetic field. We also attempt to clarify the role of anomalous charge in holographic model.
↳ hep-thhep-phnucl-thCPC(2018)·8 citations
09
Constraints on the nuclear equation of state and the neutron star structure from crustal torsional oscillations
Hajime Sotani🇯🇵 · Kei Iida🇯🇵 · Kazuhiro Oyamatsu🇯🇵
We systematically examine torsional shear oscillations of neutron star crusts by newly taking into account the possible presence of the phase of cylindrical nuclei. In this study, we neglect an effect of magnetic fields, under which the shear oscillations can be damped by the magnetic interaction. First, by identifying the low frequency quasi-periodic oscillations (QPOs) observed in the soft-gamma repeaters (SGRs) as the fundamental torsional oscillations, we constrain the slope parameter of the nuclear symmetry energy, $L$ , for reasonable values of the star's mass $M$ and radius $R$ . Meanwhile, we find that the 1st overtone of torsional oscillations obtained for given $M$ and $R$ can be expressed well as a function of a new parameter $ς \equiv (K_{0}^{4} L^{5})^{1/9}$ , where $K_{0}$ is the incompressibility of symmetric nuclear matter. Assuming that the lowest of the QPO frequencies above 500 Hz observed in SGR 1806-20 comes from the 1st overtone, we can constrain the value of $ς$ . Then, for each neutron star model, such a value of $L$ as can be obtained from the observed low frequency QPOs translates to the optimal value of $K_{0}$ via the above constraint on $ς$ . Finally, its consistency with allowed values of $K_{0}$ from empirical giant monopole resonances leads to neutron star models with relatively low mass and large radius, which are qualitatively similar to the prediction in earlier investigations. This result suggests that $L ≃ 58 - 73$ MeV, even when uncertainties in the neutron superfluid density inside the phase of cylindrical nuclei are allowed for.
↳ astro-ph.HEnucl-thMNRAS(2018)·52 citations
10
A Fixed-Target Programme at the LHC: Physics Case and Projected Performances for Heavy-Ion, Hadron, Spin and Astroparticle Studies
C. Hadjidakis🇫🇷 · D. Kikoła🇵🇱 · J.P. Lansberg🇫🇷 · L. Massacrier🇫🇷 · M.G. Echevarria🇮🇹 · A. Kusina🇵🇱 · I. Schienbein🇫🇷 · J. Seixas🇵🇹 · H.S. Shao🇫🇷 · A. Signori🇺🇸 · B. Trzeciak🇳🇱 · S.J. Brodsky🇺🇸 and 20 other authors
We review the context, the motivations and the expected performances of a comprehensive and ambitious fixed-target program using the multi-TeV proton and ion LHC beams. We also provide a detailed account of the different possible technical implementations ranging from an internal wire target to a full dedicated beam line extracted with a bent crystal. The possibilities offered by the use of the ALICE and LHCb detectors in the fixed-target mode are also reviewed.
↳ hep-exhep-phnucl-exnucl-thPhys.Rept.(2021)·128 citations
11
The $Ω (2012)$ as a hadronic molecule
M. Pavon Valderrama🇵🇱
Recently the Belle collaboration has discovered a narrow $S = - 3$ baryon, the $Ω (2012)$ . We explore the possibility that the $Ω (2012)$ is a $Ξ (1530) K ˉ$ molecule, where the binding mechanism is the coupled channel dynamics with the $Ω η$ channel. The characteristic signature of a molecular $Ω (2012)$ will be its decay into the three body channel $Ξ π K ˉ$ , for which we expect a partial decay width of $2 - 3 MeV$ . The partial decay width into the $Ξ K ˉ$ channel should lie in the range of $1 - 11 MeV$ , a figure compatible with experiment and which we have deduced from the assumption that the coupling involved in this decay is of natural size. For comparison purposes the decay of a purely compact $Ω (2012)$ into the $Ξ K ˉ$ and $Ξ π K ˉ$ channels is of the same order of magnitude as and one order of magnitude smaller than in the molecular scenario, respectively. This comparison indicates that the current experimental information is insufficient to distinguish between a compact and a molecular $Ω (2012)$ and further experiments will be required to determine its nature. A molecular $Ω (2012)$ will also imply the existence of two- and three-body molecular partners. The two-body partners comprise two $Λ$ hyperons located at $1740$ and $1950 MeV$ respectively, the first of which might correspond to the $Λ (1800)$ while the second to the $Λ (2000)$ or the $Λ (2050)$ . The three-body partners include a $Ξ (1530) K K ˉ$ and a $Ξ (1530) η K ˉ$ molecule, with masses of $M = 2385 - 2445 MeV$ and $M = 2434 - 2503 MeV$ respectively. We might be tempted to identify the first with the $Ξ (2370)$ and the latter with the $Ω (2470)$ listed in the PDG.
↳ hep-phhep-exhep-latnucl-thPRD(2018)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE