Nuclear Theory·nucl-th

Monday·April 13, 2015

14 papers—8 primary·6 cross-listed

01
Cross-checking the symmetry energy at high densities
Gao-Chan Yong🇨🇳
The nuclear symmetry energy determines the birth of neutron stars and the elementary nucleosynthesis in the universe. To constrain the nuclear symmetry energy, besides the studies in astrophysics, many terrestrial nuclear experiments are being carried out using a wide variety of advanced new facilities. In this paper, by cross-checking two unrelated experimental measurements using the newly updated transport model, we obtained a slightly soft symmetry energy at supra-saturation nuclear densities. While extrapolating to low nuclear densities, this result is compatible with the recent finding by comparing the available data on the electric dipole polarizability with the theoretical predictions. Our finding is expected to push the studies of nuclear physics and astrophysics forward.
nucl-thnucl-exPRC(2016)·36 citations
02
Collective flow without hydrodynamics: simulation results for relativistic ion collisions
Paul Romatschke🇺🇸
Flow signatures in experimental data from relativistic ion collisions are usually interpreted as a fingerprint of the presence of a hydrodynamic phase during the evolution of these systems. In this work, flow signatures arising from event-by-event viscous hydrodynamics are compared to those arising from event-by-event non-interacting particle dynamics (free-streaming), both followed by a late-stage hadronic cascade, in d+Au, 3He+Au at sqrt(s)=200 GeV and p+Pb collisions at sqrt(s)=5 TeV, respectively. For comparison, also Pb+Pb collisions at sqrt(s)=2.76 TeV are simulated. It is found that non-hydrodynamic evolution can give rise to equal or larger radial flow than hydrodynamics with eta/s=0.08 in all simulated collision systems. In light-on-heavy-ion collisions, free-streaming gives rise to triangular and quadrupolar flow comparable to or larger than that from hydrodynamics, but it generally leads to considerably smaller elliptic flow. As expected, free-streaming leads to considerably less elliptic, triangular and quadrupolar flow than hydrodynamics in nucleus-nucleus collisions, such as event-by-event Pb+Pb collisions at sqrt(s)=2.76 TeV.
nucl-thhep-phphysics.flu-dynEPJC(2015)·43 citations
03
Exotic Nuclei and Matter in a Chirally Effective Approach
S. Schramm🇩🇪
A relativistic approach to describe nuclear and in general strongly interacting matter is introduced and discussed. Here, not only the nuclear forces but also the masses of the nucleons are generated through meson fields. Within this framework it is possible to calculate properties of finite nuclei at a level of accuracy similar to dedicated relativistic nuclear structure models. Due to the more general approach, a wider range of properties of hadronic states can be investigated. A number of results for heavy and neutron-rich nuclei toward the drip line are presented.
nucl-th2 citations
04
Robust correlations between quadrupole moments of low-lying $2^{+}$ states within random-interaction ensembles
Y. Lei
In the random-interaction ensembles, three proportional correlations between quadrupole moments of the first two $I^{π} = 2^{+}$ states robustly emerge, including $Q (2_{1}^{+}) = \pm Q (2_{2}^{+})$ correlations consistently with realistic nuclear survey, and the $Q (2_{2}^{+}) = - \frac{3}{7} Q (2_{1}^{+})$ correlation, which is only observed in the $s d$ -boson space. These correlations can be microscopically characterized by the rotational SU(3) symmetry and quadrupole vibrational U(5) limit, respectively, according to the Elliott model and the $s d$ -boson mean-field theory. The anharmonic vibration may be another phenomenological interpretation for the $Q (2_{1}^{+}) = - Q (2_{2}^{+})$ correlation, whose spectral evidence, however, is insufficient.
nucl-thnucl-exPRC(2016)·7 citations
05
Proton and neutron correlations in $^{10}$ B
Yoshiko Kanada-En'yo · Hiroyuki Morita · Fumiharu Kobayashi
We investigate positive-parity states of $^{10}$ B with the calculation of antisymmetrized molecular dynamics focusing on $p n$ pair correlations. We discuss effects of the spin-orbit interaction on energy spectra and $p n$ correlations of the $J^{π} T = 1_{1}^{+} 0$ , $= 3_{1}^{+} 0$ , and $0_{1}^{+} 1$ states. The $1_{1}^{+} 0$ state has almost no energy gain of the spin-orbit interaction, whereas the $3_{1}^{+} 0$ state gains the spin-orbit interaction energy largely to come down to the ground state. We interpret a part of the two-body spin-orbit interaction in the adopted effective interactions as a contribution of the genuine $N N N$ force, and find it to be essential for the level ordering of the $3_{1}^{+} 0$ and $1_{1}^{+} 0$ states in $^{10}$ B. We also apply a $2 α + p n$ model to discuss effects of the spin-orbit interaction on $T = 0$ and $T = 1$ $p n$ pairs around the 2 $α$ core. In the spin-aligned $J^{π} T = 3^{+} 0$ state, the spin-orbit interaction affects the $(S T) = (10)$ pair attractively and keeps the pair close to the core, whereas, in the $1^{+} 0$ state, it gives a minor effect to the $(S T) = (10)$ pair. In the $0^{+} 1$ state, the $(S T) = (01)$ pair is somewhat dissociated by the spin-orbit interaction.
nucl-thPRC(2015)·16 citations
06
Extended-soft-core Baryon-Baryon ESC08 model III. S=-2 Hyperon-hyperon/nucleon Interaction
M.M. Nagels🇳🇱 · Th.A. Rijken🇯🇵 · Y. Yamamoto🇯🇵
This paper presents the Extended-Soft-Core (ESC) potentials ESC08c for baryon-baryon channels with total strangeness S=-2. The potential models for S=-2 are based on SU(3) extensions of ESC potential models for the S=0 and S=-1 sectors, which are fitted to experimental data. Flavor SU(3)-symmetry is broken only kinematically by the masses of the baryons and the mesons. For the S=-2 channels no experimental scattering data exist, and also the information from hypernuclei is rather limited. Nevertheless, in the fit to the S=0 and S=-1 sectors information from the so called NAGARA event and the $Ξ$ -well-depth has been used as constraints to determine the free parameters in the simultaneous fit of the $N N \oplus Y N \oplus Y Y$ data. Therefore, the potentials for the S=-2 sector are determined mainly by the NN-, YN-data, and SU(3)-symmetry.Various properties of the potentials are illustrated by giving results for scattering lengths, effective ranges, bound states, elastic and inelastic phase parameters, and total cross sections. Notably is the prediction of a bound state D $^{*}$ in the $Ξ N (^{3} S_{1}, I = 1)$ -channel with a binding energy $B_{E} = 1.56$ MeV. This state is deuteron-like, i.e. a member of the ${1 0^{*}}$ -decuplet. As for the normal deuteron $D = p n (^{3} S_{1} -^{3} D_{1})$ the strong tensor force is responsible for this state. The features of $Ξ$ hypernuclei predicted by ESC08c are studied on the basis of the G-matrix approch. The well-depth $U_{Ξ} = - 7.0$ MeV, and the $Ξ - ΛΛ$ conversion width is $Γ_{Ξ}^{c} = 4.5$ MeV.
nucl-thPRC(2020)·74 citations
07
Quest of $^{37} M g$ halo structure using Glauber model and microscopic relativistic mean field densities
Mahesh K. Sharma · R. N. Panda · Manoj K. Sharma · S. K. Patra
We have studied the ground state properties (binding energy and charge radius) using relativistic mean filed formalism (RMF) for Mg-isotopes in the valley of stability to drip line region. The RMF densities have been analyzed in context of reaction dynamics. The calculated results of $^{24 - 40}$ Mg+ $^{12}$ C reactions at projectile energy 240 AMeV using Glauber model with the conjunction of densities from relativistic mean field formalism are compared with experimental data. We found remarkable agreement of estimated values of reaction cross sections with experimental data except for $^{37}$ Mg isotope. In view of this, the halo status of $^{37}$ Mg is examined through higher magnitude of rms radius and small value of longitudinal momentum distribution. Finally, an effort is made to explore the structure of $^{37}$ Mg halo candidate using Glauber few body formalism.
nucl-thPRC(2016)·27 citations
08
Chiral Mirror-Baryon-Meson Model and Nuclear Matter beyond Mean-Field
Johannes Weyrich🇩🇪 · Nils Strodthoff🇩🇪 · Lorenz von Smekal🇩🇪
We consider a chiral baryon-meson model for nucleons and their parity partners in mirror assignment interacting with pions, sigma and omega mesons to describe the liquid-gas transition of nuclear matter together with chiral symmetry restoration in the high density phase. Within the mean-field approximation the model is known to provide a phenomenologically successful description of the nuclear-matter transition. Here, we go beyond this approximation and include mesonic fluctuations by means of the functional renormalization group. While these fluctuations do not lead to major qualitative changes in the phase diagram of the model, beyond mean-field, one is no-longer free to adjust the parameters so as to reproduce the binding energy per nucleon, the nuclear saturation density, and the nucleon sigma term all at the same time. However, the prediction of a clear first-order chiral transition at low temperatures inside the high baryon-density phase appears to be robust.
nucl-thhep-phPRC(2015)·57 citations
09
Nature of Radiation-Induced Defects in Quartz
Bu Wang · Yingtian Yu · Isabella Pignatelli · Gaurav N. Sant · Mathieu Bauchy
Although quartz ( $α$ -form) is a mineral used in numerous applications wherein radiation exposure is an issue, the nature of the atomistic defects formed during radiation-induced damage have not been fully clarified. Especially, the extent of oxygen vacancy formation is still debated, which is an issue of primary importance as optical techniques based on charged oxygen vacancies have been utilized to assess the level of radiation damage in quartz. In this paper, molecular dynamics (MD) simulations are applied to study the effects of ballistic impacts on the atomic network of quartz. We show that the defects that are formed mainly consist of over-coordinated Si and O, as well as Si--O connectivity defects, e.g., small Si--O rings and edge-sharing Si tetrahedra. Oxygen vacancies, on the contrary, are found in relatively low abundance, suggesting that characterizations based on $E^{'}$ centers do not adequately capture radiation-induced structural damage in quartz. Finally, we evaluate the dependence on the incident energy, of the amount of each type of the point defects formed, and quantify unambiguously the threshold displacement energies for both O and Si atoms. These results provide a comprehensive basis to assess the nature and extent of radiation damage in quartz.
↳ cond-mat.mtrl-scinucl-thJ.Chem.Phys.(2015)·2 citations
10
Coupled-channel analysis of $D^{+} \to K^{-} π^{+} π^{+}$ decay
Satoshi X. Nakamura (Osaka Univ.)🇯🇵
We perform a coupled-channel analysis of pseudodata for the D+-> K-pi+pi+ Dalitz plot. The pseudodata are generated from the isobar model of the E791 Collaboration, and are reasonably realistic. We demonstrate that it is feasible to analyze the high-quality data within a coupled-channel framework that describes the final state interaction of D+-> K-pi+pi+ as multiple rescatterings of three pseudoscalar mesons through two-pseudoscalar-meson interactions in accordance with the two-body and three-body unitarity. The two-pseudoscalar-meson interactions are designed to reproduce empirical pi pi and pi bar K scattering amplitudes. Furthermore, we also include mechanisms that are beyond simple iterations of the two-body interactions, i.e., a three-meson force, derived from the hidden local symmetry model. A picture of hadronic dynamics in D+-> K-pi+pi+ described by our coupled-channel model is found to be quite different from those of the previous isobar-type analyses. For example, we find that the D+-> K-pi+pi+ decay width can get almost triplicated when the rescattering mechanisms are turned on. Among the rescattering mechanisms, those associated with the rho(770) bar K0 channel, which contribute to D+-> K-pi+pi+ only through a channel coupling, give a large contribution, and significantly improve the quality of the fits. The K-pi+ s-wave amplitude from our analysis is reasonably consistent with those extracted from the E791 model independent partial-wave analysis; the hadronic rescattering and the coupling to the rho(770) bar K0 channel play a major role here. We also find that the dressed D+ decay vertices have phases, induced by the strong rescatterings, that strongly depend on the momenta of the final pseudoscalar mesons. Although the conventional isobar-type analyses have assumed the phases to be constant, this common assumption is not supported by our more microscopic viewpoint.
↳ hep-phhep-exnucl-thPRD(2016)·44 citations
11
Perfect-fluid behavior of a dilute Fermi gas near unitary
Gabriel Wlazłowski🇵🇱 · Wei Quan🇺🇸 · Aurel Bulgac🇺🇸
We present an ab initio calculation of the shear viscosity as a function of interaction strength in a two-component unpolarized Fermi gas near the unitary limit, within a finite temperature quantum Monte Carlo (QMC) framework and using the Kubo linear-response formalism. The shear viscosity decreases as we tune the interaction strength 1/ak_F from the Bardeen-Cooper-Schrieffer side of the Feshbach resonance towards Bose-Einstein condensation limit and it acquires the smallest value for 1/ak_F approx 0.4, with a minimum value of (eta/s)_min approx 0.2 hbar/k_B, which is about twice as small as the value reported for experiments in quark-gluon plasma (eta/s)_QGP lesssim 0.4 hbar/k_B. The Fermi gas near unitarity thus emerges as the most "perfect fluid" observed so far in nature. The clouds of dilute Fermi gas near unitarity exhibit the unusual attribute that, for the sizes realized so far in the laboratory or larger (less than 10^9 atoms), can sustain quantum turbulence below the critical temperature, but at the same time the classical turbulence is suppressed in the normal phase.
↳ cond-mat.quant-gashep-latnucl-thPRA(2015)·17 citations
12
Anomalous decay and scattering processes of the eta meson
Bastian Kubis🇩🇪 · Judith Plenter🇩🇪
We amend a recent dispersive analysis of the anomalous $η$ decay process $η \to π^{+} π^{-} γ$ by the effects of the $a_{2}$ tensor meson, the lowest-lying resonance that can contribute in the $π η$ system. While the net effects on the measured decay spectrum are small, they may be more pronounced for the analogous $η^{'}$ decay. There are nonnegligible consequences for the $η$ transition form factor, which is an important quantity for the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment. We predict total and differential cross sections, as well as a marked forward-backward asymmetry, for the crossed process $γ π^{-} \to π^{-} η$ that could be measured in Primakoff reactions in the future.
↳ hep-phhep-exnucl-exnucl-thEPJC(2015)·110 citations
13
Fission barrier, damping of shell correction and neutron emission in the fission of A $\sim$ 200
K. Mahata · S. Kailas · S. S. Kapoor
Decay of $^{210}$ Po compound nucleus formed in light and heavy-ion induced fusion reactions has been analyzed simultaneously using a consistent prescription for fission barrier and nuclear level density incorporating shell correction and its damping with excitation energy. Good description of all the excitation functions have been achieved with a fission barrier of 21.9 $\pm$ 0.2 MeV. For this barrier height, the predicted statistical pre-fission neutrons in heavy-ion fusion-fission are much smaller than the experimental values, implying the presence of dynamical neutrons due to dissipation even at these low excitation energies ( $\sim$ 50~MeV) in the mass region A $\sim$ 200. When only heavy-ion induced fission excitation functions and the pre-fission neutron multiplicities are included in the fits, the deduced best fit fission barrier depends on the assumed fission delay time during which dynamical neutrons can be emitted. A fission delay of (0.8 $\pm$ 0.1 ) $\times 1 0^{- 19}$ s has been estimated corresponding to the above fission barrier height assuming that the entire excess neutrons over and above the statistical model predictions are due to the dynamics. The present observation has implication on the study of fission time scale/ nuclear viscosity using neutron emission as a probe.
↳ nucl-exnucl-thPRC(2015)·31 citations
14
TaN molecule as a candidate to search for New physics
L.V. Skripnikov🇷🇺 · A.N. Petrov🇷🇺 · N.S. Mosyagin🇷🇺 · A.V. Titov🇷🇺 · V. V. Flambaum🇦🇺
It is demonstrated that the TaN molecule is the best candidate to search for T,P-violating nuclear magnetic quadrupole moment (MQM), it also looks promising to search for other T,P-odd effects. We report results of coupled-cluster calculations of T,P-odd effects in TaN produced by the Ta nucleus MQM, electron electric dipole moment (EDM), scalar $-$ pseudoscalar nucleus $-$ electron interactions, also of the molecule-axis hyperfine structure constant and dipole moment. Nuclear calculations of $^{181}$ Ta MQM are performed to express the T,P-odd effect in terms of the strength constants of T,P-odd nuclear forces, proton and neutron EDM, QCD parameter $θ$ and quark chromo-EDM.
↳ physics.atom-phnucl-thphysics.chem-phPRA(2015)·32 citations

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first authorsco-authorsvia INSPIRE