Nuclear Theory·nucl-th

Tuesday·December 3, 2019

14 papers—9 primary·5 cross-listed

01
Centrality dependence of multiplicity fluctuations from a hydrodynamical approach
Hong-Hao Ma🇨🇳 · Kai Lin🇨🇳 · Wei-Liang Qian🇧🇷 · Bin Wang🇨🇳
As one of the possible signals for the whereabouts of the critical point on the QCD phase diagram, recently, the multiplicity fluctuations in heavy-ion collisions have aroused much attention. It is a crucial observable of the Beam Energy Scan program of the Relativistic Heavy Ion Collider. In this work, we investigate the centrality dependence of the multiplicity fluctuations regarding the recent measurements from STAR Collaboration. By employing a hydrodynamical approach, the present study is dedicated to the noncritical aspects of the phenomenon. To be specific, in addition to the thermal fluctuations, finite volume corrections, and resonance decay at the freeze-out surface, the model is focused on the properties of the hydrodynamic expansion of the system and the event-by-event initial fluctuations. It is understood that the real signal of the critical point can only be obtained after appropriately subtracting the background, the latter is investigated in the present work. Besides the experimental data, our results are also compared to those of the hadronic resonance gas, as well as transport models.
hep-phnucl-thAdv.High Energy Phys.(2020)·3 citations
02
Minkowski-space solutions of the Schwinger-Dyson equation for the fermion propagator with the rainbow-ladder truncation
Shaoyang Jia🇺🇸 · Pieter Maris🇧🇷 · Dyana C. Duarte🇫🇷 · Tobias Frederico🇧🇷 · Wayne de Paula🇧🇷 · Emanuel Ydrefors🇫🇷
We solve the Minkowski-space Schwinger-Dyson equation (SDE) for the fermion propagator in quantum electrodynamics (QED) with massive photons. Specifically, we work in the quenched approximation within the rainbow-ladder truncation. Loop-divergences are regularized by the Pauli-Villars regularization. With moderately strong fermion-photon coupling, we find that the analytic structure of the fermion propagator consists of an on-shell pole and branch-cuts located in the timelike region. Such structures are consistent with the direct solution of the fermion propagator as functions of the complex momentum. Our method paves the way towards the calculation of the Minkowski-space Bethe-Salpeter amplitude using dressed fermion propagator.
nucl-thhep-th2 citations
03
Probing ab initio emergence of nuclear rotation
M. A. Caprio · P. J. Fasano · P. Maris · A. E. McCoy · J. P. Vary
Structural phenomena in nuclei, from shell structure and clustering to superfluidity and collective rotations and vibrations, reflect emergent degrees of freedom. Ab initio theory describes nuclei directly from a fully microscopic formulation. We can therefore look to ab initio theory as a means of exploring the emergence of effective degrees of freedom in nuclei. For the illustrative case of emergent rotational bands in the Be isotopes, we establish an understanding of the underlying oscillator space and angular momentum (orbital and spin) structure. We consider no-core configuration interaction (NCCI) calculations for 7,9,11Be with the Daejeon16 internucleon interaction. Although shell model or rotational degrees of freedom are not assumed in the ab initio theory, the NCCI results are suggestive of the emergence of effective shell model degrees of freedom (0 hbar-omega and 2 hbar-omega excitations) and LS-scheme rotational degrees of freedom, consistent with an Elliott-Wilsdon SU(3) description. These results provide some basic insight into the connection between emergent effective collective rotational and shell model degrees of freedom in these light nuclei and the underlying ab initio microscopic description.
nucl-thEPJA(2020)·28 citations
04
Nuclear Fission Dynamics: Past, Present, Needs, and Future
Aurel Bulgac · Shi Jin · Ionel Stetcu
Recent developments in theoretical modeling and in computational power have allowed us to make significant progress on a goal not achieved yet in nuclear theory: a fully microscopic theory of nuclear fission. The complete microscopic description remains a computationally demanding task, but the information that can be provided by current calculations can be extremely useful to guide and constrain phenomenological approaches. First, a truly microscopic framework that can describe the real-time dynamics of the fissioning system can justify or rule out assumptions and approximations incompatible with an accurate quantum treatment or with our understanding of the inter nucleon interactions. Second, the microscopic approach can be used to obtain trends such as: the excitation energy sharing mechanism between fission fragments (FFs) with increasing excitation energy of the fissioning system, the angular momentum content of the FFs, or even to compute observables that cannot be otherwise calculated in phenomenological approaches or even measured, as in the case of astronomical environments. Merely the characterization of the trends would be of great importance for various application. We present here arguments that a truly microscopic approach to fission does not support the assumption of adiabaticity of the large amplitude collective motion in fission, particularly starting from the outer saddle down to the scission configuration.
nucl-thFront.in Phys.(2020)·54 citations
05
HIJING can describe the anisotropy-scaled charge-dependent correlations at the Relativistic Heavy Ion Collider
Jie Zhao🇺🇸 · Yicheng Feng🇺🇸 · Hanlin Li🇨🇳 · Fuqiang Wang🇺🇸
The experimentally measured charge-depdendent correlations in heavy ion collisions have been suggested as a signature of the chiral magenetic effect (CME). Early model studies could not reproduce the measurement. For example, the Hijing model yielded far smaller magnitude for the charge-dependent correlation than observed in data. This led to the conclusion that the CME had to be invoked to explain the observed correlations in heavy ion collisions. In this paper we show that this conclusion of the CME interpretation is premature. We show that the reason that Hijing predicts a far smaller correlation than data is because the elliptic anisotrpy ( $v_{2}$ ) parameter in Hijing is too small. When properly scaled, the Hijing model can reproduce in entirety the measured correlations. We also employ the AMPT model, which has a large enough $v_{2}$ , to demonstrate that the measured data can be easily accommodated by models without invoking the CME.
nucl-thnucl-exPRC(2020)·17 citations
06
Towards a new semi-classical interpretation of the wobbling motion in $^{163}$ Lu
A. A. Raduta · R. Poenaru · C. M. Raduta
A new interpretation for the wobbling bands in $^{163}$ Lu is given within a particle-triaxial rotor semi-classical formalism. While in the previous papers the bands TSD1, TSD2, TSD3 and TSD4 are viewed as the ground, one, two and three phonon wobbling bands, here the corresponding experimental results are described as the ground band with spin equal to I=R+j, for R=0,2,4,...(TSD1), the ground band with I=R+j and R=1,3,5,...(TSD2), the one phonon excitations of TSD2 (TSD3), with the odd proton moving in the orbit $j = i_{13/2}$ , and the ground band of I=R+j, with R=1,3,5,... and $j = h_{9/2}$ (TSD4). The moments of inertia (MoI) of the core for the first three bands are the same, and considered to be free parameters. Due to the core polarization effect caused by the particle-core coupling, the MoI's for TSD4 are different. The energies and the e.m. transitions are quantitatively well described. Also, the phase diagram of the odd system is drawn. In the parameter space one indicates where the point associated with the fitted parameters is located and also which is the region of transversal wobbling mode as well as where the wobbling motion is forbidden.
nucl-thJ.Phys.G(2020)·8 citations
07
From bound states to the continuum
Calvin W. Johnson🇺🇸 · Kristina D. Launey🇺🇸 · Naftali Auerbach🇮🇱 · Sonia Bacca🇩🇪 · Bruce R. Barrett🇺🇸 · Carl Brune🇺🇸 · Mark A. Caprio🇺🇸 · Pierre Descouvemont🇧🇪 · W. H. Dickhoff🇺🇸 · Charlotte Elster🇺🇸 · Patrick J. Fasano🇺🇸 · Kevin Fossez🇺🇸 and 26 other authors
This white paper reports on the discussions of the 2018 Facility for Rare Isotope Beams Theory Alliance (FRIB-TA) topical program "From bound states to the continuum: Connecting bound state calculations with scattering and reaction theory". One of the biggest and most important frontiers in nuclear theory today is to construct better and stronger bridges between bound state calculations and calculations in the continuum, especially scattering and reaction theory, as well as teasing out the influence of the continuum on states near threshold. This is particularly challenging as many-body structure calculations typically use a bound state basis, while reaction calculations more commonly utilize few-body continuum approaches. The many-body bound state and few-body continuum methods use different language and emphasize different properties. To build better foundations for these bridges, we present an overview of several bound state and continuum methods and, where possible, point to current and possible future connections.
nucl-thnucl-exJ.Phys.G(2020)·85 citations
08
Neutralization of excited antiprotonic helium ion in collisions with helium atoms
G.Ya. Korenman🇷🇺 · S.N. Yudin🇷🇺
We consider a neutralization of excited antiprotonic helium ion accompanied by antiproton transitions to lower states in collisions with helium atoms $(p ˉ He^{2 +})_{n l} + He \to [(p ˉ He^{2 +})_{n_{f} l_{f}} e]_{1 s} + He^{+}$ in low-temperature medium. Interactions in the input and output channels are taken similar to the potentials of $H^{+} - He$ ( $X^{1} Σ$ ) and $H - He^{+}$ ( $A^{1} Σ$ ) systems, respectively. The final term is shifted down by the antiproton transition energy. Therefore initial and final terms can intersect for the suitable antiproton quantum numbers leading to an appreciable cross sections of the transitions. We have found that this process can provide an additional increase of effective annihilation rates for highly excited antiprotonic helium ion even in the low-density and temperature target corresponding to known experimental conditions.
nucl-thphysics.atom-phEur.Phys.J.D(2021)·8 citations
09
The role of the chiral phase transition in modelling the kaon to pion ratio
A. V. Friesen🇷🇺 · Yu. L. Kalinovsky🇷🇺 · V. D. Toneev🇷🇺
A sharp peak in the $K^{+} / π^{+}$ ratio in relativistic heavy-ion collision is discussed in the framework of the SU(3) Polyakov-loop extended NJL model with vector interaction. In the model, the $K^{+} / π^{+}$ ratio was calculated along the chiral phase transition line for different values of the vector coupling $g_{V}$ . We showed that the value of the vector coupling had no significant effect on the $K^{+} / π^{+}$ behaviour.
nucl-thhep-phJETP Lett.(2020)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE