Nuclear Theory·nucl-th

Thursday·June 20, 2019

9 papers—5 primary·4 cross-listed

01
Critical parameters of liquid-gas phase transition in thermal symmetric and asymmetric nuclear matter
Shen Yang · Bo Nan Zhang · Bao Yuan Sun
The properties of critical parameters and phase diagram structure of liquid-gas phase transition are investigated in thermal symmetric and asymmetric nuclear matter with the covariant density functional (CDF) theory. Although uncertainty remains in predicting the critical parameters such as the critical temperature and pressure from various CDF functionals, several correlations are explored numerically and verified to be approximately linear between them. These correlations become worse when nuclear matter is more isospin asymmetric, resulting mainly from the effects induced by symmetry energy. By looking over the isospin dependence of the critical temperature, the role of the symmetry energy in LG transition properties of asymmetric matter is realized. The change of critical temperature with isospin asymmetry is found to be correlated well with and as a consequence could be constrained by the density slope of symmetry energy at saturation density. Then, the structure of phase diagram of thermal nuclear matter is analyzed carefully. It is revealed that the contribution from symmetry energy dominates the size of liquid-gas phase coexistence area. Moreover, the specific pattern of the phase diagram could be determined by the critical temperature at non-zero isospin asymmetry, illustrated from the correlations of the temperature with pressures at several characteristic points, paving the possible way to further explore the structure of liquid-gas phase diagram of thermal nuclear matter.
nucl-thPRC(2019)·29 citations
02
Soft breathing modes in neutron--rich nuclei with the subtracted second random--phase approximation
D. Gambacurta🇷🇴 · M. Grasso🇫🇷 · O. Sorlin🇫🇷
We analyze the isoscalar response related to breathing modes with particular attention being paid to low-lying excitations in neutron--rich nuclei. We use the subtracted second random--phase approximation (SSRPA) to describe microscopically the response. By increasing the neutron excess, we study the evolution of the response in Ca isotopes going from $^{40}$ Ca to $^{48}$ Ca and to $^{60}$ Ca as well as in $N = 20$ isotones going from $^{40}$ Ca to $^{36}$ S and to $^{34}$ Si. Finally, the case of $^{68}$ Ni is investigated. We predict soft monopole modes in neutron--rich nuclei which are driven by neutron excitations. At variance with dipole pygmy modes, these neutron excitations are not only strongly dominant at the surface of the nucleus but over its entire volume. The effect of the mixing with two particle-two hole configurations induced by the SSRPA model is analyzed. The properties of such soft neutron modes are investigated in terms of their excitation energies, transition densities and wave--function components. Their collectivity is also discussed as a function of the isospin asymmetry and of the mass of the nucleus. The link between such low--energy compression modes and a compressibility modulus introduced for neutron--rich infinite matter is finally studied.
nucl-thPRC(2019)·9 citations
03
Hydrodynamical response of plane correlation in Pb+Pb collisions at $s_{NN}$ =2.76 TeV
Jing Yang · Yong Zhang
In high energy heavy-ion collisions, the final anisotropic flow coefficients and their corresponding event-plane correlations are considered as the medium evolutional response to the initial geometrical eccentricities and their corresponding participant-plane correlations. We formulate a systematic theoretical analysis to study the hydrodynamical responses concerning higher order effects in Pb+Pb collisions at $s_{NN} = 2.76$ TeV by using Monte Carlo Glauber (MC-Glauber) model. To further understand the transformations of the initial participant-plane correlation, we construct a new set of events which randomize the directions of the initial participant planes of the original events. Our results indicate that the final strong event-plane correlations are mainly transformed from the large initial eccentricities, rather than the strong participant-plane correlations. However, the large flow coefficients and the discrepancies between the flow coefficients calculated by the single-shot and event-by-event simulations in peripheral collisions are relevant to those strong initial participant-plane correlations.
nucl-thhep-thIJMPE(2020)·1 citation
04
A Survey of Nuclear Pasta in the Intermediate Density Regime I: Shapes and Energies
B. Schuetrumpf · G. Martínez-Pinedo · Md Afibuzzaman · H. M. Aktulga
Background: Nuclear pasta, emerging due to the competition between the long-range Coulomb force and the short-range strong force, is believed to be present in astrophysical scenarios, such as neutron stars and core-collapse supernovae. Its structure can have a high impact e.g. on neutrino transport or the tidal deformability of neutron stars. Purpose: We study several possible pasta configurations, all of them minimal surface configurations, which are expected to appear in the mid-density regime of nuclear pasta, i.e. around 40% of the nuclear saturation density. In particular we are interested in the energy spectrum for different pasta configurations considered. Method: Employing the density functional theory (DFT) approach, we calculate the binding energy of the different configurations for three values of the proton content XP = 1/10, 1/3 and 1/2, by optimizing their periodic length. We study finite temperature effects and the impact of electron screening. Results: Nuclear pasta lowers the energy significantly compared to uniform matter, especially for $X_{P} \geq 1/3$ . However, the different configurations have very similar binding energies. For large proton content, $X_{P} \geq 1/3$ , the pasta configurations are very stable, for lower proton content temperatures of a few MeV are enough for the transition to uniform matter. Electron screening has a small influence on the binding energy of nuclear pasta, but increases its periodic length. Conclusion: Nuclear pasta in the mid-density regime lowers the energy of the matter for all proton fractions under study. It can survive even large temperatures of several MeV. Since various configurations have very similar energy, it is to expected that many configurations can coexist simultaneously already at small temperatures.
nucl-thastro-ph.HEPRC(2019)·36 citations
05
Low-energy neutrino scattering in experiment and astrophysics
Natalie Jachowicz🇧🇪 · Nils Van Dessel🇧🇪 · Alexis Nikolakopoulos🇧🇪
We review the relevance of neutrino-nucleus interactions at energy transfers below 100 MeV for accelerator-based experiments, experiments at lower energies and for astrophysical neutrinos. The impact of low-energy scattering processes in the energy reconstruction analysis of oscillation experiments is investigated. We discuss the modeling of coherent scattering processes and compare its strength to that of inelastic interactions. The presented results are obtained within a continuum random phase approximation approach.
nucl-thJ.Phys.G(2019)·18 citations
06
QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part
Yoshitaka Hatta🇺🇸 · Xiaojun Yao🇺🇸
We present the numerical solution of the one-loop QCD evolution equation for the genuine twist-three part of the orbital angular momentum (OAM) distributions of quarks and gluons inside a longitudinally polarized nucleon. This is based on the observation that the evolution is identical to that of the Efremov-Teryaev-Qiu-Sterman function for transverse single spin asymmetry. Together with the known evolution of the Wandzura-Wilczek part, the one-loop evolution of OAM distributions is now practically under control. We also study, for the first time, the scale dependence of the potential angular momentum defined as the difference between the Ji and Jaffe-Manohar definitions of OAM.
↳ hep-phnucl-thPLB(2019)·14 citations
07
Nonlinear Langevin dynamics via holography
Bidisha Chakrabarty🇮🇳 · Joydeep Chakravarty🇮🇳 · Soumyadeep Chaudhuri🇮🇳 · Chandan Jana🇮🇳 · R. Loganayagam🇮🇳 · Akhil Sivakumar🇮🇳
In this work, we consider non-linear corrections to the Langevin effective theory of a heavy quark moving through a strongly coupled CFT plasma. In AdS/CFT, this system can be identified with that of a string stretched between the boundary and the horizon of an asymptotically AdS black-brane solution. We compute the Feynman-Vernon influence phase for the heavy quark by evaluating the Nambu-Goto action on a doubled string configuration. This configuration is the linearised solution of the string motion in the doubled black-brane geometry which has been proposed as the holographic dual of a thermal Schwinger-Keldysh contour of the CFT. Our expression for the influence phase passes non-trivial consistency conditions arising from the underlying unitarity and thermality of the bath. The local effective theory obeys the recently proposed non-linear fluctuation dissipation theorem relating the non-Gaussianity of thermal noise to the thermal jitter in the damping constant. This furnishes a non-trivial check for the validity of these relations derived in the weak coupling regime.
↳ hep-thcond-mat.stat-mechnucl-thJHEP(2020)·63 citations
08
Visible narrow cusp structure in $Λ_{c}^{+} \to p K^{-} π^{+}$ enhanced by triangle singularity
Xiao-Hai Liu · Gang Li🇨🇳 · Ju-Jun Xie🇨🇳 · Qiang Zhao🇨🇳
A resonance-like structure as narrow as 10 MeV is observed in the $K^{-} p$ invariant mass distributions in $Λ_{c}^{+} \to p K^{-} π^{+}$ at Belle. Based on the large data sample of about 1.5 million events and the small bin width of just 1 MeV for the $K^{-} p$ invariant mass spectrum, the narrow peak is found precisely lying at the $Λ η$ threshold. While lacking evidence for a quark model state with such a narrow width at this mass region, we find that this narrow structure can be naturally identified as a threshold cusp but enhanced by the nearby triangle singularity via the $Λ$ - $a_{0} (980)^{+}$ or $η$ - $Σ (1660)^{+}$ rescatterings.
↳ hep-phhep-exnucl-exnucl-thPRD(2019)·35 citations
09
Possible New Phase of Thermal QCD
Andrei Alexandru🇺🇸 · Ivan Horváth🇺🇸
Using lattice simulations, we show that there is a phase of thermal QCD, where the spectral density $ρ (λ)$ of Dirac operator changes as $1/ λ$ for the infrared eigenvalues $λ < T$ . This behavior persists over the entire low energy band we can resolve accurately, over three orders of magnitude on our largest volumes. We propose that in this "IR phase", the well-known non-interacting scale invariance at very short distances (UV, $λ \to \infty$ , asymptotic freedom), coexists with very different interacting type of scale invariance at long distances (IR, $λ < T$ ). Such dynamics may be responsible for the unusual fluidity properties of the medium observed at RHIC and LHC. We point out its connection to the physics of Banks-Zaks fixed point, leading to the possibility of massless glueballs in the fluid. Our results lead to the classification of thermal QCD phases in terms of IR scale invariance. The ensuing picture naturally subsumes the standard chiral crossover feature at $" T_{c} " \approx 155$ MeV. Its crucial new aspect is the existence of temperature $T_{I R}$ (200 MeV $< T_{I R} <$ 250 MeV) marking the onset of IR phase and possibly a true phase transition.
↳ hep-lathep-thnucl-thPRD(2019)·64 citations

Affiliations

first authorsco-authorsvia INSPIRE