Nuclear Theory·nucl-th

Tuesday·July 24, 2018

10 papers—2 primary·8 cross-listed

01
Matrix Models of Strength Distributions
Larry Zamick · Arun Kingan
In this work we use matrix models to study the problem of strength distributions. This is motivated by noticing near exponential fall offs of strengths in calculated magnetic dipole excitations. We emphasize that the quality of the exponential fall offs depend on the parameters in our matrices, especially the relative size of the couplings to the unperturbed level separations. We also find a matrix for which all transitions vanish.
nucl-thnucl-exphysics.atom-phIJMPE(2018)·5 citations
02
Short-range correlations and the charge density
Ronen Weiss🇮🇱 · Axel Schmidt🇺🇸 · Gerald A. Miller🇺🇸 · Nir Barnea🇮🇱
Sophisticated high-energy and large momentum-transfer scattering experiments combined with ab-initio calculations can reveal the short-distance behavior of nucleon pairs in nuclei. On an opposite energy and resolution scale, elastic electron scattering experiments are used to extract the charge density and charge radius of different nuclei. We show that even though the charge density has no obvious connection with nuclear short-range correlations, it can be used to extract properties of such correlations. This is accomplished by using the nuclear contact formalism to derive a relation between the charge density and the proton-proton nuclear contacts that describe the probability of two protons being at close proximity. With this relation, the values of the proton-proton contacts are extracted for various nuclei using only the nuclear charge density and a solution of the two-nucleon Schroedinger equation as inputs. For symmetric nuclei, the proton-neutron contacts can also be extracted from the charge density. Good agreement is obtained with previous extractions of the nuclear contacts. These results imply that one can predict (with reasonably good accuracy) the results of high-energy and large momentum-transfer electron-scattering experiments and ab-initio calculations of high momentum tails using only experimental data of elastic scattering experiments.
nucl-thcond-mat.quant-gasnucl-exPLB(2019)·21 citations
03
Calculation of francium hyperfine anomaly
E.A. Konovalova🇷🇺 · Yu.A. Demidov🇷🇺 · M.G. Kozlov🇷🇺 · A.E. Barzakh🇷🇺
The Dirac-Hartree-Fock plus many-body perturbation theory (DHF+MBPT) method has been used to calculate hyperfine structure constants for Fr. Calculated hyperfine structure anomaly for hydrogen-like ion has been shown to be in good agreement with analytical expressions. It has been shown that the ratio of the anomalies for $s$ and $p_{1/2}$ states is weakly dependent on the principal quantum number. Finally, we estimate Bohr--Weisskopf corrections for several Fr isotopes. Our results may be used to improve experimental accuracy for the nuclear $g$ factors of short-lived isotopes.
↳ physics.atom-phnucl-exnucl-thAtoms(2018)·11 citations
04
Deep Inelastic Scattering on an Extremal RN-AdS Black Hole
Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
We consider deep inelastic scattering (DIS) on a large nucleus described as an extremal RN-AdS black hole using the holographic principle. Using the R-current correlators we determine the structure functions as a function Bjorken-x, and map it on a finite but large nucleus with fixed atomic number. The R-ratio of the nuclear structure functions exhibit strong shadowing at low-x.
↳ hep-thhep-phnucl-thPRD(2020)·5 citations
05
Hydrodynamics with spacetime-dependent scattering length
Keisuke Fujii🇯🇵 · Yusuke Nishida🇯🇵
Hydrodynamics provides a concise but powerful description of long-time and long-distance physics of correlated systems out of thermodynamic equilibrium. Here we construct hydrodynamic equations for nonrelativistic particles with a spacetime-dependent scattering length and show that it enters constitutive relations uniquely so as to represent the fluid expansion and contraction in both normal and superfluid phases. As a consequence, we find that a leading dissipative correction to the contact density due to the spacetime-dependent scattering length is proportional to the bulk viscosity ( $ζ_{2}$ in the superfluid phase). Also, when the scattering length is slowly varied over time in a uniform system, the entropy density is found to be produced even without fluid flows in proportion to the bulk viscosity, which may be useful as a novel probe to measure the bulk viscosity in ultracold-atom experiments.
↳ cond-mat.quant-gasnucl-thphysics.flu-dynPRA(2018)·23 citations
06
Two novel approaches to the hadron-quark mixed phase in compact stars
Vahagn Abgaryan🇷🇺 · David Alvarez-Castillo🇷🇺 · Alexander Ayriyan🇷🇺 · David Blaschke🇷🇺 · Hovik Grigorian🇷🇺
First-order phase transitions, like the liquid-gas transition, proceed via formation of structures such as bubbles and droplets. In strongly interacting compact star matter, at the crust-core transition, but also at the hadron-quark transition in the core, these structures form different shapes dubbed "pasta phases". We describe two methods to obtain one-parameter families of hybrid equations of state (EoS) which mimic the thermodynamic behavior of pasta phases in between a low-density hadron and a high-density quark matter phase, thus generalizing the Maxwell construction. The first method replaces the behavior of pressure vs. chemical potential in a finite region around the critical %chemical potential pressure of the Maxwell construction by a polynomial interpolation. The second method uses extrapolations of the hadronic and quark matter EoS beyond the Maxwell point to define a mixing of both with weight functions bounded by finite limits around the Maxwell point. We apply both methods to the case of a hybrid EoS with a strong first order transition that entails the formation of a third family of compact stars and the corresponding mass twin phenomenon. We investigate for both models the robustness of this phenomenon against variation of the single parameter, the pressure increment at the critical chemical potential which quantifies the deviation from the Maxwell construction. We also show sets of results for other compact star observables than mass and radius, namely the moment of inertia and the baryon mass.
↳ astro-ph.HEhep-phnucl-thUniverse(2018)·37 citations
07
Extrapolation for meson screening masses from imaginary to real chemical potential
Masahiro Ishii🇯🇵 · Akihisa Miyahara🇯🇵 · Hiroaki Kouno🇯🇵 · Masanobu Yahiro🇯🇵
We first extend our formulation for the calculation of $π$ - and $σ$ -meson screening masses to the case of finite chemical potential $μ$ . We then consider the imaginary- $μ$ approach, which is an extrapolation method from imaginary chemical potential ( $μ = i μ_{I}$ ) to real one ( $μ = μ_{R}$ ). The feasibility of the method is discussed based on the entanglement Polyakov-loop extended Nambu--Jona-Lasinio (EPNJL) model in 2-flavor system. As an example, we investigate how reliable the imaginary- $μ$ approach is for $π$ - and $σ$ -meson screening masses, comparing "screening masses at $μ_{R}$ in the method" with "those calculated directly at $μ_{R}$ ". We finally propose the new extrapolation method and confirm its efficiency.
↳ hep-phhep-latnucl-thPRD(2019)·2 citations
08
The $π γ \to π π$ transition and the $ρ$ radiative decay width from lattice QCD
Constantia Alexandrou🇨🇾 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · John Negele🇺🇸 · Srijit Paul🇨🇾 · Marcus Petschlies🇩🇪 · Andrew Pochinsky🇺🇸 · Gumaro Rendon🇺🇸 · Sergey Syritsyn🇺🇸
We report a lattice QCD determination of the $π γ \to π π$ transition amplitude for the $P$ -wave, $I = 1$ two-pion final state, as a function of the photon virtuality and $π π$ invariant mass. The calculation was performed with $2 + 1$ flavors of clover fermions at a pion mass of approximately $320$ MeV, on a $3 2^{3} \times 96$ lattice with $L \approx 3.6$ fm. We construct the necessary correlation functions using a combination of smeared forward, sequential and stochastic propagators, and determine the finite-volume matrix elements for all $π π$ momenta up to $∣ P ∣ = 3 \frac{2 π}{L}$ and all associated irreducible representations. In the mapping of the finite-volume to infinite-volume matrix elements using the Lellouch-Lüscher factor, we consider two different parametrizations of the $π π$ scattering phase shift. We fit the $q^{2}$ and $s$ dependence of the infinite-volume transition amplitude in a model-independent way using series expansions, and compare multiple different truncations of this series. Through analytic continuation to the $ρ$ resonance pole, we also determine the $π γ \to ρ$ resonant transition form factor and the $ρ$ meson photocoupling, and obtain $∣ G_{ρ π γ} ∣ = 0.0802 (32) (20)$ .
↳ hep-lathep-phnucl-thPRD(2018)·83 citations
09
Quarkonium tomography of heavy ion collisions at the LHC
Ivan Vitev🇺🇸
Quarkonium production in high-energy hadronic collisions provides a fundamental test of QCD. Its modification in a nuclear medium is a sensitive probe of the space-time temperature profile and transport properties of the QGP, yielding constraints complementary to the ones obtained from the quenching of light hadrons and jets, and open heavy flavor. In these proceedings, we report new results for the suppression of high transverse momentum charmonium [ $J / ψ, ψ (2 S)$ ] and bottomonium [ $Υ (1 S), Υ (2 S), Υ (3 S)$ ] states in Pb+Pb collisions at the Large Hadron Collider. Our theoretical formalism combines the collisional dissociation of quarkonia, as they propagate in the quark-gluon plasma, with the thermal wavefunction effects due to the screening of the $Q Q ˉ$ attractive potential in the medium. We find that a good description of the relative suppression of the ground and higher excited quarkonium states, transverse momentum and centrality distributions is achieved, when comparison to measurements at a center-of-mass energy of 2.76 TeV is performed. Theoretical predictions for the highest Pb+Pb center-of-mass energy of 5.02 TeV at the LHC, where new experimental results are being finalized are presented. Preliminary calculations for smaller systems, such as Xe+Xe are also shown. Last but not least, the potential of jet substructure to shed light in the mechanisms of heavy flavor production is discussed.
↳ hep-phnucl-thNPA(2019)·1 citation
10
Nonlinear chiral transport from holography
Yanyan Bu🇨🇳 · Tuna Demircik🇮🇱 · Michael Lublinsky🇮🇱
Nonlinear transport phenomena induced by the chiral anomaly are explored within a 4D field theory defined holographically as $U (1)_{V} \times U (1)_{A}$ Maxwell-Chern-Simons theory in Schwarzschild- $A d S_{5}$ . First, in presence of external electromagnetic fields, a general form of vector and axial currents is derived. Then, within the gradient expansion up to third order, we analytically compute all (over 50) transport coefficients. A wealth of higher order (nonlinear) transport phenomena induced by chiral anomaly are found beyond the Chiral Magnetic and Chiral Separation Effects. Some of the higher order terms are relaxation time corrections to the lowest order nonlinear effects. The charge diffusion constant and dispersion relation of the Chiral Magnetic Wave are found to receive anomaly-induced non-linear corrections due to e/m background fields. Furthermore, there emerges a new gapless mode, which we refer to as {\it Chiral Hall Density Wave}, propagating along the background Poynting vector.
↳ hep-thhep-phnucl-thJHEP(2019)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE