Nuclear Theory·nucl-th

Thursday·June 2, 2016

7 papers—6 primary·1 cross-listed

01
How many-body correlations and $α$ -clustering shape $^{6}$ He
Carolina Romero-Redondo🇺🇸 · Sofia Quaglioni🇺🇸 · Petr Navratil🇨🇦 · Guillaume Hupin🇫🇷
The Borromean $^{6}$ He nucleus is an exotic system characterized by two `halo' neutrons orbiting around a compact $^{4}$ He (or $α$ ) core, in which the binary subsystems are unbound. The simultaneous reproduction of its small binding energy and extended matter and point-proton radii has been a challenge for {\em ab initio} theoretical calculations based on traditional bound-state methods. Using soft nucleon-nucleon interactions based on chiral effective field theory potentials, we show that supplementing the model space with $^{4}$ He+ $n$ + $n$ cluster degrees of freedom largely solves this issue. We analyze the role played by the $α$ -clustering and many-body correlations, and study the dependence of the energy spectrum on the resolution scale of the interaction.
nucl-thPRL(2016)·43 citations
02
Systematic study of infrared energy corrections in truncated oscillator spaces
Alexander Arzhanov · Tomás R. Rodríguez · Gabriel Martínez-Pinedo
We study the convergence properties of nuclear binding energies and two-neutron separation energies obtained with self-consistent mean-field calculations based on the Hartree-Fock-Bogolyubov (HFB) method with Gogny-type effective interactions. Owing to lack of convergence in a truncated working basis, we employ and benchmark one of the recently proposed infrared energy correction techniques to extrapolate our results to the limit of an infinite model space. We also discuss its applicability to global calculations of nuclear masses.
nucl-thPRC(2016)·8 citations
03
Quantum corrections to the Relativistic mean-field theory
Sergei P. Maydanyuk (1 and 2) · Peng-Ming Zhang (1) · Ahmed Bakry (1) ((1) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China, (2) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kiev, 03680, Ukraine)
In this paper, we compare the RMF theory and the model of deformed oscillator shells (DOS) in description of the quantum properties of the bound states of the spherically symmetric light nuclei. We obtain an explicit analytical relation between differential equations for the RMF theory and DOS model, which determine wave functions for nucleons. On such a basis we perform analysis of correspondence of quantum properties of nuclei. We find: (1) Potential $V_{R M F}$ of the RMF theory for nucleons has the wave functions $f$ and $g$ with joint part $h$ coincident exactly with the nucleon wave function of DOS model with potential $V_{shell}$ . But, a difference between $V_{R M F}$ and $V_{shell}$ is essential for any nucleus. (2) The nucleon wave functions and densities obtained by the DOS and RMF theories are essentially different. The nucleon densities of the RMF theory contradict to knowledge about distribution of the proton and neutron densities inside the nuclei obtained from experimental data. This indicates that $g$ and $f$ have no sense of the wave functions of quantum physics. But, $h$ provides proper description of quantum properties of nucleons inside the nucleus. (3) We calculate meson function $w^{0}$ and potential $V_{w}$ in RMF theory based on the found nucleon density. (4) $f$ and $g$ are not solutions of Dirac equation with $V_{w}$ . If the meson theory describes quantum properties of nucleus well, then a difference between $V_{w}$ and $V_{R M F}$ should be as small as possible. We introduce new quantum corrections characterizing difference between these potentials. We find that (a) The function $w^{0}$ should be reinforced strongly, (b) The corrections are necessary to describe the quantum properties of the nuclei.
nucl-thhep-thnucl-exquant-ph0 citations
04
Influence of short-range correlations in neutrino-nucleus scattering
Tom Van Cuyck🇧🇪 · Natalie Jachowicz🇧🇪 · Raúl González Jiménez🇧🇪 · Marco Martini🇧🇪 · Vishvas Pandey🇧🇪 · Jan Ryckebusch🇧🇪 · Nils Van Dessel🇧🇪
Background: Nuclear short-range correlations (SRCs) are corrections to mean-field wave functions connected with the short-distance behavior of the nucleon-nucleon interaction. These SRCs provide corrections to lepton- nucleus cross sections as computed in the impulse approximation (IA). Purpose: We want to investigate the influence of SRCs on the one-nucleon (1N) and two-nucleon (2N) knockout channel for muon-neutrino induced processes on a $^{12}$ C target at energies relevant for contemporary measurements. Method: The model adopted in this work, corrects the impulse approximation for SRCs by shifting the com- plexity induced by the SRCs from the wave functions to the operators. Due to the local character of the SRCs, it is argued that the expansion of these operators can be truncated at a low order. Results: The model is compared with electron-scattering data, and two-particle two-hole responses are presented for neutrino scattering. The contributions from the vector and axial-vector parts of the nuclear current as well as the central, tensor and spin-isospin part of the SRCs are studied. Conclusions: Nuclear SRCs affect the 1N knockout channel and give rise to 2N knockout. The exclusive neutrino-induced 2N knockout cross section of SRC pairs is shown and the 2N knockout contribution to the QE signal is calculated. The strength occurs as a broad background which extends into the dip region.
nucl-thhep-exhep-phnucl-exPRC(2016)·68 citations
05
Baryon transition form factors at the pole
L. Tiator🇩🇪 · M. Döring🇺🇸 · R. L. Workman🇺🇸 · M. Hadžimehmedović🇧🇦 · H. Osmanović🇧🇦 · R. Omerović🇧🇦 · J. Stahov🇧🇦 · A. Švarc🇭🇷
Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the $G_{M}$ , $G_{E}$ , and $G_{C}$ form factors for the $Δ (1232)$ resonance excitation at the Breit-Wigner resonance and pole positions up to $Q^{2} = 5$ GeV $^{2}$ . We also explore the $E / M$ and $S / M$ ratios as functions of $Q^{2}$ . For pole and residue extraction, we apply the Laurent + Pietarinen method.
nucl-thnucl-exPRC(2016)·21 citations
06
State-of-the-art of beyond mean field theories with nuclear density functionals
J. Luis Egido
We present an overview of beyond mean field theories (BMFT) based on the generator coordinate method (GCM) and the recovery of symmetries used in nuclear physics with effective forces. After a reminder of the Hartree-Fock-Bogoliubov (HFB) theory a discussion of the shortcomings of any mean field approximation (MFA) is presented. The recovery of the symmetries spontaneously broken in the HFB approach, in particular the angular momentum, is necessary, among others, to describe excited states and transitions. Particle number projection is needed to guarantee the right number of protons and neutrons. Furthermore a projection before the variation prevents the pairing collapse in the weak pairing regime. The lack of fluctuations around the average values of the MFA is a shortcoming of this approach. To build in correlations in BMFT one selects the relevant degrees of freedom: quadrupole, octupole and the pairing vibrations as well as the single particle ones. In the GCM the operators representing these degrees of freedom are used as coordinates to generate a collective subspace. The highly correlated GCM wave function is finally written as a linear combination of a projected basis of this space. The variation of the coefficients of the linear combination leads to the Hill-Wheeler equation. We discuss the classical beta and gamma vibrations by considering the quadrupole operators as coordinates. We present pairing fluctuations by considering the pairing gaps as generator coordinates. Lastly the explicit consideration of the time reversal symmetry breaking in the HFB wave function by the cranking procedure allows the alignment of nucleon pairs opening a new dimension in the BMFT calculations. Abundant calculations with the Gogny force illustrate the state-of-the-art of BMFTs with density functionals. We conclude with a thorough discussion on the potential poles of the theory.
nucl-thnucl-exPhys.Scripta(2016)·77 citations
07
Universal off-equilibrium scaling of critical cumulants in the QCD phase diagram
Swagato Mukherjee🇺🇸 · Raju Venugopalan🇺🇸 · Yi Yin🇺🇸
Exploiting the universality between the QCD critical point and the three dimensional Ising model, closed form expressions derived (arXiv:1506.00645 ) for non-equilibrium critical cumulants on the crossover side of the critical point reveal that they can differ both in magnitude and sign from equilibrium expectations. We demonstrate here that key elements of the Kibble-Zurek framework of non-equilibrium phase transitions can be employed to describe the dynamics of these critical cumulants. Our results suggest that observables sensitive to critical dynamics in heavy-ion collisions should be expressible as universal scaling functions, thereby providing powerful model independent guidance in searches for the QCD critical point.
↳ hep-phhep-thnucl-thPRL(2016)·93 citations

Affiliations

first authorsco-authorsvia INSPIRE

How many-body correlations and α-clustering shape 6He

Systematic study of infrared energy corrections in truncated oscillator spaces

Quantum corrections to the Relativistic mean-field theory

Influence of short-range correlations in neutrino-nucleus scattering

Baryon transition form factors at the pole

State-of-the-art of beyond mean field theories with nuclear density functionals

Universal off-equilibrium scaling of critical cumulants in the QCD phase diagram

Affiliations

How many-body correlations and $α$ -clustering shape $^{6}$ He