Nuclear Theory·nucl-th

Wednesday·April 27, 2016

10 papers—7 primary·3 cross-listed

01
Distribution amplitudes of radially-excited pi- and K-mesons
Bo-Lin Li🇨🇳 · Lei Chang🇨🇳 · Fei Gao🇨🇳 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪 · Hong-Shi Zong🇨🇳
A symmetry-preserving truncation of the two-body bound-state problem in relativistic quantum field theory is used to compute the leading-twist parton distribution amplitudes (PDAs) for the first radial excitations of the $π$ - and $K$ -mesons. In common with ground states in these channels, the PDAs are found to be dilated with respect to the relevant conformal-limit form and skewed toward the heavier valence-quark in asymmetric systems. In addition, the PDAs of radially-excited pseudoscalar mesons are not positive definite, owing to the fact that dynamical chiral symmetry breaking (DCSB) forces the leptonic decay constant of such states to vanish in the chiral limit. These results highlight that DCSB is expressed visibly in every pseudoscalar meson constituted from light-quarks. Hence, so long as its impact is empirically evident in the pseudoscalar members of a given spectrum level, it is unlikely that chiral symmetry is restored in any of the hadrons that populate this level.
nucl-thhep-lathep-phnucl-exPRD(2016)·45 citations
02
Higher order anisotropies in the Buda-Lund model: Disentangling flow and density field anisotropies
Sándor Lökös🇭🇺 · Máté Csanád🇭🇺 · Tamás Csörgő🇸🇰 · Boris Tomášik🇭🇺
The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and fits the observed elliptic flow and oscillating HBT radii successfully. Due to fluctuations in energy depositions, the fireball shape however fluctuates on an event-by-event basis. The transverse plane asymmetry can be translated into a series of multipole anisotropy coefficients. These anisotropies then result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we detail an extension of the Buda-Lund model to multipole anisotropies and investigate the resulting flow coefficients and oscillations of HBT radii.
nucl-thhep-phEPJA(2016)·8 citations
03
Gauge angle dependence in TDHFB calculations of $^{20}$ O + $^{20}$ O head-on collisions with the Gogny interaction
Yukio Hashimoto · Guillaume Scamps
A numerical method to solve the TDHFB equations by using a hybrid basis of the two-dimensional harmonic oscillator eigenfunctions and one-dimensional Lagrange mesh with the Gogny effective interaction is applied to the head-on collisions of the superfluid nuclei $^{20}$ O's. Taking the energies around the barrier top energy, the trajectories, pairing energies, and numbers of transferred nucleons are displayed. Their dependence on the relative gauge angle at the initial time is studied by taking typical sample points of the gauge angle. It turned out that the functional form of the flux of the neutrons across a section plane is proportional to the sine of the two times of the gauge angle.
nucl-thPRC(2016)·42 citations
04
Saturation of Nuclear Matter and Roles of Many-Body Forces: nuclear matter in neutron stars probed by nucleus-nucleus scattering
Y.Sakuragi
Yoichiro Nambu put a great foot print in nuclear physics in the era of its fundamental developments including his pioneering insight into essential ingredients of repulsive core of nuclear force and its relation to the saturation of nuclear matter. The present review article focuses onto recent developments of the interaction models between colliding nuclei in terms of Brueckner's G-matrix theory staring from realistic nuclear forces and the saturation property of symmetric nuclear matter as well as neutron-star matter. A recently proposed unique scenario of extracting the saturation property of nuclear matter and stiffness of neutron stars through the analysis of nucleus-nucleus elastic scattering in laboratories is presented in some detail.
nucl-thhep-phPTEP(2016)·12 citations
05
Algebraic model for single-particle energies of $Λ$ hypernuclei
L. Fortunato🇮🇹 · K. Hagino🇯🇵
A model is proposed for the spectrum of $Λ$ hypernuclei based on the $u (3) \times u (2)$ Lie algebra, in which the internal degrees of freedom of the spin-1/2 $Λ$ particle are treated in the Fermionic $u (2)$ scheme, while the motion of the hyperon inside a nucleus is described in the Bosonic $u (3)$ harmonic oscillator scheme. Within this model, a simple formula for single-particle energies of the $Λ$ particle is obtained from the natural dynamical symmetry. The formula is applied to the experimental data on the reaction spectroscopy for the $_{Λ}^{89}$ Y and $_{Λ}^{51}$ V hypernuclei, providing a clear theoretical interpretation of the observed structures.
nucl-thhep-ph1 citation
06
Wounded quarks in A+A, p+A, and p+p collisions
Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱 · Maciej Rybczynski🇵🇱
We explore predictions of the wounded quark model for particle production and properties of the initial state formed in ultrarelativistic heavy-ion collisions. The approach is applied uniformly to A+A collisions in a wide collision energy range, as well as for p+A and p+p collisions at the CERN Large Hadron Collider (LHC). We find that generically the predictions from wounded quarks for such features as eccentricities or initial sizes are close (within 15\%) to predictions of the wounded nucleon model with an amended binary component. A larger difference is found for the size in p+Pb system, where the wounded quark model yields a smaller (more compact) initial fireball than the standard wounded nucleon model. The inclusion of subnucleonic degrees of freedom allows us to analyze p+p collisions in an analogous way, with predictions that can be used in further collective evolution. The approximate linear dependence of particle production in A+A collisions on the number of wounded quarks, as found in previous studies, makes the approach based on wounded quarks natural. Importantly, at the LHC energies we find approximate uniformity in particle production from wounded quarks, where at a given collision energy per nucleon pair similar production of initial entropy per source is needed to explain the particle production from p+p collisions up to A+A collisions. We also discuss the sensitivity of the wounded quark model predictions to distribution of quarks in nucleons, distribution of nucleons in nuclei, and to the quark-quark inelasticity profile in the impact parameter. In our procedure, the quark-quark inelasticity profile is chosen in such a way that the experiment-based parametrization of the proton-proton inelasticity profile is properly reproduced. The parameters of the overlaid multiplicity distribution is fixed from p+p and p+Pb data.
nucl-thnucl-exPRC(2016)·79 citations
07
The power of two: Assessing the impact of a second measurement of the weak-charge form factor of 208Pb
J. Piekarewicz🇺🇸 · A. Linero🇺🇸 · P. Giuliani🇺🇸 · E. Chicken🇺🇸
[Background] Besides its intrinsic value as a fundamental nuclear-structure observable, the weak-charge density of 208Pb - a quantity that is closely related to its neutron distribution - is of fundamental importance in constraining the equation of state of neutron-rich matter. [Purpose] To assess the impact that a second electroweak measurement of the weak-charge form factor of 208Pb may have on the determination of its overall weak-charge density. [Methods] Using the two putative experimental values of the form factor, together with a simple implementation of Bayes' theorem, we calibrate a theoretically sound - yet surprisingly little known - symmetrized Fermi function, that is characterized by a density and form factor that are both known exactly in closed form. [Results] Using the charge form factor of 208Pb as a proxy for its weak-charge form factor, we demonstrate that using only two experimental points to calibrate the symmetrized Fermi function is sufficient to accurately reproduce the experimental charge form factor over a significant range of momentum transfers. [Conclusions] It is demonstrated that a second measurement of the weak-charge form factor of 208Pb supplemented by a robust theoretical input in the form of the symmetrized Fermi function, would place significant constraints on the neutron distribution of 208Pb and, ultimately, on the equation of state of neutron-rich matter.
nucl-thnucl-exPRC(2016)·66 citations
08
Model independent analysis of nearly Lévy correlations
T. Novák🇭🇺 · T. Csörgő🇭🇺 · H. C. Eggers🇿🇦 · M. de Kock🇿🇦
A model-independent method for the analysis of the two-particle short-range correlations is presented, that can be utilized to describe e.g. Bose-Einstein (HBT), dynamical (ridge) or other correlation functions, that have a nearly Lévy or streched exponential shape. For the special case of Lévy exponent alpha = 1, the earlier Laguerre expansions are recovered, for the alpha = 2 special case, a new expansion method is obtained for nearly Gaussian correlation functions. Multi-dimensional Lévy expansions are also introduced and their potential application to analyze rigde correlation data is discussed.
↳ physics.data-anhep-exhep-phnucl-ex+1Acta Phys.Polon.Supp.(2016)·15 citations
09
Second-order hydrodynamics for fermionic cold atoms: Detailed analysis of transport coefficients and relaxation times
Yuta Kikuchi · Kyosuke Tsumura · Teiji Kunihiro
We give a detailed derivation of the second-order (local) hydrodynamics for Boltzmann equation with an external force by using the renormalization group method. In this method, we solve the Boltzmann equation faithfully to extract the hydrodynamics without recourse to any ansatz. Our method leads to microscopic expressions of not only all the transport coefficients that are of the same form as those in Chapman-Enskog method but also those of the viscous relaxation times $τ_{i}$ that admit physically natural interpretations. As an example, we apply our microscopic expressions to calculate the transport coefficients and the relaxation times of the cold fermionic atoms in a quantitative way, where the transition probability in the collision term is given explicitly in terms of the $s$ -wave scattering length $a_{s}$ . We thereby discuss the quantum statistical effects, temperature dependence, and scattering-length dependence of the first-order transport coefficients and the viscous relaxation times: It is shown that as the temperature is lowered, the transport coefficients and the relaxation times increase rapidly because Pauli principle acts effectively. On the other hand, as $a_{s}$ is increased, these quantities decrease and become vanishingly small at unitarity because of the strong coupling. The numerical calculation shows that the relation $τ_{π} = η / P$ , which is derived in the relaxation-time approximation and used in most of literature without almost any foundation, turns out to be satisfied quite well, while the similar relation for the relaxation time $τ_{J}$ of the heat conductivity is satisfied only approximately with a considerable error.
↳ cond-mat.quant-gasnucl-thphysics.flu-dyn0 citations
10
The Operator Product Expansion Beyond Leading Order for Two-Component Fermions
Samuel B. Emmons🇺🇸 · Daekyoung Kang🇺🇸 · Lucas Platter🇺🇸
We consider a homogeneous, balanced gas of strongly interacting fermions in two spin states interacting through a large scattering length. Finite range corrections are needed for a quantitative description of data which experiments and numerical simulations have provided. We use a perturbative field theoretical framework and a tool called the Operator Product Expansion (OPE), which together allow for the expression of finite range corrections to the universal relations and momentum distribution. Using the OPE, we derive the $1/ k^{6}$ part of the momentum tail, which is related to the sum of the derivative of the energy with respect to the finite range and the averaged kinetic energy of opposite spin pairs. By comparing the $1/ k^{4}$ term and the $1/ k^{6}$ correction in the momentum distribution to provided Quantum Monte Carlo (QMC) data, we show that including the $1/ k^{6}$ part offers marked improvements. Our field theoretical approach allows for a clear understanding of the role of the scattering length and finite effective range in the universal relations and the momentum distribution.
↳ cond-mat.quant-gashep-phnucl-thPRA(2016)·8 citations

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