Nuclear Theory·nucl-th

Tuesday·March 29, 2016

11 papers—6 primary·5 cross-listed

01
Test of the Glauber Formula for Nucleon-Deuteron Scattering at Intermediate Energies
V. I. Kovalchuk
A high-precision test of the Glauber formula for the amplitude of nucleon-deuteron scattering is performed. Nucleon-nucleon amplitudes used in the calculations depend on the spins of interacting particles, phase shifts, and mixing parameters. These amplitudes were derived by using the Nijmegen potentials. The differential cross sections for nucleon-deuteron scattering were calculated for the projectile-nucleon energies of 65, 95, 135, 150, 190, and 250~MeV, and the results of these calculations were compared with experimental data.
nucl-thPhys.Atom.Nucl.(2012)·3 citations
02
Understanding transport simulations of heavy-ion collisions at 100 and 400 AMeV: Comparison of heavy ion transport codes under controlled conditions
Jun Xu🇨🇳 · Lie-Wen Chen🇨🇳 · ManYee Betty Tsang🇺🇸 · Hermann Wolter🇩🇪 · Ying-Xun Zhang🇨🇳 · Joerg Aichelin🇫🇷 · Maria Colonna🇮🇹 · Dan Cozma🇷🇴 · Pawel Danielewicz🇺🇸 · Zhao-Qing Feng🇨🇳 · Arnaud Le Fevre🇩🇪 · Theodoros Gaitanos🇬🇷 and 19 other authors
Transport simulations are very valuable for extracting physics information from heavy-ion collision experiments. With the emergence of many different transport codes in recent years, it becomes important to estimate their robustness in extracting physics information from experiments. We report on the results of a transport code comparison project. 18 commonly used transport codes were included in this comparison: 9 Boltzmann-Uehling-Uhlenbeck-type codes and 9 Quantum-Molecular-Dynamics-type codes. These codes have been required to simulate Au+Au collisions using the same physics input for mean fields and for in-medium nucleon-nucleon cross sections, as well as the same initialization set-up, the impact parameter, and other calculational parameters at 100 and 400 AMeV incident energy. Among the codes we compare one-body observables such as rapidity and transverse flow distributions. We also monitor non-observables such as the initialization of the internal states of colliding nuclei and their stability, the collision rates and the Pauli blocking. We find that not completely identical initializations constitute partly for different evolutions. Different strategies to determine the collision probabilities, and to enforce the Pauli blocking, also produce considerably different results. There is a substantial spread in the predictions for the observables, which is much smaller at the higher incident energy. We quantify the uncertainties in the collective flow resulting from the simulation alone as about $30%$ at 100 AMeV and $13%$ at 400 AMeV, respectively. We propose further steps within the code comparison project to test the different aspects of transport simulations in a box calculation of infinite nuclear matter. This should, in particular, improve the robustness of transport model predictions at lower incident energies where abundant amounts of data are available.
nucl-thnucl-exPRC(2016)·186 citations
03
Exploring Dense and Cold QCD in Magnetic Fields
E. J. Ferrer🇺🇸 · V. de la Incera🇺🇸
Strong magnetic fields are commonly generated in off-central relativistic heavy-ion collisions in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab and in the Large Hadron Collider at CERN and have been used to probe the topological configurations of the QCD vacua. A strong magnetic field can affect the character and location of the QCD critical point, influence the QCD phases, and lead to anomalous transport of charge. To take advantage of the magnetic field as a probe of QCD at higher baryon densities, we are going to need experiments capable to scan the lower energy region. In this context, the nuclotron-based ion collider facility (NICA) at JINR offers a unique opportunity to explore such a region and complement alternative programs at RHIC and other facilities. In this paper we discuss some relevant problems of the interplay between QCD and magnetic fields and the important role the experiments at NICA can play in tackling them.
nucl-thhep-phnucl-exEPJA(2016)·17 citations
04
The Dubna-Mainz-Taipei Dynamical Model for $π N$ Scattering and $π$ Electromagnetic Production
Shin Nan Yang🇹🇼
Some of the featured results of the Dubna-Mainz-Taipei (DMT) dynamical model for $π N$ scattering and $π^{0}$ electromagnetic production are summarized. These include results for threshold $π^{0}$ production, deformation of $Δ (1232)$ , and the extracted properties of higher resonances below 2 GeV. The excellent agreement of DMT model's predictions with threshold $π^{0}$ production data, including the recent precision measurements from MAMI establishes results of DMT model as a benchmark for experimentalists and theorists in dealing with threshold pion production.
nucl-thhep-phJPS Conf.Proc.(2016)·1 citation
05
Quark-Jet model for transverse momentum dependent fragmentation functions
W. Bentz🇯🇵 · A. Kotzinian🇦🇲 · H. H. Matevosyan🇦🇺 · Y. Ninomiya🇯🇵 · A. W. Thomas🇦🇺 · K. Yazaki🇯🇵
In order to describe the hadronization of polarized quarks, we discuss an extension of the quark-jet model to transverse momentum dependent fragmentation functions. The description is based on a product ansatz, where each factor in the product represents one of the transverse momentum dependent splitting functions, which can be calculated by using effective quark theories. The resulting integral equations and sum rules are discussed in detail for the case of inclusive pion production. In particular, we demonstrate that the 3-dimensional momentum sum rules are satisfied naturally in this transverse momentum dependent quark-jet model. Our results are well suited for numerical calculations in effective quark theories, and can be implemented in Monte-Carlo simulations of polarized quark hadronization processes.
nucl-thhep-exhep-phPRD(2016)·16 citations
06
Inclusive electron scattering within the SuSAv2-MEC approach
G.D. Megias🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · T.W. Donnelly🇺🇸
We present our recent progress on the relativistic modeling of electron-nucleus reactions and compare our predictions with inclusive $^{12}$ C ( $e, e^{'}$ ) experimental data in a wide kinematical region. The model, originally based on the superscaling phenomenon shown by electron-nucleus scattering data, has recently been improved through the inclusion of Relativistic Mean Field theory effects that take into account the enhancement of the transverse scaling function compared with its longitudinal counterpart. We also discuss the impact of meson-exchange currents (MEC) through the analysis of two-particle two-hole longitudinal and transverse contributions to electromagnetic response functions evaluated within the framework of the relativistic Fermi gas. The formalism is also extended to include the complete inelastic spectrum -- resonant, non-resonant and deep inelastic scattering (DIS). The results show quite good agreement with data over the whole range of energy transfer, including the dip region between the quasielastic peak and the $Δ$ resonance.
nucl-thhep-exhep-phPRD(2016)·112 citations
07
Strangeness $S = - 1$ hyperon-nucleon scattering in covariant chiral effective field theory
Kai-Wen Li🇨🇳 · Xiu-Lei Ren🇨🇳 · Li-Sheng Geng🇨🇳 · Bing-Wei Long🇨🇳
Motivated by the successes of covariant baryon chiral perturbation theory in one-baryon systems and in heavy-light systems, we study relevance of relativistic effects in hyperon-nucleon interactions with strangeness $S = - 1$ . In this exploratory work, we follow the covariant framework developed by Epelbaum and Gegelia to calculate the $Y N$ scattering amplitude at leading order. By fitting the five low-energy constants to the experimental data, we find that the cutoff dependence is mitigated, compared with the heavy-baryon approach. Nevertheless, the description of the experimental data remains quantitatively similar at leading order.
↳ hep-phnucl-thPRD(2016)·45 citations
08
Update of HKN Nuclear PDFs
Masanori Hirai🇯🇵
We discuss consistency of the nuclear effects between the electromagnetic and weak interactions. In order to study a possibility of different nuclear effects in the neutrino DIS process, double differential cross section data are compared with these values obtained by the HKN07 nuclear parton distribution functions (nPDFs). Discrepancies are found in the small and large- $x$ regions, and difference of kinematical value $y$ dependence exists between the $ν$ and $ν ˉ$ data around $x = 0.35$ . Moreover, we study statistical significance of the neutrino DIS data in each $x$ bin and discuss about the possibility of the different nuclear modifications.
↳ hep-phhep-exnucl-exnucl-thJPS Conf.Proc.(2016)·4 citations
09
The mutable nature of particle-core excitations with spin in the one-valence-proton nucleus 133Sb
G. Bocchi🇮🇹 · S. Leoni🇮🇹 · B. Fornal🇵🇱 · G. Colo'🇮🇹 · P.F. Bortignon🇮🇹 · S. Bottoni🇮🇹 · A. Bracco🇮🇹 · C. Michelagnoli🇫🇷 · D. Bazzacco🇮🇹 · A. Blanc🇫🇷 · G. De France🇫🇷 · M. Jentschel🇫🇷 and 34 other authors
The gamma-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between gamma-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 micros isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, reveals a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus 132Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin.
↳ nucl-exnucl-thPLB(2016)·33 citations
10
Transverse wobbling motion in $^{134}$ Ce and $^{136}$ Nd
C. M. Petrache · S. Guo
The existence of one-phonon and possible two-phonon transverse wobbling bands is proposed for the first time in two even-even nuclei, $^{134}$ Ce and $^{136}$ Nd. The predominant $E 2$ character of the $Δ I = 1$ transitions connecting the one-phonon wobbling band in $^{134}$ Ce to the two-quasiparticle yrast band supports the wobbling interpretation. The extracted wobbling frequencies decrease with increasing spin, indicating the transverse character of the wobbling motion, with the angular momenta of the two quasiparticles aligned perpendicular to the axis of collective rotation. A candidate for two-phonon wobbling motion is also proposed in $^{136}$ Nd. The wobbling frequencies calculated in the harmonic frozen approximation are in good agreement with the experimental ones for both the $^{134}$ Ce and $^{136}$ Nd nuclei.
↳ nucl-exnucl-th4 citations
11
Progress in Many Body Theory with the Equation of Motion method. Time dependent Density Matrix meets Self-Consistent RPA. Applications to solvable Models
Peter Schuck🇫🇷 · Mitsuru Tohyama🇯🇵
The Bogoliubov-Born-Green-Kirkwood-Yvon or Time-Dependent Density Matrix (TDDM) hierarchy of equations for higher density matrices is truncated at the three body level in approximating the three body correlation function by a quadratic form of two body ones, closing the equations in this way. The procedure is discussed in detail and it is shown in non-trivial model cases that the approximate inclusion of three body correlation functions is very important to obtain precise results. A small amplitude approximation of this time dependent nonlinear equation for the two body correlation function is performed (STDDM*-b) and it is shown that the one body sector of this generalised non-linear second RPA equation is equivalent to the Self-Consistent RPA (SCRPA) approach which had been derived previously by different techniques. It is discussed in which way SCRPA also contains the three body correlations. TDDM and SCRPA are tested versus exactly solvable model cases.
↳ cond-mat.str-elnucl-thPRB(2016)·31 citations

Affiliations

first authorsco-authorsvia INSPIRE