Nuclear Theory·nucl-th

Wednesday·August 26, 2015

8 papers—4 primary·4 cross-listed

01
A Method to Calculate Fission-Fragment Yields $Y (Z, N)$ versus Proton and Neutron Number in the Brownian Shape-Motion Model. Application to calculations of U and Pu charge yields
P. Moller · T. Ichikawa
We propose a method to calculate the two-dimensional (2D) fission-fragment yield $Y (Z, N)$ versus both proton and neutron number, with inclusion of odd-even staggering effects in both variables. The approach is to use Brownian shape-motion on a macroscopic-microscopic potential-energy surface which, for a particular compound system is calculated versus four shape variables: elongation (quadrupole moment $Q_{2}$ ), neck $d$ , left nascent fragment spheroidal deformation $ϵ_{f1}$ , right nascent fragment deformation $ϵ_{f2}$ and two asymmetry variables, namely proton and neutron numbers in each of the two fragments. The extension of previous models 1) introduces a method to calculate this generalized potential-energy function and 2) allows the correlated transfer of nucleon pairs in one step, in addition to sequential transfer. In the previous version the potential energy was calculated as a function of $Z$ and $N$ of the compound system and its shape, including the asymmetry of the shape. We outline here how to generalize the model from the "compound-system" model to a model where the emerging fragment proton and neutron numbers also enter, over and above the compound system composition.
nucl-thEPJA(2015)·35 citations
02
Is hadronic flow produced in p--Pb collisions at the Large Hadron Collider?
You Zhou🇩🇰 · Xiangrong Zhu🇨🇳 · Pengfei Li🇨🇳 · Huichao Song🇨🇳
Using the Ultra-relativistic Quantum Molecular Dynamics ({\tt UrQMD}) model, we investigate the azimuthal correlations in p--Pb collisions at $s_{_{NN}} = 5.02$ TeV. It is shown that the simulated hadronic p--Pb system can not generate the collective flow signatures, but mainly behaves as a non-flow dominant system. However, the characteristic $v_{2} (p_{T})$ mass-ordering of pions, kaons and protons is observed in {\tt UrQMD} simulations, which is the consequence of hadronic interactions and not necessarily associated with strong fluid-like expansions.
nucl-thnucl-exEPJ Web Conf.(2016)·0 citations
03
Scaling functions of two-neutron separation energies of $^{20} C$ with finite range potentials
M. A. Shalchi · M. R. Hadizadeh · M. T. Yamashita · Lauro Tomio · T. Frederico
The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus $^{20} C$ .
nucl-thEPJ Web Conf.(2016)·0 citations
04
Nuclear Mass Predictions for the Crustal Composition of Neutron Stars: A Bayesian Neural Network Approach
R. Utama · J. Piekarewicz · H. B. Prosper
Besides their intrinsic nuclear-structure value, nuclear mass models are essential for astrophysical applications, such as r-process nucleosynthesis and neutron-star structure. To overcome the intrinsic limitations of existing "state-of-the-art" mass models, we propose a refinement based on a Bayesian Neural Network (BNN) formalism. A novel BNN approach is implemented with the goal of optimizing mass residuals between theory and experiment. A significant improvement (of about 40%) in the mass predictions of existing models is obtained after BNN refinement. Moreover, these improved results are now accompanied by proper statistical errors. Finally, by constructing a "world average" of these predictions, a mass model is obtained that is used to predict the composition of the outer crust of a neutron star. The power of the Bayesian neural network method has been successfully demonstrated by a systematic improvement in the accuracy of the predictions of nuclear masses. Extension to other nuclear observables is a natural next step that is currently under investigation.
nucl-thastro-ph.HEastro-ph.SRnucl-exPRC(2016)·211 citations
05
Strong Decays of Charmed Baryons in Heavy Hadron Chiral Perturbation Theory: An Update
Hai-Yang Cheng🇹🇼 · Chun-Khiang Chua🇹🇼
We first give a brief overview of the charmed baryon spectroscopy and discuss their possible structure and spin-parity assignments in the quark model. With the new Belle measurement of the widths of $Σ_{c} (2455)$ and $Σ_{c} (2520)$ and the recent CDF measurement of the strong decays of $Λ_{c} (2595)$ and $Λ_{c} (2625)$ , we give updated coupling constants in heavy hadron chiral perturbation theory. We find $g_{2} = 0.56 5_{- 0.024}^{+ 0.011}$ for $P$ -wave transitions between $s$ -wave and $s$ -wave baryons, and $h_{2}$ , one of the couplings responsible for $S$ -wave transitions between $s$ -wave and $p$ -wave baryons, is extracted from $Λ_{c} (2595)^{+} \to Λ_{c}^{+} π π$ to be $0.63 \pm 0.07$ . It is substantially enhanced compared to the old value of order 0.437. With the help from the quark model, two of the couplings $h_{10}$ and $h_{11}$ responsible for $D$ -wave transitions between $s$ -wave and $p$ -wave baryons are determined from $Σ_{c} (2880)$ decays. There is a tension for the coupling $h_{2}$ as its value extracted from $Λ_{c} (2595)^{+} \to Λ_{c}^{+} π π$ will imply $Ξ_{c} (2790)^{0} \to Ξ_{c}^{'} π$ and $Ξ_{c} (2815)^{+} \to Ξ_{c}^{*} π$ rates slightly above the current limits. It is conceivable that SU(3) flavor symmetry breaking can help account for the discrepancy.
↳ hep-phhep-exnucl-thPRD(2015)·105 citations
06
Chiral dynamics of S-wave baryon resonances
Bingwei Long🇨🇳
As the pion mass approaches a critical value $m_{π}^{⋆}$ from below, an $S$ -wave resonance crosses pion-baryon threshold and becomes a bound state with arbitrarily small binding energy, thus driving the scattering length to diverge. I explore the consequences of chiral symmetry for the values of $m_{π}$ close to $m_{π}^{⋆}$ . It turns out that chiral symmetry is crucial for an $S$ -wave resonance to be able to stand very near threshold and in the meantime to remain narrow, provided that the mass splitting is reasonably small. The effective range of pion-baryon scattering is unexpectedly large, proportional to $4 π f_{π}^{2} / m_{π}^{3}$ when $m_{π}$ is around $m_{π}^{⋆}$ . As a result, this unexpected large length scale causes universality relations to break down much sooner than naively expected.
↳ hep-phnucl-thPRD(2016)·8 citations
07
Antiproton-proton interaction and related hadron physics
Xian-Wei Kang🇩🇪
Antinucleon-nucleon interaction has been established in chiral effective field theory. The strong threshold enhancement observed in the reactions $J / ψ \to γ p p$ and $e^{+} e^{-} \to p p$ are interpreted by the strong $p p$ interaction. Concerning the channel $J / ψ \to γ p p$ , the topic on the $p p$ bound state is also discussed.
↳ hep-phhep-exnucl-thPoS(2016)·2 citations
08
Dilepton rate and quark number susceptibility with the Gribov action
Aritra Bandyopadhyay🇮🇳 · Najmul Haque🇺🇸 · Munshi G. Mustafa🇮🇳 · Michael Strickland🇺🇸
We use a recently obtained resummed quark propagator at finite temperature which takes into account both the chromoelectric scale gT and the chromomagnetic scale g^2T through the Gribov action. The electric scale generates two massive modes whereas the magnetic scale produces a new massless spacelike mode in the medium. Moreover, the non-perturbative quark propagator is found to contain no discontinuity in contrast to the standard perturbative hard thermal loop approach. Using this non-perturbative quark propagator and self-consistent vertices, we compute the non-perturbative dilepton rate at vanishing three-momentum at one-loop order. The resulting rate has a rich structure at low energies due to the inclusion of the non-perturbative magnetic scale. We also calculate the quark number susceptibility, which is related to the conserved quark number density fluctuation in the deconfined state. Both the dilepton rate and quark number susceptibility are compared with results from lattice quantum chromodynamics and the standard hard thermal loop approach. Finally, we discuss how the absence of a discontinuity in the imaginary part of the non-perturbative quark propagator makes the results for both dilepton production and quark number susceptibility dramatically different from those in perturbative approaches and seemingly in conflict with known lattice data.
↳ hep-phnucl-thPRD(2016)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE