Nuclear Theory·nucl-th

Tuesday·September 10, 2019

15 papers—9 primary·6 cross-listed

01
Searching for $^{4} L i$ by momentum correlation function of $p -^{3} H e$
Bao-Shan Xi🇨🇳 · Zheng-Qiao Zhang🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳
The observed heaviest anti-nucleus so far is $^{4} H e$ which is found in relativistic heavy ion collider in 2011. The yield of $^{4} L i$ is four times bigger than that of $^{4} H e$ according to the thermal model. From previous scattering experiment, we know that the $^{4} L i$ has a very short life time about $1.197 \times 1 0^{- 22} s$ . It decays into $^{3} H e$ and $p$ . In experiment, the correlation function of $p -^{3} H e$ will offer us a method to observe $^{4} L i$ by CPT symmetry. In this paper, we use the blast-wave model and Lednicky-Lyuboshitz analytical model to obtain a prediction of the correlation function of $p -^{3} H e$ with/without $^{4} L i$ decay in Au + Au collisions at $S_{N N}$ = 200 GeV. The correlation function with $^{4} L i$ decay is found to exhibit a peak at $k^{*} \approx$ 0.073GeV/ $c$ . The results offer a guide for the experimental search for $^{4} L i$ in relativistic heavy ion collision.
nucl-thnucl-exPRC(2020)·10 citations
02
Electromagnetic field from asymmetric to symmetric heavy ion collision at 200 GeV/c
Yi-Lin Cheng🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳 · Jin-Hui Chen🇨🇳 · Chen Zhong🇨🇳
Electromagnetic fields produced in relativistic heavy-ion collisions are affected by the asymmetry of the projectile-target combination as well as the different initial configurations of the nucleus. In this study, the results of the electric and magnetic fields produced for different combinations of ions, namely $^{12}$ C + $^{197}$ Au, $^{24}$ Mg + $^{197}$ Au, $^{64}$ Cu + $^{197}$ Au, and $^{197}$ Au + $^{197}$ Au at $s_{N N} = 200$ GeV are demonstrated with a multi-phase transport model (AMPT). The configuration of the distribution of nucleons of $^{12}$ C is initialized by a Woods-Saxon spherical structure, a three- $α$ -clustering triangular structure or a three- $α$ -clustering chain structure. It was observed that the electric and magnetic fields display different behavioral patterns for asymmetric combinations of the projectile and target nuclei as well as for different initial configurations of the carbon nucleus. The major features of the process are discussed.
nucl-thnucl-exPRC(2019)·20 citations
03
Finite-size scaling phenomenon of nuclear liquid--gas phase transition probes
H. L. Liu🇨🇳 · Y. G. Ma🇨🇳 · D. Q. Fang🇨🇳
Based on the isospin-dependent quantum molecular dynamics model, finite-size scaling effects on nuclear liquid--gas phase transition probes are investigated by studying the de-excitation processes of six thermal sources of different sizes with the same initial density and similar $N / Z$ . Using several probes including the total multiplicity derivative ( $d M_{t o t} / d T$ ), second moment parameter ( $M_{2}$ ), intermediate mass fragment (IMF) multiplicity ( $N_{I M F}$ ), Fisher's power-law exponent ( $τ$ ), and Ma's nuclear Zipf's law exponent ( $ξ$ ), the relationship between the phase transition temperature and the source size has been established. It is observed that the phase transition temperatures obtained from the IMF multiplicity, Fisher's exponent, and Ma's nuclear Zipf's law exponent have a strong correlation with the source size. Moreover, by employing the finite-size scaling law, the critical temperature $T_{c}$ and the critical exponent $ν$ have been obtained for infinite nuclear matter.
nucl-thnucl-exPRC(2019)·15 citations
04
The energy and scale dependence of $q^$ and the JET puzzle
Amit Kumar🇺🇸 · Abhijit Majumder🇺🇸 · Chun Shen🇺🇸
We present an attempt to probe the underlying structure of the quark-gluon plasma (QGP) at high resolution, based on the extracted jet transport coefficient $q^$ . We argue that the exchanged momentum $k$ between the hard parton and the medium varies over a range of scales, and for $k \geq$ 1 GeV, $q^$ can be expressed in terms of a parton distribution function (PDF). Because the mass of a QGP constituent is unknown, we define a scaling variable $x_{N}$ to represent the ratio of the parton momentum to the momentum of a self-contained section of the plasma which has a mass of 1 GeV. This scaling variable is used to parametrize the QGP-PDF. Calculations, based on this reconstructed $q^$ are compared to data sensitive to the hardcore of jets $i . e .,$ the single hadron suppression in terms of the nuclear modification factor $R_{AA}$ and the azimuthal anisotropy parameter $v_{2}$ , as a function of transverse momentum $p_{T}$ , centrality and energy of the collision. It is demonstrated that the scale evolution of the QGP-PDF is responsible for the reduction in the normalization of $q^$ between fits to Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) data; a puzzle, first discovered by the JET collaboration.
nucl-thhep-phnucl-exPRC(2020)·51 citations
05
IRDFF-II: A New Neutron Metrology Library
A. Trkov🇦🇹 · P.J. Griffin🇺🇸 · S.P. Simakov🇩🇪 · L.R. Greenwood🇺🇸 · K.I. Zolotarev🇷🇺 · R. Capote🇦🇹 · D.L. Aldama🇨🇺 · V. Chechev🇷🇺 · C. Destouches🇫🇷 · A.C. Kahler🇨🇭 · C. Konno🇯🇵 · M. Koštál🇨🇿 and 12 other authors
High quality nuclear data is the most fundamental underpinning for all neutron metrology applications. This paper describes the release of version II of the International Reactor Dosimetry and Fusion File (IRDFF-II) that contains a consistent set of nuclear data for fission and fusion neutron metrology applications up to 60~MeV neutron energy. The library is intended to support: a) applications in research reactors; b) safety and regulatory applications in the nuclear power generation in commercial fission reactors; and c) material damage studies in support of the research and development of advanced fusion concepts. The paper describes the contents of the library, documents the thorough verification process used in its preparation, and provides an extensive set of validation data gathered from a wide range of neutron benchmark fields. The new \mbox{IRDFF-II} library includes 119 metrology reactions, four cover material reactions to support self-shielding corrections, five metrology metrics used by the dosimetry community, and cumulative fission products yields for seven fission products in three different neutron energy regions. In support of characterizing the measurement of the residual nuclei from the dosimetry reactions and the fission product decay modes, the present document lists the recommended decay data, particle emission energies and probabilities for 68 activation products. It also includes neutron spectral characterization data for 29 neutron benchmark fields for the validation of the library contents. The IRDFF-II library and comprehensive documentation is available online at https://www-nds.iaea.org/IRDFF/. Evaluated cross sections can be compared with experimental data and other evaluations at https://www-nds.iaea.org/exfor/endf.htm. The new library is expected to become the international reference in neutron metrology for multiple applications.
nucl-thnucl-exNucl.Data Sheets(2020)·58 citations
06
$Δ$ Contribution to $pp \to pp π^{0}$
Venkataraya🇮🇳 · Sujith Thomas🇮🇳 · G. Ramachandran🇮🇳
A model independent discussion of $Δ -$ production in $pp \to pp π^{0}$ is presented and the $Δ -$ contributions to the 16 $pp \to pp π^{0}$ partial wave amplitudes are identified taking the $D s$ and $S d$ channels also into consideration.
nucl-th2 citations
07
Statistical Assemblies of Particles with Spin
G. Ramachandran
Spin, $s$ in quantum theory can assume only half odd integer or integer values. For a given $s$ , there exist $n = 2 s + 1$ states $∣ s, m ⟩$ , $m = s, s - 1, ........, - s$ . A statistical assembly of particles (like a beam or target employed in experiments in physics) with the lowest value of spin $s = \frac{1}{2}$ can be described in terms of probabilities $p_{m}$ assigned to the two states $m = \pm \frac{1}{2}$ . A generalization of this concept to higher spins $s > \frac{1}{2}$ leads only to a particularly simple category of statistical assemblies known as `Oriented systems'. To provide a comprehensive description of all realizable categories of statistical assemblies in experiments, it is advantageous to employ the generators of the Lie group $S U (n)$ . The probability domain then gets identified to the interior of regular polyhedra in $ℜ^{n - 1},$ where the centre corresponds to an unpolarized assembly and the vertices represent `pure' states. All the other interior points correspond to `mixed' states. The higher spin system has embedded within itself a set of $s (2 s + 1)$ independent axes, which are determinable empirically. Only when all these axes turn out to be collinear, the simple category of `Oriented systems' is realized, where probabilities $p_{m}$ are assigned to the states $∣ s, m ⟩$ . The simplest case of higher spin $s = 1$ provides an illustrative example, where additional features of `aligned' and more general `non oriented' categories are displayed.
nucl-thquant-ph0 citations
08
Application of Principal Component Analysis to establish proper basis for flow studies in heavy-ion collisions
Igor Altsybeev
It is shown that Principal Component Analysis (PCA) applied to event-by-event single-particle distributions in A-A collisions allows establishing the most optimal basis for anisotropic flow studies from data itself, in contrast to manual selection of the basis functions. PCA coefficients for azimuthal particle distributions are identical to Fourier coefficients from a conventional analysis techniques. PCA applied in longitudinal dimension reveals optimal basis that is similar to Legendre polynomial series. Analysis in both dimensions simultaneously allows studying the coupling of the longitudinal structure of events with the azimuthal anisotropy of particle emission.
nucl-thnucl-exPhys.Part.Nucl.(2020)·4 citations
09
Influence of the tensor interaction on heavy-ion fusion cross sections
K. Godbey · Lu Guo · A.S. Umar
[Background] While the tensor interaction has been shown to significantly affect the nuclear structure of exotic nuclei, its influence on nuclear reactions has only recently been investigated. The primary reason for this neglect is the fact that most studies of nuclear dynamics do not include the tensor force at all in their models. Indeed, only a few Skyrme parametrizations consider the tensor interaction in parameter determination. With modern research facilities extending our ability to probe exotic nuclei, a correct description of nuclear dynamics and heavy-ion fusion is vital to both supporting and leading experimental efforts. [Method] Fusion cross sections are calculated using ion-ion potentials generated by the fully microscopic density-constrained time-dependent Hartree-Fock (DC-TDHF) method with the complete Skyrme tensor interaction. [Results] For light nuclei, the tensor force only slightly changes the sub-barrier fusion cross sections at very low energies. Heavier nuclei, however, begin to exhibit a substantial hindrance effect in the sub-barrier region. This effect is strongest in spin-unsaturated systems, though can manifest in other configurations as well. Static, ground state deformation effects of the tensor force can also affect cross sections by shifting the fusion barrier. [Conclusions] The tensor interaction has a measurable effect on the fusion cross sections of nuclei spanning the nuclear chart. The effect comes from both static effects present in the ground state and dynamic processes arising from the time evolution of the system. This motivates the development of a modern Skyrme parameter set that includes all time-odd and tensor terms and that studies moving forward should include the tensor force to ensure a more robust and complete description of nuclei.
nucl-thPRC(2019)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE