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
10
Aspects of isentropic trajectories in chiral effective models
Rainer Stiele🇮🇹 · Wanda Maria Alberico🇮🇹 · Andrea Beraudo🇮🇹 · Renan Câmara Pereira🇵🇹 · Pedro Costa🇵🇹 · Hubert Hansen🇫🇷 · Mario Motta🇮🇹
The evolution of the fireball in heavy ion collisions is an isentropic process, meaning that it follows a trajectory of constant entropy per baryon in the phase diagram of the strong interaction. Responsible for the collective acceleration of the fireball is the speed of sound of the system, while fluctuations of conserved charges are encoded in quark-number susceptibilities: together, they leave their imprint in final observables. Here, this isentropic evolution will be analysed within chiral effective models that account for both chiral and center symmetry breaking, two central aspects of QCD. Our discussion focusses on the impact on the isentropic trajectories of the treatment of high-momentum modes, of the meson contribution to thermodynamics and of the number of quark flavours.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2020)·0 citations
11
Yield ratio of neutrons to protons in $^{12} C (d, n)^{13}$ N and $^{12} C (d, p)^{13}$ C from 0.6 MeV to 3 MeV
W. J. Li🇨🇳 · Y. G. Ma🇨🇳 · G. Q. Zhang🇨🇳 · X. G. Deng🇨🇳 · M. R. Huang🇨🇳 · A. Bonasera🇺🇸 · D. Q. Fang🇨🇳 · J. Q. Cao🇨🇳 · Q. Deng🇨🇳 · Y. Q. Wang🇨🇳 · Q. T. Lei🇨🇳
The neutron yield in $^{12}$ C(d,n) $^{13}$ N and the proton yield in $^{12} C (d, p)^{13}$ C have been measured by deuteron beam from 0.6 MeV to 3 MeV which is delivered from a 4-MeV electro static accelerator bombarding on the thick carbon target. The neutrons are detected at $0°$ , $24°$ , $48°$ and the protons at $135°$ in the lab frame. The ratios of the neutron yield to the proton one have been calculated and can be used as an effective probe to pin down the resonances. The resonances are found at 1.4 MeV, 1.7 MeV, 2.5 MeV in $^{12} C (d, p)^{13}$ C and at 1.6 MeV, 2.7 MeV in $^{12}$ C(d,n) $^{13}$ N. This method provides a way to reduce the systematic uncertainty and helps to confirm more resonances in compound nuclei.
↳ nucl-exnucl-thNucl.Sci.Tech.(2019)·12 citations
12
Impact of Uncertainties in Astrophysical Reaction Rates on Nucleosynthesis in the $ν p$ Process
T. Rauscher · N. Nishimura · G. Cescutti · R. Hirschi · A. St.J. Murphy · C. Fröhlich
The $ν p$ process appears in proton-rich, hot matter which is expanding in a neutrino wind and may be realised in explosive environments such as core-collapse supernovae or in outflows from accretion disks. The impact of uncertainties in nuclear reaction cross sections on the finally produced abundances has been studied by applying Monte Carlo variation of all astrophysical reaction rates in a large reaction network. As the detailed astrophysical conditions of the $ν p$ process still are unknown, a parameter study was performed, with 23 trajectories covering a large range of entropies and $Y_{e}$ . The resulting abundance uncertainties are given for each trajectory. The $ν p$ process has been speculated to contribute to the light $p$ nuclides but it was not possible so far to reproduce the solar isotope ratios. It is found that it is possible to reproduce the solar $^{92}$ Mo/ $^{94}$ Mo abundance ratio within nuclear uncertainties, even within a single trajectory. The solar values of the abundances in the Kr-Sr region relative to the Mo region, however, cannot be achieved within a single trajectory. They may still be obtained from a weighted superposition of different trajectories, though, depending on the actual conditions in the production site. For a stronger constraint of the required conditions, it would be necessary to reduce the uncertainties in the 3 $α$ and $^{56}$ Ni(n,p) $^{56}$ Co rates at temperatures $T > 3$ GK.
↳ astro-ph.HEnucl-exnucl-thJPS Conf.Proc.(2020)·5 citations
13
Confinement of two-body systems and calculations in $d$ dimensions
E. Garrido · A.S. Jensen
A continuous transition for a system moving in a three-dimensional (3D) space to moving in a lower-dimensional space, 2D or 1D, can be made by means of an external squeezing potential. A squeeze along one direction gives rise to a 3D to 2D transition, whereas a simultaneous squeeze along two directions produces a 3D to 1D transition, without going through an intermediate 2D configuration. In the same way, for a system moving in a 2D space, a squeezing potential along one direction produces a 2D to 1D transition. In this work we investigate the equivalence between this kind of confinement procedure and calculations without an external field, but where the dimension $d$ is taken as a parameter that changes continuously from $d = 3$ to $d = 1$ . The practical case of an external harmonic oscillator squeezing potential acting on a two-body system is investigated in details. For the three transitions considered, 3D~ $\to$ ~2D, 2D~ $\to$ ~1D, and 3D~ $\to$ ~1D, a universal connection between the harmonic oscillator parameter and the dimension $d$ is found. This relation is well established for infinitely large 3D scattering lengths of the two-body potential for 3D~ $\to$ ~2D and 3D~ $\to$ ~1D transitions, and for infinitely large 2D scattering length for the 2D~ $\to$ ~1D case. For finite scattering lengths size corrections must be applied. The traditional wave functions for external squeezing potentials are shown to be uniquely related with the wave functions for specific non-integer dimension parameters, $d$ .
↳ physics.atm-clusnucl-thphysics.opticsquant-phPRResearch(2019)·9 citations
14
$J / ψ$ Production Dynamics: Event shape, Multiplicity and Rapidity dependence in Proton+Proton Collisions at LHC energies using PYTHIA8
Anisa Khatun🇮🇳 · Dhananjaya Thakur🇮🇳 · Suman Deb🇮🇳 · Raghunath Sahoo🇮🇳
High-multiplicity pp collisions at the Large Hadron Collider (LHC) energies have created special importance in view of the Underlying Event (UE) observables. The recent results of LHC, such as long range angular correlation, flow-like patterns, strangeness enhancement etc. in high multiplicity events are not yet completely understood. In the same direction, the understanding of multiplicity dependence of J/ $ψ$ production is highly necessary. Transverse spherocity, which is an event shape variable, helps to investigate the particle production by isolating the hard and the soft components. In the present study, we have investigated the multiplicity dependence of J/ $ψ$ production at mid-rapidity and forward rapidity through the transverse spherocity analysis and tried to understand the role of jets by separating the isotropic and jetty events from the minimum bias collisions. We have analyzed the J/ $ψ$ production at the mid-rapidity and forward rapidities via dielectron and dimuon channels, respectively using 4C tuned PYTHIA8 event generator. The analysis has been performed in two different center-of-mass energies: $s$ = 5.02 and 13 TeV, to see the energy dependence of jet contribution to the multiplicity dependence study of J/ $ψ$ production. Furthermore, we have studied the production dynamics through the dependence of thermodynamic parameters on event multiplicity and transverse spherocity.
↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2020)·15 citations
15
$Z_{c} (4430)$ , $Z_{c} (4200)$ , $Z_{1} (4050)$ , and $Z_{2} (4250)$ as triangle singularities
Satoshi X. Nakamura (University of Science and Technology of China)🇨🇳
$Z_{c} (4430)$ discovered in $B ˉ^{0} \to ψ (2 S) K^{-} π^{+}$ , $Z_{c} (4200)$ found in $B ˉ^{0} \to J / ψ K^{-} π^{+}$ , and $Z_{1} (4050)$ and $Z_{2} (4250)$ observed in $B ˉ^{0} \to χ_{c 1} K^{-} π^{+}$ are candidates of charged charmonium-like states. All surviving theoretical models interpreted these candidates as four-quark states, until we recently identified a compelling alternative. We discuss that kinematical singularities in triangle loop diagrams induce a resonance-like behavior that can consistently explain the properties (such as spin-parity, mass, width, and Argand plot) of $Z_{c} (4430)$ , $Z_{c} (4200)$ , $Z_{1} (4050)$ and $Z_{2} (4250)$ from experiments. In terms of the triangle singularities, we can also naturally understand interesting experimental findings such as the appearance (absence) of $Z_{c} (4200)$ ( $Z_{c} (4430)$ )-like contribution in $Λ_{b}^{0} \to J / ψ p π^{-}$ , and the highly asymmetric shape of the spectrum bump for $Z_{1} (4050)$ ; the other theoretical models have not successfully addressed these points. Although Pakhlov et al. proposed another triangle diagram to generate a $Z_{c} (4430)$ -like bump, we argue that this scenario is very unlikely.
↳ hep-phhep-exnucl-thAIP Conf.Proc.(2020)·3 citations

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