Nuclear Theory·nucl-th

Thursday·March 22, 2018

14 papers—9 primary·5 cross-listed

01
[Submitted on 20 Mar 2018]
Towards observation of three-nucleon short-range correlations in high Q^2 A(e, e')X reactions
Donal B. Day Leonid L. Frankfurt · Misak M. Sargsian · Mark I. Strikman
We present a detailed study of kinematical and dynamical conditions necessary for probing highly elusive three-nucleon short range correlations~(3N-SRCs) in nuclei through inclusive electron scattering. The kinematic requirements that should be satisfied in order to isolate 3N-SRCs in inclusive processes are derived. We demonstrate that a sequence of two short-range NN interactions represents the main mechanism for 3N-SRCs in inclusive processes. Within this mechanism we predict a quadratic dependence of the inclusive cross section ratios of nuclei to $^{3}$ He in the 3N-SRC region to the same ratio measured in 2N-SRC domain. The extended analysis of the available data satisfying the necessary 3N-SRC kinematical conditions is presented. This analysis provides tantalizing signatures of scaling associated with the onset of 3N-SRC dominance. The same data are also consistent with the prediction of the quadratic relation between the ratios measured in the 3N and 2N-SRC regions for nuclei ranging $4 \leq A \leq 197$ . This agreement made it possible to extract $a_{3} (A)$ , the probability of 3N-SRCs relative to the A=3 nucleus. We find $a_{3} (A)$ to be significantly larger in magnitude than the analogous parameter, $a_{2} (A)$ , for 2N-SRCs.
Comments:
34 pages and 18 figures, version published in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1803.07629 [pdf]
PRC(2023)·17 citations
02
[Submitted on 20 Mar 2018]
The puzzling two-proton decay of $^{67}$ Kr
S.M. Wang · W. Nazarewicz
Two-proton (2 $p$ ) radioactivity is a rare decay mode found in a few proton-unbound nuclei. The $2 p$ -decay lifetime and properties of emitted protons carry invaluable information on nuclear structure in the presence of low-lying proton continuum. The recently measured $2 p$ decay of $^{67}$ Kr [Phys. Rev. Lett. 117, 162501 (2016)] turned out to be unexpectedly fast. Since $^{67}$ Kr is expected to be a deformed system, we investigate the impact of deformation effects on the $2 p$ radioactivity. We apply the recently developed Gamow coupled-channel framework, which allows for a precise description of three-body systems in the presence of rotational and vibrational couplings. This is the first application of a three-body approach to a two-nucleon decay from a deformed nucleus. We show that deformation couplings significantly increase the $2 p$ decay width of $^{67}$ Kr; this finding explains the puzzling experimental data. The calculated angular proton-proton correlations reflect a competition between $1 p$ and $2 p$ decay modes in this nucleus.
Comments:
3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.07656 [pdf]
PRL(2018)·58 citations
03
[Submitted on 21 Mar 2018]
Prolate-to-oblate shape phase transitions in neutron-rich odd-mass nuclei
K. Nomura · R. Rodríguez-Guzmán · L. M. Robledo
We investigate the prolate-to-oblate shape phase transitions in the neutron-rich Pt, Os and Ir nuclei in the mass $A \approx 190$ region. The Hamiltonian of the interacting boson-fermion model, used to describe the odd-mass $^{185 - 199}$ Pt, $^{185 - 193}$ Os and $^{185 - 195}$ Ir isotopes, is partially constructed by using as a microscopic input the results of constrained self-consistent mean-field calculations within the Hartree-Fock-Bogoliubov method with the Gogny force. The remaining few parameters are adjusted to experimental data in the odd systems. In this way the calculations reasonably describe the spectroscopic properties of the odd-mass systems considered. Several calculated observables for the odd-mass nuclei, especially the low-energy excitation spectra and the effective deformation parameters, point to a prolate-oblate shape transition as a function of the neutron number for all the isotopic chains considered and similar to the one already observed in the neighboring even-even systems.
Comments:
12 pages, 17 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1803.07802 [pdf]
PRC(2018)·17 citations
04
[Submitted on 21 Mar 2018]
Microscopic description of triaxiality in Ru isotopes with covariant energy density functional theory
Z. Shi · Z. P. Li
The triaxiality in nuclear low-lying states has attracted great interests for many years. Recently, the reduced transition probabilities for levels near the ground state in $^{110}$ Ru have been measured and provided strong evidences for a triaxial shape of this nucleus. The aim of this work is to provide a microscopic study of low-lying states for the Ru isotopes with $A \sim 100$ and to examine in detail the role of triaxiality, and the evolution of quadrupole shapes with the isospin and spin degrees of freedom. The low-lying excitation spectra and transition probabilities of even-even Ru isotopes are described at the beyond mean-field level by solving a five-dimensional collective Hamiltonian with parameters determined by constrained self-consistent mean-field calculations based on the relativistic energy density functional PC-PK1. The calculated energy surfaces, low-energy spectra, intraband and interband transition rates, as well as some characteristic collective observables, such as $E (4_{g.s.}^{+}) / E (2_{g.s.}^{+})$ , $E (2_{γ}^{+}) / E (4_{g.s.}^{+})$ , $B (E 2; 2_{g.s.}^{+} \to 0_{g.s.}^{+})$ , and $γ$ band staggerings are in a good agreement with the available experimental data. The main features of the experimental low-lying excitation spectra and electric transition rates are well reproduced, and thus strongly support the onset of triaxiality in the low-lying excited states of the Ru isotopes around $^{110}$ Ru.
Comments:
10 pages, 8 figures, 1 table, accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1803.07805 [pdf]
PRC(2018)·21 citations
05
[Submitted on 21 Mar 2018]
Analyses of multi-pion Hanbury-Brown-Twiss correlations for the pion-emitting sources with Bose-Einstein condensation
Ghulam Bary🇨🇳 · Peng Ru🇨🇳 · Wei-Ning Zhang🇨🇳
We calculate the three- and four-particle correlations of identical pions in an evolving pion gas (EPG) model with Bose-Einstein condensation. The multi-pion correlation functions in the EPG model are analyzed in different momentum intervals and compared with the experimental data for Pb-Pb collisions at $s_{N N} = 2.76$ TeV. It is found that the multi-pion correlation functions and cumulant correlation functions are sensitive to the condensation fraction of the EPG sources in the low average transverse-momentum intervals of the three and four pions. The model results of the multi-pion correlations are consistent with the experimental data in a considerable degree, which gives a source condensation fraction between 16~--~47\%.
Comments:
31 pages, 19 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.07902 [pdf]
J.Phys.G(2018)·16 citations
06
[Submitted on 21 Mar 2018]
Mean free path and shear viscosity in central $^{129}$ Xe+ $^{119}$ Sn collisions below 100 MeV/nucleon
H. L. Liu🇨🇳 · Y. G. Ma🇨🇳 · A. Bonasera🇺🇸 · X. G. Deng🇨🇳 · O. Lopez🇫🇷 · M. Veselský🇸🇰
Thermal and transport properties of hot nuclear matter formed in central $^{129}$ Xe + $^{119}$ Sn collisions at the Fermi energy are investigated using the isospin-dependent quantum molecular dynamical (IQMD) model. Temperature ( $T$ ), average density ( $ρ$ ), chemical potential ( $μ$ ), mean momentum ( $P$ ), shear viscosity ( $η$ ) and entropy density ( $s$ ) are obtained from the phase-space information. The mean free path ( $λ_{nn}$ ) and the in-medium nucleon-nucleon cross section ( $σ_{nn}$ ) in the highest compressible stage at different incident energies are deduced and compared with the experimental results from Phys. Rev. C $90$ (2014) 064602. The result shows that $λ_{nn}$ and $σ_{nn}$ have the same trend and similar values as the experimental results when the beam energy is greater than 40 MeV/u at maximum compressed state. Furthermore, the derived shear viscosity over entropy density ( $η / s$ ) shows a decreasing behaviour to a saturated value around $\frac{3}{4 π}$ as a function of incident energy.
Comments:
8 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1803.07945 [pdf]
PRC(2017)·18 citations
07
[Submitted on 21 Mar 2018]
Long-wavelength phonons in the crystalline and pasta phases of neutron-star crusts
David Durel🇫🇷 · Michael Urban🇫🇷
We study the long-wavelength excitations of the inner crust of neutron stars, considering three phases: cubic crystal at low densities, rods and plates near the core-crust transition. To describe the phonons, we write an effective Lagrangian density in terms of the coarse-grained phase of the neutron superfluid gap and of the average displacement field of the clusters. The kinetic energy, including the entrainment of the neutron gas by the clusters, is obtained within a superfluid hydrodynamics approach. The potential energy is determined from a model where clusters and neutron gas are considered in phase coexistence, augmented by the elasticity of the lattice due to Coulomb and surface effects. All three phases show strong anisotropy, i.e., angle dependence of the phonon velocities. Consequences for the specific heat at low temperature are discussed.
Comments:
12 pages, 8 figures. mistakes in equations (27-30) corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1803.07967 [pdf]
PRC(2018)·19 citations
08
[Submitted on 21 Mar 2018]
Photonuclear reaction as a probe for $α$ -clustering nuclei in the quasi-deuteron region
B. S. Huang · Y. G. Ma · W. B. He
Photon-nuclear reaction in a transport model frame, namely an Extended Quantum Molecular Dynamics (EQMD) model, has been realised at the photon energy of 70-140 MeV in the quasi-deuteron (QD) regime. For an important application, we pay a special focus on photonuclear reactions of $^{12}$ C( $γ$ ,np) $^{10}$ B where $^{12}$ C is considered as different configurations including $α$ -clustering. Obvious differences for some observables have been observed among different configurations, which can be attributed to spatial-momentum correlation of a neutron-proton pair inside nucleus, and therefore it gives us a sensitive probe to distinguish the different configurations including $α$ clustering with the help of the photonuclear reaction mechanism.
Comments:
8 pages, 7figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1803.07972 [pdf]
PRC(2017)·41 citations
09
[Submitted on 21 Mar 2018]
Collective flows of $^{16}$ O + $^{16}$ O collisions with $α$ -clustering configurations
Chen-Chen Guo · Wan-Bing He · Yu-Gang Ma
The main purpose of the present paper is to discuss whether or not the collective flows in heavy-ion collision at Fermi energy can be taken as a tool to investigate the cluster configuration in light nuclei. In practice, within an Extended Quantum Molecular Dynamics model, four $α$ -clustering (linear chain, kite, square, and tetrahedron) configurations of $^{16}$ O are employed in the initialization, $^{16}$ O+ $^{16}$ O around Fermi energy (40 - 60 MeV $/$ nucleon) with impact parameter 1 - 3 fm are simulated, the directed and elliptic flows are analyzed. It is found that collective flows are influenced by the different $α$ -clustering configurations, and the directed flow of free protons is more sensitive to the initial cluster configuration than the elliptic flow. Nuclear reaction at Fermi energy can be taken a useful way to study cluster configuration in light nuclei.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1803.07978 [pdf]
Chin.Phys.Lett.(2017)·15 citations
10
[Submitted on 20 Mar 2018] (cross-list from hep-ph)
Dynamical Gauge Boson of Hidden Local Symmetry within the Standard Model
Koichi Yamawaki🇯🇵
The Standard Model (SM) Higgs Lagrangian is straightforwardly rewritten into the {\it scale-invariant} nonlinear sigma model $G / H = [S U (2)_{L} \times S U (2)_{R}] / S U (2)_{V} ≃ O (4) / O (3)$ , with the (approximate) scale symmetry realized nonlinearly by the (pseudo) dilaton ( $=$ SM Higgs). It is further gauge equivalent to that having the symmetry $O (4)_{global} \times O (3)_{local}$ , with $O (3)_{local}$ being the Hidden Local Symmetry (HLS). In the large $N$ limit of the scale-invariant version of the Grassmannian model $G / H = O (N) / [O (N - 3) \times O (3)]$ $≃ O (N)_{global} \times [O (N - 3) \times O (3)]_{local}$ , identical to the SM for $N \to 4$ , we show that the kinetic term of the HLS gauge bosons ("SM rho") $ρ_{μ}$ of the $O (3)_{local} ≃ [S U (2)_{V}]_{local}$ are dynamically generated by the nonperturbative dynamics of the SM itself. The dynamical SM rho stabilizes the skyrmion ("SM skyrmion") $X_{s}$ as a dark matter candidate within the SM: The mass $M_{X_{s}} = O (10 GeV)$ consistent with the direct search experiments implies the induced HLS gauge coupling $g_{_{HLS}} = O (1 0^{3})$ , which realizes the relic abundance, $Ω_{X_{s}} h^{2} = O (0.1)$ . If instead $g_{_{HLS}} ≲ 3.5$ ( $M_{ρ} ≲ 1.2$ TeV), the SM rho could be detected with "narrow width" $≲ 100 GeV$ at LHC, having all the " $a = 2$ results" of the generic HLS Lagrangian $L_{A} + a L_{V}$ , i.e., $ρ$ -universality, KSRF relations and the vector meson dominance, independently of " $a$ ". There exists the second order phase phase transition to the unbroken phase having massless $ρ_{μ}$ and massive $π$ (no longer NG bosons), both becoming massless free particles just on the transition point (scale-invariant ultraviolet fixed point).The results readily apply to the 2-flavored QCD as well.
Comments:
52 pages, for readability preliminary formal discussions moved to appendix, some phenomenological comments added, typos corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1803.07271 [pdf]
10 citations
11
[Submitted on 20 Mar 2018] (cross-list from hep-ph)
Photoproduction of light vector mesons in Xe-Xe ultraperipheral collisions at the LHC and the nuclear density of Xe-129
V. Guzey (St. Petersburg, INP and Jyvaskyla U. and Helsinki Inst. of Phys.)🇷🇺 · E. Kryshen🇷🇺 · M. Zhalov (St. Petersburg, INP)🇷🇺
We make predictions for cross sections of $ρ$ and $ϕ$ vector meson photoproduction in ultraperipheral Xe-Xe collisions at $s_{N N} = 5.44$ TeV. Analyzing the momentum transfer distribution of $ρ$ mesons in this process, we explore the feasibility of extracting the nuclear density of $^{129}$ Xe, which is needed in searches for dark matter with Xenon-based detectors.
Comments:
8 pages, 4 figures. Final published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.07638 [pdf]
PLB(2018)·9 citations
12
[Submitted on 21 Mar 2018] (cross-list from hep-ph)
Phenomenological study on the decay widths of $Υ (n S) \to d ˉ^{*} (2380) + X$
Chao-Yi Lü🇨🇳 · P. Wang🇨🇳 · Y. B. Dong🇨🇳 · P. N. Shen🇨🇳 · Z. Y. Zhang🇨🇳 · D. M. Li🇨🇳
The decay widths of $Υ (n S)$ $\to$ $d ˉ^{*} (2380) + X$ with $n = 1, 2, 3$ are studied in a phenomenological way. With the help of crossing symmetry, the decay widths are obtained by investigating the imaginary part of the forward scattering amplitudes between $d^{*}$ and $Υ (n S)$ . The wave functions of $d^{*}$ and deuteron obtained in previous studies are used for calculating the amplitude. The interaction between $d^{*}$ ( $d$ ) and $Υ$ is governed by the quark-meson interaction where the coupling constant is determined by fitting the observed widths of $Υ (n S)$ $\to$ $d ˉ + X$ . The numerical results show that the decay widths of $Υ (n S)$ $\to$ $d ˉ^{*} + X$ are about $2 - 10$ times smaller than that of $d ˉ + X$ . The calculated momentum of $d^{*} ˉ$ is in the range $0.3 - 0.8$ GeV. Therefore, it is very likely that one can find $d ˉ^{*} (2380)$ in these semi-inclusive decay processes.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.07795 [pdf]
CPC(2018)·4 citations
13
[Submitted on 21 Mar 2018] (cross-list from hep-ph)
Some intriguing aspects of multiparticle production processes
Grzegorz Wilk🇵🇱 · Zbigniew Włodarczyk🇵🇱
Multiparticle production processes provide valuable information about the mechanism of the conversion of the initial energy of projectiles into a number of secondaries by measuring their multiplicity distributions and their distributions in phase space. They therefore serve as a reference point for more involved measurements. Distributions in phase space are usually investigated using the statistical approach, very successful in general but failing in cases of small colliding systems, small multiplicities, and at the edges of the allowed phase space, in which cases the underlying dynamical effects competing with the statistical distributions take over. We discuss an alternative approach, which applies to the whole phase space without detailed knowledge of dynamics. It is based on a modification of the usual statistics by generalizing it to a superstatistical form. We stress particularly the scaling and self-similar properties of such an approach manifesting themselves as the phenomena of the log-periodic oscillations and oscillations of temperature caused by sound waves in hadronic matter. Concerning the multiplicity distributions we discuss in detail the phenomenon of the oscillatory behaviour of the modified combinants apparently observed in experimental data.
Comments:
Review article, to be published in Int. J. Mod. Phys. A (2018), 50 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.07832 [pdf]
Int.J.Mod.Phys.A(2018)·26 citations
14
[Submitted on 21 Mar 2018] (cross-list from hep-ph)
The approach to equilibrium of a quarkonium in a quark-gluon plasma
Jean-Paul Blaizot🇫🇷 · Miguel Angel Escobedo🇫🇮
We derive equations of motion for the reduced density matrix of a heavy quarkonium in contact with a quark-gluon plasma in thermal equilibrium. These equations allow in particular a proper treatment of the regime when the temperature of the plasma is comparable to the binding energy of the quarkonium. These equations are used to study how the quarkonium approaches equilibrium with the plasma, and we discuss the corresponding entropy increase, or free energy decrease, depending on the temperature regime. The effect of collisions can be accounted for by the generalization of the imaginary potential introduced in previous studies, and from which collision rates are derived. An important outcome of the present analysis is that this imaginary potential has a sizeable dependence on the energy of the relevant transitions.
Comments:
47 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.07996 [pdf]
PRD(2018)·101 citations

Affiliations

first authorsco-authorsvia INSPIRE