Nuclear Theory·nucl-th

Tuesday·October 22, 2019

11 papers—8 primary·3 cross-listed

01
[Submitted on 18 Oct 2019]
Theoretical study of deeply virtual Compton scattering off $^{4}$ He
Sara Fucini🇮🇹 · Sergio Scopetta🇮🇹 · Michele Viviani🇮🇹
An interesting breakthrough in understanding the elusive inner content of nuclear systems in terms of partonic degrees of freedom is represented by deeply virtual Compton scattering processes. In such a way, tomographic view of nuclei and bound nucleons in coordinate space could be achieved for the first time. Moreover, nowadays experimental results for such a process considering $^{4}$ He targets recently released at Jefferson Lab are available. In this talk, the recent results of our rigorous Impulse Approximation for DVCS off $^{4}$ He, in terms of state-of-the-art models of the nuclear spectral function and of the parton structure of the bound proton, able to explain present data, has been shown.
Comments:
9 pages, 5 figures, prepared for the proceedings for the 24th edition of European Few Body Conference, Surrey, UK, 2-6 September 2019. arXiv admin note: substantial text overlap with arXiv:1910.07458
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1910.08550 [pdf]
SciPost Phys.Proc.(2020)·0 citations
02
[Submitted on 18 Oct 2019]
Neutron spin dynamics in polarized targets
Vladimir Gudkov🇺🇸 · Hirohiko M. Shimizu🇯🇵
We present neutron elastic scattering amplitude for arbitrary polarized target in irreducible spherical tensor representation. The general approach for the description of neutron spin dynamics for the propagation trough the medium with an arbitrary polarization is discussed in a relation to the search for time reversal invariance violation in neutron scattering.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1910.08598 [pdf]
PRC(2020)·10 citations
03
[Submitted on 19 Oct 2019]
Ground state properties and shape evolution in Pt isotopes within the covariant density functional theory
Younes El Bassem · Mostafa Oulne
In this work, the ground-state properties of the platinum isotopic chain, 160-238Pt, are studied within the covariant density functional theory. The calculations are carried out for a large number of even-even Pt isotopes by using the density-dependent point-coupling and the density dependent meson-exchange effective interactions. All ground-state properties such as the binding energy, separation energy, two-neutron shell gap, rms-radii for neutrons and protons and quadrupole deformation are discussed and compared with available experimental data, and with the predictions of some nuclear models such as the Relativistic Mean Field (RMF) model with NL3 functional and the Hartree Fock Bogoliubov (HFB) method with SLy4 Skyrme force. The shape phase transition for Pt isotopic chain is also studied. Its corresponding total energy curves as well as the potential energy surfaces confirm the transition from prolate to oblate shapes at 188Pt contrary to some studies predictions and in agreement with others. Overall, a good agreement is found between the calculated and experimental results wherever available.
Comments:
13 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.08775 [pdf]
IJMPE(2019)·2 citations
04
[Submitted on 20 Oct 2019]
A Nuclear Structure Model for Double Charge-Exchange Processes
V. dos S. Ferreira🇧🇷 · A. R. Samana🇧🇷 · F. Krmpotić🇦🇷 · M. Chiapparini🇧🇷
A new model, based on the BCS approach, is specially designed to describe nuclear phenomena $(A, Z) \to (A, Z \pm 2)$ of double-charge exchange (DCE). After being proposed, and applied in the particle-hole limit, by one of the authors (F. Krmpotić [1]), so far it was never been applied within the BCS mean-field framework, nor has its ability to describe DCE processes been thoroughly explored. It is a natural extension of the pn-QRPA model, developed by Halbleib and Sorensen [2] to describe the single $β$ -decays $(A, Z) \to (A, Z \pm 1)$ , to the DCE processes. As such, it exhibits several advantages over the pn-QRPA model when is used in the evaluation of the double beta decay (DBD) rates. For instance, i) the extreme sensitivity of the nuclear matrix elements (NMEs) on the model parametrization does not occur, ii) it allows to study NMEs, not only for the fundamental state in daughter nuclei, as the pn-QRPA model does, but also for all final $0^{+}$ and $2^{+}$ states, accounting at the same time their excitation energies and the corresponding DBD Q-values, iii) together with the DBD-NMEs it provides also the energy spectra of Fermi and Gamow-Teller DCE transition strengths, as well as the locations of the corresponding resonances and their sum rules, iv) the latter are relevant for both the DBD and the DCE reactions, since the involved nuclear structure is the same; this correlation does not exist within the pn-QRPA model. As an example, detailed numerical calculations are presented for the $(A, Z) \to (A, Z + 2)$ process in $^{48}$ Ca $\to^{48}$ Ti and the $(A, Z) \to (A, Z - 2)$ process in $^{96}$ Ru $\to^{96}$ Mo, involving all final $0^{+}$ states and $2^{+}$ states.
Comments:
17 pages, 9 figures. To be submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.09059 [pdf]
PRC(2020)·12 citations
05
[Submitted on 21 Oct 2019]
Effects of Pauli blocking on pion production in central collisions of neutron-rich nuclei
Natsumi Ikeno🇯🇵 · Akira Ono🇯🇵 · Yasushi Nara🇯🇵 · Akira Ohnishi🇯🇵
Pauli blocking is carefully investigated for the processes of $N N \to N Δ$ and $Δ \to N π$ in heavy-ion collisions, aiming at a more precise prediction of the $π^{-} / π^{+}$ ratio which is an important observable to constrain the high-density symmetry energy. We use the AMD+JAM approach, which combines the antisymmetrized molecular dynamics for the time evolution of nucleons and the JAM model to treat processes for $Δ$ resonances and pions. As is known in general transport-code simulations, it is difficult to treat Pauli blocking very precisely due to unphysical fluctuations and additional smearing of the phase-space distribution function, when Pauli blocking is treated in the standard method of JAM. We propose an improved method in AMD+JAM to use the Wigner function precisely calculated in AMD as the blocking probability. Different Pauli blocking methods are compared in heavy-ion collisions of neutron-rich nuclei, $^{132} Sn +^{124} Sn$ , at 270 MeV/nucleon. With the more accurate method, we find that Pauli blocking is stronger, in particular for the neutron in the final state in $N N \to N Δ$ and $Δ \to N π$ , compared to the case with a proton in the final state. Consequently, the $π^{-} / π^{+}$ ratio becomes higher when the Pauli blocking is improved, the effect of which is found to be comparable to the sensitivity to the high-density symmetry energy.
Comments:
10 pages, 5 figures, 1 table: The title is changed. All figures are updated. Table 1 is added
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1910.09173 [pdf]
PRC(2020)·13 citations
06
[Submitted on 21 Oct 2019]
A new probe to study symmetry energy at low density by deuteron breakup reaction
Xiao Liang · Li Ou · Zhigang Xiao
The reactions of nucleon and polarized deuteron scattered off a heavy target at large impact parameter with intermediate energies have been investigated by using the improved quantum molecular dynamics model. It is found that, due to the difference effect of isovector potential on proton and neutron, there is a significant difference between the angle distribution of elastic scattering protons and neutrons. To overcome the lack of monochromatic neutron beam, the reaction of polarized deuteron peripherally scattered off the heavy target is used to replace the reaction of individual proton and neutron scattered off heavy target to study the isospin effect. It is found that the distributions of elastic scattering angle of proton and neutron originating from the breakup of deuteron are very similar to the results of the individual proton- and neutron-induced reaction. A new probe more effective and more clean, namely the difference between elastic scattering angle of proton and neutron originating from the breakup of polarized deuteron, is promoted to constrain the symmetry energy at subsaturation density.
Comments:
16 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.09176 [pdf]
PRC(2020)·6 citations
07
[Submitted on 21 Oct 2019]
Charge and isospin fluctuations in a non-ideal pion gas with dynamically fixed particle number
E.E. Kolomeitsev🇸🇰 · D.N. Voskresensky🇷🇺 · M.E. Borisov🇷🇺
We study the behavior of the non-ideal pion gas with the dynamically fixed number of particles, formed on an intermediate stage in ultra-relativistic heavy-ion collisions. The pion spectrum is calculated within the self-consistent Hartree approximation. General expressions are derived for cross-covariances of the number of various particle species in the pion gas of an arbitrary isospin composition. The behavior of the cross-variances is analyzed for the temperature approaching from above the maximal critical temperature of the Bose-Einstein condensation for the pion species $a = \pm, 0$ , i.e. for $T > max T_{cr}^{a}$ . It is shown that in case of the system with equal averaged numbers of isospin species, the variance of the charge, $Q = N_{+} - N_{-}$ , diverges at $T \to T_{cr} = T_{cr}^{a}$ , whereas variances of the total particle number, $N = N_{+} + N_{-} + N_{0}$ , and of a relative abundance of charged and neutral pions, $G = (N_{+} + N_{-}) /2 - N_{0}$ , remain finite in the critical point. Then fluctuations are studied in the pion gas with small isospin imbalance $0 < ∣ G ∣ ≪ N$ and $0 < ∣ Q ∣ ≪ N$ \, and shifts of the effective masses, chemical potentials and values of critical temperatures are calculated for various pion species, and the highest critical temperature, $\mbox ma x T_{cr}^{a}$ is found, above which the pion system exists in the non-condensed phase. Various pion cross variances are calculated for $T > \mbox ma x T_{cr}^{a}$ , which prove to be strongly dependent on the isospin composition of the system, whereas the variances of $N$ and $G$ are found to be independent on the isospin imbalance up to the term linear in $G / N$ and $Q / N$ .
Comments:
27 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1910.09334 [pdf]
EPJA(2021)·6 citations
08
[Submitted on 21 Oct 2019]
Description of continuum structures in a discrete basis: Three-body resonances and two-nucleon decays
J. Casal · M. Rodríguez-Gallardo · J. M. Arias · J. Gómez-Camacho · L. Fortunato · A. Vitturi
Weakly bound and unbound three-body nuclei are studied by using the pseudostate method within the hyperspherical formalism. After introducing the theoretical framework, the method is applied first to the $^{9}$ Be nucleus, showing a good agreement with the available data for its low-lying dipole response. Then, recent results on the structure and decay of the two-neutron emitters $^{26}$ O and $^{16}$ Be are presented. In particular, the role of the $n$ - $n$ correlation in shaping their properties is discussed.
Comments:
Proceedings of the 24th European Conference of Few-Body Problems in Physics (EFB24); SciPost contribution
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.09418 [pdf]
SciPost Phys.Proc.(2020)·2 citations
09
[Submitted on 18 Oct 2019] (cross-list from hep-ph)
Renormalization and Matching for the Collins-Soper Kernel from Lattice QCD
Markus A. Ebert🇺🇸 · Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸
The Collins-Soper kernel, which governs the energy evolution of transverse-momentum dependent parton distribution functions (TMDPDFs), is required to accurately predict Drell-Yan like processes at small transverse momentum, and is a key ingredient for extracting TMDPDFs from experiment. Earlier we proposed a method to calculate this kernel from ratios of the so-called quasi-TMDPDFs determined with lattice QCD, which are defined as hadronic matrix elements of staple-shaped Euclidean Wilson line operators. Here we provide the one-loop renormalization of these operators in a regularization-independent momentum subtraction (RI $^{'}$ /MOM) scheme, as well as the conversion factor from the RI $^{'}$ /MOM-renormalized quasi-TMDPDF to the $MS$ scheme. We also propose a procedure for calculating the Collins-Soper kernel directly from position space correlators, which simplifies the lattice determination.
Comments:
27 pages + appendices, 5 figures; v2: journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1910.08569 [pdf]
JHEP(2020)·79 citations
10
[Submitted on 20 Oct 2019] (cross-list from hep-ph)
High Energy Hadron Production, Self-Organized Criticality and Absorbing State Phase Transition
P.Castorina🇮🇹 · H.Satz🇩🇪
In high energy nuclear collisions, production rates of light nuclei agree with the predictions of an ideal gas at a temperature $T = 155 \pm 10$ MeV. In an equilibrium hadronic medium of this temperature, light nuclei cannot survive. In this contribution, we suggest that the observed behavior is due to an evolution in global non-equilibrium, leading to self-organized criticality and to hadron formation as an absorbing state phase transition for color degrees of freedom. At the confinement point, the initial quark-gluon medium becomes quenched by the vacuum, breaking up into all allowed free hadronic and nuclear mass states, without (or with a very short-live) subsequent formation of thermal hadronic medium.
Comments:
Plenary talk - Strangeness in Quark Matter - JUne 2019 - Bari - Italy - typos correction
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1910.09029 [pdf]
Springer Proc.Phys.(2020)·1 citation
11
[Submitted on 21 Oct 2019] (cross-list from hep-ph)
Feasibility study of the $K^{+} d \to K^{0} pp$ reaction for the " $Θ^{+}$ " pentaquark
Takayasu Sekihara🇯🇵 · Hyun-Chul Kim🇯🇵 · Atsushi Hosaka🇯🇵
We investigate theoretically the $K^{0} p$ invariant mass spectrum of the $K^{+} d \to K^{0} pp$ reaction and scrutinize how the signal of the " $Θ^{+}$ " pentaquark, if it exists, emerges in the $K^{0} p$ spectrum. The most prominent advantage of this reaction is that we can clearly judge whether the " $Θ^{+}$ " exists or not as a direct-formation production without significant backgrounds, in contrast to other reactions such as photoproduction and $π$ -induced productions. We show that while the impulse or single-step scattering process can cover the " $Θ^{+}$ " energy region with an initial kaon momentum $k_{lab} \approx 0.40 GeV / c$ in the laboratory frame, the contributions from double-step processes may have a potential possibility to reach the " $Θ^{+}$ " energy region with a higher kaon momentum $k_{lab} \sim 1 GeV / c$ . Assuming that the full decay width of the " $Θ^{+}$ " is around $0.5 MeV$ , we predict that the magnitude of the peak corresponding to the " $Θ^{+}$ " is around a few hundred $μ b$ to $1 mb$ with the momentum of the kaon beam $k_{lab} \approx 0.40 GeV / c$ while it is around $≲ 1 μ b$ with $k_{lab} \approx 0.85 GeV / c$ . Thus, the " $Θ^{+}$ " peak is more likely to be seen at $k_{lab} \approx 0.40 GeV / c$ than at $k_{lab} \approx 0.85 GeV / c$ .
Comments:
14 pages. 11 figures. Three more figures are included and the text was revised
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1910.09252 [pdf]
PTEP(2020)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE