Nuclear Theory·nucl-th

Monday·March 30, 2020

10 papers—4 primary·6 cross-listed

01
Calibration of Energy Density Functionals with Deformed Nuclei
N. Schunck · J. O'Neal · M. Grosskopf · E. Lawrence · S.M. Wild
Nuclear density functional theory is the prevalent theoretical framework for accurately describing nuclear properties at the scale of the entire chart of nuclides. Given an energy functional and a many-body scheme (e.g., single- or multireference level), the predictive power of the theory depends strongly on how the parameters of the energy functionals have been calibrated with experimental data. Expanded algorithms and computing power have enabled recent optimization protocols to include data in deformed nuclei in order to optimize the coupling constants of the energy functional. The primary motivation of this work is to test the robustness of such protocols with respect to some of the technical and numerical details of the underlying calculations, especially when the calibration explores a large parameter space. To this end, we quantify the effect of these uncertainties on both the optimization and statistical emulation of composite objective functions. We also emphasize that Bayesian calibration can provide better estimates of the theoretical errors used to define objective functions.
nucl-thJ.Phys.G(2020)·12 citations
02
Three-body vs. dineutron approach to two-neutron radiative capture in $^{6}$ He
L.V. Grigorenko · N.B. Shulgina · M.V. Zhukov
The low-energy behavior of the strength function for the $1^{-}$ soft dipole excitation in $^{6}$ He is studied theoretically. Use of very large basis sizes and well-grounded extrapolation procedures allows to move to energies as small as 1 keV, at which the low-energy asymptotic behavior of the E1 strength function seems to be achieved. It is found that the low-energy behavior of the strength function is well described in the effective three-body "dynamical dineutron model". The astrophysical rate for the $α$ + $n$ + $n \to^{6}$ He+ $γ$ is calculated. Comparison with the previous calculations is performed.
nucl-thPLB(2020)·2 citations
03
Anomalous chiral transports and spin polarization in heavy-ion collisions
Yu-Chen Liu🇨🇳 · Xu-Guang Huang🇨🇳
Relativistic heavy-ion collisions create hot quark-gluon plasma as well as very strong electromagnetic (EM) and fluid vortical fields. The strong EM field and vorticity can induce intriguing macroscopic quantum phenomena such as chiral magnetic, chiral separation, chiral electric separation, and chiral vortical effects as well as the spin polarization of hadrons. These phenomena provide us with experimentally feasible means to study the nontrivial topological sector of quantum chromodynamics, the possible parity violation of strong interaction at high temperature, and the subatomic spintronics of quark-gluon plasma. These studies, both in theory and in experiments, are strongly connected with other subfields of physics such as condensed matter physics, astrophysics, and cold atomic physics, and thus form an emerging interdisciplinary research area. We give an introduction to the aforementioned phenomena induced by the EM field and vorticity and an overview of the current status of their experimental research in heavy-ion collisions. We also briefly discuss spin hydrodynamics as well as chiral and spin kinetic theories.
nucl-thhep-phnucl-exNucl.Sci.Tech.(2020)·120 citations
04
Nonperturbative Effects on Radiative Energy Loss of Heavy Quarks
Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸
The radiative energy loss of fast partons traveling through the quark-gluon plasma (QGP) is commonly studied within perturbative QCD (pQCD). Nonperturbative (NP) effects, which are expected to become important near the critical temperature, have been much less investigated. Here, we utilize a recently developed $T$ -matrix approach to incorporate NP effects for gluon emission off heavy quarks propagating through the QGP. We set up four cases that contain, starting from a Born diagram calculation with color-Coulomb interaction, an increasing level of NP components, by subsequently including (remnants of) confining interactions, resummation in the heavy-light scattering amplitude, and off-shell spectral functions for both heavy and light partons. For each case we compute the power spectra of the emitted gluons, heavy-quark transport coefficients (drag and transverse-momentum broadening, $q^$ ), and the path-length dependent energy loss within a "QGP brick" at fixed temperature. Investigating the differences in these quantities between the four cases illustrates how NP mechanisms affect gluon radiation processes. While the baseline perturbative processes experience a strong suppression of soft radiation due to thermal masses of the emitted gluons, confining interactions, ladder resummations and broad spectral functions (re-)generate a large enhancement toward low momenta and low temperatures. For example, for a 10 GeV charm quark at 200 MeV temperature, they enhance the transport coefficients by up to a factor of 10, while the results smoothly converge to perturbative results at sufficiently hard scales.
nucl-thhep-phnucl-exJHEP(2020)·23 citations
05
Franz-Keldysh effect in strong-field QED
Hidetoshi Taya🇨🇳
We studied a QED analog of the Franz-Keldysh effect, and the interplay between the non-perturbative (the Schwinger mechanism) and the perturbative particle production mechanism from the vacuum in the presence of a strong slow field superimposed by a weak field. We found that the Franz-Keldysh effect significantly affects the particle production: (i) the perturbative particle production occurs even below the threshold energy; (ii) the perturbative production becomes the most efficient just above the threshold energy; and (iii) an oscillating behavior appears in the production number above the threshold energy. These non-trivial changes are suppressed only weakly by powers of the critical field strength of QED. A relation to the dynamically assisted Schwinger mechanism and implications to experiments are also discussed.
↳ hep-phhep-thnucl-thphysics.plasm-ph+1PRD(2019)·31 citations
06
Charged multi-hadron systems in lattice QCD+QED
S. R. Beane🇺🇸 · W. Detmold🇺🇸 · R. Horsley🇬🇧 · M. Illa🇪🇸 · M. Jafry🇺🇸 · D. J. Murphy🇺🇸 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · P. E. Shanahan🇺🇸 · H. Stüben🇩🇪 and 4 other authors
Systems with the quantum numbers of up to twelve charged and neutral pseudoscalar mesons, as well as one-, two-, and three-nucleon systems, are studied using dynamical lattice quantum chromodynamics and quantum electrodynamics (QCD+QED) calculations and effective field theory. QED effects on hadronic interactions are determined by comparing systems of charged and neutral hadrons after tuning the quark masses to remove strong isospin breaking effects. A non-relativistic effective field theory, which perturbatively includes finite-volume Coulomb effects, is analyzed for systems of multiple charged hadrons and found to accurately reproduce the lattice QCD+QED results. QED effects on charged multi-hadron systems beyond Coulomb photon exchange are determined by comparing the two- and three-body interaction parameters extracted from the lattice QCD+QED results for charged and neutral multi-hadron systems.
↳ hep-lathep-phnucl-thPRD(2021)·88 citations
07
Light Meson Parton Distribution Functions from Basis Light-Front Quantization and QCD Evolution
Jiangshan Lan🇨🇳 · Chandan Mondal🇨🇳 · Shaoyang Jia🇺🇸 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸
We investigate the parton distribution functions (PDFs) of the pion and kaon from the eigenstates of a light-front effective Hamiltonian in the constituent quark-antiquark representation suitable for low-momentum scale applications. By taking these scales as the only free parameters, the valence quark distribution functions of the pion, after QCD evolving, are consistent with the E615 experiment at Fermilab. In addition, the ratio of the up quark distribution in the kaon to that in the pion also agrees with the NA3 experimental result at CERN.
↳ hep-phnucl-thHadron 2019, 581-585·4 citations
08
Cross sections for 2-to-1 meson-meson scattering
Wan-Xia Li🇨🇳 · Xiao-Ming Xu🇨🇳 · H. J. Weber🇺🇸
We study the processes $K K ˉ \to ϕ$ , $π D \to D^{*}$ , $π D ˉ \to D ˉ^{*}$ , and the production of $ψ (3770)$ , $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ mesons in collisions of charmed mesons or charmed strange mesons. The process of 2-to-1 meson-meson scattering involves a quark and an antiquark from the two initial mesons annihilating into a gluon and subsequently the gluon being absorbed by the spectator quark or antiquark. Transition amplitudes for the scattering process derive from the transition potential in conjunction with mesonic quark-antiquark wave functions and the relative-motion wave function of the two initial mesons. We derive these transition amplitudes in the partial wave expansion of the relative-motion wave function of the two initial mesons so that parity and total-angular-momentum conservation are maintained. We calculate flavor and spin matrix elements in accordance with the transition potential and unpolarized cross sections for the reactions using the transition amplitudes. Cross sections for the production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ relate to nodes in their radial wave functions. We suggest the production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ as probes of hadronic matter that results from the quark-gluon plasma created in ultrarelativistic heavy-ion collisions.
↳ hep-phnucl-thEPJC(2021)·5 citations
09
Reexamination of $^{6}$ Li scattering as a Probe to Investigate the Isoscalar Giant Resonances in Nuclei
J. C. Zamora🇧🇷 · C. Sullivan🇺🇸 · R.G.T. Zegers🇺🇸 · N. Aoi🇯🇵 · L. Batail🇫🇷 · D. Bazin🇺🇸 · M. Carpenter🇺🇸 · J.J. Carroll🇺🇸 · I. Deloncle🇫🇷 · Y.D. Fang🇯🇵 · H. Fujita🇯🇵 · U. Garg🇺🇸 and 28 other authors
Inelastic $^{6}$ Li scattering at 100 MeV/u on $^{12}$ C and $^{93}$ Nb have been measured with the high-resolution magnetic spectrometer Grand Raiden. The magnetic-rigidity settings of the spectrometer covered excitation energies from 10 to 40 MeV and scattering angles in the range $0^{\circ} < θ_{lab.} < 2^{\circ}$ . The isoscalar giant monopole resonance was selectively excited in the present data. Measurements free of instrumental background and the very favorable resonance-to-continuum ratio of $^{6}$ Li scattering allowed for precise determination of the $E 0$ strengths in $^{12}$ C and $^{93}$ Nb. It was found that the monopole strength in $^{12}$ C exhausts $52 \pm 3^{(stat.)} \pm 8^{(sys.)}$ \% of the energy-weighted sum rule (EWSR), which is considerably higher than results from previous $α$ -scattering experiments. The monopole strength in $^{93}$ Nb exhausts $92 \pm 4^{(stat.)} \pm 1 0^{(sys.)}$ \% of the EWSR, and it is consistent with measurements of nuclei with mass number of $A \approx 90$ . Such comparison indicates that the isoscalar giant monopole resonance distributions in these nuclei are very similar, and no influence due to nuclear structure was observed.
↳ nucl-exnucl-thPRC(2020)·5 citations
10
Quark and pion condensates at finite isospin density in chiral perturbation theory
Prabal Adhikari🇺🇸 · Jens O. Andersen🇳🇴
In this paper, we consider two-flavor QCD at zero temperature and finite isospin chemical potential ( $μ_{I}$ ) using a model-independent analysis within chiral perturbation theory at next-to-leading order. We calculate the effective potential, the chiral condensate and the pion condensate in the pion-condensed phase at both zero and nonzero pionic source. We compare our finite pionic source results for the chiral condensate and the pion condensate with recent (2+1)-flavor lattice QCD results and find that they are in excellent agreement.
↳ hep-phhep-latnucl-thEPJC(2020)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE