Nuclear Theory·nucl-th

Wednesday·January 31, 2018

13 papers—6 primary·7 cross-listed

01
Poincaré-covariant analysis of heavy-quark baryons
Si-Xue Qin🇨🇳 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪
We use a symmetry-preserving truncation of meson and baryon bound-state equations in quantum field theory in order to develop a unified description of systems constituted from light- and heavy-quarks. In particular, we compute the spectrum and leptonic decay constants of ground-state pseudoscalar- and vector-mesons: $q^{'} q ˉ$ , $Q^{'} Q ˉ$ , with $q^{'}, q = u, d, s$ and $Q^{'}, Q = c, b$ ; and the masses of $J^{P} = 3/ 2^{+}$ baryons and their first positive-parity excitations, including those containing one or more heavy quarks. This Poincaré-covariant analysis predicts that such baryons have a complicated angular momentum structure. For instance, the ground states are all primarily $S$ -wave in character, but each possesses $P$ -, $D$ - and $F$ -wave components, with the $P$ -wave fraction being large in the $q q q$ states; and the first positive-parity excitation in each channel has a large $D$ -wave component, which grows with increasing current-quark mass, but also exhibits features consistent with a radial excitation. The configuration space extent of all such baryons decreases as the mass of the valence-quark constituents increases.
nucl-thhep-phPRD(2018)·60 citations
02
$Δ (1232)$ -Resonance in the Hydrogen Spectrum
Franziska Hagelstein (AEC Bern)🇨🇭
The electromagnetic excitation of the $Δ (1232)$ -resonance plays an appreciable role in the Lamb shift and hyperfine structure of muonic and electronic hydrogen. Its effect appears at the subleading order $O (α^{5})$ , together with other proton-polarizability contributions from forward two-photon exchange. We use the large- $N_{c}$ relations for the nucleon-to-delta transition form factors to compute the effect of the $Δ (1232)$ in the hydrogen spectrum. We pay particular attention to a subtile difference between predictions based on a direct calculation of the two-photon exchange (or Compton scattering amplitudes) and predictions based on the $Δ (1232)$ -production photoabsorption cross sections. The mismatch is explained by studying the dispersion relations for tree-level Compton scattering off the proton in more details.
nucl-thhep-phFew Body Syst.(2018)·16 citations
03
Evidence for rotational to vibrational evolution along the yrast line in the odd-A rare-earth nuclei
H. B. Zhou · S. Huang · G. X. Dong · Z. X. Shen · H. J. Lu · L. L. Wang · X. J. Sun · F. R. Xu
The phase transition of nuclei to increasing angular momentum (or spin) and excitation energy is one of the most fundamental topics of nuclear structure research. The odd-N nuclei with A equal 160 are widely considered belonging to the well-deformed region, and their excitation spectra are energetically favored to exhibit the rotational characteristics. In the present work, however, there is evidence indicating that the nuclei can evolve from rotation to vibration along the yrast lines while increasing spin. The simple method, named as E-Gamma Over Spin (E-GOS) curves, would be used to discern the evolution from rotational to vibrational structure in nuclei as a function of spin. In addition, in order to get the insight into the rotational-like properties of nuclei, theoretical calculations have been performed for the yrast bands of the odd-A rare-earth nuclei using the total Routhian surfaces (TRS) model. The TRS plots indicate that the 165Yb and 157Dy isotopes have stable prolate shapes at low spin states. At higher rotational frequency (larger than 0.50 MeV), a distinct decrease in the quadrupole deformation is predicted by the calculations, and the isotopes becomes rigid in the gamma deformation.
nucl-thNucl.Phys.Rev.(2018)·0 citations
04
Systematic few-body analysis of eta-d, eta-3He and eta-4He interaction at low energies
A.Fix🇷🇺 · O.Kolesnikov🇷🇺
The Alt-Grassberger-Sandhas N-body theory is used to study interaction of eta-mesons with d, 3He, and 4He. Separable expansion of the subamplitudes is adopted to convert the integral equations into the quasi-two-body form. The resulting formalism is applied to fit the existing data for low-energy eta production on few-nucleon targets. On the basis of this fitting procedure the scattering lengths a_{eta d}, a_{eta 3He}, a_{eta 4He} as well as the subthreshold behaviour of the elementary eta-N scattering amplitude are obtained.
nucl-thPRC(2018)·6 citations
05
Quantum mechanical description of excitation energy distribution of the reaction residue in nucleon-induced inclusive one-nucleon knockout reactions
Kazuyuki Ogata
Understanding of inclusive one-nucleon knockout reactions for long-lived fission fragments (LLFPs) is crucial for nuclear transmutation studies. However, the particle and heavy ion transport code system (PHITS) severely overshoots the inclusive one-nucleon knockout cross sections sigma_-1N. Therefore development of a reaction model for describing the inclusive one-nucleon knockout processes is necessary. A key is specification of the position and the momentum of a nucleon inside a nucleus to be struck by the incident nucleon. In this paper the semiclassical distorted wave model incorporating the Wigner transform of the one-body nuclear density matrix is applied to the calculation of excitation energy distributions of reaction residues. Decay of a residue is described by introducing a threshold parameter for the minimum excitation energy of it. With reasonable values of the parameter, the measured sigma_-1N for several LLFPs are reproduced by the proposed reaction model. The incident energy dependence of sigma_-1N is found to be governed by that of the nucleon-nucleon cross sections at energies higher than about 75 MeV. At low energies, the nuclear absorption and the Coulomb penetrability also become important. The energy dependence of neutron-induced sigma_-1N is predicted and found to be quite different from that of proton induced one. The proposed reaction model is shown to be promising in discussing the energy dependence of nucleon-induced inclusive one-nucleon knockout processes. The energy dependence of the measured sigma_-1p for 107Pd above 100 MeV is, however, not explained by the present calculation.
nucl-th0 citations
06
Isoscalar and Isovector spin response in $s d -$ shell nuclei
H. Sagawa · T. Suzuki
The spin magnetic dipole transitions and the neutron-proton spin-spin correlations in $s d -$ shell even-even nuclei with $N = Z$ are investigated using shell model wave functions taking into accout enhanced isoscalar (IS) spin-triplet pairing as well as the effective spin operators. It was shown that the IS pairing and the effective spin operators gives a large quenching effect on the IV spin transitions to be consistent with observed data by $(p, p^{'})$ experiments. On the other hand, the observed IS spin strength show much smaller quenching effect than expected by the calculated results. The IS pairing gives a substantial quenching effect on the spin magnetic dipole transitions, especially on the isovector (IV) ones. Consequently, an enhanced isoscalar spin-triplet pairing interaction enlarges the proton-neutron spin-spin correlation deduced from the difference between the isoscalar (IS) and the IV sum rule strengths. The beta-decay rates and the IS magnetic moments of $s d -$ shell are also examined in terms of the IS pairing as well as the effective spin operators.
nucl-thPRC(2018)·10 citations
07
Vacuum-like jet fragmentation in a dense QCD medium
P. Caucal🇫🇷 · E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · G. Soyez🇫🇷
We study the fragmentation of a jet propagating in a dense quark-gluon plasma. Using a leading, double-logarithmic approximation in perturbative QCD, we compute for the first time the effects of the medium on the vacuum-like emissions. We show that, due to the scatterings off the plasma, the in-medium parton showers differ from the vacuum ones in two crucial aspects: their phase-space is reduced and the first emission outside the medium can violate angular ordering. We compute the jet fragmentation function and find results in qualitative agreement with measurements at the LHC.
↳ hep-phnucl-thPRL(2018)·155 citations
08
What does the matter created in high multiplicity proton-nucleus collisions teach us about the 3-D structure of the proton?
K. Dusling🇺🇸 · M. Mace🇺🇸 · R. Venugopalan🇺🇸
The study of multiparticle correlations and collectivity in the hot and dense matter created in collisions of heavy-ions as well as those of smaller systems such as proton--heavy-ion collisions has progressed to the point where detailed knowledge of the three-dimensional structure of the proton is needed to confront experimental data. We discuss results from a simple proof-of-principle initial state parton model which reproduces many features of the data on proton--heavy-ion collisions that are often ascribed to hydrodynamic flow. We outline how this model can be further improved with particular emphasis on missing elements in our understanding of the dynamical spatial and momentum structure of the proton.
↳ hep-phnucl-exnucl-thPoS(2018)·7 citations
09
$N^{*}$ Production from $e^{+} e^{-}$ Annihilations
Bing-Song Zou🇨🇳
Up to now, the $N^{*}$ production from $e^{+} e^{-}$ annihilations has been studied only around charmonium region. Charmonium decays to $N^{*}$ s are analogous to (time-like) EM form factors in that the charm quark annihilation provides a nearly pointlike (ggg) current. Complementary to other sources, such as $π N$ , $e N$ and $γ N$ reactions, this new source for $N^{*}$ spectroscopy has a few advantages, such as an isospin filter and a low spin filter. The experimental results on $N^{*}$ from $e^{+} e^{-}$ annihilations and their phenomenological implications are reviewed. Possible new sources on $N^{*}$ production from $e^{+} e^{-}$ annihilations are discussed.
↳ hep-phhep-exnucl-exnucl-th5 citations
10
Chiral Lagrangians with decuplet baryons to one loop
Shao-Zhou Jiang🇨🇳 · Yan-Rui Liu🇨🇳 · Hong-Qian Wang🇨🇳 · Qin-He Yang🇨🇳
We construct the relativistic chiral Lagrangians with decuplet baryons up to the order $O (p^{4})$ (one loop). For the meson-decuplet-decuplet couplings, there are 1, 13, 55, and 548 terms in the $O (p^{1})$ - $O (p^{4})$ order Lagrangians, respectively. For the meson-octet-decuplet Lagrangians, the number of independent terms from $O (p^{1})$ to $O (p^{4})$ are 1, 5, 67, and 611, respectively. For convenience of applications, the $π ΔΔ$ and $π N Δ$ chiral Lagrangians are picked out. This new form of $Δ$ Lagrangians is equivalent to the original isovector-isospinor one and we establish relations between these two forms.
↳ hep-phnucl-thPRD(2018)·7 citations
11
Comparing many-body approaches against the helium atom exact solution
Jing Li🇫🇷 · N. D. Drummond🇬🇧 · Peter Schuck🇫🇷 · Valerio Olevano🇫🇷
Over time, many different theories and approaches have been developed to tackle the many-body problem in quantum chemistry, condensed-matter physics, and nuclear physics. Here we use the helium atom, a real system rather than a model, and we use the exact solution of its Schrödinger equation as a benchmark for comparison between methods. We present new results beyond the random-phase approximation (RPA) from a renormalized RPA (r-RPA) in the framework of the self-consistent RPA (SCRPA) originally developed in nuclear physics, and compare them with various other approaches like configuration interaction (CI), quantum Monte Carlo (QMC), time-dependent density-functional theory (TDDFT), and the Bethe-Salpeter equation on top of the GW approximation. Most of the calculations are consistently done on the same footing, e.g. using the same basis set, in an effort for a most faithful comparison between methods.
↳ physics.atom-phcond-mat.othernucl-thSciPost Phys.(2019)·7 citations
12
Heavy flavour in high-energy nuclear collisions: theory overview of transport calculations
Andrea Beraudo🇮🇹
Transport calculations are the tool to study medium modifications of heavy-flavour particle distributions in high-energy nuclear collisions. We give a brief overview on their state-of-the art, on the information one can extract, on the questions remaining open and on further analysis to carry out in the near future.
↳ hep-phnucl-exnucl-thFrascati Phys.Ser.(2017)·0 citations
13
On chiral extrapolations of charmed meson masses and coupled-channel reaction dynamics
Xiao-Yu Guo🇩🇪 · Yonggoo Heo🇩🇪 · Matthias F.M. Lutz🇩🇪
We perform an analysis of QCD lattice data on charmed meson masses. The quark-mass dependence of the data set is used to gain information on the size of counter terms of the chiral Lagrangian formulated with open-charm states with J^P= 0^- and J^P =1^- quantum numbers. Of particular interest are those counter terms that are active in the exotic flavour sextet channel. A chiral expansion scheme where physical masses enter the extrapolation formulae is developed and applied to the lattice data set. Good convergence properties are demonstrated and an accurate reproduction of the lattice data based on ensembles of PACS-CS, MILC, ETMC and HSC with pion and kaon masses smaller than 600 MeV is achieved. It is argued that a unique set of low-energy parameters is obtainable only if additional information from HSC on some scattering observables is included in our global fits. The elastic and inelastic s-wave pi D and eta D scattering as considered by HSC is reproduced faithfully. Based on such low-energy parameters we predict 15 phase shifts and in-elasticities at physical quark masses but also for an additional HSC ensemble at smaller pion mass. In addition we find a clear signal for a member of the exotic flavour sextet states in the eta D channel, below the bar K D_s threshold. For the isospin violating strong decay width of the D_{s0}(2317) we obtain the range (104-116) keV.
↳ hep-lathep-phnucl-thPRD(2018)·85 citations

Affiliations

first authorsco-authorsvia INSPIRE