Nuclear Theory·nucl-th

Monday·July 13, 2015

5 papers—3 primary·2 cross-listed

01
[Submitted on 10 Jul 2015]
Microscopic calculations based on chiral two- and three-nucleon forces for proton- and $^{4}$ He-nucleus scattering
Masakazu Toyokawa · Masanobu Yahiro · Takuma Matsumoto · Kosho Minomo · Kazuyuki Ogata · Michio Kohno
We investigate the effects of chiral three-nucleon force (3NF) on proton scattering at 65 MeV and $^{4}$ He scattering at 72 MeV/nucleon from heavier targets, using the standard microscopic framework composed of the Brueckner-Hartree-Fock (BHF) method and the $g$ -matrix folding model. For nuclear matter, the $g$ matrix is evaluated from chiral two-nucleon force (2NF) of N $^{3}$ LO and chiral 3NF of NNLO by using the BHF method. Since the $g$ matrix thus obtained is numerical and nonlocal, an optimum local form is determined from the on-shell and near-on-shell components of $g$ matrix that are important for elastic scattering. For elastic scattering, the optical potentials are calculated by folding the local chiral $g$ matrix with projectile and target densities. This microscopic framework reproduces the experimental data without introducing any adjustable parameter. Chiral-3NF effects are small for proton scattering, but sizable for $^{4}$ He scattering at middle angles where the data are available. Chiral 3NF, mainly in the 2 $π$ -exchange diagram, makes the folding potential less attractive and more absorptive for all the scattering.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.02807 [pdf]
PRC(2015)·49 citations
02
[Submitted on 10 Jul 2015]
The Hypercentral Constituent Quark Model and its symmetry
M.M. Giannini🇮🇹 · E. Santopinto🇮🇹
The hypercentral CQM, which is inspired by Lattice QCD calculations for quark-antiquark potentials, is presented, stressing its underlying symmetry. Its results for the spectrum, the helicity amplitudes and the elastic form factors are briefly reported. In the latter case the model has allowed to show, for the first time in the framework of a quark model, that relativistic effects are responsible for a deviation from the usually accepted dipole behaviour, in agreement with recent data taken at the Jefferson Lab.
Comments:
Workshop Symmetries in Nuclear Structure, Erice March 23-30, 2003, in honor of the 60th birthday of Franco Iachello Published in Symmetries in nuclear structure, Science and culture Series, Physics 24, 384-389, (A. Vitturi, R. F. Casten eds.) World Scientific, Singapore 2004
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.02817 [pdf]
0 citations
03
[Submitted on 10 Jul 2015]
Relativistic second-order dissipative hydrodynamics at finite chemical potential
Amaresh Jaiswal🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇵🇱
Starting from the Boltzmann equation in the relaxation time approximation and employing a Chapman-Enskog like expansion for the distribution function close to equilibrium, we derive second-order evolution equations for the shear stress tensor and the dissipative charge current for a system of massless quarks and gluons. The transport coefficients are obtained exactly using quantum statistics for the phase space distribution functions at non-zero chemical potential. We show that, within the relaxation time approximation, the second-order evolution equations for the shear stress tensor and the dissipative charge current can be decoupled. We find that, for large values of the ratio of chemical potential to temperature, the charge conductivity is small compared to the coefficient of shear viscosity. Moreover, we show that in the relaxation-time approximation, the limiting behaviour of the ratio of heat conductivity to shear viscosity is qualitatively similar to that obtained for a strongly coupled conformal plasma.
Comments:
v3: 6 pages, 2 figure, published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1507.02849 [pdf]
PLB(2015)·73 citations
04
[Submitted on 10 Jul 2015] (cross-list from hep-ph)
Intriguing aspects of meson condensation
Andrea Mammarella🇮🇹 · Massimo Mannarelli🇮🇹
We analyze various aspects of pion and kaon condensation in the framework of chiral perturbation theory. Considering a system at vanishing temperature and varying the isospin chemical potential and the strange quark chemical potential we reproduce known results about the phase transition to the pion condensation phase and to the kaon condensation phase. However, we obtain mesonic mixings and masses in the condensed phases that are in disagreement with the results reported in previous works. Our findings are obtained both by a theory group analysis and by direct calculation by means of the same low-energy effective Lagrangian used in previous works. We also study the leptonic decay channels in the normal phase and in the pion condensed phase, finding that some of these channels have a peculiar nonmonotonic behavior as a function of the isospin chemical potential. Regarding the semileptonic decays, we find that that they should be efficient feeding processes for the stable charged pion state.
Comments:
15 pages, 6 figures, minor changes, references added, to appear on Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1507.02934 [pdf]
PRD(2015)·38 citations
05
[Submitted on 10 Jul 2015] (cross-list from hep-ph)
Muon g-2 estimates : Can one trust Effective Lagrangians and global fits ?
M. Benayoun🇫🇷 · P. David🇫🇷 · L. DelBuono🇫🇷 · F. Jegerlehner🇩🇪
Previous studies have shown that the Hidden Local Symmetry (HLS) Model, supplied with appropriate symmetry breaking mechanisms, provides an Effective Lagrangian (BHLS) which encompasses a large number of processes within a unified framework; a global fit procedure allows for a simultaneous description of the e+ e- annihilation into the 6 final states $π^{+} π^{-}$ , $π^{0} γ$ , $η γ$ , $π^{+} π^{-} π^{0}$ , $K^{+} K^{-}$ , $K_{l} K_{s}$ and includes the dipion spectrum in the {\tau} decay and some more light meson decay partial widths. The contribution to the muon anomalous magnetic moment $a_{t h}$ of these annihilation channels over the range of validity of the HLS model (up to 1.05 GeV) is found much improved compared to its partner derived from integrating the measured spectra directly. However, most spectra for the process $e^{+} e^{-} \to π^{+} π^{-}$ undergo overall scale uncertainties which dominate the other sources, and one may suspect some bias in the dipion contribution to $a_{t h}$ . However, an iterated fit algorithm, shown to lead to unbiased results by a Monte Carlo study, is defined and applied succesfully to the $e^{+} e^{-} \to π^{+} π^{-}$ data samples from CMD2, SND, KLOE, BaBar and BESSIII. The iterated fit solution is shown to be further improved and leads to a value for $a_{μ}$ different from $a_{e x p}$ above the 4 $σ$ level. The contribution of the $π^{+} π^{-}$ intermediate state up to 1.05 GeV to $a_{t h}$ derived from the iterated fit benefits from an uncertainty about 3 times smaller than the corresponding usual estimate. Therefore, global fit techniques are shown to work and lead to improved unbiased results.
Comments:
version enlarged to include the recent BESS dipion spectrum within the global analysis. version accepted for publication in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1507.02943 [pdf]
EPJC(2015)·67 citations

Affiliations

first authorsco-authorsvia INSPIRE

Microscopic calculations based on chiral two- and three-nucleon forces for proton- and 4He-nucleus scattering

The Hypercentral Constituent Quark Model and its symmetry

Relativistic second-order dissipative hydrodynamics at finite chemical potential

Intriguing aspects of meson condensation

Muon g-2 estimates : Can one trust Effective Lagrangians and global fits ?

Affiliations

Microscopic calculations based on chiral two- and three-nucleon forces for proton- and $^{4}$ He-nucleus scattering