17480164
A Hidden Local Field Theory Description of Dileptons in Relativistic Heavy Ion Collisions
Using the notion of “hadronic freedom” inferred from the vector manifestation of hidden local symmetry we argue that, contrary to the commonly held belief, the dileptons measured in relativistic heavy-ion collisions do not carry useful information directly relevant to the spontaneous breaking of chiral symmetry and hence to the mechanism for mass generation of light-quark hadrons. The dileptons emitted from those vector mesons whose masses are shifted by the vacuum change in temperature and/or density are strongly suppressed in the hadronic free region between the chiral restoration point and the “flash point” at which the vector mesons recover ∼ > 90% of their free-space on-shell masses and the full strong coupling strength. The spectral function deduced from the dilepton measurements reflects predominantly those vector mesons decaying at the “flash temperature” Tflash ∼ 120 MeV. Thus, � ≈ + � � ∗
59140707
Non-degenerate shell-model effective interactions from the Okamoto–Suzuki and Krenciglowa–Kuo iteration methods
Abstract We present calculations of shell-model effective interactions for both degenerate and non-degenerate model spaces using the Krenciglowa–Kuo (KK) and the extended Krenciglowa–Kuo iteration method recently developed by Okamoto, Suzuki et al. (EKKO). The starting point is the low-momentum nucleon–nucleon interaction V low − k obtained from the N3LO chiral two-nucleon interaction. The model spaces spanned by the sd and sdpf shells are both considered. With a solvable model, we show that both the KK and EKKO methods are convenient for deriving the effective interactions for non-degenerate model spaces. The EKKO method is especially desirable in this situation since the vertex function Z ˆ -box employed therein is well behaved while the corresponding vertex function Q ˆ -box employed in the Lee–Suzuki (LS) and KK methods may have singularities. The converged shell-model effective interactions given by the EKKO and KK methods are equivalent, although the former method is considerably more efficient. The degenerate sd-shell effective interactions given by the LS method are practically identical to those from the EKKO and KK methods. Results of the sd one-shell and sdpf two-shell calculations for 18O, 18F, 19O and 19F using the EKKO effective interactions are compared, and the importance of an inter-space consistency between the sd and sdpf calculations is discussed.
1719527
Shell model description of the 14C dating beta decay with Brown-Rho-scaled NN interactions.
We present shell model calculations for the beta decay of 14C to the 14N ground state, treating the states of the A=14 multiplet as two 0p holes in an 16O core. We employ low-momentum nucleon-nucleon (NN) interactions derived from the realistic Bonn-B potential and find that the Gamow-Teller (GT) matrix element is too large to describe the known lifetime. By using a modified version of this potential that incorporates the effects of Brown-Rho scaling medium modifications, we find that the GT matrix element vanishes for a nuclear density around 85% that of nuclear matter. We find that the splitting between the (J(pi),T)=(1(+),0) and (J(pi),T)=(0(+),1) states in 14N is improved using the medium-modified Bonn-B potential and that the transition strengths from excited states of 14C to the 14N ground state are compatible with recent experiments.
119201718
Nuclear chiral dynamics and thermodynamics
This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit �(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependence of the chiral (quark) condensate is investigated.
117100679
Shell-model descriptions of mass 16-19 nuclei with chiral two- and three-nucleon interactions
Shell-model calculations for several mass 16-19 nuclei are performed using the N$^3$LO two-nucleon potential $V_{2N}$ with and without the addition of an in-medium three-nucleon potential $V_{3N}^{med}$, which is a density-dependent effective two-nucleon potential recently derived from the leading-order chiral three-nucleon force $V_{3N}$ by Holt, Kaiser, and Weise. We first calculate the $V_{low-k}$ low-momentum interactions from $V_{2N}$ and $V_{3N}^{med}$. The shell-model effective interactions for both the $sd$ one-shell and $sdpf$ two-shell model spaces are then obtained from these low-momentum interactions using respectively the Lee-Suzuki and the recently developed Okamoto and Suzuki iteration methods. 
The effects of $V_{3N}^{med}$ to the low-lying states of $^{18}O$, $^{18}F$, $^{19}O$ and $^{19}F$ are generally small and attractive, mainly lowering the ground-state energies of these nuclei and making them in better agreements with experiments than those calculated with $V_{2N}$ alone. The excitation spectra of these nuclei are not significantly affected by $V_{3N}^{med}$. The low-lying spectra of these nuclei calculated with the $sd$ and $sdpf$ model spaces are closely similar to each other. Our shell-model calculations for $^{16}O$ indicate that the $V_{3N}^{med}$ interaction is important and desirable for the binding energy of this nucleus.
119225778
Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms
We have measured the angular distribution of recoiling daughter nuclei emitted from the Gamow-Teller {beta} decay of spin-polarized {sup 80}Rb. The asymmetry of this distribution vanishes to lowest order in the standard model (SM) in pure Gamow-Teller decays, producing an observable very sensitive to new interactions. We measure the non-SM contribution to the asymmetry to be A{sub T}=0.015{+-}0.029 (stat) {+-}0.019 (syst), consistent with the SM prediction. We constrain higher-order SM corrections using the measured momentum dependence of the asymmetry, and their remaining uncertainty dominates the systematic error. Future progress in determining the weak magnetism term theoretically or experimentally would reduce the final errors. We describe the resulting constraints on fundamental four-Fermi tensor interactions.