119114137
Low-momentum NN interactions and all-order summation of ring diagrams of symmetric nuclear matter
We study the equation of state for symmetric nuclear matter using a ring-diagram approach in which the particle-particle hole-hole (pphh) ring diagrams within a momentum model space of decimation scale \ensuremath{\Lambda} are summed to all orders. The calculation is carried out using the renormalized low-momentum nucleon-nucleon ($\mathit{NN}$) interaction ${V}_{\mathrm{low}\text{\ensuremath{-}}k}$, which is obtained from a bare $\mathit{NN}$ potential by integrating out the high-momentum components beyond \ensuremath{\Lambda}. The bare $\mathit{NN}$ potentials of CD-Bonn, Nijmegen, and Idaho have been employed. The choice of \ensuremath{\Lambda} and its influence on the single particle spectrum are discussed. Ring-diagram correlations at intermediate momenta ($k\ensuremath{\simeq}2 {\mathrm{fm}}^{\ensuremath{-}1}$) are found to be particularly important for nuclear saturation, suggesting the necessity of using a sufficiently large decimation scale so that the above momentum region is not integrated out. Using ${V}_{\mathrm{low}\text{\ensuremath{-}}k}$ with $\ensuremath{\Lambda}~3 {\mathrm{fm}}^{\ensuremath{-}1}$, we perform a ring-diagram computation with the above potentials, which all yield saturation energies $E/A$ and Fermi momenta ${k}_{F}^{(0)}$ considerably larger than the empirical values. On the other hand, similar computations with the medium-dependent Brown-Rho scaled $\mathit{NN}$ potentials give satisfactory results of $E/A\ensuremath{\simeq}\ensuremath{-}15$ MeV and ${k}_{F}^{(0)}\ensuremath{\simeq}1.4 {\mathrm{fm}}^{\ensuremath{-}1}$. The effect of this medium dependence is well reproduced by an empirical three-body force of the Skyrme type.
119273892
Understanding Dilepton Production in Heavy Ion Collisions by Vector Mesons of Different Varieties
A simple schematic model anchored on the notion of hadronic freedom inferred from hidden local symmetry in the vector manifestation, the infinite tower of vector mesons in holographic QCD and "stickiness" of $\pi\pi$ interactions inferred from dispersion relations is used to describe the dileptons produced in relativistic heavy ion collisions at PHENIX/RHIC. It is shown that due to the near "blindness" of dileptons to Brown-Rho scaling, those dileptons with invariant mass less than $m_\rho=770$ MeV come mostly from pion-composites that we interpret as "transient $\rho$'s."
13937403
Hans Bethe: The Nuclear Many Body Problem
We discuss the work of Hans Bethe and others in formulating a theoretical foundation for the nuclear shell model. Written for a general audience, this article describes the evolution from Brueckner's reaction matrix theory to the Moszkowski-Scott separation method and ultimately to the Reference Spectrum method of Bethe, Brandow, and Petschek. We also discuss connections with the recently developed low momentum nucleon-nucleon interactions.
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, � ≈ + � � ∗
103944970
Nuclear thermodynamics from chiral low-momentum interactions
We investigate the thermodynamic equation of state of isospin-symmetric nuclear matter with microscopic nuclear forces derived within the framework of chiral effective field theory. Two- and three-body nuclear interactions constructed at low-resolution scales form the basis for a perturbative calculation of the finite-temperature equation of state. The nuclear force models and many-body methods are benchmarked against bulk properties of isospin-symmetric nuclear matter at zero temperature, which are found to be well reproduced when chiral nuclear interactions constructed at the lowest resolution scales are employed. The calculations are then extended to finite temperatures, where we focus on the liquid-gas phase transition and the associated critical point. The Maxwell construction is applied to construct the physical equation of state, and the value of the critical temperature is determined to be ${T}_{c}=17.2$\char21{}19.1 MeV, in good agreement with the value extracted from multifragmentation reactions of heavy ions.
119297098
Chiral Fermi liquid approach to neutron matter
We present a microscopic calculation of the complete quasiparticle interaction, including central as well as noncentral components, in neutron matter from high-precision two- and three-body forces derived within the framework of chiral effective field theory. The contributions from two-nucleon forces are computed in many-body perturbation theory to first and second order (without any simplifying approximations). In addition we include the leading-order one-loop diagrams from the N2LO chiral three-nucleon force, which contribute to all Fermi liquid parameters except those associated with the center-of-mass tensor interaction. The relative-momentum dependence of the quasiparticle interaction is expanded in Legendre polynomials up to L=2. Second-order Pauli blocking and medium polarization effects act coherently in specific channels, namely for the Landau parameters f_1, h_0 and g_0, which results in a dramatic increase in the quasiparticle effective mass as well as a decrease in both the effective tensor force and the neutron matter spin susceptibility. For densities greater than about half nuclear matter saturation density \rho_0, the contributions to the Fermi liquid parameters from the leading-order chiral three-nucleon force scale in all cases approximately linearly with the nucleon density. The largest effect of the three-nucleon force is to generate a strongly repulsive effective interaction in the isotropic spin-independent channel. We show that the leading-order chiral three-nucleon force leads to an increase in the spin susceptibility of neutron matter, but we observe no evidence for a ferromagnetic spin instability in the vicinity of the saturation density \rho_0. This work sets the foundation for future studies of neutron matter response to weak and electromagnetic probes with applications to neutron star structure and evolution.
16582639
Three-nucleon interactions: A Frontier in nuclear structure
Three‐nucleon interactions are a frontier in understanding and predicting the structure of strongly‐interacting matter in laboratory nuclei and in the cosmos. We present results and discuss the status of first calculations with microscopic three‐nucleon interactions beyond light nuclei. This coherent effort is possible due to advances based on effective field theory and renormalization group methods in nuclear physics.
20907443
Three-body forces and proton-rich nuclei.
We present the first study of three-nucleon (3N) forces for proton-rich nuclei along the N=8 and N=20 isotones. Our results for the ground-state energies and proton separation energies are in very good agreement with experiment where available, and with the empirical isobaric multiplet mass equation. We predict the spectra for all N=8 and N=20 isotones to the proton dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In all other cases, we provide first predictions based on nuclear forces. Our results are also very promising for studying isospin symmetry breaking in medium-mass nuclei based on chiral effective field theory.
119226065
Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes
We study the spectra of neutron-rich oxygen isotopes based on chiral two- and three-nucleon interactions. First, we benchmark our many-body approach by comparing ground-state energies to coupled-cluster results for the same two-nucleon interaction, with overall good agreement. We then calculate bound excited states in 21, 22, 23O , focusing on the role of three-nucleon forces, in the standard sd shell and an extended $ sdf_{7/2}p_{3/2}$ valence space. Chiral three-nucleon forces provide important one- and two-body contributions between valence neutrons. We find that both these contributions and an extended valence space are necessary to reproduce key signatures of novel shell evolution, such as the N = 14 magic number and the low-lying states in 21O and 23O , which are too compressed with two-nucleon interactions only. For the extended space calculations, this presents first work based on nuclear forces without adjustments. Future work is needed and open questions are discussed.
7592155
New precision mass measurements of neutron-rich calcium and potassium isotopes and three-nucleon forces.
We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system, the mass of 51K was measured for the first time, and the precision of the (51,52)Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, 52Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces.
7797374
First direct double-β decay Q-value measurement of 82Se in support of understanding the nature of the neutrino.
In anticipation of results from current and future double-β decay studies, we report a measurement resulting in a (82)Se double-β decay Q value of 2997.9(3) keV, an order of magnitude more precise than the currently accepted value. We also present preliminary results of a calculation of the (82)Se neutrinoless double-β decay nuclear matrix element that corrects in part for the small size of the shell model single-particle space. The results of this work are important for designing next generation double-β decay experiments and for the theoretical interpretations of their observations.