Search results for "gold"

Model independent Higgs boson mass limits at LEP

1993

We derive model-independent constraints on Higgs mass and couplings from associated signals for higher masses, accessible at LEP2. This work is motivated by the fact that, in many extensions of the standard model, the Higgs boson can have substantial "invisible" decay modes, for example, into light or massless weakly interacting Goldstone bosons associated to the spontaneous violation of lepton number below the weak scale.

Nuclear reactions in collisions of very heavy ions at energies below and near the barrier

2008

Working group on goldstone boson production and decay

2008

This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dynamics Workshop in Mainz, September 1–5, 1997. For the production aspects we discuss π0 and η production in nucleon-nucleon collisions and the behaviour of hadrons in various sum rules. For the decays we present a discussion on various K, η and π decay channels. Other aspects discussed are a new treatment of meson-meson scattering, the light-by-light contribution to the muon anomalous magnetic moment and progress in various aspects of the p 6 generating functional in the mesonic sector.

Photonic Nambu-Goldstone bosons

2017

We study numerically the spatial dynamics of light in periodic square lattices in the presence of a Kerr term, emphasizing the peculiarities stemming from the nonlinearity. We find that, under rather general circumstances, the phase pattern of the stable ground state depends on the character of the nonlinearity: the phase is spatially uniform if it is defocusing whereas in the focusing case, it presents a chess board pattern, with a difference of $\pi$ between neighboring sites. We show that the lowest lying perturbative excitations can be described as perturbations of the phase and that finite-sized structures can act as tunable metawaveguides for them. The tuning is made by varying the in…

Low-energy constants from resonance chiral theory

2008

I discuss the recent attempts to build an effective chiral Lagrangian incorporating massive resonance states. A useful approximation scheme to organize the resonance Lagrangian is provided by the large-Nc limit of QCD. Integrating out the resonance fields, one recovers the usual chiral perturbation theory Lagrangian with explicit values for the low-energy constants, parameterized in terms of resonance masses and couplings. The resonance chiral theory generates Green functions that interpolate between QCD and chiral perturbation theory. Analyzing these Green functions, both for large and small momenta, one gets QCD constraints on the resonance couplings and, therefore, information on the low…

Interpolating between low and high energy QCD via a 5D Yang-Mills model

2005

We describe the Goldstone bosons of massless QCD together with an infinite number of spin-1 mesons. The field content of the model is SU(Nf)xSU(Nf) Yang-Mills in a compact extra-dimension. Electroweak interactions reside on one brane. Breaking of chiral symmetry occurs due to the boundary conditions on the other brane, away from our world, and is therefore spontaneous. Our implementation of the holographic recipe maintains chiral symmetry explicit throughout. For intermediate energies, we extract resonance couplings. These satisfy sum rules due to the 5D nature of the model. These sum rules imply, when taking the high energy limit, that perturbative QCD constraints are satisfied. We also il…

Chiral perturbation theory: Introduction and recent results in the one-nucleon sector

2009

We provide an introduction to the basic concepts of chiral perturbation theory and discuss some recent developments in the manifestly Lorentz-invariant formulation of the one-nucleon sector.

Nature of the axial-vector mesons from their N-c behavior within the chiral unitary approach

2008

By describing within the chiral unitary approach the g-wave interaction of the vector meson nonet with the octet of pseudoscalar Goldstone bosons, we find that the main component of the axial-vector mesons -b(1)(1235), h(1)(1170), h(1)(1380), a(1)(1260), f(1)(1285) and the two states associated to the K-1(1270)- does not follow the QCD dependence on the number of colors for ordinary q (q) over bar mesons.

Liquid-liquid phase coexistence in gold clusters. 2D or not 2D?

2006

The thermodynamics of gold cluster anions (${\mathrm{Au}}_{N}^{\ensuremath{-}}$, $N=11,\dots{},14$) is investigated using quantum molecular dynamics. Our simulations suggest that ${\mathrm{Au}}_{N}^{\ensuremath{-}}$ may exhibit a novel, freestanding planar liquid phase which dynamically coexists with a normal three-dimensional liquid. Upon cooling with experimentally realizable cooling rates, the entropy-favored three-dimensional liquid clusters often supercool and solidify into the ``wrong'' dimensionality. This indicates that experimental validation of theoretically predicted ${\mathrm{Au}}_{N}^{\ensuremath{-}}$ ground states might be more complicated than hitherto expected.

Appearance of Fermion-Condensation Quantum Phase Transition in Fermi Systems

2014

As high-\(T_c\) superconductors are represented primarily by 2D layered structures, in Sect. 5.1 we discuss the superconducting state of a 2D liquid of heavy electrons, and within the framework of Gor’kov microscopic equations construct the Green functions of the FC state. On the other hand, our study can easily be generalized to the 3D case. To show that there is no fundamental difference between the 2D and 3D cases, we derive Green’s functions for the 3D case in Sect. 5.1.1. In Sect. 5.2, we consider the dispersion law and lineshape of single-particle excitations. Section 5.3 is devoted to the behavior of heavy-electron liquid with FC in magnetic field. In Sect. 5.4, we analyze conditions…