Search results for "Pion decay constant"
showing 10 items of 15 documents
Low energy properties of color-flavor locked superconductors
2005
We discuss some low energy properties of color-flavor locked (CFL) superconductors. First, we study how an external magnetic field affects their Goldstone physics in the chiral limit, stressing that there is a long-range component of the field that penetrates the superconductor. We note that the most remarkable effect of the applied field is giving a mass to the charged pions and kaons. By estimating this effect, we see that for values $e B \sim 2 f_\pi \Delta$, where $\Delta$ is the quark gap, and $f_\pi$ the pion decay constant, the charged Goldstone bosons become so heavy, that they turn out to be unstable. The symmetry breaking pattern is then changed, agreeing with that of the magnetic…
Infrared enhanced analytic coupling and chiral symmetry breaking in QCD
2005
We study the impact on chiral symmetry breaking of a recently developed model for the QCD analytic invariant charge. This charge contains no adjustable parameters, other than the QCD mass scale $\Lambda$, and embodies asymptotic freedom and infrared enhancement into a single expression. Its incorporation into the standard form of the quark gap equation gives rise to solutions for the dynamically generated mass that display a singular confining behaviour at the origin. Using the Pagels-Stokar method we relate the obtained solutions to the pion decay constant $f_{\pi}$, and estimate the scale parameter $\Lambda$, in the presence of four active quarks, to be about 880 MeV.
Chiral restoration from pionic atoms?
2002
We evaluate widths and shifts of pionic atoms using a theoretical microscopical potential in which the pion decay constant $f_\pi$ is changed by an in--medium density dependent one ($f_\pi(\rho)$), predicted by different partial Chiral restoration calculations. We show that the results obtained for shifts and widths are worse than if this modification were not implemented. On the other hand, we argue that in microscopic many body approaches for the pion selfenergy, based on effective Lagrangians, the mechanisms responsible for the change of $f_\pi$ in the medium should be automatically incorporated. Therefore, the replacement of $f_\pi$ by $f_\pi(\rho)$ in the many body derivation of the mi…
Correlators of left charges and weak operators in finite volume chiral perturbation theory
2002
We compute the two-point correlator between left-handed flavour charges, and the three-point correlator between two left-handed charges and one strangeness violating \Delta I=3/2 weak operator, at next-to-leading order in finite volume SU(3)_L x SU(3)_R chiral perturbation theory, in the so-called epsilon-regime. Matching these results with the corresponding lattice measurements would in principle allow to extract the pion decay constant F, and the effective chiral theory parameter g_27, which determines the \Delta I = 3/2 amplitude of the weak decays K to \pi\pi as well as the kaon mixing parameter B_K in the chiral limit. We repeat the calculations in the replica formulation of quenched c…
Weak production of strange Ξ baryons off the nucleon
2019
The authors would like to thank Luis Alvarez-Ruso and Manuel Jose Vicente Vacas for useful discussions. One of the authors (MRA) would like to thank the pleasant hospitality at University of Granada where part of the work has been done.
Towards a determination of the chiral couplings at NLO in 1/N-C: L-8(r)(μ) and C-38(r)(μ)
2007
14 pages.-- ISI Article Identifier: 000244120200039.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0610290
Low-energy couplings of QCD from topological zero-mode wave functions
2003
By matching 1/m^2 divergences in finite-volume two-point correlation functions of the scalar or pseudoscalar densities with those obtained in chiral perturbation theory, we derive a relation between the Dirac operator zero-mode eigenfunctions at fixed non-trivial topology and the low-energy constants of QCD. We investigate the feasibility of using this relation to extract the pion decay constant, by computing the zero-mode correlation functions on the lattice in the quenched approximation and comparing them with the corresponding expressions in quenched chiral perturbation theory.
Form-factors and current correlators: chiral couplingsL10r(μ) andC87r(μ) at NLO in 1/NC
2008
Using the resonance chiral theory Lagrangian, we perform a calculation of the vector and axial-vector two-point functions at the next-to-leading order (NLO) in the 1/N-C expansion. We have analyzed these correlators within the single-resonance approximation and have also investigated the corrections induced by a second multiplet of vector and axial-vector resonance states. Imposing the correct QCD short-distance constraints, one determines the difference of the two correlators Pi(t) equivalent to Pi(VV)(t)-Pi(AA)(t) in terms of the pion decay constant and resonance masses. Its low momentum expansion fixes then the low-energy chiral couplings L 1 0 and C 8 7 at NLO, keeping full control of t…
The vector form factor at the next-to-leading order in 1/N(C): chiral couplings L9(mu) and C88(mu) - C90(mu)
2010
24 páginas, 3 figuras, 2 tablas.-- arXiv:1011.5771v1.
Vector Mesons and Dence Skyrmion Matter
2004
In our continuing effort to understand hadronic matter at high density, we have developed a unified field theoretic formalism for dense skyrmion matter using a single Lagrangian to describe simultaneously both matter and meson fluctuations and studied in-medium properties of hadrons. Dropping the quartic Skyrme term, we incorporate into our previous Lagrangian the vector mesons rho and omega in a form which is consistent with the symmetries of QCD. The results that we have obtained, reported here, expose a hitherto unsuspected puzzle associated with the role the omega meson plays at short distance. Since the omega meson couples to baryon density, it leads to a pseudo-gap scenario for the ch…