5,612 research outputs found
Staggered Heavy Baryon Chiral Perturbation Theory
Although taste violations significantly affect the results of staggered
calculations of pseudoscalar and heavy-light mesonic quantities, those entering
staggered calculations of baryonic quantities have not been quantified. Here I
develop staggered chiral perturbation theory in the light-quark baryon sector
by mapping the Symanzik action into heavy baryon chiral perturbation theory.
For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are
calculated to third order in partially quenched and fully dynamical staggered
chiral perturbation theory. To this order the expansion includes the leading
chiral logarithms, which come from loops with virtual decuplet-like states, as
well as terms the order of the cubed pion mass, which come from loops with
virtual octet-like states. Taste violations enter through the meson propagators
in loops and tree-level terms the order of the squared lattice spacing. The
pattern of taste symmetry breaking and the resulting degeneracies and mixings
are discussed in detail. The resulting chiral forms are appropriate to lattice
results obtained with operators already in use and could be used to study the
restoration of taste symmetry in the continuum limit. I assume that the fourth
root of the fermion determinant can be incorporated in staggered chiral
perturbation theory using the replica method.Comment: 54 pages; v2: corrected discussion in Sec. III.C, conclusions
unchange
Standard-model particles and interactions from field equations on spin 9+1 dimensional space
We consider a Dirac equation set on an extended spin space that contains
fermion and boson solutions. At given dimension, it determines the scalar
symmetries. The standard field equations can be equivalently written in terms
of such degrees of freedom, and are similarly constrained. At 9+1 dimensions,
the SU(3) X SU(2)_L X U(1) gauge groups emerge, as well as solution
representations with quantum numbers of related gauge bosons, leptons, quarks,
Higgs-like particles and others as lepto-quarks. Information on the coupling
constants is also provided; e. g., for the hypercharge g'=(1/2) sqrt(3/5) ~
>.387, at tree level.Comment: 13 pages, Fig. 1(a)-(d
Goldstone boson counting in linear sigma models with chemical potential
We analyze the effects of finite chemical potential on spontaneous breaking
of internal symmetries within the class of relativistic field theories
described by the linear sigma model. Special attention is paid to the emergence
of ``abnormal'' Goldstone bosons with quadratic dispersion relation. We show
that their presence is tightly connected to nonzero density of the Noether
charges, and formulate a general counting rule. The general results are
demonstrated on an SU(3)xU(1) invariant model with an SU(3)-sextet scalar
field, which describes one of the color-superconducting phases of QCD.Comment: 10 pages, REVTeX4, 4 eps figures, v2: general discussion in Sec. IV
expanded and improved, references added, other minor corrections throughout
the tex
Comment on "The Phenomenology of a Nonstandard Higgs Boson in W_L W_L Scattering"
We show that in Composite Higgs models, the coupling of the Higgs resonance
to a pair of bosons is weaker than the corresponding Standard Model
coupling, provided the Higgs arises from electroweak doublets only. This is
partly due to the effects of the nonlinear realization of the chiral symmetries
at the compositeness scale.Comment: 6 pages, BU-HEP 94-2
Power law in a gauge-invariant cut-off regularisation
We study one-loop quantum corrections of a compactified Abelian 5d gauge
field theory. We use a cut-off regularisation procedure which respects the
symmetries of the model, i.e. gauge invariance, exhibits the expected
power-like divergences and therefore allows the derivation of power-law
behavior of the effective 4d gauge coupling in a coherent manner.Comment: 5 pages, 1 figure, 5 graphs, few references added, to appear in
Phys.Rev. Rapid Communication
Comparison of 1/mQ^2 Corrections in Mesons and Baryons
We extend our relativistic quark model to the study of the decay Lambda_b ->
Lambda_c ell nu and verify that the model satisfies the heavy-quark symmetry
constraints at order 1/mQ^2. We isolate a strong dependence on a parameter
which measures the relative distortion in the light-quark wave functions of the
Lambda_b and Lambda_c. This parameter and the 1/mQ^2 corrections turn out to be
small. The dependence on a corresponding parameter in the meson case leads to
large 1/mQ^2 corrections.Comment: 9 pages, LaTeX, 3 self-contained LaTeX figures in separate fil
Factorization, Power Corrections, and the Pion Form Factor
This letter is an investigation of the pion form factor utilizing recently
developed effective field theory techniques. The primary results reported are:
Both the transition and electromagnetic form factors are corrected at order
. However, these corrections only arise due to time ordered products
which are sensitive to soft components of the pion. The usual higher twist wave
function corrections contribute only at order , when the quark
mass vanishes. In the case of the electromagnetic form factor the
power correction is enhanced by a power of relative to the
leading order result of Brodsky and Lepage, if the scale is
non-perturbative. This enhanced correction could explain the discrepancy with
the data.Comment: Published, extended, versio
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