4,408 research outputs found
More on Symmetries in Heavy Quark Effective Theory
We present a general classification of all normal and ``chiral" symmetries of
heavy quark effective theories. Some peculiarities and conondrums associated
with the ``chiral" symmetries are discussed.Comment: 15 pages, preprint UR-1320, ER40685-77
Anthropic tuning of the weak scale and of m_u/m_d in two-Higgs-doublet models
It is shown that in a model in which up-type and down-type fermions acquire
mass from different Higgs doublets, the anthropic tuning of the Higgs mass
parameters can explain the fact that the observed masses of the and
quarks are nearly the same with slightly heavier. If Yukawa couplings are
assumed not to "scan" (vary among domains), this would also help explain why
the t quark is much heavier than the b quark. It is also pointed out that the
existence of dark matter invalidates some earlier anthropic arguments against
the viability of domains where the Standard Model Higgs has positive ,
but makes other even stronger arguments possible.Comment: 31 pages, 7 figure
A Truly Minimal Left-Right Symmetric Extension of the Standard Model
By invoking the existence of a general custodial O(2) symmetry, a minimal
Left-Right symmetric model based on the gauge group G=SU(2)L SU(2)R U(1)BL is
shown to require the existence of only two physical Higgs bosons. The lighter
Higgs is predicted to have a small mass which could be evaluated by standard
perturbation theory. The fermionic mass matrices are recovered by insertion of
ad hoc fermion-Higgs interactions. The model is shown to be undistinguishable
from the standard model at the currently reachable energies.Comment: 1 figure in a separate ps fil
B Meson Transitions into Higher Mass Charmed Resonances
We use QCD sum rules to estimate the universal form factors describing the
semileptonic B decays into excited charmed resonances, such as the and
states and belonging to the heavy
quark doublet, and the and states and
belonging to the s_\ell^P={5\2}^- doublet.Comment: LaTex, 14 pages, 1 figur
A Traceable Ground to On-Orbit Radiometric Calibration System for the Solar Reflective Wavelength Region
This paper describes the combination of a Mie scattering spectral BSDF and BTDF albedo standard whose calibration is traceable to the NIST SIRCUS Facility or the NIST STARR II Facility. The Space-based Calibration Transfer Spectroradiometer (SCATS) sensor uses a simple, invariant optical configuration and dedicated narrow band spectral channel modules to provide very accurate, polarization-insensitive, stable measurements of earth albedo and lunar disk albedo. Optical degradation effects on calibration stability are eliminated through use of a common optical system for observations of the Sun, Earth, and Moon. The measurements from space would be traceable to SI units through preflight calibrations of radiance and irradiance at NIST's SIRCUS facility and the invariant optical system used in the sensor. Simultaneous measurements are made in multiple spectral channels covering the solar reflective wavelength range of 300 nm to 2.4 microns. The large dynamic range of signals is handled by use of single-element, highly-linear detectors, stable discrete electronic components, and a non imaging optical configuration. Up to 19 spectral modules can be mounted on a single-axis drive to give direct pointing at the Earth and at least once per orbit view of the Sun and Moon. By observing the Sun on every orbit, the most stringent stability requirements of the system are limited to short time periods. The invariant optical system for both radiance and irradiance measurements also give excellent transfer to-orbit SI traceability. Emerging instrumental requirements for remotely sensing tropospheric trace species have led to a rethinking by some of the paradigm for Systeme International d'Unites (SI) traceability of the spectral irradiance and radiance radiometric calibrations to spectral albedo (sr(exp -1)) which is not a SI unit. In the solar reflective wavelength region the spectral albedo calibrations are tied often to either the spectral albedo of a solar diffuser or the Moon. This new type of Mie scattering diffuser (MSD) is capable of withstanding high temperatures, and is more Lambertian than Spectralon(tm). It has the potential of covering the entire solar reflective wavelength region. Laboratory measurements have shown that the specular reflectance component is negligible, and indicate that internal absorption by multiple scattering is small. This MSD, a true volume diffuser, exhibits a high degree of radiometric stability which suggests that measurements at the National Institute of Standards and Technology (NIST) could provide a spectral albedo standard. Measurements have been made of its radiometric stability under a simulated space environment of high energy gamma rays, high energy protons, and UV radiation from ambient down to the vacuum ultraviolet H Lyman alpha at 121.6 nm for its eventual use in space as a solar diffuser
Three Jet Events and New Strong Couplings at LEP and NLC
We study the effects of new dimension--6 operators, resulting from a general
invariant effective Lagrangian, on
three jet production at LEP and at the Next Linear Collider. Contributions to
the total event rate and to some event shape variables are analysed in order to
establish bounds on these operators.Comment: 5 pages, LaTeX, 1 Figur
Baryon Masses at Second Order in Chiral Perturbation Theory
We analyze the baryon mass differences up to second order in chiral
perturbation theory, including the effects of decuplet intermediate states. We
show that the Coleman--Glashow relation has computable corrections of order
. These corrections are numerically small, and in agreement
with the data. We also show that corrections to the equal-spacing rule
are dominated by electromagnetic contributions, and that the Gell-Mann--Okubo
formula has non-analytic corrections of order which cannot be
computed from known matrix elements. We also show that the baryon masses cannot
be used to extract model-independent information about the current quark
masses.Comment: 11 pages, 1 uu-encoded figure, LBL-34779, UCB-PTH-93/2
Systematic Low-Energy Effective Field Theory for Magnons and Holes in an Antiferromagnet on the Honeycomb Lattice
Based on a symmetry analysis of the microscopic Hubbard and t-J models, a
systematic low-energy effective field theory is constructed for hole-doped
antiferromagnets on the honeycomb lattice. In the antiferromagnetic phase,
doped holes are massive due to the spontaneous breakdown of the
symmetry, just as nucleons in QCD pick up their mass from spontaneous chiral
symmetry breaking. In the broken phase the effective action contains a
single-derivative term, similar to the Shraiman-Siggia term in the square
lattice case. Interestingly, an accidental continuous spatial rotation symmetry
arises at leading order. As an application of the effective field theory we
consider one-magnon exchange between two holes and the formation of two-hole
bound states. As an unambiguous prediction of the effective theory, the wave
function for the ground state of two holes bound by magnon exchange exhibits
-wave symmetry.Comment: 33 pages, 6 figure
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group
We revisit an old idea that gravity can be unified with Yang-Mills theory by
enlarging the gauge group of gravity formulated as gauge theory. Our starting
point is an action that describes a generally covariant gauge theory for a
group G. The Minkowski background breaks the gauge group by selecting in it a
preferred gravitational SU(2) subgroup. We expand the action around this
background and find the spectrum of linearized theory to consist of the usual
gravitons plus Yang-Mills fields charged under the centralizer of the SU(2) in
G. In addition, there is a set of Higgs fields that are charged both under the
gravitational and Yang-Mills subgroups. These fields are generically massive
and interact with both gravity and Yang-Mills sector in the standard way. The
arising interaction of the Yang-Mills sector with gravity is also standard.
Parameters such as the Yang-Mills coupling constant and Higgs mass arise from
the potential function defining the theory. Both are realistic in the sense
explained in the paper.Comment: 61 pages, no figures (v2) some typos correcte
Vector Meson Exchanges and CP Asymmetry in
Using a current algebra framework, we discuss the contribution of vector
meson exchanges to the CP violating asymmetry in the decay
, resulting from the interference of the
amplitude with the radiative correction
.Comment: 9 pages (plain-TEX), IC/93/186, UTS-DFT-93-18, (two figures not
included
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