2,795 research outputs found
Higgs Mass in the Standard Model from Coupling Constant Reduction
Plausible interrelations between parameters of the standard model are
studied. The empirical value of the top quark mass, when used in the
renormalization group equations, suggests that the ratio of the colour SU(3)
gauge coupling , and the top coupling is independent of the
renormalization scale. On the other hand, variety of top-condensate models
suggest that the Higgs self-coupling is proportional to .
Invoking the requirement that the ratio is independent of
the renormalization scale , fixes the Higgs mass. The pole mass of the Higgs
[which differs from the renormalization group mass by a few percent] is found
to be GeV for the one-loop equations and GeV for the
two-loop equations.Comment: 17 pages RevTeX including 7 figure
Chiral Lagrangian Parameters for Scalar and Pseudoscalar Mesons
The results of a high-statistics study of scalar and pseudoscalar meson
propagators in quenched lattice QCD are presented. For two values of lattice
spacing, ( fm) and 5.9 ( fm), we
probe the light quark mass region using clover improved Wilson fermions with
the MQA pole-shifting ansatz to treat the exceptional configuration problem.
The quenched chiral loop parameters and are determined
from a study of the pseudoscalar hairpin correlator. From a global fit to the
meson correlators, estimates are obtained for the relevant chiral Lagrangian
parameters, including the Leutwyler parameters and . Using the
parameters obtained from the singlet and nonsinglet pseudoscalar correlators,
the quenched chiral loop effect in the nonsinglet scalar meson correlator is
studied. By removing this QCL effect from the lattice correlator, we obtain the
mass and decay constant of the ground state scalar, isovector meson .Comment: 36 pages, 12 figures, LaTe
Quenched divergences in the deconfined phase of SU(2) gauge theory
The spectrum of the overlap Dirac operator in the deconfined phase of
quenched gauge theory is known to have three parts: exact zeros arising from
topology, small nonzero eigenvalues that result in a non-zero chiral
condensate, and the dense bulk of the spectrum, which is separated from the
small eigenvalues by a gap. In this paper, we focus on the small nonzero
eigenvalues in an SU(2) gauge field background at and . This
low-lying spectrum is computed on four different spatial lattices (,
, , and ). As the volume increases, the small eigenvalues
become increasingly concentrated near zero in such a way as to strongly suggest
that the infinite volume condensate diverges.Comment: 12 pages, 3 figures, version to appear in Physical Review
Quenched Chiral Artifacts for Wilson-Dirac Fermions
We examine artifacts associated with the chiral symmetry breaking induced
through the use of Wilson-Dirac fermions in lattice Monte Carlo computations.
For light quark masses, the conventional quenched theory can not be defined
using direct Monte Carlo methods due to the existence of nonintegrable poles in
physical quantities. These poles are associated with the real eigenvalue
spectrum of the Wilson-Dirac operator. We show how this singularity structure
can be observed in the analysis of both QED in two dimensions and QCD in four
dimensions.Comment: 32 pages (Latex) including 13 figures (EPS
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Microgravimetric immunosensor for direct detection of aerosolized influenza A virus particles.
The development and characterization of a quartz crystal microbalance (QCM) sensor for the direct detection of aerosolized influenza A virions is reported. Self-assembled monolayers (SAMs) of mercaptoundecanoic acid (MUA) are formed on QCM gold electrodes to provide a surface amenable for the immobilization of anti-influenza A antibodies using NHS/EDC coupling chemistry. The surface-bound antibody provides a selective and specific sensing interface for the capture of influenza virions. A nebulizer is used to create aerosolized samples and is directly connected to a chamber housing the antibody-modified crystal ("immunochip"). Upon exposure to the aerosolized virus, the interaction between the antibody and virus leads to a dampening of the oscillation frequency of the quartz crystal. The magnitude of frequency change is directly related to virus concentration. Control experiments using aerosols from chicken egg allantoic fluid and an anti-murine antibody based immunosensor confirm that the observed signal originates from specific viral binding on the chip surface. Step-by-step surface modification of MUA assembly, antibody attachment, and antibody-virus interaction are characterized by atomic force microscopy (AFM) imaging analysis. Using the S/N = 3 principle, the limit of detection is estimated to be 4 virus particles/mL. The high sensitivity and real-time sensing scheme presented here can play an important role in the public health arena by offering a new analytical tool for identifying bio-contaminated areas and assisting in timely patient diagnosis
Neutrino masses and mixings
We propose a novel theoretical understanding of neutrino masses and mixings,
which is attributed to the intrinsic vector-like feature of the regularized
Standard Model at short distances. We try to explain the smallness of Dirac
neutrino masses and the decoupling of the right-handed neutrino as a free
particle. Neutrino masses and mixing angles are completely related to each
other in the Schwinger-Dyson equations for their self-energy functions. The
solutions to these equations and a possible pattern of masses and mixings are
discussed.Comment: LaTex 11 page
A relativistic calculation of super-Hubble suppression of inflation with thermal dissipation
We investigated the evolution of the primordial density perturbations
produced by inflation with thermal dissipation. A full relativistic analysis on
the evolution of initial perturbations from the warm inflation era to a
radiation-dominated universe has been developed. The emphasis is on tracking
the ratio between the adiabatic and the isocurvature mode of the initial
perturbations. This result is employed to calculate a testable factor: the
super-Hubble suppression of the power spectrum of the primordial perturbations.
We show that based on the warm inflation scenario, the super-Hubble suppression
factor, , for an inflation with thermal dissipation is at least 0.5. This
prediction does not depend on the details of the model parameters. If is
larger than 0.5, it implies that the friction parameter is larger than
the Hubble expansion parameter during the inflation era.Comment: 22 pages, 3 figures, use RevTex, accepted by Class. Quant. Gra
Quantum properties of general gauge theories with composite and external fields
The generating functionals of Green's functions with composite and external
fields are considered in the framework of BV and BLT quantization methods for
general gauge theories. The corresponding Ward identities are derived and the
gauge dependence is investigatedComment: 24 pages, LATEX, slightly changed to clarify the essential new aspect
concerning composite fields depending on external ones; added formulas
showing lack of (generalized) nilpotence of operators appearing in the Ward
identitie
1/N_c Corrections to the Hadronic Matrix Elements of Q_6 and Q_8 in K --> pi pi Decays
We calculate long-distance contributions to the amplitudes A(K^0 --> pi pi,
I) induced by the gluon and the electroweak penguin operators Q_6 and Q_8,
respectively. We use the 1/N_c expansion within the effective chiral lagrangian
for pseudoscalar mesons. In addition, we adopt a modified prescription for the
identification of meson momenta in the chiral loop corrections in order to
achieve a consistent matching to the short-distance part. Our approach leads to
an explicit classification of the loop diagrams into non-factorizable and
factorizable, the scale dependence of the latter being absorbed in the
low-energy coefficients of the effective theory. Along these lines we calculate
the one-loop corrections to the O(p^0) term in the chiral expansion of both
operators. In the numerical results, we obtain moderate corrections to
B_6^(1/2) and a substantial reduction of B_8^(3/2).Comment: 32 pages, LaTeX, 8 eps figures. One reference added, to appear in
Phys. Rev.
Anomalous Chiral Behavior in Quenched Lattice QCD
A study of the chiral behavior of pseudoscalar masses and decay constants is
carried out in quenched lattice QCD with Wilson fermions. Using the modified
quenched approximation (MQA) to cure the exceptional configuration problem,
accurate results are obtained for pion masses as low as 200 MeV. The
anomalous chiral log effect associated with quenched loops is studied
in both the relation between vs. and in the light-mass
behavior of the pseudoscalar and axial vector matrix elements. The size of
these effects agrees quantitatively with a direct measurement of the
hairpin graph, as well as with a measurement of the topological susceptibility,
thus providing several independent and quantitatively consistent determinations
of the quenched chiral log parameter . For with
clover-improved fermions all results are consistent with
.Comment: 51 pages, 20 figures, Late
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