10,990 research outputs found
Hoelder Inequalities and QCD Sum-Rule Bounds on the Masses of Light Quarks
QCD Laplace Sum-Rules must satisfy a fundamental Hoelder inequality if they
are to consistently represent an integrated hadronic spectral function. The
Laplace sum-rules of pion currents is shown to violate this inequality unless
the and quark masses are sufficiently large, placing a lower bound on
, the SU(2)-invariant combination of the light-quark masses.Comment: 3 pages, latex, write-up of talk presented at DPF 200
Improvement of Renormalization-Scale Uncertainties Within Empirical Determinations of the b-Quark Mass
Accurate determinations of the MS-bar b-quark mass from
experimental data currently contain three
comparable sources of uncertainty; the experimental uncertainty from moments of
this cross-section, the uncertainty associated with , and the
theoretical uncertainty associated with the renormalization scale. Through
resummation of all logarithmic terms explicitly determined in the perturbative
series by the renormalization-group (RG) equation, it is shown that the
renormalization-scale dependence is virtually eliminated as a source of
theoretical uncertainty in . This resummation also reduces the
estimated effect of higher-loop perturbative contributions, further reducing
the theoretical uncertainties in . Furthermore, such resummation
techniques improve the agreement between the values of the MS-bar b-quark mass
extracted from the various moments of [], obviating the need to
choose an optimummoment for determining . Resummation techniques are
also shown to reduce renormalization-scale dependence in the relation between
b-quark MS-bar and pole mass and in the relation between the pole and
mass.Comment: 19 pages, latex2e, 6 eps figures contained in latex file. Errors
corrected in equations (20)--(22
Higher Order Stability of a Radiatively Induced 220 GeV Higgs Mass
The effective potential for radiatively broken electroweak symmetry in the
single Higgs doublet Standard Model is explored to four sequentially subleading
logarithm-summation levels (5-loops) in the dominant Higgs self-interaction
couplant . We augment these results with all contributing leading
logarithms in the remaining large but sub-dominant Standard Model couplants
(t-quark, QCD and gauge couplants) as well as next to
leading logarithm contributions from the largest of these, the t-quark and QCD
couplants. Order-by-order stability is demonstrated for earlier leading
logarithm predictions of an order 220 GeV Higgs boson mass in conjunction with
fivefold enhancement of the value for over that anticipated from
conventional spontaneous symmetry breaking.Comment: revtex, 6 pages. Analysis and text is expanded in revised versio
Results from the Blazar Monitoring Campaign at the Whipple 10m Gamma-ray Telescope
In September 2005, the observing program of the Whipple 10 m gamma-ray
telescope was redefined to be dedicated almost exclusively to AGN monitoring.
Since then the five Northern Hemisphere blazars that had already been detected
at Whipple are monitored routinely each night that they are visible. Thanks to
the efforts of a large number of multiwavelength collaborators, the first year
of this program has been very successful. We report here on the analysis of
Markarian 421 observations taken from November, 2005 to May, 2006 in the
gamma-ray, X-ray, optical and radio bands.Comment: 4 pages; contribution to the 30th International Cosmic Ray
Conference, Merida, Mexico, July 200
Constraints on QCD sum-rules from the Hölder inequalities
A new technique based on H\"older's integral inequality is applied to QCD sum-rules to provide fundamental constraints on the sum-rule parameters. These constraints must be satisfied if the sum-rules are to consistently describe integrated physical cross-sections, but these constraints do not require any experimental data and therefore can be applied to any hadronic spectral function. As an illustration of this technique the Laplace sum-rules of the light-quark correlation function for the vector and the axial-vector currents are examined in detail. We find examples of inconsistency between the inequalities and sum-rule parameters used in some previous analyses of the vector and axial-vector channels
NLTT5306: The shortest Period Detached White Dwarf + Brown Dwarf Binary
We have spectroscopically confirmed a brown dwarf mass companion to the
hydrogen atmosphere white dwarf NLTT5306. The white dwarf's atmospheric
parameters were measured using Sloan Digital Sky Survey and X-Shooter
spectroscopy as T_eff=7756+/-35K and log(g)=7.68+/-0.08, giving a mass for the
primary of M_WD=0.44+/-0.04 M_sun, at a distance of 71+/-4 pc with a cooling
age of 710+/-50 Myr. The existence of the brown dwarf secondary was confirmed
through the near-infrared arm of the X-Shooter data and a spectral type of
dL4-dL7 was estimated using standard spectral indices. Combined radial velocity
measurements from the Sloan Digital Sky Survey, X-Shooter and the Hobby-Eberly
Telescope's High Resolution Spectrograph of the white dwarf gives a minimum
mass of 56+/-3 M_jup for the secondary, confirming the substellar nature. The
period of the binary was measured as 101.88+/-0.02 mins using both the radial
velocity data and i'-band variability detected with the INT. This variability
indicates 'day' side heating of the brown dwarf companion. We also observe
H{\alpha} emission in our higher resolution data in phase with the white dwarf
radial velocity, indicating this system is in a low level of accretion, most
likely via a stellar wind. This system represents the shortest period white
dwarf + brown dwarf binary and the secondary has survived a stage of common
envelope evolution, much like its longer period counterpart, WD0137-349. Both
systems likely represent bona-fide progenitors of cataclysmic variables with a
low mass white dwarf and a brown dwarf donor.Comment: 9 pages, 11 figures, accepted for publication in MNRA
Land use change detection with LANDSAT-2 data for monitoring and predicting regional water quality degradation
The author has identified the following significant results. Comparison between LANDSAT 1 and 2 imagery of Arkansas provided evidence of significant land use changes during the 1972-75 time period. Analysis of Arkansas historical water quality information has shown conclusively that whereas point source pollution generally can be detected by use of water quality data collected by state and federal agencies, sampling methodologies for nonpoint source contamination attributable to surface runoff are totally inadequate. The expensive undertaking of monitoring all nonpoint sources for numerous watersheds can be lessened by implementing LANDSAT change detection analyses
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