929 research outputs found
Bottom-Tau Yukawa Unification in the Next-to-Minimal Supersymmetric Standard Model
We discuss the unification of the bottom quark and tau lepton Yukawa
couplings within the framework of the next-to-minimal supersymmetric standard
model. We compare the allowed regions of the - plane to those
in the minimal supersymmetric standard model, and find that over much of the
parameter space the deviation between the predictions of two models is small,
and nearly always much less than the effect of current theoretical and
experimental uncertainties in the bottom quark mass and the strong coupling
constant. However over some regions of parameter space top-bottom Yukawa
unification cannot be achieved. We also discuss the scaling of the light
fermion masses and mixing angles, and show that to within current uncertainties
the results of recent texture analyses performed for the minimal model also
apply to the next-to-minimal model.Comment: Southampton preprint SHEP 93/94-15, This is a latex file with
postscript figures attached to the end of the documen
Weak force detection using a double Bose-Einstein condensate
A Bose-Einstein condensate may be used to make precise measurements of weak
forces, utilizing the macroscopic occupation of a single quantum state. We
present a scheme which uses a condensate in a double well potential to do this.
The required initial state of the condensate is discussed, and the limitations
on the sensitivity due to atom collisions and external coupling are analyzed.Comment: 12 pages, 2 figures, Eq.(41) has been correcte
Bi-large Neutrino Mixing and Mass of the Lightest Neutrino from Third Generation Dominance in a Democratic Approach
We show that both small mixing in the quark sector and large mixing in the
lepton sector can be obtained from a simple assumption of universality of
Yukawa couplings and the right-handed neutrino Majorana mass matrix in leading
order. We discuss conditions under which bi-large mixing in the lepton sector
is achieved with a minimal amount of fine-tuning requirements for possible
models. From knowledge of the solar and atmospheric mixing angles we determine
the allowed values of sin \theta_{13}. If embedded into grand unified theories,
the third generation Yukawa coupling unification is a generic feature while
masses of the first two generations of charged fermions depend on small
perturbations. In the neutrino sector, the heavier two neutrinos are model
dependent, while the mass of the lightest neutrino in this approach does not
depend on perturbations in the leading order. The right-handed neutrino mass
scale can be identified with the GUT scale in which case the mass of the
lightest neutrino is given as (m_{top}^2/M_{GUT}) sin^2 \theta_{23} sin^2
\theta_{12} in the limit sin \theta_{13} = 0. Discussing symmetries we make a
connection with hierarchical models and show that the basis independent
characteristic of this scenario is a strong dominance of the third generation
right-handed neutrino, M_1, M_2 < 10^{-4} M_3, M_3 = M_{GUT}.Comment: typos correcte
A tale of two capitalisms: preliminary spatial and historical comparisons of homicide rates in Western Europe and the USA
This article examines comparative homicide rates in the United States and Western Europe in an era of increasingly globalized neoliberal economics. The main finding of this preliminary analysis is that historical and spatial correlations between distinct forms of political economy and homicide rates are consistent enough to suggest that social democratic regimes are more successful at fostering the socio-cultural conditions necessary for reduced homicide rates. Thus Western Europe and all continents and nations should approach the importation of American neo-liberal economic policies with extreme caution. The article concludes by suggesting that the indirect but crucial causal connection between political economy and homicide rates, prematurely pushed into the background of criminological thought during the âcultural turnâ, should be returned to the foreground
Radiation dose differences between thoracic radiotherapy planning CT and thoracic diagnostic CT scans
Purpose: To compare the absorbed dose from computed tomography (CT) in radiotherapy planning (RP CT) against those from diagnostic CT (DG CT) examinations and to explore the possible reasons for any dose differences.
Method: Two groups of patients underwent CT-scans of the thorax with either DG-CT (n=55) or RP-CT (n=55). Patients from each group had similar weight and body mass index (BMI) and were divided into low (25). Parameters including CTDIvol, DLP and scan length were compared.
Results: The mean CTDIvol and DLP values from RP-CT (38.1 mGy, 1472 mGy·cm) are approximately four times higher than for DG-CT (9.63 mGy, 376.5 mGy·cm). For low BMI group, the CTDIvol in the RP-CT scans (36.4 mGy) is 6.3 times higher than the one in the DG-CT scans (5.8 mGy). For high BMI group, the CTDIvol in the RP-CT (39.6 mGy) is 2.5 times higher than the one in the DG-CT scans (15.8 mGy). In the DG-CT scans a strong negative linear correlation between noise index (NI) and mean CTDIvol was observed (r =-0.954, p=0.004); the higher NI, the lower CTDIvol. This was not the case in the RP-DG scans.
Conclusion: The absorbed radiation dose is significantly higher and less BMI dependent for RP-CT scans compared to DG-CT. Image quality requirements of the examinations should be researched to ensure that radiation doses are not unnecessarily high
Stereoscopic Analysis of the 19 May 2007 Erupting Filament
A filament eruption, accompanied by a B9.5 flare, coronal dimming and an EUV
wave, was observed by the Solar TERrestrial Relations Observatory (STEREO) on
19 May 2007, beginning at about 13:00 UT. Here, we use observations from the
SECCHI/EUVI telescopes and other solar observations to analyze the behavior and
geometry of the filament before and during the eruption. At this time, STEREO A
and B were separated by about 8.5 degrees, sufficient to determine the
three-dimensional structure of the filament using stereoscopy. The filament
could be followed in SECCHI/EUVI 304 A stereoscopic data from about 12 hours
before to about 2 hours after the eruption, allowing us to determine the 3D
trajectory of the erupting filament. From the 3D reconstructions of the
filament and the chromospheric ribbons in the early stage of the eruption,
simultaneous heating of both the rising filamentary material and the
chromosphere directly below is observed, consistent with an eruption resulting
from magnetic reconnection below the filament. Comparisons of the filament
during eruption in 304 A and Halpha show that when it becomes emissive in He
II, it tends to disappear in Halpha, indicating that the disappearance probably
results from heating or motion, not loss, of filamentary material.Comment: Accepted for publication in Solar Physic
On Yukawa quasi-unification with mu<0
Although recent data on the muon anomalous magnetic moment strongly disfavor
the constrained minimal supersymmetric standard model with mu<0, they cannot
exclude it because of theoretical ambiguities. We consider this model
supplemented by a Yukawa quasi-unification condition which allows an acceptable
b-quark mass. We find that the cosmological upper bound on the lightest
sparticle relic abundance is incompatible with the data on the branching ratio
of b-->s gamma, which is evaluated by including all the next-to-leading order
corrections. Thus, this scheme is not viable.Comment: 4 pages including 3 figures, Revte
Softening the Supersymmetric Flavor Problem in Orbifold GUTs
The infra-red attractive force of the bulk gauge interactions is applied to
soften the supersymmetric flavor problem in the orbifold SU(5) GUT of Kawamura.
Then this force aligns in the infra-red regime the soft supersymmetry breaking
terms out of their anarchical disorder at a fundamental scale, in such a way
that flavor-changing neutral currents as well as dangerous CP-violating phases
are suppressed at low energies. It is found that this dynamical alignment is
sufficiently good compared with the current experimental bounds, as long as the
diagonalization matrices of the Yukawa couplings are CKM-like.Comment: 15 pages,4 figure
Charged Higgs bosons in the Next-to MSSM (NMSSM)
The charged Higgs boson decays and
are studied in the framework of the next-to Minimal Supersymmetric Standard
Model (NMSSM). It is found that the decay rate for can
exceed the rates for the and channels both below and above
the top-bottom threshold. The dominance of is most readily
achieved when has a large doublet component and small mass. We also study
the production process at the LHC followed by the decay
which leads to the signature . We suggest
that is a promising discovery channel for a light charged
Higgs boson in the NMSSM with small or moderate and dominant decay
mode . This signature can also arise from
the Higgsstrahlung process followed by the decay . It is shown that there exist regions of parameter space where these
processes can have comparable cross sections and we suggest that their
respective signals can be distinguished at the LHC by using appropriate
reconstruction methods.Comment: 20 pages, 22 eps figures, more reference adde
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