166 research outputs found
SUSY-GUTs, SUSY-Seesaw and the Neutralino Dark Matter
We will consider a SUSY-SU(5) with one right-handed neutrino with a large top
like Yukawa coupling. Assuming universal soft masses at high scale we compute
the low-energy spectrum and subsequently the neutralino LSP relic density
taking also into consideration SU(5) as well as the see-saw running effects
above the gauge coupling unification scale. We found that there exists no
viable region in parameter space for \tan\beta \ler ~35. The
coannihilation process starts becoming efficient for \tan\beta \ger 35-40.
However, this process is significantly constrained by the limited range in
which the stau is lighter than the neutralino. In fact, for a given
we find that there exists an upper bound on the lightest neutralino mass
() in this region. The A-pole funnel region appears at very large
, while the focus-point region does not make an
appearance till large (), namely a few TeV. Large terms at
high scale can lead to extended regions consistent with WMAP constraints and
remove the upper bounds in the stau coannihilation regions.Comment: 18 pages, 7 figures; references added, figure added, improved
discussions in text, to appear in JHE
Smearing Formula for Higher-Order Effective Classical Potentials
In the variational approach to quantum statistics, a smearing formula
describes efficiently the consequences of quantum fluctuations upon an
interaction potential. The result is an effective classical potential from
which the partition function can be obtained by a simple integral. In this
work, the smearing formula is extended to higher orders in the variational
perturbation theory. An application to the singular Coulomb potential exhibits
the same fast convergence with increasing orders that has been observed in
previous variational perturbation expansions of the anharmonic oscillator with
quartic potential.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at
http://www.physik.fu-berlin.de/~kleinert/kleiner_re267/preprint.htm
Inclusive Jet Production, Parton Distributions, and the Search for New Physics
Jet production at the Tevatron probes some of the smallest distance scales
currently accessible. A gluon distribution that is enhanced at large x compared
to previous determinations provides a better description of the Run 1b jet data
from both CDF and D0. However, considerable uncertainty still remains regarding
the gluon distribution at high x. In this paper, we examine the effects of this
uncertainty, and of the remaining uncertainties in the NLO QCD theory, on jet
cross section comparisons to Run 1b data. We also calculate the range of
contributions still possible from any new physics. Predictions are also made
for the expanded kinematic range expected for the ongoing Run 2 at the Tevatron
and for the LHC.Comment: 50 pages, 31 figures, RevTe
The Higgs intense--coupling regime in constrained SUSY models and its astrophysical implications
We analyze the Higgs intense--coupling regime, in which all Higgs particles
of the Minimal Supersymmetric Standard Model are light with masses of the same
order and the value of \tb the ratio of vacuum expectation values of the two
Higgs fields is large, in the framework of Supergravity scenarios with
non--universal soft Supersymmetry breaking scalar masses in the Higgs sector.
In particular, we calculate the relic density abundance of the lightest
neutralino candidate for cold dark matter and the rates in direct and indirect
detection at present and future experiments. We first show that while in the
mSUGRA model this regime is disfavored by present data, there are regions in
the parameter space of models with non--universal Higgs masses where it can
occur. We then show that because of the large value of and the
relatively low values of the neutral Higgs boson masses, the cross section for
neutralino--nucleon scattering is strongly enhanced in this regime and would
allow for the observation of a signal in direct detection experiments such as
CDMS--Soudan. The expected sensitivity of gamma--ray detectors like GLAST might
be also sufficient to observe the annihilation of neutralinos in such a regime.Comment: 19 pages, 5 figure
The relationship between alcohol consumption and related harm among young university students
Issue addressed: Research has shown that Australian university students consume alcohol at a higher level than their peers from the general population and are therefore more likely to witness and experience alcohol-related harm. This study measured the prevalence of alcohol consumption among 18–24-year-old university students and the association between alcohol consumption and witnessed and experienced harms. Methods: A random cross-sectional sample of university students aged 18–24 years (n = 2466) was recruited via the University Survey Office and through random intercept at campus market day. All participants completed an online survey that included the Alcohol Use Disorders Identification Test, Alcohol Problems Scale and an additional scale measuring witnessed harm. Results: Principal Components Analysis revealed three factors within the Alcohol Problems Scale; i.e. Criminal and Aggressive Behaviour, Health and Emotional Harms and Sexual Harms. Students who consume alcohol at high-risk levels were significantly more likely to score highly on each factor, 1.6 times more likely to experience harm and 1.1 times more likely to witness harm than students who consume alcohol at low-risk levels. Conclusions: The positive association between alcohol consumption and alcohol-related harm supports previous findings. This study adds previous research through the categorisation of harm into factors
Evidence for Planet-induced Chromospheric Activity on HD 179949
We have detected the synchronous enhancement of Ca II H & K emission with the
short-period planetary orbit in HD 179949. High-resolution spectra taken on
three observing runs extending more than a year show the enhancement coincides
with phi ~ 0 (the sub-planetary point) of the 3.093-day orbit with the effect
persisting for more than 100 orbits. The synchronous enhancement is consistent
with planet-induced chromospheric heating by magnetic rather than tidal
interaction. Something which can only be confirmed by further observations.
Independent observations are needed to determine whether the stellar rotation
is sychronous with the planet's orbit. Of the five 51 Peg-type systems
monitored, HD 179949 shows the greatest chromospheric H & K activity. Three
others show significant nightly variations but the lack of any phase coherence
prevents us saying whether the activity is induced by the planet. Our two
standards, tau Ceti and the Sun, show no such nightly variations.Comment: 10 pages, 6 figures. Submitted to Ap
International Reference Life Cycle Data System (ILCD) Handbook: Review Schemes for Life Cycle Assessment
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