3,372 research outputs found
Non-renormalizable Yukawa Interactions and Higgs Physics
We explore a scenario in the Standard Model in which dimension four Yukawa
couplings are either forbidden by a symmetry, or happen to be very tiny, and
the Yukawa interactions are dominated by effective dimension six interactions.
In this case, the Higgs interactions to the fermions are enhanced in a large
way, whereas its interaction with the gauge bosons remains the same as in the
Standard Model. In hadron colliders, Higgs boson production via gluon gluon
fusion increases by a factor of nine. Higgs decay widths to fermion
anti-fermion pairs also increase by the same factor, whereas the decay widths
to photon photon and gamma Z are reduced. Current Tevatron exclusion range for
the Higgs mass increases to ~ 142-200 GeV in our scenario, and new physics must
appear at a scale below a TeV.Comment: 5 pages, 4 figure
Quark lepton unification in higher dimensions
The idea of unifying quarks and leptons in a gauge symmetry is very
appealing. However, such an unification gives rise to leptoquark type gauge
bosons for which current collider limits push their masses well beyond the TeV
scale. We present a model in the framework of extra dimensions which breaks
such quark-lepton unification symmetry via compactification at the TeV scale.
These color triplet leptoquark gauge bosons, as well as the new quarks present
in the model, can be produced at the LHC with distinctive final state
signatures. These final state signals include high p_T multi-jets and
multi-leptons with missing energy, monojets with missing energy, as well as the
heavy charged particles passing through the detectors, which we also discuss
briefly. The model also has a neutral Standard Model singlet heavy lepton which
is stable, and can be a possible candidate for the dark matter.Comment: 28 pages, 5 eps figure
Biased discrete symmetry and domain wall problem
We reconsider a cosmological evolution of domain walls produced by
spontaneous breaking of an approxime discrete symmetry. We show, that domain
walls may never collapse even if the standard bound on the vacuum energy
asymmetry is satisfied. Instead of disappearing, these defects may form stable
``bound states'' - double wall systems. Possible stability of such a wall is a
dynamical question and consequently restricts the allowed range of parameters.
In particular, in the two Higgs doublet standard model with an anomalous Z(2)
symmetry, the above restriction suggests the mass of the pseudoscalar Higgs
(would be axion) being close to the mass of the scalar one.Comment: 15 pages, latex, no figure
Negative Giant Longitudinal Magnetoresistance in NiMnSb/InSb: An interface effect
We report on the electrical and magneto-transport properties of the contact
formed between polycrystalline NiMnSb thin films grown using pulsed laser
deposition (PLD) and n-type degenerate InSb (100) substrates. A negative giant
magnetoresistance (GMR) effect is observed when the external magnetic field is
parallel to the surface of the film and to the current direction. We attribute
the observed phenomenon to magnetic precipitates formed during the magnetic
film deposition and confined to a narrow layer at the interface. The effect of
these precipitates on the magnetoresistance depends on the thermal processing
of the system.Comment: 14 pages, 4 figure
Challenging empowerment: AIDS-affected southern African children and the need for a multi-level relational approach
Critics of empowerment have highlighted the concept's mutability, focus on individual transformation, one-dimensionality and challenges of operationalisation. Relating these critiques to children's empowerment raises new challenges. Drawing on scholarship on children's subjecthood and exercise of power, alongside empirical research with children affected by AIDS, I argue that empowerment envisaged as individual self-transformation and increased capacity to act independently offers little basis for progressive change. Rather it is essential to adopt a relational approach that recognises the need to transform power relationships at multiple levels. This analysis has implications for our wider understanding of empowerment in the 21st century. © The Author(s) 2013.This research was funded by DFID
The measurement of primary productivity in a high-rate oxidation pond (HROP)
A high-rate oxidation pond is studied as a model system for comparing 14C and oxygen evolution methods as tools for measuring primary productivity in hypertrophic aquatic systems. Our results indicate that at very dense algal populations (up to 5 mg chl. a l−1) and high photosynthetic rates, 14C based results may severely underestimate primary productivity, unless a way is found to keep incubation times very short. Results obtained with our oxygen electrode were almost an order of magnitude higher than those obtained by all 14C procedures. These higher values correspond fairly well with a field-tested computer-simulation model, as well as with direct harvest data obtained at the same pond when operated under similar conditions. The examination of the size-fractionation of the photosynthetic activity underscored the important contribution of nannoplanktonic algae to the total production of the syste
Surface and interface study of pulsed-laser-deposited off-stoichiometric NiMnSb thin films on Si(100) substrate
We report a detailed study of surface and interface properties of
pulsed-laser deposited NiMnSb films on Si (100) substrate as a function of film
thickness. As the thickness of films is reduced below 35 nm formation of a
porous layer is observed. Porosity in this layer increases with decrease in
NiMnSb film thickness. These morphological changes of the ultra thin films are
reflected in the interesting transport and magnetic properties of these films.
On the other hand, there are no influences of compositional in-homogeneity and
surface/interface roughness on the magnetic and transport properties of the
films.Comment: 13 pages, 7 figures, Submitted to Phys. Rev.
Ignorance based inference of optimality in thermodynamic processes
We derive ignorance based prior distribution to quantify incomplete
information and show its use to estimate the optimal work characteristics of a
heat engine.Comment: Latex, 10 pages, 3 figure
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