5,431 research outputs found
Towards testing a two-Higgs-doublet model with maximal CP symmetry at the LHC: construction of a Monte Carlo event generator
A Monte Carlo event generator is constructed for a two-Higgs-doublet model
with maximal CP symmetry, the MCPM. The model contains five physical Higgs
bosons; the , behaving similarly to the standard-model Higgs boson, two
extra neutral bosons and , and a charged pair . The special
feature of the MCPM is that, concerning the Yukawa couplings, the bosons ,
and couple directly only to the second generation fermions but
with strengths given by the third-generation-fermion masses. Our event
generator allows the simulation of the Drell-Yan-type production processes of
, and in proton-proton collisions at LHC energies. Also the
subsequent leptonic decays of these bosons into the , and channels are studied as well as the dominant
background processes. We estimate the integrated luminosities needed in
collisions at center-of-mass energies of 8 TeV and 14 TeV for significant
observations of the Higgs bosons , and in these muonic
channels
Effective Two Higgs Doublets in Nonminimal Supersymmetric Models
The Higgs sectors of supersymmetric extensions of the Standard Model have two
doublets in the minimal version (MSSM), and two doublets plus a singlet in two
others: with (UMSSM) and without (NMSSM) an extra U(1)'. A very concise
comparison of these three models is possible if we assume that the singlet has
a somewhat larger breaking scale compared to the electroweak scale. In that
case, the UMSSM and the NMSSM become effectively two-Higgs-doublet models
(THDM), like the MSSM. As expected, the mass of the lightest CP-even neutral
Higgs boson has an upper bound in each case. We find that in the NMSSM, this
bound exceeds not very much that of the MSSM, unless tan(beta) is near one.
However, the upper bound in the UMSSM may be substantially enhanced.Comment: 8 pages, 1 table, 3 figure
HYDROGEOCHEMICAL CONDITION OF THE PIKROLIMNI LAKE (KILKIS GREECE)
In order to understand the hydrogeochemical conditions of the basin of Pikrolimni we collected water samples from the borehole in the thermal spa of Pikrolimni and samples of brine and sediments from the lake. We also sampled fresh water of the region. The depth of the borehole in the thermal spa is approximately 250 meters. This water is naturally sparkling, with a metallic aftertaste and a slight organic smell. The samples were taken twice during the year: in summer (8/2002) and in winter (2003). The analytical scheme includes field measurements of temperature, conductivity and pH. Major ions (Na+, K+, Ca2+, Mg2\ CI", Br, S04 2", C03 2", HC03", N03"), F and Br were determined, in laboratory, according to standard analytical methods. Samples were also subjected to isotopie analysis of δ Ο and δ2Η. The results from the chemical analyses of the samples, show that the waters taken from the borehole, are of the type Mg- (Na-Ca)-HCC>3 and the salts of the lake are of the type Na-CI- (CO3-S04). The salts of the lake result from mixing and condensation of the waters which are accumulated in the basin of the lake, and come not only from sources that feed the lake, e.g. waters from borehole, but also from rain water. The waters of these sources are mainly of meteoritic origin and circulate deeply, mixing probably with salt water of deeper and probably of warmer horizons. The latter comes in agreement with the hydrothermal field, which exists in the area. From hydrochemical data, the brines of summer clearly correspond to waters, which have been submitted under high degree of evaporation: they are residual mother solutions before the step of the precipitation of halite. During winter, dilution of brines and dissolution of depositing minerals by fresh water are observed. On the other hand, evaporating conditions are created in the lake during summer
Determining the global minimum of Higgs potentials via Groebner bases - applied to the NMSSM
Determining the global minimum of Higgs potentials with several Higgs fields
like the next-to-minimal supersymmetric extension of the Standard Model (NMSSM)
is a non-trivial task already at the tree level. The global minimum of a Higgs
potential can be found from the set of all its stationary points defined by a
multivariate polynomial system of equations. We introduce here the algebraic
Groebner basis approach to solve this system of equations. We apply the method
to the NMSSM with CP conserving as well as CP violating parameters. The results
reveal an interesting stationary-point structure of the potential. Requiring
the global minimum to give the electroweak symmetry breaking observed in Nature
excludes large parts of the parameter space.Comment: 10 pages, 2 figure
Exploring the anthelmintic properties of Australian native shrubs with respect to their potential role in livestock grazing systems
We measured in vitro anthelmintic activity in extracts from 85 species of Australian native shrub, with a view to identifying species able to provide a degree of worm control in grazing systems. Approximately 40% of the species showed significant activity in inhibiting development of Haemonchus contortus larvae. The most active extracts showed IC50 values of 60–300 mg/ml. Pre-incubation with polyvinylpolypyrrolidine removed the activity from some extracts, implicating tannins as the bioactive agent, while in other cases the pre-incubation had no effect, indicating the presence of other anthelmintic compounds. Plant reproductive maturity (onset of flowering or fruiting) was associated with increasing anthelmintic activity in some species. Variability was observed between plants of the same species growing in different environments, while variation between individual plants of the same species within a single field suggests the existence of distinct chemotypes. Significant activity against adult H. contortus worms in vitro was also demonstrated in a limited number of extracts tested against this life stage. Our study indicates that there is potential for Australian native shrubs to play an anthelmintic role in grazing systems, and highlights some plant biology factors which will need to be considered in order to maximize any anthelmintic effects.A. C. Kotze, J. O’Grady, J. Emms, A. F. Toovey, S. Hughes, P. Jessop, M. Bennell P. E. Vercoe and D. K. Revel
Inflection point inflation within supersymmetry
We propose to address the fine tuning problem of inflection point inflation
by the addition of extra vacuum energy that is present during inflation but
disappears afterwards. We show that in such a case, the required amount of fine
tuning is greatly reduced. We suggest that the extra vacuum energy can be
associated with an earlier phase transition and provide a simple model, based
on extending the SM gauge group to SU(3)_C \times SU(2)_L\times U(1)_Y\times
U(1)_{B-L}, where the Higgs field of U(1)_{B-L} is in a false vacuum during
inflation. In this case, there is virtually no fine tuning of the soft SUSY
breaking parameters of the flat direction which serves as the inflaton.
However, the absence of radiative corrections which would spoil the flatness of
the inflaton potential requires that the U(1)_{B-L} gauge coupling should be
small with g_{B-L}\leq 10^{-4}.Comment: 6 pages, 1 figur
Sfermion Precision Measurements at a Linear Collider
At future e+- e- linear colliders, the event rates and clean signals of
scalar fermion production - in particular for the scalar leptons - allow very
precise measurements of their masses and couplings and the determination of
their quantum numbers. Various methods are proposed for extracting these
parameters from the data at the sfermion thresholds and in the continuum. At
the same time, NLO radiative corrections and non-zero width effects have been
calculated in order to match the experimental accuracy. The substantial mixing
expected for the third generation sfermions opens up additional opportunities.
Techniques are presented for determining potential CP-violating phases and for
extracting tan(beta) from the stau sector, in particular at high values. The
consequences of possible large mass differences in the stop and sbottom system
are explored in dedicated analyses.Comment: Expanded version of contributions to the proceedings of ICHEP'02
(Amsterdam) and LCWS 2002 (Jeju Island
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Origins of the sarsen megaliths at Stonehenge
The sources of the stone used to construct Stonehenge around 2500 BCE have been debated for over four centuries. The smaller “bluestones” near the center of the monument have been traced to Wales, but the origins of the sarsen (silcrete) megaliths that form the primary architecture of Stonehenge remain unknown. Here, we use geochemical data to show that 50 of the 52 sarsens at the monument share a consistent chemistry and, by inference, originated from a common source area. We then compare the geochemical signature of a core extracted from Stone 58 at Stonehenge with equivalent data for sarsens from across southern Britain. From this, we identify West Woods, Wiltshire, 25 km north of Stonehenge, as the most probable source area for the majority of sarsens at the monument
Symmetries and renormalisation in two-Higgs-doublet models
We discuss the classification of symmetries and the corresponding symmetry
groups in the two-Higgs-doublet model (THDM). We give an easily useable method
how to determine the symmetry class and corresponding symmetry group of a given
THDM Higgs potential. One of the symmetry classes corresponds to a Higgs
potential with several simultaneous generalised CP symmetries. Extending the CP
symmetry of this class to the Yukawa sector in a straightforward way, the
so-called maximally-CP-symmetric model (MCPM) is obtained. We study the
evolution of the quartic Higgs-potential parameters under a change of
renormalisation point. Finally we compute the so called oblique parameters S,
T, and U, in the MCPM and we identify large regions of viable parameter space
with respect to electroweak precision measurements. We present the
corresponding allowed regions for the masses of the physical Higgs bosons.
Reasonable ranges for these masses, up to several hundred GeV, are obtained
which should make the (extra) Higgs bosons detectable in LHC experiments.Comment: 16 pages, 2 figure
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