37 research outputs found
Higgs Sector of the Minimal Left-Right Symmetric Model
We perform an exhaustive analysis of the most general Higgs sector of the
minimal left-right symmetric model (MLRM). We find that the CP properties of
the vacuum state are connected to the Higgs spectrum: if CP is broken
spontaneously, the MLRM does not approach the Standard Model in the limit of a
decoupling left-right symmetry breaking scale. Depending on the size of the CP
phases scenarios with extra non-decoupling flavor-violating doublet Higgses or
very light SU(2) triplet Higgses emerge, both of which are ruled out by
phenomenology. For zero CP phases the non-standard Higgses decouple only if a
very unnatural fine-tuning condition is fulfilled. We also discuss
generalizations to a non-minimal Higgs sector.Comment: brief discussion of non-minimal Higgs sectors added, journal versio
The Supersymmetric Particle Spectrum
We examine the spectrum of supersymmetric particles predicted by grand
unified theoretical (GUT) models where the electroweak symmetry breaking is
accomplished radiatively. We evolve the soft supersymmetry breaking parameters
according to the renormalization group equations (RGE). The minimization of the
Higgs potential is conveniently described by means of tadpole diagrams. We
present complete one-loop expressions for these minimization conditions,
including contributions from the matter and the gauge sectors. We concentrate
on the low fixed point region (that provides a natural explanation
of a large top quark mass) for which we find solutions to the RGE satisfying
both experimental bounds and fine-tuning criteria. We also find that the
constraint from the consideration of the lightest supersymmetric particle as
the dark matter of the universe is accommodated in much of parameter space
where the lightest neutralino is predominantly gaugino. The supersymmetric mass
spectrum displays correlations that are model-independent over much of the GUT
parameter space.Comment: 62 pages + 10 PS figures included (uuencoded), MAD/PH/80
QCD Corrections to B -> X_{d,s} nu nubar, B_{d,s} -> l^+l^-, K -> pi nu nubar and K_L -> mu^+ mu^- in the MSSM
We compute for the first time QCD corrections to the rare decays B -> X_{d,s}
nu nubar, B_{d,s} -> l^+ l^-, K -> pi nu nubar and K_L -> mu^+ mu^-, where l=e
or mu, in the context of a supersymmetric extension of the Standard Model (SM)
with minimal flavour violation and new operators, in addition to those present
in the SM. Assuming that the gluino is heavy, we consider an effective theory
which consists of charged and neutral Higgs particles, charginos and squarks.
We evaluate the QCD corrections to box and Z^0-penguin diagrams with top-quark,
charged Higgs boson, chargino and squark exchanges, as well as to neutral Higgs
boson penguin diagrams. We provide a compendium of analytic formulae for the
Wilson coefficients, which are valid for arbitrary values of tan(beta) (the
ratio of the vacuum expectation values of the two Higgs fields) except for the
case of the neutral Higgs-boson contributions. These contributions have been
obtained at large tan(beta), which may compensate for the inevitable
suppression by the masses of the light leptons in decays based on the b -> s
(d) l^+ l^- transition. We investigate the dependence of the various branching
ratios on the renormalization scale mu, which is the main theoretical
uncertainty in the short-distance calculation. We find that the mu dependence
of the branching ratios is considerably reduced once the QCD corrections are
taken into account. The contributions of new operators are found to be dominant
at large tan(beta) in B_{d,s} -> mu^+ mu^- while they are subleading in B ->
X_{d,s} nu nubar and completely negligible in kaon decays.Comment: 47 pages, 9 figures; version to appear in Nucl. Phys.
Possible Signals of Constrained Minimal Supersymmetry at a High Luminosity Fermilab Tevatron Collider
We study the most promising signals of Constrained Minimal Supersymmetry
detectable at a luminosity upgraded 2 TeV Fermilab Tevatron collider. Using a
full event-level Monte Carlo based on Pythia/Jetset, we simulate the trilepton
signal examining in detail the effect of constraints on the parameter space. We
also simulate the monolepton and dilepton signals, the missing E_T + jets
signal, and the signals of stop production in supersymmetry all with full
Standard Model backgrounds with realistic detector cuts. We find that large
fractions of parameter space can be probed (or eliminated if no signal is
found), but mass limits on charginos and neutralinos are not possible based
solely on the trilepton signal. Detection efficiencies depend strongly on
supersymmetry parameters beyond simply the neutralino and chargino masses;
analyses (experimental or theoretical) that do not include this will draw
misleading conclusions. Finally, we comment on how searches at LEP II will
complement searches at Fermilab.Comment: 30 pages, LaTeX, 11 figures, now uses epsf.sty. Reference in text has
been corrected; references added. Figures have been included using uufiles.
Compressed PS file with embedded figures available via anonymous ftp at
ftp://williams.physics.lsa.umich.edu/pub/preprints/UM-TH-95-14.ps.
Social preferences and network structure in a population of reef manta rays
Understanding how individual behavior shapes the structure and ecology ofpopulations is key to species conservation and management. Like manyelasmobranchs, manta rays are highly mobile and wide ranging species threatened byanthropogenic impacts. In shallow-water environments these pelagic rays often formgroups, and perform several apparently socially-mediated behaviors. Group structuresmay result from active choices of individual rays to interact, or passive processes.Social behavior is known to affect spatial ecology in other elasmobranchs, but this isthe first study providing quantitative evidence for structured social relationships inmanta rays. To construct social networks, we collected data from more than 500groups of reef manta rays over five years, in the Raja Ampat Regency of West Papua.We used generalized affiliation indices to isolate social preferences from non-socialassociations, the first study on elasmobranchs to use this method. Longer lastingsocial preferences were detected mostly between female rays. We detectedassortment of social relations by phenotype and variation in social strategies, with theoverall social network divided into two main communities. Overall network structurewas characteristic of a dynamic fission-fusion society, with differentiated relationshipslinked to strong fidelity to cleaning station sites. Our results suggest that fine-scaleconservation measures will be useful in protecting social groups of M. alfredi in theirnatural habitats, and that a more complete understanding of the social nature of mantarays will help predict population response
Shrinking into the big city: influence of genetic and environmental factors on urban dragon lizard morphology and performance capacity
Urban wildlife faces a novel set of challenges resulting in selective pressure that can lead to population-level changes. We studied Australian water dragons (Intellagama lesueurii) from urban and natural populations to test if urban populations differed in body size, shape, and performance capacity. If urban-derived morphology has arisen through selection, we predicted distinct morphological differences between wild dragons from urban and natural areas in both adult and hatchling life-stages. Urban hatchlings were morphologically distinct (shorter body lengths and longer limbs) from natural populations, while urban adult males continued this trend but only for body size (shorter body lengths). We then experimentally reared hatchlings originating from urban and natural populations within urban- and natural-style enclosures (2 × 2 factorial design) for a year to determine if differences in morphology and performance capacity (sprint speed, endurance, and clinging ability) were related to either the individual’s origin population or developmental environment. Yearlings reared in urban-style enclosures, irrespective of population origin, had smaller body sizes compared to those from natural-style enclosures, suggesting developmental environment was affecting their morphology. Despite this difference in body size, yearling dragon performance capacity was not significantly different between treatments. Overall, this study provides evidence of a complex relationship driving urban-divergent morphology – whereby urban dragons emerge as smaller hatchlings with longer limbs (innate traits) and are then further influenced by the urban environments that they develop in (phenotypic plasticity); however, and potentially owing to behavioral, ecological, and demographical differences, these changes appear to be sex-specific
Genotypes_13 markers
Genotypes for four city parks (CP1, CP2 and CP3), three isolated non-urban (INU1, INU2 and INU3) and three connected non-urban populations (CNU1, CNU2 and CNU3) of eastern water dragons (Intellagama lesueurii). 13 microsatellite markers are included (taken from Frere et al., 2012) in the file, File is in the format accepted for GeneALEx
Data from: Archipelagos of the Anthropocene: rapid and extensive differentiation of native terrestrial vertebrates in a single metropolis
Some of the best evidence for rapid evolutionary change comes from studies of archipelagos and oceanic islands. City parks are analogous systems as they create geographically isolated green spaces that differ in size, structure, and complexity. Very little, however, is known about whether city parks in single urban centres drive selection and result in the diversification of native species. Here, we provide evidence for the rapid genetic and morphological differentiation of a native lizard (Intellagama lesueurii) at four geographically close yet unconnected parks within one city. Year of establishment of each city park varied from 1855 (oldest) to 2001 (youngest) equating to a generation time range of 32 to three generations. Genetic divergence among city park populations was large despite the small pairwise geographic distances (< 5km) and found to be two to three times higher for microsatellites and three to 33 times higher for mtDNA relative to non-urban populations. Patterns of morphological differentiation were also found to be most extensive among the four city park populations. In contrast to non-urban populations, city park populations showed significant differentiation in relative body size, relative head and limb morphology and relative forelimb and hindlimb length. Crucially, we show that these patterns of differentiation are unlikely to have been caused by founder events and/or drift alone. Our results suggest that city park ‘archipelagos’ could represent theatres for rapid evolution that may, in time, favour adaptive diversification
A common system controls the induction of very different genes. The class-A beta-lactamase of Proteus vulgaris and the enterobacterial class-C beta-lactamase.
Among the Enterobacteriaceae, Proteus vulgaris is exceptional in the inducible production of a 29-kDa beta-lactamase (cefuroximase) with an unusually high activity towards the beta-lactamase-stable oximino-cephalosporins (e.g. cefuroxime and cefotaxime). Sequencing of the corresponding gene, cumA, showed that the derived CumA beta-lactamase belonged to the molecular class A. The structural gene was under the direct control of gene cumR, which was transcribed backwards and whose initiation codon was 165 bp away from that of the beta-lactamase gene. This resembled the arrangement of structural and regulator genes ampC and ampR of the 39-kDa molecular-class-C beta-lactamase AmpC present in many enterobacteria. Moreover, cloned genes ampD and ampG for negative modulation and signal transduction of AmpC beta-lactamase induction, respectively, were also able to restore constitutively CumA overproducing and non-inducible P. vulgaris mutants to the inducible, wild-type phenotype. The results indicate that controls of the induction phenomena are equivalent for the CumA and AmpC beta-lactamase. Very different structural genes can thus be under the control of identical systems