Anomalous Dimensions of High Twist Operators in QCD at N→1N \rightarrow 1 and large $Q^2

The anomalous dimensions of high-twist operators in deeply inelastic scattering ($\gamma_{2n}$) are calculated in the limit when the moment variable $N \rightarrow 1$ (or $x_B\rightarrow 0$) and at large $Q^2$ (the double logarithmic approximation) in perturbative QCD. We find that the value of $\gamma_{2n}(N-1)$ in this approximation behaves as ${N_c \alpha_S \over \pi (N-1)} n^2(1 + {\delta \over 3} (n^2-1))$ where $\delta \approx 10^{-2}$. This implies that the contributions of the high-twist operators give rise to an earlier onset of shadowing than was estimated before. The derivation makes use of a Pomeron exchange approximation, with the Pomerons interacting attractively. We find that they behave as a system of fermions.Comment: jytex (see macros directory), 18 pages , 9 figures, uuencoded at back of file, FERMILAB-PUB-93/243-

Background Dependent Lorentz Violation: Natural Solutions to the Theoretical Challenges of the OPERA Experiment

To explain both the OPERA experiment and all the known phenomenological constraints/observations on Lorentz violation, the Background Dependent Lorentz Violation (BDLV) has been proposed. We study the BDLV in a model independent way, and conjecture that there may exist a "Dream Special Relativity Theory", where all the Standard Model (SM) particles can be subluminal due to the background effects. Assuming that the Lorentz violation on the Earth is much larger than those on the interstellar scale, we automatically escape all the astrophysical constraints on Lorentz violation. For the BDLV from the effective field theory, we present a simple model and discuss the possible solutions to the theoretical challenges of the OPERA experiment such as the Bremsstrahlung effects for muon neutrinos and the pion decays. Also, we address the Lorentz violation constraints from the LEP and KamLAMD experiments. For the BDLV from the Type IIB string theory with D3-branes and D7-branes, we point out that the D3-branes are flavour blind, and all the SM particles are the conventional particles as in the traditional SM when they do not interact with the D3-branes. Thus, we not only can naturally avoid all the known phenomenological constraints on Lorentz violation, but also can naturally explain all the theoretical challenges. Interestingly, the energy dependent photon velocities may be tested at the experiments.Comment: RevTex4, 14 pages, minor corrections, references adde

Non-minimal neutral Higgs bosons at LEP2

We study the phenomenology of the neutral Higgs sector of a non-SUSY non-minimal Standard Model. Models with more than one Higgs doublet are possible, and may contain neutral Higgs scalars with branching ratios significantly different to those of the Minimal Standard Model Higgs boson. We show how these differences may be exploited at LEP2 in order to distinguish the non-minimal Standard Model from the minimal version.Comment: 12 pages inc 4 figures, Latex, to appear in Physics Letters

Revisiting the Higgs Mass and Dark Matter in the CMSSM

Taking into account the available accelerator and astrophysical constraints, the mass of the lightest neutral Higgs boson h in the minimal supersymmetric extension of the Standard Model with universal soft supersymmetry-breaking masses (CMSSM) has been estimated to lie between 114 and ~ 130 GeV. Recent data from ATLAS and CMS hint that m_h ~ 125 GeV, though m_h ~ 119 GeV may still be a possibility. Here we study the consequences for the parameters of the CMSSM and direct dark matter detection if the Higgs hint is confirmed, focusing on the strips in the (m_1/2, m_0) planes for different tan beta and A_0 where the relic density of the lightest neutralino chi falls within the range of the cosmological cold dark matter density allowed by WMAP and other experiments. We find that if m_h ~ 125 GeV focus-point strips would be disfavoured, as would the low-tan beta stau-chi and stop -chi coannihilation strips, whereas the stau-chi coannihilation strip at large tan beta and A_0 > 0 would be favoured, together with its extension to a funnel where rapid annihilation via direct-channel H/A poles dominates. On the other hand, if m_h ~ 119 GeV more options would be open. We give parametrizations of WMAP strips with large tan beta and fixed A_0/m_0 > 0 that include portions compatible with m_h = 125 GeV, and present predictions for spin-independent elastic dark matter scattering along these strips. These are generally low for models compatible with m_h = 125 GeV, whereas the XENON100 experiment already excludes some portions of strips where m_h is smaller.Comment: 24 pages, 9 figure

Colliders and Cosmology

Dark matter in variations of constrained minimal supersymmetric standard models will be discussed. Particular attention will be given to the comparison between accelerator and direct detection constraints.Comment: Submitted for the SUSY07 proceedings, 15 pages, LaTex, 26 eps figure

Large mass splittings between charged and neutral Higgs bosons in the MSSM

We show that large ($> 100$ GeV) mass splittings between the charged Higgs boson ($H^\pm$) and the neutral Higgs bosons ($H^0$ and $A^0$) are possible in the Minimal Supersymmetric Standard Model (MSSM). Such splittings occur when the $\mu$ parameter is considerably larger than the common SUSY scale, $M_{SUSY}$, and have significant consequences for MSSM Higgs searches at future colliders.Comment: 11 pages, LaTex, 5 figures, version to appear in Phys. Lett.

Diverse pollination systems of the twin-spurred orchid genus Satyrium in African grasslands

The large terrestrial orchid genus Satyrium underwent evolutionary radiations in the Cape floral region and the grasslands of southern and eastern Africa. These radiations were accompanied by tremendous diversification of the unusual twin-spurred flowers that characterize the genus, but pollination data required to interpret these patterns of floral evolution have been lacking for grassland species in the genus. Here we document pollinators, nectar properties, and levels of pollination success for 11 grassland Satyrium species in southern and south-central Africa. Pollinators of these species include bees, beetles, butterflies, hawkmoths, noctuid moths, long-proboscid flies, and sunbirds. Most species appear to be specialized for pollination by one functional pollinator group. Long-proboscid fly pollination systems are reported for the first time in Satyrium (in S. macrophyllum and a high-altitude form of S. neglectum). Floral morphology, especially spur length and rostellum structure, differs markedly among plants with different pollinators, while nectar volume, concentration, and sugar composition are fairly uniform across species. Most taxa exhibited high levels of pollination success (>50% of flowers pollinated), a trend that can be attributed to the presence of nectar in the twin spurs

Charged Higgs bosons in the Next-to MSSM (NMSSM)

The charged Higgs boson decays $H^\pm\to W^\pm A_1$ and $H^\pm\to W^\pm h_i$ are studied in the framework of the next-to Minimal Supersymmetric Standard Model (NMSSM). It is found that the decay rate for $H^\pm\to W^\pm A_1$ can exceed the rates for the $\tau^\pm\nu$ and $tb$ channels both below and above the top-bottom threshold. The dominance of $H^\pm\to W^\pm A_1$ is most readily achieved when $A_1$ has a large doublet component and small mass. We also study the production process $pp\to H^\pm A_1$ at the LHC followed by the decay $H^\pm\to W^\pm A_1$ which leads to the signature $W^\pm A_1 A_1$. We suggest that $p p\to H^\pm A_1$ is a promising discovery channel for a light charged Higgs boson in the NMSSM with small or moderate $\tan\beta$ and dominant decay mode $H^\pm \to W^\pm A_1$. This $W^\pm A_1 A_1$ signature can also arise from the Higgsstrahlung process $pp\to W^\pm h_1$ followed by the decay $h_1\to A_1 A_1$. 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

Towards a transferable and cost-effective plant AFLP protocol

Amplified fragment length polymorphism (AFLP) is a powerful fingerprinting technique that is widely applied in ecological and population genetic studies. However, its routine use has been limited by high costs associated with the optimization of fluorescently labelled markers, especially for individual study systems. Here we develop a low-cost AFLP protocol that can be easily transferred between distantly related plant taxa. Three fluorescently labelled EcoRI-primers with anchors that target interspecifically conserved genomic regions were used in combination with a single non-labelled primer in our AFLP protocol. The protocol was used to genotype one gymnosperm, two monocot and three eudicot plant genera representing four invasive and four native angiosperm species (Pinus pinaster (Pinaceae), Pennisetum setaceum and Poa annua (Poaceae), Lantana camara (Verbenaceae), Bassia diffusa (Chenopodiaceae), Salvia lanceolata, Salvia africana-lutea, and Salvia africanacaerulea (Lamiaceae)). Highly polymorphic and reproducible genotypic fingerprints (between 37–144 polymorphic loci per species tested) were obtained for all taxa tested. Our single protocol was easily transferred between distantly related taxa. Measures of expected heterozygosity ranged from 0.139 to 0.196 for P. annua and from 0.168 to 0.272 for L. camara which compared well with previously published reports. In addition to ease of transferability of a single AFLP protocol, our protocol reduces costs associated with commercial kits by almost half. The use of highly conserved but abundant anchor sequences reduces the need for laborious screening for usable primers that result in polymorphic fingerprints, and appears to be the main reason for ease of transferability of our protocol between distantly related taxa