SUSY Particle Production at the Tevatron

The calculation of the next-to-leading order SUSY-QCD corrections to the production of squarks, gluinos and gauginos at the Tevatron is reviewed. The NLO corrections stabilize the theoretical predictions of the various production cross sections significantly and lead to sizeable enhancements of the most relevant cross sections for scales near the average mass of the produced massive particles. We discuss the phenomenological consequences of the results on present and future experimental analyses.Comment: 13 pages, latex, 9 figures, further extended versio

Lepton flavour violating stau decays versus seesaw parameters: correlations and expected number of events for both seesaw type-I and II

In minimal supergravity (mSugra), the neutrino sector is related to the slepton sector by means of the renormalization group equations. This opens a door to indirectly test the neutrino sector via measurements at the LHC. Concretely, for the simplest seesaw type-I, we present the correlations between seesaw parameters and ratio of stau lepton flavour violating (LFV) branching ratios. We find some simple, extreme scenarios for the unknown right-handed parameters, where ratios of LFV rates correlate with neutrino oscillation parameters. On the other hand, we scan the mSugra parameter space, for both seesaw type-I and II, to find regions where LFV stau decays can be maximized, while respecting low-energy experimental bounds. We estimate the expected number of events at the LHC for a sample luminosity of L = 100 fb^{-1}.Comment: 10 pages, 6 figures, 1 table, to appear in the proceedings of DISCRETE'08 Symposium on Prospects in the Physics of Discrete Symmetries, 11-16 December 2008, Valencia, Spain; some comments adde

Precision Measurements of Higgs Couplings: Implications for New Physics Scales

The measured properties of the recently discovered Higgs boson are in good agreement with predictions from the Standard Model. However, small deviations in the Higgs couplings may manifest themselves once the currently large uncertainties will be improved as part of the LHC program and at a future Higgs factory. We review typical new physics scenarios that lead to observable modifications of the Higgs interactions. They can be divided into two broad categories: mixing effects as in portal models or extended Higgs sectors, and vertex loop effects from new matter or gauge fields. In each model we relate coupling deviations to their effective new physics scale. It turns out that with percent level precision the Higgs couplings will be sensitive to the multi-TeV regime.Comment: Invited review for Journal of Physics G, 33pp; v2: references added and improved discussion of operator basis in section 2.

QCD Corrections to SUSY Higgs Production: The Role of Squark Loops

We calculate the two-loop QCD corrections to the production of the neutral supersymmetric Higgs bosons via the gluon fusion mechanism at hadron colliders, including the contributions of squark loops. To a good approximation, these additional contributions lead to the same QCD corrections as in the case where only top and bottom quark loops are taken into account. The QCD corrections are large and increase the Higgs production cross sections significantly.Comment: 5 pages, latex, 2 figure

Pair Production of Neutral Higgs Particles in Gluon--Gluon Collisions

Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high--energy colliders. Several mechanisms give rise to multi--Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon--gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension.Comment: 23 pages, latex, 9 figures appended as uuencoded fil

The constancy of global regulation across a species: the concentrations of ppGpp and RpoS are strain-specific in Escherichia coli.

BACKGROUND: Sigma factors and the alarmone ppGpp control the allocation of RNA polymerase to promoters under stressful conditions. Both ppGpp and the sigma factor σS (RpoS) are potentially subject to variability across the species Escherichia coli. To find out the extent of strain variation we measured the level of RpoS and ppGpp using 31 E. coli strains from the ECOR collection and one reference K-12 strain. RESULTS: Nine ECORs had highly deleterious mutations in rpoS, 12 had RpoS protein up to 7-fold above that of the reference strain MG1655 and the remainder had comparable or lower levels. Strain variation was also evident in ppGpp accumulation under carbon starvation and spoT mutations were present in several low-ppGpp strains. Three relationships between RpoS and ppGpp levels were found: isolates with zero RpoS but various ppGpp levels, strains where RpoS levels were proportional to ppGpp and a third unexpected class in which RpoS was present but not proportional to ppGpp concentration. High-RpoS and high-ppGpp strains accumulated rpoS mutations under nutrient limitation, providing a source of polymorphisms. CONCLUSIONS: The ppGpp and σS variance means that the expression of genes involved in translation, stress and other traits affected by ppGpp and/or RpoS are likely to be strain-specific and suggest that influential components of regulatory networks are frequently reset by microevolution. Different strains of E. coli have different relationships between ppGpp and RpoS levels and only some exhibit a proportionality between increasing ppGpp and RpoS levels as demonstrated for E. coli K-12

Molecular Dynamics Simulation Of Gas Transport And Adsorption In Ultra-Tight Formations

Kerogen, which plays a very important part in reservoir characterization for ultra-tight formations, is also involved in the storage and production of hydrocarbons in shale. In this work, we study the kerogen structure and its interaction with insitu hydrocarbons to fully understand the fluid flow and adsorption mechanisms in the shale. Also the advancement in pore network modelling has greatly helped the understanding of mesoscale fluid flow. In this work, transport of methane in a type II marine environment kerogen model is studied using molecular dynamics simulations. Non Equilibrium Molecular Dynamics Simulations (NEMDS) using GROMACS code and Grand Canonical Monte Carlo (GCMC) using the RASPA code have been applied to simulate the adsorption and transport of ethane, carbon dioxide and methane in nanoscale environment. In this work, we used the kerogen and silica pore models to represent an organic and inorganic nanopore channels, respectively. The initial configuration models are then energy minimized, and both constant-temperature constant-volume (NVT) simulations and then constant-temperature constant-pressure (NPT) simulations are performed to obtain the final structure. For our pore network model, we used the Delaunay triangulation method to build a network model and then employed capillary pressure simulations. The simulation results from molecular simulations transport diffusivities show that as pressure increases the transport diffusion coefficients increase. Methane has a higher diffusivity in kerogen than ethane at the same temperature and pressure conditions. For adsorption, results show that CO2 has the largest adsorption capacity for both organic and inorganic pores, hence, a good candidate for enhanced gas recovery and carbon sequestration in depleted shale gas reservoirs. The amount of adsorption is more in organic pores for all studied gases, which implies that shale reservoirs with higher total organic carbon (TOC) will turn to trap more gases restricting flow and production

SM and MSSM Higgs Boson Production: Spectra at large transverse Momentum

Strategies for Higgs boson searches require the knowledge of the total production cross section and the transverse momentum spectrum. The large transverse momentum spectrum of the Higgs boson produced in gluon fusion can be quite different in the Standard Model and the Minimal Supersymmetric Standard Model. In this paper we present a comparison of the Higgs transverse momentum spectrum obtained using the PYTHIA event generator and the HIGLU program as well as the program HQT, which includes NLO corrections and a soft gluon resummation for the region of small transverse momenta. While the shapes of the spectra are similar for the Standard Model, significant differences are observed in the spectra of Minimal Supersymmetric Standard Model benchmark scenarios with large tan(beta).Comment: 8 pages, 13 figure

Formation and Decay of Scalar Leptoquarks/Squarks in ep collisions

The cross sections for the formation of scalar resonances, leptoquarks or squarks, in electron/positron-proton collisions at HERA are presented including next-to-leading order QCD corrections. Depending mildly on the mass of the resonances, the K-factors increase the production cross sections by up to 30% if the target quarks are valence quarks. The QCD corrections to the partial decay widths of leptoquarks/squarks to leptons and quarks are small. The electron spectrum in the decays is softened nevertheless by perturbative gluon radiation at a level of 3.4 GeV for a leptoquark/squark mass of 200 GeV.Comment: 10 pages, LaTex file with 3 figures, uses axodraw.sty (included

Top quark associated production of topcolor pions at hadron colliders

We investigate the associated production of a neutral physical pion with top quarks in the context of topcolor assisted technicolor. We find that single-top associated production does not yield viable rates at either the Tevatron or LHC. tt-associated production at the Tevatron is suppressed relative to Standard Model ttH, but at the LHC is strongly enhanced and would allow for easy observation of the main decay channels to bottom quarks, and possible observation of the decay to gluons.Comment: 13 pages, 4 figures, submitted to PR