Associated central exclusive production of charged Higgs bosons

We propose central exclusive production of a charged Higgs boson in association with a W boson as a possible signature of certain types of extended Higgs sectors. We calculate the cross section and find that the rate at the LHC could be large enough to allow observation in some models with two Higgs doublets, where the charged Higgs and at least one of the neutral scalars can be light enough. We use the two-Higgs doublet model as a prototype and consider two distinct regions of parameter space, but we also briefly discuss the prospects for the next-to-minimal supersymmetric standard model, where the charged Higgs may very well be quite light.Comment: 9 pages, 5 figures. Minor changes, references added. Version to appear in PR

Rapidity gaps at HERA and the Tevatron from soft colour exchanges

Models based on soft colour exchanges to rearrange colour strings in the final state provide a general framework for both diffractive and non-diffractive events in ep and hadron-hadron collisions. We study two such models and find that they can reproduce rapidity gap data from both HERA and the Tevatron. We also discuss the influence of parton cascades and multiple interactions on the results.Comment: 4 pages, 4 EPS figures, presented at UK Phenomenology Workshop on Collider Physics, Durham. Uses iopart.cl

Higgs boson production via Double Pomeron Exchange at the LHC

We study Higgs boson production via Double Pomeron Exchange allowing for the presence of Pomeron remnants. We estimate the number of events produced at the LHC collider, as a function of the Higgs boson mass and its decay channel. The model which successfully describes the high mass dijet spectrum observed at Tevatron (run I) is used to predict rates of events with tagged protons for the acceptance range of the CMS/Totem experiments. Sizeable cross-sections and encouraging event selection signals are found, demonstrating especially for smaller Higgs boson masses the importance to study the diffractive channels. Tagging of the Pomeron remnants can be exploited to achieve a good resolution on the Higgs boson mass for inclusive diffractive events, by optimizing an intermediary analysis between higher cross-sections of the fully {\it inclusive} mode (all Pomeron remnants) and cleaner signals of the {\it exclusive} mode (without Pomeron remnants).Comment: 6 pages, 4 eps.figure

Eight decades of adaptive changes in herring reproductive investment: the joint effect of environment and exploitation

publishedVersio

Diffractive Higgs boson production at the Tevatron and LHC

Improved possibilities to find the Higgs boson in diffractive events, having less hadronic activity, depend on whether the cross section is large enough. Based on the soft color interaction models that successfully describe diffractive hard scattering at HERA and the Tevatron, we find that only a few diffractive Higgs events may be produced at the Tevatron, but we predict a substantial rate at the LHC.Comment: 4 pages, 4 figures, uses Revtex

Color Evaporation and Elastic Υ\Upsilon Photoproduction at DESY HERA

The diffractive photoproduction of vector mesons is usually described considering the two-gluon (Pomeron) exchange, non-diagonal parton distributions and the contribution of the real part to the cross section. In this letter we analyze the diffractive photoproduction of the $\Upsilon$ at HERA using an alternative model, the Color Evaporation Model (CEM), where the cross section is simply determined by the boson-gluon cross section and an assumption for the production of the colorless state. We verify that, similarly to the $J/\Psi$ case, the HERA data for this process can be well described by the CEM. Moreover, we propose the analyzes of the ratio $R = \sigma_{\Upsilon} / \sigma_{J/\Psi}$ to discriminate between the distinct approaches.Comment: 7 pages, 3 figures, accepted for publication in PRD (Brief Reports

The influence of process conditions during pulp storage on the optical properties of Norway spruce high-yield pulps

The influence of process conditions during pulp storage on the optical properties of Norway spruce mechanical pulps. Nordic Pulp & Paper Research Journal, Access to the published version may require subscription. N.B. When citing this work, cite the original published paper. The aim of this work was to study the influence of process conditions (time, pH, temperature and consistency) on the optical properties of mechanical pulps during storage in a clean system as a reference for further work. Laboratory storage trials were performed with unbleached and hydrogen-peroxide bleached wellwashed Norway spruce pulps. In general, the pulp darkened during storage due to an increase in light absorption, especially at shorter wavelengths. After long storage times, the light absorption coefficient, k had increased also at longer wavelengths. No specific peaks were seen in k-spectra. The increase in light absorption was most rapid initially, during the first four hours, for all pulps when stored at high temperature (80°C), and then proceeded more slowly. The corresponding change in colour, measured as a* and b*, was shifted towards red and somewhat towards yellow, and over longer periods of storage, the shift towards yellow became greater. Time and temperature were found to have the largest impact. The effects were similar regardless of the starting pH (4.3-9.7) and pulp consistency (5%-25%). The hydrogen-peroxide bleached pulps were more sensitive to storage compared to the unbleached pulp at temperatures above 50°C. At storage times of up to four hours, the unbleached pulp showed no loss of brightness at either of the storage temperatures. A slightly less bleached pulp darkened more than a highly bleached pulp at all wavelengths. The only difference measured between the two pulps was that the less bleached pulp had a higher content of iron. This higher iron content may be at least part of the reason for the more extensive darkening

Theories for the Fermi Scale

I give a short review of our present understanding of new theories of the electroweak scale, with emphasis on recent progress. Plenary talk at the EPS 2007 Conference at Manchester.Comment: 14 pages, EPS 2007 Conferenc

Virtual signatures of dark sectors in Higgs couplings

Where collider searches for resonant invisible particles loose steam, dark sectors might leave their trace as virtual effects in precision observables. Here we explore this option in the framework of Higgs portal models, where a sector of dark fermions interacts with the standard model through a strong renormalizable coupling to the Higgs boson. We show that precise measurements of Higgs-gauge and triple Higgs interactions can probe dark fermions up to the TeV scale through virtual corrections. Observation prospects at the LHC and future lepton colliders are discussed for the so-called singlet-doublet model of Majorana fermions, a generalization of the bino-higgsino scenario in supersymmetry. We advocate a two-fold search strategy for dark sectors through direct and indirect observables.Comment: 20 pages, 7 figures, 1 tabl