Higgs Production at NNLO

We describe the calculation of inclusive Higgs boson production at hadronic colliders at next-to-next-to-leading order (NNLO) in perturbative quantum chromodynamics. We have used the technique developed in reference [4]. Our results agree with those published earlier in the literature.Comment: Talk given at PASCOS'03, TIFR, Mumbai, LaTeX, 5 page

The effect of ecosystem change, restoration, and plant diversity on thermally imaged surface temperature

The objective of this dissertation was to test and quantify the hypothesis from ecosystem thermodynamics: that the surface temperature of a terrestrial ecosystem changes with the state of the ecosystem in general, and with plant species diversity in particular. Daytime surface temperature of vegetated terrestrial ecosystems has been hypothesized to decrease with increased biomass and diversity as they in turn increase transpiration, respiration, physical thermal inertia, and productivity, thereby reducing the portion of energy re-emitted as thermal radiation. The hypothesis is tested, and the results and applications are discussed, within the context of ecosystem restoration. I investigated the relationship between ecosystem surface temperature and time since restoration, type of restoration methods, and changes in ecological attributes, including plant species diversity, in two projects restoring temperate wooded ecosystems. The first restoration studied, described in Chapter 2, was a 500+ ha project restoring farmland to oak woodland, spread over 31 fields. Thermal images from 4 space-based instruments along with 12 years of in-situ sampled ecological data of the project were analyzed and compared. Significant decreases in daytime summer surface temperature (4.5 °C in 12 years), and summer diurnal temperature variation (5 °C in 8 years) over time since restorations were found. The study also found a significant relationship between increased plant species diversity and decreased surface temperature when controlling for plant cover and other vegetation attributes. Native plant species had a more pronounced relationship with surface temperature than exotic ones. The results from this study supported the hypothesis, quantified its effect, and showed how thermal imaging from space-based instruments may be used to assess the progress of restoration and the increase in species diversity. The second project studied, in Chapters 3 and 4, was of application of multiple overlapping restoration treatments to experimental plots at two former farmland sites already planted with trees, and one abandoned gravel pit. The main experimental restoration treatment was the transfer of topsoil from a donor forest. On top of the topsoil, further additions were made of woody debris, shrub plantings, and shade shelters. In-situ sampled ecological differences between experimental restoration treatments and controls were assessed in Chapter 3 and thermal differences in Chapter 4. Results from Chapter 3 indicated that most native forest plant species survived within the topsoil as it was transferred from the forest, and re-sprouted in the experimental plots on the second season after the transfer. The plant species community of topsoil recipient plots was significantly different from both recipient and donor site control plots as it contained both the transferred plant species and the species already present at the recipient sites. There was no significant effect on the plant community found from the woody debris, shrub plantings, or shade shelter treatments. Since significant ecological differences were found in Chapter 3, it would be possible to find thermal differences in the same plots in Chapter 4 if the hypothesized relationship was true. To overcome the spatial and temporal resolution limitations of space-based instruments, an Unmanned Aerial Vehicle (UAV)-borne thermal camera was utilized to image the sites four times per day over 9 days. It was found that topsoil recipient plots in the gravel pit site, as well as the smaller and flatter of the two reforestation sites, had significantly lower temperatures than controls (7.0 °C and 2.0 °C respectively) and that the difference in temperature peaked at 2 pm. In the larger and more heterogeneous reforestation site, the normalized surface temperature was only significantly lower than controls (0.7 °C) at 8 pm. There was a significant negative correlation between native forest plant species and surface temperature at all three sites. The combined evidence from the two projects studied was that temperate wooded ecosystems undergoing restoration decreased in their daytime surface temperature and diurnal temperature variation over time, and compared to controls. This decrease is partly due to increasing species diversity. These results support the existence and the direction of the hypothesized, and before this mostly untested, relationship between ecosystem change (including species diversity) and temperature. It also provides examples of the relative significance and quantity of the same relationship using more ecological, and thermal imaging, data over a longer time-span than in previous studies. Both Chapters 2 and 4 found evidence for native and later succession forest plant species having a stronger effect on surface temperature than non-native and ruderal plant species. The dissertation makes a case for thermal imaging to be used both to evaluate and monitor the progress of restoration, and to quantify the ecosystem service of thermal buffering provided by restoration. It also demonstrates the relative strengths and limitations of space-based and UAV-borne thermal imaging instruments

Parton distribution functions from the precise NNLO QCD fit

We report the parton distribution functions (PDFs) determined from the NNLO QCD analysis of the world inclusive DIS data with account of the precise NNLO QCD corrections to the evolution equations kernel. The value of strong coupling constant \alpha_s^{NNLO}(M_Z)=0.1141(14), in fair agreement with one obtained using the earlier approximate NNLO kernel by van Neerven-Vogt. The intermediate bosons rates calculated in the NNLO using obtained PDFs are in agreement to the latest Run II results.Comment: 8 pages, LATEX, 2 figures (EPS

Threshold Corrections in Precision LHC Physics: QED otimes QCD

With an eye toward LHC processes in which theoretical precisions of 1 percent are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200

Probing small-x parton densities in proton- proton (-nucleus) collisions in the very forward direction

We present calculations of several pp scattering cross sections with potential applications at the LHC. Significantly large rates for momentum fraction, x, as low as 10^-7 are obtained, allowing for possible extraction of quark and gluon densities in the proton and nuclei down to these small x values provided a detector with good acceptance at maximal rapidities is used.Comment: 14 pages, LaTeX, 12 figures, uses revtex.st

Z-prime Gauge Bosons at the Tevatron

We study the discovery potential of the Tevatron for a Z-prime gauge boson. We introduce a parametrization of the Z-prime signal which provides a convenient bridge between collider searches and specific Z-prime models. The cross section for p pbar -> Z-prime X -> l^+ l^- X depends primarily on the Z-prime mass and the Z-prime decay branching fraction into leptons times the average square coupling to up and down quarks. If the quark and lepton masses are generated as in the standard model, then the Z-prime bosons accessible at the Tevatron must couple to fermions proportionally to a linear combination of baryon and lepton numbers in order to avoid the limits on Z--Z-prime mixing. More generally, we present several families of U(1) extensions of the standard model that include as special cases many of the Z-prime models discussed in the literature. Typically, the CDF and D0 experiments are expected to probe Z-prime-fermion couplings down to 0.1 for Z-prime masses in the 500--800 GeV range, which in various models would substantially improve the limits set by the LEP experiments.Comment: 34 pages, 13 figure

The spin-dependent two-loop splitting functions

We present a complete description of the calculation of the spin-dependent next-to-leading order splitting functions. The calculation is performed in the light-cone gauge. We give results for different prescriptions for the Dirac matrix $\gamma_5$ in $d=4-2 \epsilon$ dimensions and provide the link to the results in dimensional reduction.Comment: 25 pages, including 3 figures and 4 tables (4 additional style files included

On next-to-eikonal exponentiation

The eikonal approximation is at the heart of many theoretical and phenomenological studies involving multiple soft gauge boson emissions in high energy physics. We describe our efforts towards the extension of the eikonal approximation for scattering amplitudes to the first subleading power in the soft momentum.Comment: Proc. of "Loops and Legs in Quantum Field Theory", April, 2010, W\"orlitz, German

The Physcomitrella patens unique alpha-dioxygenase participates in both developmental processes and defense responses

[Background] Plant α-dioxygenases catalyze the incorporation of molecular oxygen into polyunsaturated fatty acids leading to the formation of oxylipins. In flowering plants, two main groups of α-DOXs have been described. While the α-DOX1 isoforms are mainly involved in defense responses against microbial infection and herbivores, the α-DOX2 isoforms are mostly related to development. To gain insight into the roles played by these enzymes during land plant evolution, we performed biochemical, genetic and molecular analyses to examine the function of the single copy moss Physcomitrella patens α-DOX (Ppα-DOX) in development and defense against pathogens.[Results] Recombinant Ppα-DOX protein catalyzed the conversion of fatty acids into 2-hydroperoxy derivatives with a substrate preference for α-linolenic, linoleic and palmitic acids. Ppα-DOX is expressed during development in tips of young protonemal filaments with maximum expression levels in mitotically active undifferentiated apical cells. In leafy gametophores, Ppα-DOX is expressed in auxin producing tissues, including rhizoid and axillary hairs. Ppα-DOX transcript levels and Ppα-DOX activity increased in moss tissues infected with Botrytis cinerea or treated with Pectobacterium carotovorum elicitors. In B. cinerea infected leaves, Ppα-DOX-GUS proteins accumulated in cells surrounding infected cells, suggesting a protective mechanism. Targeted disruption of Ppα-DOX did not cause a visible developmental alteration and did not compromise the defense response. However, overexpressing Ppα-DOX, or incubating wild-type tissues with Ppα-DOX-derived oxylipins, principally the aldehyde heptadecatrienal, resulted in smaller moss colonies with less protonemal tissues, due to a reduction of caulonemal filament growth and a reduction of chloronemal cell size compared with normal tissues. In addition, Ppα-DOX overexpression and treatments with Ppα-DOX-derived oxylipins reduced cellular damage caused by elicitors of P. carotovorum.[Conclusions] Our study shows that the unique α-DOX of the primitive land plant P. patens, although apparently not crucial, participates both in development and in the defense response against pathogens, suggesting that α-DOXs from flowering plants could have originated by duplication and successive functional diversification after the divergence from bryophytes.This work was supported by Agencia Nacional de Investigación e Innovación (ANII) [grants FCE2007_376, FCE2011_6095, fellowships BE_POS_2009_726 (A. Castro) and BE_POS_2010_2533 (L. Machado)], UdelaR Uruguay/CSIC Spain (Joint project), the Swedish Research Council, and Programa de Desarrollo de las Ciencias Básicas (PEDECIBA) Uruguay. The Ppα-DOX cDNA was obtained from the RIKEN Biological Research Center, Tsukuba, Japan

Next-to-Next-to-Leading Order Higgs Production at Hadron Colliders

The Higgs boson production cross section at pp and p\bar{p} colliders is calculated in QCD at next-to-next-to-leading order (NNLO). We find that the perturbative expansion of the production cross section is well behaved and that scale dependence is reduced relative to the NLO result. These findings give us confidence in the reliability of the prediction. We also report an error in the NNLO correction to Drell-Yan production.Comment: 5 pages, 4 figures, minor change