Reparameterization Invariance for Collinear Operators

We discuss restrictions on operators in the soft-collinear effective theory (SCET) which follow from the ambiguity in the decomposition of collinear momenta and the freedom in the choice of light-like basis vectors $n$ and $\bar n$. Invariance of SCET under small changes in $n$ and/or $\bar n$ implies a symmetry of the effective theory that constrains the form of allowed operators with collinear fields. The restrictions occur at a given order in the power counting as well as between different orders. As an example, we present the complete set of higher order operators that are related to the collinear quark kinetic term.Comment: 11 page

Graphical amplitudes from SCET

We discuss the relationship between the graphical amplitudes T, C, P, ... used to parameterize nonleptonic B decay amplitudes, and matrix elements of operators in the soft-collinear effective theory (SCET) at leading order in \Lambda/m_b. Using the SU(3) flavor symmetry of the weak Hamiltonian we derive all-order constraints on the electroweak penguin contributions to the Wilson coefficients of SCET operators.Comment: 7 pages; one additional relation included, minor corrections. version published in Physics Letters

Theory of hadronic B decays

I give an overview of the theory of hadronic nonleptonic B decays into two light mesons. Using the soft-collinear effective theory (SCET), a factorization theorem for these processes has been proven to leading order in 1/mb. The phenomenological implications of this factorization relation for B-> \pi\pi decays are discussed, together with the prospects for determining the weak phase \alpha(\phi_2) from these modes.Comment: Contribution to the 3rd Conference on Flavor Physics and CP Violation (FPCP04), Daegu, Korea; 9 pages, 2 figure

On Power Suppressed Operators and Gauge Invariance in SCET

The form of collinear gauge invariance for power suppressed operators in the soft-collinear effective theory is discussed. Using a field redefinition we show that it is possible to make any power suppressed ultrasoft-collinear operators invariant under the original leading order gauge transformations. Our manipulations avoid gauge fixing. The Lagrangians to O(lambda^2) are given in terms of these new fields. We then give a simple procedure for constructing power suppressed soft-collinear operators in SCET_II by using an intermediate theory SCET_I.Comment: 15 pages, journal versio

Chiral symmetry and exclusive B decays in the SCET

We describe a chiral formalism for processes involving both energetic hadrons and soft Goldstone bosons, which extends the application of soft-collinear effective theory to multibody B decays. The nonfactorizable helicity amplitudes for heavy meson decays into multibody final states satisfy symmetry relations analogous to the large energy form factor relations, which are broken at leading order in Lambda/mb by calculable factorizable terms. We use the chiral effective theory to compute the leading corrections to these symmetry relations in B -> M_n pi ell\bar\nu and B -> M_n pi e+e- decays.Comment: 6 pages, 1 figure; typos correcte

Identifying genes that impact on aroma profiles produced by Saccharomyces cerevisiae and the production of higher alcohols

CITATION: Styger, G., Jacobson, D. & Bauer, F. 2011. Identifying genes that impact on aroma profiles produced by Saccharomyces cerevisiae and the production of higher alcohol. Applied Microbiology and Biotechnology, 91(3):713-30, doi:10.1007/s00253-011-3237-z.The original publication is available at http://www.springerlink.com/content/526367083qt666t3/During alcoholic fermentation, many volatile aroma compounds are formed by Saccharomyces cerevisiae, including esters, fatty acids, and higher alcohols. While the metabolic network that leads to the formation of these compounds is reasonably well mapped, surprisingly little is known about specific enzymes involved in specific reactions, the regulation of the network, and the physiological roles of individual pathways within the network. Furthermore, different yeast strains tend to produce significantly different aroma profiles. These differences are of tremendous biotechnological interest, since producers of alcoholic beverages such as wine and beer are searching for means to diversify and improve their product range. Various factors such as the redox, energy, and nutritional balance of a cell have previously been suggested to directly or indirectly affect and regulate the network. To gain a better understanding of the regulations and physiological role of this network, we screened a subset of the EUROSCARF strain deletion library for genes that, when deleted, would impact most significantly on the aroma profile produced under fermentative conditions. The 10 genes whose deletion impacted most significantly on higher alcohol production were selected and further characterized to assess their mode of action within or on this metabolic network. This is the first description of a large-scale screening approach using aroma production as the primary selection criteria, and the data suggest that many of the identified genes indeed play central and direct roles within the aroma production network of S. cerevisiae.Publishers' VersionPost prin

Power Counting in the Soft-Collinear Effective Theory

We describe in some detail the derivation of a power counting formula for the soft-collinear effective theory (SCET). This formula constrains which operators are required to correctly describe the infrared at any order in the Lambda_QCD/Q expansion (lambda expansion). The result assigns a unique lambda-dimension to graphs in SCET solely from vertices, is gauge independent, and can be applied independent of the process. For processes with an OPE the lambda-dimension has a correspondence with dynamical twist.Comment: 12 pages, 1 fig, journal versio