19 research outputs found
In-Frame and Unmarked Gene Deletions in Burkholderia cenocepacia via an Allelic Exchange System Compatible with Gateway Technology
Burkholderia cenocepacia is an emerging opportunistic pathogen causing life-threatening infections in immunocompromised individuals and in patients with cystic fibrosis, which are often difficult, if not impossible, to treat. Understanding the genetic basis of virulence in this emerging pathogen is important for the development of novel treatment regimes. Generating deletion mutations in genes predicted to encode virulence determinants is fundamental to investigating the mechanisms of pathogenesis. However, there is a lack of appropriate selectable and counter-selectable markers for use in B. cenocepacia, making its genetic manipulation problematic. Here we describe a Gateway-compatible allelic exchange system based on the counter-selectable pheS gene and I-SceI homing endonuclease. The system provides efficiency in cloning homology regions of target genes, and allows the generation of precise and unmarked gene deletions in B. cenocepacia. As a proof of concept, we demonstrate its utility by deleting the Bcam1349 gene, encoding a c-di-GMP responsive regulator protein important for biofilm formation
Effective Theory Description of Weak Annihilation in B-> Xu l nu Decays
The semileptonic B-> Xu l nu decays allow a pretty clean determination of the
CKM matrix element |Vub|. Nevertheless, the presence of weak-annihilation
effects near the end-point of the q2 spectrum introduces uncertainties in the
inclusive calculation, requiring the use of non-perturbative techniques like
heavy meson chiral perturbation theory and large NC limit.Comment: 3 pages, 2 figures. To appear in the proceedings of the 7th
International Conference on Hyperons, Charm And Beauty Hadrons (BEACH 2006),
2nd-8th July 2006, Lancaster, Englan
B_s --> mu+ mu- decay in the R-parity violating minimal supergravity
We study B_s --> mu+ mu- in the context of the R-parity violating minimal
supergravity in the high tan beta regime. We find that the lowest value of the
branching ratio can go well below the present LHCb sensitivity and hence B_s
--> mu+ mu- can even be invisible to the LHC. We also find that the present
upper bound on Br(B_s --> mu+ mu-) puts strong constraint on the minimal
supergravity parameter space. The constraints become more severe if the upper
bound is close to its standard model prediction.Comment: 18 pages, 10 figures; version to be published in European Physical
Journal
B^0-\bar{B}^0 mixing and B \to X_s \gamma decay in the third type 2HDM: effects of NLO QCD contributions
In this paper, we calculated the next-to-leading order (NLO) new physics
contributions to the mass splitting \dmd and the branching ratio \brbxsga
induced by the charged Higgs loop diagrams in the third type of
two-Higgs-doublet models (model III) and draw the constraints on the free
parameters of model III. For the model III under consideration, we found that
(a) an upper limit |\ltt|\leq 1.7 is obtained from the precision data of
\dmd=0.502 \pm 0.007 ps^{-1}, while |\ltt| \approx 0.5 is favored
phenomenologicaly; (b) for decay, the NLO QCD contributions
tend to cancel the LO new physics contributions; (c) a light charged Higgs
boson with a mass around or even less than 200 GeV is still allowed at NLO
level by the measured branching ratio \brbxsga: numerically, 188 \leq \mh
\leq 215 GeV for (|\ltt|,|\lbb|)=(0.5,18); (d) the NLO QCD contributions
tend to cancel the LO contributions effectively, the lower limit on \mh is
consequently decreased by about 200 GeV; (e) the allowed region of \mh will
be shifted toward heavy mass end for a non-zero relative phase between
the Yukawa couplings \ltt and \lbb. The numerical results for the
conventional model II are also presented for the sake of a comparison.Comment: 42 pages, 18 eps figures, Revtex, new references adde
The Top Quark Decay Vertex in Standard Model Extensions
New physics interactions can affect the strength and structure of the
vertex. We investigate the magnitudes and phases of "anomalous" contributions
to this vertex in a two-Higgs doublet and the minimal supersymmetric extension
of the standard model, and in a top-color assisted technicolor (TC2) model.
While the magnitudes of the anomalous couplings remain below 1 percent in the
first two models, TC2 interactions can reduce the left-chiral coupling by
several percent.Comment: Latex, 27 pages, 14 figure
Collider aspects of flavour physics at high Q
This review presents flavour related issues in the production and decays of
heavy states at LHC, both from the experimental side and from the theoretical
side. We review top quark physics and discuss flavour aspects of several
extensions of the Standard Model, such as supersymmetry, little Higgs model or
models with extra dimensions. This includes discovery aspects as well as
measurement of several properties of these heavy states. We also present public
available computational tools related to this topic.Comment: Report of Working Group 1 of the CERN Workshop ``Flavour in the era
of the LHC'', Geneva, Switzerland, November 2005 -- March 200