Lithographically fabricated point contacts serve as important examples of mesoscopic conductors, as electrodes for molecular electronics, and as ultra-sensitive transducers for mechanical motion. We have developed a reproducible technique for fabrica
ting metallic point contacts though electromigration. We employ fast analog feedback in a four-wire configuration in combination with slower computer controlled feedback to avoid catastrophic instability. This hybrid system allows electromigration to proceed while dissipating approximately constant power in the wire. We are able to control the final resistance of the point contact precisely below 5 kOmega and to within a factor of three when the target resistance approaches 12 kOmega where only a single conducting channel remains.
We calculate the production of a W boson in association with up to two jets including at least one b-jet to next-to-leading order (NLO) in QCD at the CERN Large Hadron Collider with 7 TeV center-of-mass energy. Both exclusive and inclusive event cros
s section and b-jet cross sections are presented. The calculation is performed consistently in the five-flavor-number scheme where both q anti-q and bq (q == b) initiated parton level processes are included at NLO QCD. We study the residual theoretical uncertainties of the NLO predictions due to the renormalization and factorization scale dependence, to the uncertainty from the parton distribution functions, and to the values of alpha_s and the bottom-quark mass.
