A model for the probabilistic function followed in Wikipedia edition is presented and compared with simulations and real data. It is argued that the probability to edit is proportional to the editors number of previous editions (preferential attachme
nt), to the editors fitness and to an ageing factor. Using these simple ingredients, it is possible to reproduce the results obtained for Wikipedia edition dynamics for a collection of single pages as well as the averaged results. Using a stochastic process framework, a recursive equation was obtained for the average of the number of editions per editor that seems to describe the editing behaviour in Wikipedia.
Many stochastic time series can be described by a Langevin equation composed of a deterministic and a stochastic dynamical part. Such a stochastic process can be reconstructed by means of a recently introduced nonparametric method, thus increasing th
e predictability, i.e. knowledge of the macroscopic drift and the microscopic diffusion functions. If the measurement of a stochastic process is affected by additional strong measurement noise, the reconstruction process cannot be applied. Here, we present a method for the reconstruction of stochastic processes in the presence of strong measurement noise, based on a suitably parametrized ansatz. At the core of the process is the minimization of the functional distance between terms containing the conditional moments taken from measurement data, and the corresponding ansatz functions. It is shown that a minimization of the distance by means of a simulated annealing procedure yields better results than a previously used Levenberg-Marquardt algorithm, which permits a rapid and reliable reconstruction of the stochastic process.
The ATLAS experiment sensitivity to top quark Flavour Changing Neutral Current (FCNC) decays was studied at LHC using ttbar events. While one of the top quarks is expected to follow the dominant Standard Model decay t->bW, the other decays through a
FCNC channel, i.e. t-> Z u(c), t-> gamma u(c) or t-> g u(c). Different types of analyses, applied to each FCNC decay mode, were compared. The FCNC branching ratio sensitivity (assuming a 5sigma signal significance) and 95% confidence level limits on the branching ratios (in the hypothesis of signal absence) were obtained.
