The ATLAS experiment is preparing for data taking at 14 TeV collision energy. A rich discovery physics program is being prepared in addition to the detailed study of Standard Model processes which will be produced in abundance. The ATLAS multi-level trigger system is designed to accept one event in 2 • 10B to enable the selection of rare and unusual physics events. The ATLAS calorimeter system is a precise instrument, which includes liquid Argon electromagnetic and hadronic components as well as a scintillator-tile hadronic calorimeter. All these components are used in the various levels of the trigger system. A wide physics coverage is ensured by inclusively selecting events with candidate electrons, photons, taus, jets or those with large missing transverse energy. The commissioning of the trigger system is being performed with cosmic ray events and by replaying simulated Monte Carlo events through the trigger and data acquisition system.

Multivariate classification methods based on machine learning techniques play a fundamental role in today's high-energy physics analyses dealing with ever smaller signal in ever larger data sets. TMVA is a toolkit integrated in the ROOT framework which implements a large variety of multivariate classification algorithms ranging from simple rectangular cut optimisation and likelihood estimators, over linear and non-linear discriminants to more recent developments like boosted decision trees, rule fitting and support vector machines. All classifiers can be trained, tested and evaluated simultaneously. They all see the same training are then afterwards also tested on the same independent test data allowing meaningful comparisons between the methods for a particular use case. Here, an overview about the package and the classifiers currently implemented is presented.

We present updated results on time-dependent CP -violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 62 million Υ (4S) → BB decays collected between 1999 and 2001 by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. In this sample we study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP -violating asymmetry, which in the Standard Model is proportional to sin2β, is derived from the decay time distributions in such events. We measure sin2β = 0.75 ± 0.09 (stat) ± 0.04 (syst) and |λ| = 0.92 ± 0.06 (stat) ± 0.02 (syst). The latter is consistent with the Standard Model expectation of no direct CP violation. These results are preliminary.

We have performed a search for the rare leptonic decay B + → µ + ν µ with data collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II storage ring. In a sample of 88.4 million BB pairs, we find no significant evidence for a signal and set an upper limit on the branching fraction B(B + → µ + ν µ ) < 6.6 × 10 −6 at the 90% confidence level.

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