Physics with B-mesons in ATLAS

B-physics is an importany part of studies with the LHC beams at low luminosities. Effective B-meson reconstruction with exclusive semileptonic modes in the ATLAS can produce a clean sample of events for detailed physics analysis with first data. The analysis includes measurements of B-meson mass and proper lifetime to verify performance of the Inner Detector and to estimate background and trigger efficiencies for rare decays. The b-quark fragmentation with low pt, bbbar correlations and pt compensation will be studied in events with reconstructed B-mesons. The underlying event multiplisities in such events will be mesured and compared with data from Leading jet analysis.