Prospects for single top cross-section measurements in ATLAS

At the LHC, the production of single top events account for a fourth of the overall top quark production. With a cross-section of about 300~pb, the LHC should lead to a clear evidence of the single top production mechanisms and open a new era of precision measurements in this field. With more than two millions of single top events produced every year during a low luminosity run, a precise determination of all contributions to the total single-top cross-section will provide valuable tests of the electro-weak production and constitute the first direct measurement of V_tb at the few percent level of precision. The interpretation of cross-section measurements also constitute a powerful probe for new physics, via the search for evidence of anomalous couplings to the top quark or the measurements of additional bosonic contributions to the production mechanisms. We describe in this report some possible strategies to measure all three components of the single top cross-section: the s-channel, the gluon-fusion channel and the associated production of a top and a W~boson. These mechanisms result in a very disctinct final state and topologies, and require and require the development of specific selections. The analyses are presented and their performance is assessed in terms of statistical sensitivity and systematic uncertainties. The measurements are in most cases dominated by systematic uncertainties and show the need for early strategies devoted to the control of experimental biases, modeling effects and reliable background determinations.