Hard spectator interactions in B→ππB→ππ at order αs2

I compute the hard spectator interaction   amplitude in B→ππB→ππ at NLO, i.e., at O(αs2). This special part of the amplitude, whose LO starts at O(αs)O(αs), is defined in the framework of QCD factorization. QCD factorization allows to separate the short- and the long-distance physics in leading power in an expansion in ΛQCD/mbΛQCD/mb, where the short-distance physics can be calculated in a perturbative expansion in αsαs.In this calculation it is necessary to obtain an expansion of Feynman integrals in powers of ΛQCD/mbΛQCD/mb. I will present a general method to obtain this expansion in a systematic way once the leading power is given as an input. This method is based on differential equation techniques and easy to implement in a computer algebra system.The numerical impact on amplitudes and branching ratios is considered. The NLO contributions of the hard spectator interactions are important but small enough for perturbation theory to be valid.