We report on a search for the day-night asymmetry of the Be-7 solar neutrino
rate measured by Borexino at the Laboratori Nazionali del Gran Sasso (LNGS),
Italy. The measured value, Adn=0.001 +- 0.012 (stat) +- 0.007 (syst), shows the
absence of a significant asymmetry. This result alone rejects the so-called LOW
solution at more than 8.5 sigma. Combined with the other solar neutrino data,
it isolates the Large Mixing Angle (LMA) -- MSW solution at DeltaChi2 > 190
without relying on the assumption of CPT symmetry in the neutrino sector. We
also show that including the day-night asymmetry, data from Borexino alone
restricts the MSW neutrino oscillations to the LMA solution at 90% confidence
level. \\ ( http://arxiv.org/abs/1104.2150 ,  547kb)