The Lorentz force between D0 and D6 branes in string and M(atrix) theory

We use different techniques to analyze the system formed by a D0-brane and a D6-brane (with background gauge fields) in relative motion. In particular , using the closed string formalism of boosted boundary states, we show the presence of a term linear in the velocity corresponding to the Lorentz for ce experienced by the D0-brane moving in the magnetic background produced b y the D6-brane. This term, that was missed in previous analyses of this sys tem, comes entirely from the R-R odd spin structure and is also reproduced by a M(atrix) theory calculation.