The Gemara teaches:
One who intended to lift a plant detached from the ground on and mistakenly severed a plant still attached to the ground, which under other circumstances constitutes performance of the prohibited labor of reaping, is exempt from bringing a sin-offering for his mistaken act, since he did not intend to perform an act of cutting [be-shogeg]. One who performs an action unawares [mitasek], i.e., he had no intention to perform the act at all, incurs no liability whatsoever. One who intended to cut a detached plant and unwittingly severed a plant still attached to the ground, Rava said: He too is exempt. Abayye said that he is liable because he intended to perform a standard act of cutting. Since he intended to perform that act, and he carried out his intent, the Torah characterizes it as unwitting and not as unawares.
Rava explains that the source of his ruling stems from a that teaches that
…a stricture with regard to other mitzvot that is greater than the stricture with regard to Shabbat is that, with regard to other mitzvot, one who performs an act unwittingly without intent is liable to bring a sin-offering, which is not the case with regard to Shabbat.
Apparently, the phrase unwittingly without intent refers to the case above disputed by Abayye and Rava. Therefore, this is proof for Rava’s opinion that, with regard to, one who acts unawares, i.e., whose action resulted from involvement in another matter and who had no intention to perform an action that is prohibited [mitasek], is not considered to have performed an unwitting act.
The fundamental difference between unwitting [be-shogeg] and unawares [mitasek] is that one who acts unwittingly intends to perform the action in the manner that he performs it. However, due to forgetfulness or some other reason, he was not conscious of the fact that it is prohibited. Acting unawares refers to circumstances where one has no intent to perform the action at all. Everyone agrees that one who acts unawares is exempt with regard to the halakhot of, since the Torah prohibited only planned, thoughtful labor. An action performed without intent to perform that action is excluded from that category. On the other hand, with regard to prohibited foods and forbidden relations, even one who acts unawares is liable because, ultimately, he derives a forbidden pleasure. As far as other transgressions, where one does not enjoy physical pleasure, the extent of the liability of one who acts unawares is unclea