  In the present work the detection, by means of a nondemolition measurement,
of a Yukawa term, coexisting simultaneously with gravity, has been considered.
In other words, a nondemolition variable for the case of a particle immersed in
a gravitational field containing a Yukawa term is obtained. Afterwards the
continuous monitoring of this nondemolition parameter is analyzed, the
corresponding propagator is evaluated, and the probabilities associated with
the possible measurement outputs are found. The relevance of these kind of
proposals in connection with some unified theories of elementary particles has
been underlined.
