  We study Jack characters, which are the coefficients of the power-sum
expansion of Jack symmetric functions with a suitable normalization. These
quantities have been introduced by Lassalle who formulated some challenging
conjectures about them. We conjecture existence of a weight on non-oriented
maps (i.e., graphs drawn on non-oriented surfaces) which allows to express any
given Jack character as a weighted sum of some simple functions indexed by
maps. We provide a candidate for this weight which gives a positive answer to
our conjecture in some, but unfortunately not all, cases. In particular, it
gives a positive answer for Jack characters specialized on Young diagrams of
rectangular shape. This candidate weight attempts to measure, in a sense, the
non-orientability of a given map.
