  The longitudinal asymmetry in relativistic heavy ion collisions arises from
the fluctuation in the number of nucleons involved. This asymmetry causes a
rapidity shift in the center of mass of the participating zone. Both the
rapidity shift and the longitudinal asymmetry have been found to be significant
at the top CERN Large Hadron Collider (LHC) energy for collisions of identical
nuclei, and the longitudinal asymmetry is important for reconstructing the
colliding vertex and correcting the rapidity shift. However, much discussion of
the longitudinal asymmetry has treated the initial condition as a nonzero
momentum contributed only by the number of participants, i.e., the asymmetry
depends only on the number of participating nucleons. So we naturally raise a
physical problem, can other initial conditions, such as two typical initial
conditions for nuclei, geometric configuration, and momentum distribution,
provide effects on the longitudinal asymmetry? Therefore, in this work we
consider other effects on the longitudinal asymmetry other than the fluctuation
in the number of participants, e.g., the {\alpha} clustering structure as well
as the intrinsic momentum distribution in the target and projectile nuclei for
the collisions in the framework of a multiphase transport (AMPT) model. By
introducing systems with different {\alpha}-clustering structure and intrinsic
momentum distribution, we calculated the ratio of the rapidity distributions of
different systems and extracted expansion coefficients to analyze the
difference contributed by these factors. ...
