  The scenario of twin coronal mass ejections (CMEs), i.e., a fast and wide
primary CME (priCME) preceded by previous CMEs (preCMEs), has been found to be
favorable to a more efficient particle acceleration in large solar energetic
particle (SEP) events. Here, we study 19 events during 2007--2014 associated
with twin-CME eruptions but without large SEP observations at L1 point. We
combine remote-sensing and in situ observations from multiple spacecraft to
investigate the role of magnetic connectivity in SEP detection and the CME
information in 3-dimensional (3D) space. We study one-on-one correlations of
the priCME 3D speed, flare intensity, suprathermal backgrounds, and height of
CME-CME interaction with the SEP intensity. Among these, the priCME speed is
found to correlate with the SEP peak intensity at the highest level. We use the
projection correlation method to analyze the correlations between combinations
of these multiple independent factors and the SEP peak intensity. We find that
the only combination of two or more parameters that has higher correlation with
the SEP peak intensity than the CME speed is the CME speed combined with the
propagation direction. This further supports the dominant role of the priCME in
controlling the SEP enhancements, and emphasizes the consideration of the
latitudinal effect. Overall, the magnetic connectivity in longitude as well as
latitude and the relatively lower priCME speed may explain the existence of the
twin-CME SEP-poor events. The role of the barrier effect of preCME(s) is
discussed for an event on 2013 October 28.
