I will give a full description of Arthur's packets on the field of complex numbers. In this case,
the situation is particularly simple because the classification of the unitary dual is known after
Barbasch's work.
Links:
[1] http://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] http://www.mpim-bonn.mpg.de/de/node/3444
[3] http://www.mpim-bonn.mpg.de/de/node/6370