“…For basic concepts of this theory see Dunkl's pioneering work [16] and, for instance, the survey article by Rösler [35]. Harmonic analysis related to the Dunkl harmonic oscillator (DHO in short) has been intensively studied in recent years by the authors [29,30,31,43,44] and many other mathematicians, see, e.g., [3,6,7,12,13,26,46] and references therein. A commonly appearing assumption in this literature is that the underlying multiplicity function is non-negative.…”