  We study the Calogero--Moser derivative NLS equation $$ i \partial_t u
+\partial_{xx} u + (D+|D|)(|u|^2) u =0 $$ posed on the Hardy-Sobolev space
$H^s_+(\mathbb{R})$ with suitable $s>0$. By using a Lax pair structure for this
$L^2$-critical equation, we prove global well-posedness for $s \geq 1$ and
initial data with sub-critical or critical $L^2$-mass $\| u_0 \|_{L^2}^2 \leq 2
\pi$. Moreover, we prove uniqueness of ground states and also classify all
traveling solitary waves. Finally, we study in detail the class of
multi-soliton solutions $u(t)$ and we prove that they exhibit energy cascades
in the following strong sense such that $\|u(t)\|_{H^s} \sim_s |t|^{2s}$ as $t
\to \pm \infty$ for every $s > 0$. \end{abstract}
