(the data frequently contains more than one jet[@CMS]). In the matrix element for jets +$\nu \bar{\nu}$ will appear $$g_X^Q\frac{g^2}{4c^2_W}
\frac{1}{p^2 -m_Z^2 +im_Z\Gamma_Z}
 (\bar{Q} \g^\a P_X Q )
( \overline{\nu}\g_\a P_L\nu)$$ whereas, for DM production via the $\bar{\chi} \g^\mu\g_5 \chi$ current, this is replaced by: $$\frac{c_{QX,A}}{\Lambda^2}
(\bar{Q} \g^\a P_X Q )
 (\overline{\chi}\g_\a\g_5 \chi)~~.$$ Then the full matrix element must be squared, and integrated over the phase space of $N$ jets and two invisible particles. The invisibles can be treated as a single particle of variable mass $p^2 = M^2_{inv}$, using the identity d\_[N+2]{} &=& \^4(P\_[in]{}- q\_i -p) \_[i:1..N]{} ( ) (2)\^3 dp\^2 \^4(p-p\_- p\_[|]{})   . Neglecting spin correlations and the dark matter mass, the invisible phase space integral over the gamma-matrix trace for the invisible fermions gives $M^2_{inv}/(8\pi)$ for $\chi$s, and $3M^2_{inv}/(16\pi)$ for neutrinos. For neutrinos in the final state, $M_{inv}^2 = m_Z^2$ due to the delta-function-like behaviour of the $Z$ propagator-squared. However, for dark matter, the $d M^2_{inv}$ phase space integral will privilege larger values of $M^2_{inv}$. Treating the $N$ jets of the event as a particle of negligeable mass, the upper bound on $M_{inv}^2$ is $ \gsim 4 \ETm^2$, where $\ETm$ is the invisible transverse energy. The CMS study 