corresponds to interactions with the quarks in the target nuclei. In the case of neutralino dark matter, this can occur through either $t$-channel CP-even Higgs exchange, or $s$-channel squark exchange:

(222,254)(3,4.3) (5.,20.)(20.,10.)(0.,)[/Straight]{}[0]{} (0.,18.0)\[b\][$\chi^0$]{} (20.,-5.0)(20.,10.0)(0.,)[/ScalarDash]{}[0]{} ( 5.,-15.0)(20.,-5.0)(0.,)[/Straight]{}[+1]{} (0.,-18.0)\[b\][$q$]{} (25.,0.0)\[b\][$H, h$]{} (20.,10.)(35.,20.)(0.,)[/Straight]{}[0]{} (20.,-5.)(35.,-15.0)(0.,)[/Straight]{}[+1]{} (40.,18.0)\[b\][$\chi^0$]{} (40.,-18.)\[b\][$q$]{} (70.,14.)(85.,3.)(0.,)[/Straight]{}[0]{} (65.,12.0)\[b\][$\chi^0$]{}

(70.,-7.0)(85.,3.0)(0.,)[/Straight]{}[+1]{} (65.,-9.0)\[b\][$q$]{}

(85.,3.)(105.,3.0)(0.,)[/ScalarDash]{}[0]{} (95.,9.)\[t\][$\tilde{q}$]{}

(120.,14.)(105.,3.0)(0.,)[/Straight]{}[0]{} (125.,12.)\[b\][$\chi^0$]{}

(120.,-7.)(105.,3.0)(0.,)[/Straight]{}[-1]{} (125.,-9.)\[b\][$q$]{}

The second term corresponds to interactions with the gluons in the target through a loop diagram (a quark/squark loop in the case of supersymmetry). $f^{(p)}_{TG}$ is given by $1 -f^{(p)}_{T_u}-f^{(p)}_{T_d}-f^{(p)}_{T_s} 
\approx 0.84$, and analogously, $f^{(n)}_{TG} \approx 0.83$.

Besides its mass, the only thing we need to know about the WIMP itself to calculate this cross section are its couplings to quarks, $a_q$. In the case of neutralino dark matter, the value of this coupling depends on many features of the supersymmetric spectrum. The contribution resulting from Higgs exchange depends on the neutralino composition, as well as the Higgs masses and couplings.

In the case of heavy squarks, small wino component and little mixing between the CP-even Higgs bosons ($\cos \alpha \approx 1$), neutralino-nuclei elastic scattering is dominated by $H$ exchange with strange and bottom quarks, leading to a neutralino-nucleon cross section approximately given by: $$\sigma_{\chi N} \sim 