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Associate production

 Even if the cross sections for the associative Higgs production shown in fig. 2.1c and fig. 2.1d are low compared to the total Higgs cross section, they can be of interest since the final states have some clear signatures which can be used in the difficult intermediate mass region for the Higgs (section 2.6.1). The calculated cross section are shown in fig. 2.2.

The associative production with a W vector boson was first mentioned in [11] where the expression for the cross section in a slightly more modern notation is
 \begin{align}
 \sigma({p p \rightarrow WH + X}) &= \frac{g^4}{768\pi}
 \iint \fr...
 ...r{d}}(x_1,Q^2)]\cdot\\  & \quad f_{W}(x_1 x_2 s) {d}x_1 {d}x_2 \notag\end{align}
for W +H production. For the W -H production the quark fu,fd and anti-quark f$\scriptstyle\bar{u}$,f$\scriptstyle\bar{d}$ structure functions are interchanged. The value of fW is given by the expression
 \begin{align}
 f_{W}(y) &= \frac{1}{y}
 \sqrt{1 - \frac{(m_{H}+m_{W})^2}{y}}
 \s...
 ...W}^2}{y}
 \right\} \cdot \\  & \quad
 \frac{1}{(1-m_{W}/y)^2}. \notag\end{align}
For a Higgs mass of 150 GeV the production cross section is around 1 pb or 4% of the gluon fusion cross section. With the present structure functions available the uncertainty in the cross section is around 30%. However, this uncertainty can to a large extent be reduced by using single W production as a reference process [12]. At LHC energies it is estimated that

 
$\displaystyle{\frac{\sigma({p p \rightarrow WH + X})}{\sigma({p p \rightarrow W + X})}}$ $\displaystyle\simeq$ 3.5 $\displaystyle\cdot$ 10- 8 (26)

with the uncertainty from structure functions instead now only 7%. This way of reducing the uncertainty in production cross section from reference processes could also be employed for other production channels.

The other associative production of interest is the H t$\bar{t}$ process. The cross section was first calculated by Kunszt in [13] with further details in [14]. Since ten different Feynman diagrams contribute to the process just in lowest order the calculation is complicated and no derivation will be given here. For Higgs masses below 200 GeV the cross section is around a factor 5 below the cross section for associative production with a W, while for Higgs masses above 500 GeV it reaches above the WH cross section but is still far below the gluon fusion cross section.

In the case of a supersymmetric Higgs sector the cross sections for the fermionic and bosonic associative production will change in different ways from the standard model values.


next up previous contents
Next: Higgs decays Up: Higgs Production Previous: Vector boson fusion
Ulrik Egede
1/8/1998