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Charged Higgs sector

MSEL = 23
ISUB =
143 $\mathrm{f}_i \overline{\mathrm{f}}_j \to \H ^+$
161 $\mathrm{f}_i \mathrm{g}\to \mathrm{f}_k \H ^+$
401 $\mathrm{g}\mathrm{g}\to \overline{\mathrm{t}}\b\H ^+$
402 $\mathrm{q}\overline{\mathrm{q}}\to \overline{\mathrm{t}}\b\H ^+$

A charged Higgs doublet, $\H ^{\pm}$, is included in the program. This doublet may be the one predicted in the MSSM scenario, see section [*], or in any other scenario. The $\tan\beta$ parameter, which is relevant also for neutral Higgs couplings, is set via PARU(141) or, if SUSY is switched on, via RMSS(5).

The basic subprocess for charged Higgs production in hadron colliders is ISUB = 143. However, this process is dominated by $\t\overline{\mathrm{b}}\to \H ^+$, and so depends on the choice of $\t $ parton distribution, if non-vanishing. A better representation is provided by subprocess 161, $\mathrm{f}\mathrm{g}\to \mathrm{f}' \H ^+$; i.e. actually $\overline{\mathrm{b}}\mathrm{g}\to \overline{\mathrm{t}}\H ^+$. It is therefore recommended to use 161 and not 143; to use both would be double-counting.

A further step is to include the initial state gluon splitting $\mathrm{g}\to \b\overline{\mathrm{b}}$ as part of the matrix element, as in process 401. Using both 161 and 401 again would involve doublecounting, but now the issue is more complicated, since 401 may be expected to give the better description at large $p_{\perp\b }$ and 161 the better at small $p_{\perp\b }$, so some matching may be the best solution [Bor99]. Process 402 gives a less important contribution, that can be added without doublecounting. (The situation is similar to that for processes 3, 32, 121 and 122 for neutral Higgs production.)

A major potential source of charged Higgs production is top decay. It is possible to switch on the decay channel $\t\to \b\H ^+$. Top will then decay to $\H ^+$ a fraction of the time, whichever way it is produced. The branching ratio is automatically calculated, based on the $\tan\beta$ value and masses. It is possible to only have the $\H ^+$ decay mode switched on, in which case the cross section is reduced accordingly.

Pair production of the charged Higgs is also possible through its electromagnetic charge; see section [*] below.


next up previous contents
Next: Higgs pairs Up: Higgs Production Previous: Extended neutral Higgs sector   Contents
Stephen Mrenna 2007-10-30