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Compositeness and anomalous couplings

ISUB =
20 $\mathrm{f}_i \overline{\mathrm{f}}_j \to \gamma \mathrm{W}^+$
165 $\mathrm{f}_i \overline{\mathrm{f}}_i \to \mathrm{f}_k \overline{\mathrm{f}}_k$ (via $\gamma^* / \mathrm{Z}^0$)
166 $\mathrm{f}_i \overline{\mathrm{f}}_j \to \mathrm{f}_k \overline{\mathrm{f}}_l$ (via $\mathrm{W}^{\pm}$)
381 $\mathrm{f}_i \mathrm{f}_j \to \mathrm{f}_i \mathrm{f}_j$
382 $\mathrm{f}_i \overline{\mathrm{f}}_i \to \mathrm{f}_k \overline{\mathrm{f}}_k$

Some processes are implemented to allow the introduction of anomalous coupling, in addition to the Standard Model ones. These can be switched on by ITCM(5) $\geq 1$; the default ITCM(5) = 0 corresponds to the Standard Model behaviour.

In processes 381 and 382, the quark substructure is included in the left-left isoscalar model [Eic84,Chi90] for ITCM(5) = 1, with compositeness scale $\Lambda$ given in RTCM(41) (default 1000 GeV) and sign $\eta$ of interference term in RTCM(42) (default $+1$; only other alternative $-1$). The above model assumes that only $\u $ and $\d $ quarks are composite (at least at the scale studied); with ITCM(5) = 2 compositeness terms are included in the interactions between all quarks. When ITCM(5) = 0, the two processes are equivalent with 11 and 12. A consistent set of high-$p_{\perp}$ jet production processes in compositeness scenarios is thus obtained by combining 381 and 382 with 13, 28, 53 and 68.

The processes 165 and 166 are basically equivalent to 1 and 2, i.e. $\gamma^* / \mathrm{Z}^0$ and $\mathrm{W}^{\pm}$ exchange, respectively, but with less detail (no mass-dependent width, etc.). The reason for this duplication is that the resonance treatment formalism of processes 1 and 2 could not easily be extended to include other than $s$-channel graphs. In processes 165 and 166, only one final-state flavour is generated at the time; this flavour should be set in KFPR(165,1) and KFPR(166,1), respectively. For process 166 one gives the down-type flavour, and the program will associate the up-type flavour of the same generation. Defaults are 11 in both cases, i.e. $\mathrm{e}^+\mathrm{e}^-$ and $\mathrm{e}^+ \nu_{\mathrm{e}}$ ( $\mathrm{e}^- \overline{\nu}_{\mathrm{e}}$) final states. While ITCM(5) = 0 gives the Standard Model results, ITCM(5) = 1 contains the left-left isoscalar model (which does not affect process 166), and ITCM(5) = 3 the helicity-non-conserving model (which affects both) [Eic84,Lan91]. Both models above assume that only $\u $ and $\d $ quarks are composite; with ITCM(5) = 2 or 4, respectively, contact terms are included for all quarks in the initial state. The relevant parameters are RTCM(41) and RTCM(42), as above.

Note that processes 165 and 166 are book-kept as $2 \to 2$ processes, while 1 and 2 are $2 \to 1$ ones. This means that the default $\mathrm{Q}^2$ scale in parton distributions is $p_{\perp}^2$ for the former and $\hat{s}$ for the latter. To make contact between the two, it is recommended to set MSTP(32) = 4, so as to use $\hat{s}$ as scale also for processes 165 and 166.

In process 20, for $\mathrm{W}\gamma$ pair production, it is possible to set an anomalous magnetic moment for the $\mathrm{W}$ in RTCM(46) ( $= \eta = \kappa-1$; where $\kappa = 1$ is the Standard Model value). The production process is affected according to the formulae of [Sam91], while $\mathrm{W}$ decay currently remains unaffected. It is necessary to set ITCM(5) = 1 to enable this extension.


next up previous contents
Next: Excited fermions Up: Non-Standard Physics Previous: Leptoquarks   Contents
Stephen Mrenna 2007-10-30