<chapter name="Compositeness Processes"> 
 
<h2>Compositeness Processes</h2> 
 
Compositeness scenarios may give rise to sharp resonances of excited 
quarks and leptons. An excited copy of the first generation is 
implemented, consisting of spin 1/2 particles. The possibility of 
contact interactions between SM fermions is also implemented in the 
context of <ei>2 &rarr; 2</ei> quark or fermion-lepton scattering. 
 
<p/> 
Related to excited fermions, the current implementation contains gauge 
interaction production by quark-gluon fusion or lepton-photon fusion 
and contact interaction production by quark-quark or quark-antiquark 
scattering. For both the <ei>2 &rarr; 1</ei> and <ei>2 &rarr; 2</ei> processes 
a non-trivial angular dependence is included in the decay, however, 
only decays into gauge bosons are supported, i.e. not decays through 
contact interactions. In additions to the compositeness scale and couplings 
listed below, you are expected to change the excited-fermion masses in 
accordance with what is desired. See <ref>Bau90</ref> for conventions. 
 
<p/> 
The contact interactions are implemented according to <ref>Eic83</ref>. 
The processes include the SM contributions as well as interference. 
For this reason the processes below converge toward the SM equivalents 
when the contact interaction contributions are close to zero, e.g. 
<code>HardQCD:qq2qq</code> and <code>HardQCD:qqbar2qqbarNew</code> in 
the case of quark scattering. 
 
<p/> 
It should also be noted that the <ei>gamma*/Z/Z'</ei> production process 
available with <ei>NewGaugeBoson:ffbar2gmZZprime</ei> is prepared for 
pair-production of excited quarks and leptons, assuming the same gauge 
couplings as for the non-excited fermions. What is missing is the 
actual decay channels in the list of <ei>Z'</ei> decay modes, which 
have to be added by hand, e.g. by 
<br/>32:addChannel = 1 1. 100 4000001 -4000001 
<br/>You can use <ei>Zprime:gmZmode</ei> to decide which gauge boson 
propagators actually are included in the simulation, and thus e.g. 
switch off the <ei>Z'</ei> part of the propagator. You may also want to 
switch off other decay channels and set the minimal mass to be at the 
threshold for the studied pair production (or suitably below it, 
if the excited fermions have a non-negligible width). 
 
<h3>Excited fermions, production processes</h3> 
 
A few different production processes have been implemented, which normally 
would not overlap and therefore could be run together. 
 
<flag name="ExcitedFermion:all" default="off"> 
Common switch for the group of implemented processes that produce an 
excited fermion. 
</flag> 
 
<flag name="ExcitedFermion:dg2dStar" default="off"> 
Scatterings <ei>d g &rarr; d^*</ei>. 
Code 4001. 
</flag> 
 
<flag name="ExcitedFermion:ug2uStar" default="off"> 
Scatterings <ei>u g &rarr; u^*</ei>. 
Code 4002. 
</flag> 
 
<flag name="ExcitedFermion:sg2sStar" default="off"> 
Scatterings <ei>s g &rarr; s^*</ei>. 
Code 4003. 
</flag> 
 
<flag name="ExcitedFermion:cg2cStar" default="off"> 
Scatterings <ei>c g &rarr; c^*</ei>. 
Code 4004. 
</flag> 
 
<flag name="ExcitedFermion:bg2bStar" default="off"> 
Scatterings <ei>b g &rarr; b^*</ei>. 
Code 4005. 
</flag> 
 
<flag name="ExcitedFermion:egm2eStar" default="off"> 
Scatterings <ei>e gamma &rarr; e^*</ei>. 
Code 4011. 
</flag> 
 
<flag name="ExcitedFermion:mugm2muStar" default="off"> 
Scatterings <ei>mu gamma &rarr; mu^*</ei>. 
Code 4013. 
</flag> 
 
<flag name="ExcitedFermion:taugm2tauStar" default="off"> 
Scatterings <ei>tau gamma &rarr; tau^*</ei>. 
Code 4015. 
</flag> 
 
<flag name="ExcitedFermion:qq2dStarq" default="off"> 
Scatterings <ei>q q(bar) &rarr; d^* q(bar)</ei>. 
Code 4021. 
</flag> 
 
<flag name="ExcitedFermion:qq2uStarq" default="off"> 
Scatterings <ei>q q(bar) &rarr; u^* q(bar)</ei>. 
Code 4022. 
</flag> 
 
<flag name="ExcitedFermion:qq2sStarq" default="off"> 
Scatterings <ei>q q(bar) &rarr; s^* q(bar)</ei>. 
Code 4023. 
</flag> 
 
<flag name="ExcitedFermion:qq2cStarq" default="off"> 
Scatterings <ei>q q(bar) &rarr; c^* q(bar)</ei>. 
Code 4024. 
</flag> 
 
<flag name="ExcitedFermion:qq2bStarq" default="off"> 
Scatterings <ei>q q(bar) &rarr; b^* q(bar)</ei>. 
Code 4025. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2eStare" default="off"> 
Scatterings <ei>q qbar &rarr; e^*+- e^-+</ei>. 
Code 4031. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2nueStarnue" default="off"> 
Scatterings <ei>q qbar &rarr; nu_e^* nu_ebar</ei>. 
Code 4032. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2muStarmu" default="off"> 
Scatterings <ei>q qbar &rarr; mu^*+- mu^-+</ei>. 
Code 4033. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2numuStarnumu" default="off"> 
Scatterings <ei>q qbar &rarr; nu_mu^* nu_mubar</ei>. 
Code 4034. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2tauStartau" default="off"> 
Scatterings <ei>q qbar &rarr; tau^*+- tau^-+</ei>. 
Code 4035. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2nutauStarnutau" default="off"> 
Scatterings <ei>q qbar &rarr; nu_tau^* nu_taubar</ei>. 
Code 4036. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2eStareStar" default="off"> 
Scatterings <ei>q qbar &rarr; e^*+- e^*-+</ei>. 
Code 4051. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2nueStarnueStar" default="off"> 
Scatterings <ei>q qbar &rarr; nu_e^* nu_e^*bar</ei>. 
Code 4052. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2muStarmuStar" default="off"> 
Scatterings <ei>q qbar &rarr; mu^*+- mu^*-+</ei>. 
Code 4053. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2numuStarnumuStar" default="off"> 
Scatterings <ei>q qbar &rarr; nu_mu^* nu_mu^*bar</ei>. 
Code 4054. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2tauStartauStar" default="off"> 
Scatterings <ei>q qbar &rarr; tau^*+- tau^*-+</ei>. 
Code 4055. 
</flag> 
 
<flag name="ExcitedFermion:qqbar2nutauStarnutauStar" default="off"> 
Scatterings <ei>q qbar &rarr; nu_tau^* nu_tau^*bar</ei>. 
Code 4056. 
</flag> 
 
<h3>Excited fermions, parameters</h3> 
 
The basic couplings of the model are 
 
<parm name="ExcitedFermion:Lambda" default="1000." min="100."> 
Compositeness scale <ei>Lambda</ei> in GeV. 
</parm> 
 
<parm name="ExcitedFermion:coupF" default="1.0" min="0.0"> 
Strength <ei>f</ei> of the <ei>SU(2)</ei> coupling. 
</parm> 
 
<parm name="ExcitedFermion:coupFprime" default="1.0" min="0.0"> 
Strength <ei>f'</ei> of the <ei>U(1)</ei> coupling. 
</parm> 
 
<parm name="ExcitedFermion:coupFcol" default="1.0" min="0.0"> 
Strength <ei>f_c</ei> of the <ei>SU(3)</ei> coupling. 
</parm> 
 
<parm name="ExcitedFermion:contactDec" default="1.0" min="0.0"> 
Strength of contact-interaction decay channels, implemented as 
three-body decays <ei>l^* &rarr; l f fbar</ei> for excited leptons 
and neutrinos, where unity corresponds to the same normalization 
as for the production channels. 
</parm> 
 
<h3>Contact interactions, production processes</h3> 
 
The processes including contact interactions are 
 
<flag name="ContactInteractions:QCqq2qq" default="off"> 
Scatterings <ei>q q &rarr; q q</ei> including contact interactions. 
Code 4201. 
</flag> 
 
<flag name="ContactInteractions:QCqqbar2qqbar" default="off"> 
Scatterings <ei>q qbar &rarr; q' qbar'</ei> including contact interactions. 
Code 4202. 
</flag> 
 
<flag name="ContactInteractions:QCffbar2eebar" default="off"> 
Scatterings <ei>f fbar &rarr; e- e+</ei> including contact interactions. 
Code 4203. 
</flag> 
 
<flag name="ContactInteractions:QCffbar2mumubar" default="off"> 
Scatterings <ei>f fbar &rarr; mu- mu+</ei> including contact interactions. 
Code 4204. 
</flag> 
 
<flag name="ContactInteractions:QCffbar2tautaubar" default="off"> 
Scatterings <ei>f fbar &rarr; tau- tau+</ei> including contact interactions. 
Code 4205. 
</flag> 
 
<h3>Contact interactions, parameters</h3> 
 
<modeopen name="ContactInteractions:nQuarkNew" default="3" min="0" max="5"> 
Number of allowed outgoing new quark flavours in the above 
<ei>q qbar &rarr; q' qbar'</ei> process. Similar to <ei>HardQCD:nQuarkNew</ei> 
for the QCD processes. 
</modeopen> 
 
<parm name="ContactInteractions:Lambda" default="1000." min="100."> 
Compositeness scale <ei>Lambda</ei> in GeV. Its overall normalization 
is largely a matter of convention. The choice made here for the 
<ei>q qbar &rarr; l- l+</ei> processes is such that the pure contact 
interaction part of the left-left interactions (i.e. disregarding 
<ei>gamma^*</ei>, <ei>Z^0</ei> and interference terms) has the form 
<ei>d(sigmaHat)/d(tHat) = pi * uHat^2 / (3 * sHat^2 * Lambda^4)</ei>. 
The corresponding part of the <ei>q qbar &rarr; q' qbar'</ei> cross section 
is a factor 3 larger from colour. 
</parm> 
 
<modepick name="ContactInteractions:etaLL" default="0" min="-1" max="1"> 
Helicity parameter. 
<option value="1"></option> 
<option value="0"></option> 
<option value="-1"></option> 
</modepick> 
 
<modepick name="ContactInteractions:etaRR" default="0" min="-1" max="1"> 
Helicity parameter. 
<option value="1"></option> 
<option value="0"></option> 
<option value="-1"></option> 
</modepick> 
 
<modepick name="ContactInteractions:etaLR" default="0" min="-1" max="1"> 
Helicity parameter. 
<option value="1"></option> 
<option value="0"></option> 
<option value="-1"></option> 
</modepick> 
 
<modepick name="ContactInteractions:etaRL" default="0" min="-1" max="1"> 
Helicity parameter. Implemented only for the <ei>q qbar &rarr; l- 
l+</ei> process.  <option value="1"></option> <option 
value="0"></option> <option value="-1"></option> 
</modepick> 
 
</chapter> 
 
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