A Kaluza-Klein Gluon Model with FCNC Decay to a Single Top Quark
This model allows for FCNC interactions of the Kaluza-Klein gluon and in particular focuses on the flavor-violating decay of the KKg to a top quark and a charm quark.
Corresponding Authors
- Elizabeth Drueke (Michigan State University)
- Reinhard Schwienhorst (Michigan State University)
- Natascia Vignaroli (Michigan State University)
Other Contributors
- Joseph Nutter (Michigan State University)
- Devin G. E. Walker (SLAC National Accelerator Laboratory)
- Jiang-Hao Yu (The University of Texas at Austin)
- R. Sekhar Chivukula (Michigan State University)
- Elizabeth H. Simmons (Michigan State University)
Description of the Model
Colored vector bosons from new strong dynamics, Kaluza-Klein gluons or KKg’s (G*) in a dual 5D picture, have been searched for mainly in the t-tbar channel. The analysis in 1409.7607v2 analyzes the tc decay as depicted below: The benchmark adopted here is a simple renormalizable model of an extended color gauge sector, which realizes next-to-minimal flavor violation (NMFV). In this model, the third generation quarks couple differently than the light quarks under an extended
$SU(3)_1 \times SU(3)_2$
color gauge group. The mixing between light and third generation quarks is induced by the interactions of all three generation quarks with a set of new heavy vector-like quarks. Gluon-gluon fusion production is forbidden at tree level by SU(3)_C gauge invariance.
The G* decay widths are:
$\Gamma[G^{*} \to t\bar t] = \frac{g^2_s}{24\pi} M_{G^{*}}\cot^2\omega \sqrt{1-4 \frac{m^2_t}{M^2_{G^{*}}}} (1+2\frac{m^2_t}{M^2_{G^{*}}}),$ \newline $\Gamma[G^{*} \to b\bar b] = \frac{g^2_s}{24\pi} M_{G^{*}}\cot^2\omega,$ \newline $\Gamma[G^{*} \to j j] = \frac{g^2_s}{6\pi} M_{G^{*}}\tan^2\omega.$
Additionally, the NMFV flavor structure of the model generates a G* to tc flavor violating decay with rate
$\Gamma[G^{*} \to t_L \bar c_L]=\Gamma[G^{*} \to c_L \bar t_L]\simeq \left(V_{cb}\right)^2 \frac{g^2_s}{48\pi} M_{G^{*}} \left( \cot\omega+\tan\omega \right)^2,$
where
$V_{cb}=0.0415$
is the CKM matrix element.
See more details in
Model Files
- proc_card: for generation of 500 GeV KKg (place in Cards/)
- run_card: for generation of 500 GeV KKg (place in Cards/)
- kkg_FV: the model and parameter cards for specific mass generations
Generation specifics
In 1409.7607v2, the samples were generated with the KKg mass as the scale, dsqrt_q2fact1, and dsqrt_q2fact2 in the run_card.dat file. These samples were also generated without MadGraph cuts as demonstrated in the run_card.dat file for 500 GeV mass included above. The specific generations run were
p p > kkg > b~ c l- vl~ @1 p p > kkg > b c~ l+ vl @2
To generate the settings for a specific KKg mass, change the param_card.dat in the generation directory to the card of the appropriate mass in the param_cards directory (included as part of the model zip file). It is important to do this immediately before generating events. Within these files,
\text{cteta } $=\cot\omega$
The default value is
$\cot\omega=2.6$,
which corresponds to a width of about 25% of the KKg mass.
Related Models
Attachments (4)
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KKg.png
(1.7 KB
) - added by 9 years ago.
Feynman Diagram for kkg > tc
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proc_card_mg5.dat
(1.9 KB
) - added by 9 years ago.
process card for a 500 GeV mass KKg
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run_card.dat
(13.8 KB
) - added by 9 years ago.
run card for a 500 GeV mass KKg
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kkg_FV.zip
(28.9 KB
) - added by 9 years ago.
model
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