# A Coloron Model with a Decay to a Single Top Quark

This model introduces a heavy scalar color octet, the coloron. It is produced through gluon fusion and decays 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)
• Devin G. E. Walker (SLAC National Accelerator Laboratory)
• Jiang-Hao Yu (The University of Texas at Austin)

## Other Contributors

• Joseph Nutter (Michigan State University)
• R. Sekhar Chivukula (Michigan State University)
• Elizabeth H. Simmons (Michigan State University)

## Description of the Model

The color octet (GH) is a neutral heavy hadronic resonance. The Feynman diagram for the production of GH and its decay to a single top quark and a charm quark is shown below. The single production of GH can be described by the effective coupling

with

Note that single production is suppressed by a factor

which is an accidental suppression factor coming from the loop. Above the threshold for decays into a single top quark, GH has two main decay modes: the decay into gluons, which occurs at loop-level similar to single coloron production, and the flavor-violating decay into tc. The corresponding rates are:

We set u=mu (the stability of the potential forbids mu>u); and consider for simplicity the set of

values that give a 50% GH decay into tc and 50% into gg. GH is a very narrow resonance, with a width of the order of 10-4 GeV.

See more details in

## Generation specifics

In 1409.7607v2, the samples were generated with the coloron 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 for 500 GeV mass included above. The specific generations run were

p p > GH, GH > b c~ l+ vl @1 GHT=1 QED=2
p p > GH, GH > b~ c l- vl~ @2 GHT=1 QED=2


To generate the settings for a specific coloron mass, use the appropriate model directory contained in the Octet-tcgg zip file. Parameter card files are included for the combination of settings that gives a branching ratio of 0.5 to tc. For other BR values, please see 1409.7607v2.