Version 5 (modified by druekeel, 5 years ago) (diff)

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# A Kaluza-Klein Gluon Model

## Authors

• Elizabeth Drueke (Michigan State University)
• Joseph Nutter (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)
• 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

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. The model reproduces the CKM mixing and generates flavor-changing neutral currents (FCNCs) from non-standard interactions. Due to the specific structure of the model, dangerous FCNCs are naturally suppressed and a large portion of the model parameter space is allowed by the data on meson mixing process and on

The model has the color gauge structure

The extended color symmetry is broken down to

by the (diagonal) expectation value,

of a scalar field Phi which transforms as a

under the color gauge structure. It is assumed that color gauge breaking occurs at a scale much higher than the electroweak scale, u>>v.

Breaking the color symmetry induces a mixing between the

gauge fields

which is diagonalized by a rotation determined by

where g_s is the QCD strong coupling and g_1, g_2 are the SU(3)_1 and SU(3)_2 gauge couplings, respectively. The mixing diagonalization reveals two color vector boson mass eigenstates: the mass-less SM gluon and a new massive color-octet vector boson G* given by

In the NMFV model, the third generation quarks couple differently than the light quarks under the extended color group.

as well as a new weak-doublet of vector-like quarks, transform as

under the color gauge group, while the light generation quarks are charged under SU(3)_2 and transform as

The G* interactions with the color currents associated with SU(3)_1 and SU(3)_2 are given by

The G* can be produced at the LHC by quark-antiquark fusion determined by the G* coupling to light quarks

Gluon-gluon fusion production is forbidden at tree level by SU(3)_C gauge invariance.

The G* decay widths are:

Additionally, the NMFV flavor structure of the model generates a G* to tc flavor violating decay with rate

where

is the CKM matrix element. Note here that G* FCNCs are induced by the mixing among left-handed quarks generated by the exchange of heavy vector-like quarks. This mixing is controlled by the 3x3 matrices U_L and D_L in the up- and down-quark sectors, respectively. In particular, the

flavor violating decay is controlled by the

element. The CKM mixing matrix is given by

At first order in the mixing parameters,

The non-diagonal elements of D_L are strongly constrained by the data on

So

is thus forced to be small and, as a consequence,

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 mass as the scale, dsqrt_q2fact1, and dsqrt_q2fact2 in the run_card. These samples were also generated without the pre-included MadGraph cuts as demonstrated in the run_card.dat 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 a specific mass, param_card.dat in the generation file to the card of the appropriate mass in the param_cards directory (included as part of the model zip file).