Version 9 (modified by druekeel, 5 years ago) (diff)


A Color Triplet Model with Decay to Top and Bottom Quark

This model introduces a heavy hadronic resonance with fractional electric charge (color triplet). The color triplet is produced in quark-quark collisions (not quark-antiquark) and decays to a top quark and a bottom quark.

Corresponding Authors

  • Elizabeth Drueke (Michigan State University)
  • Reinhard Schwienhorst (Michigan State University)

Other Contributors

  • Natascia Vignaroli (Michigan State University)
  • Joseph Nutter (Michigan State University)
  • Devin G. E. Walker (SLAC National Accelerator Laboratory)
  • Jiang-Hao Yu (The University of Texas at Austin)
  • Tao Han (University of Pittsburg)
  • Ian Lewis (University of Wisconsin)
  • Zhen Liu (University of Wisconsin)

Description of the Model

The color-triplet (Phi) is a heavy hadronic resonance with fractional electric charge. The Feynman diagram for decay to tb is below.

Feynman Diagram for trip > tb

In particular, it is possible to produce triplet, anti-triplet, and sextet particles; but the LHC is a proton-proton machine and so the triplet production is enhanced by the parton-parton luminosity of the quark-quark initial state. The contributing quark-quark initial states are QQ, QU, QD, and UD, where Q, U, and D denote the SM quark doublet, up-type singlet, and down-type singlet, respectively.

The decay width of the color~triplet to tb is given by

$\Gamma (\Phi \to t\,b ) = \frac{g_{\Phi}^2}{8\pi}(1-x_t^2)^2 + {\mathcal O}(x_f\times x_b) + {\mathcal O}(x_b^2) \;,$


$x_t=\frac{m_t}{m_\Phi}$ \rm{ and } $x_b=\frac{m_b}{m_\Phi}$

and the color triplet coupling to tb is given by


Here, q3trip is the


coupling to tb.

See more details in

Model Files

Generation specifics

In 1409.7607v2, the samples were generated with the color triplet 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 > t b, t > b l+ vl @1
p p > t~ b~, t~ > b~ l- vl~ @2

The resonanceWidth macro can be run to determine the width of the color triplet resonance, which is the WSIX parameter input for the file in the model directory.

To generate the settings for a specific color triplet mass, change the MSIX parameter to the mass of the particle in GeV and the WSIX parameter as described above in the file of the model.

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