Version 4 (modified by druekeel, 2 years ago) (diff) 

A Color Triplet 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)
 JiangHao Yu (The University of Texas at Austin)
 Tao Han (University of Wisconsin)
 Ian Lewis (University of Wisconsin)
 Zhen Liu (University of Wisconsin)
Description of the Model
The colortriplet (Phi) is a heavy hadronic resonance with fractional electric charge. The Feynman diagram for decay to tb is below.
In particular, it is possible to produce triplet, antitriplet, and sextet particles; but the LHC is a protonproton machine and so the triplet production is enhanced by the partonparton luminosity of the quarkquark initial state. The contributing quarkquark initial states are QQ, QU, QD, and UD, where Q, U, and D denote the SM quark doublet, uptype singlet, and downtype singlet, respectively. The diquark particles could be the spin0 scalars with
quantum numbers
and the spin1 vectors
To produce the tb final state, the charge of the colored particle needs to be 1/3. The gaugeinvariant Lagrangian can be written as:
where
with the
Pauli matrices
and color factor
The couplings to QQ, and to U and D, are given, respectively, by
Here a, and b are quark color indices, and j is the diquark color index with
where N_D is the dimension of the (N_D=3) antitriplet or (N_D=6) sextet representation. C denotes charge conjugation, and alpha and beta are the fermion generation indices. After electroweak symmetry breaking, all of the SM fermions are in the mass eigenstates. The relevant couplings of the colored diquark to the top quark and the bottom quark are then given by
where
are the chiral projection operators. Assuming that the flavorchanging neutral coupling is small, the thirdgeneration couplings are
The decay width of the color~triplet to tb is given by
where
and the color triplet coupling to tb is given by
See more details in
Model Files
 proc_card: for generation of 500 GeV triplet (place in Cards/)
 run_card: for generation of 500 GeV triplet (place in Cards/)
 Width Macro: macro to generate widths for triplet at different masses
 modcolorS_trip: the model
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 preincluded 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 p p > t~ b~, t~ > b~ l vl~
The resonanceWidth macro can be run to determine the WSIX parameter input for the parameters.py file in the model file.
To generate a specific mass, change the MSIX parameter to the mass of the particle in GeV and the WSIX parameter as described above in the parameters.py file of the model.
Attachments

ColorResSig1.png
(1.5 KB) 
added by druekeel 2 years ago.
Feynman Diagram for trip > tb

proc_card_mg5.dat
(1.9 KB) 
added by druekeel 2 years ago.
for generation of 500 GeV triplet (place in Cards/)

resonanceWidth.C
(2.9 KB) 
added by druekeel 2 years ago.
macro to generate widths for triplet at different masses

run_card.dat
(13.8 KB) 
added by druekeel 2 years ago.
for generation of 500 GeV triplet (place in Cards/)

modcolorS_trip.zip
(11.9 KB) 
added by druekeel 2 years ago.
model