# B, T, X, Y production with coupling to first, second or third generation SM quarks¶

Khadeejah Bepari, Andy Buckley, Jack Burton, Jon Butterworth, Louie Corpe, Dan Ping (Joanna) Huang, Puwen Sun, Ben Waugh

Vector-Like quarks (VLQ) are hypothetical coloured, non-chiral, spin-1/2 particles. While fourth-generation quarks with chiral couplings are in general excluded by measurements at the LHC and elsewhere [110], vector-like quarks are not, and remain the simplest example of coloured fermions not yet excluded by data [66]. VLQs occur in several non-supersymmetric theories beyond-the-standard model that propose solutions to the hierarchy problem, offering mechanisms by which the Higgs mass is stabilised [66]. New sources of CP violation can also be introduced by these new particles [100].

An extensive study of these models using Contur 1.2.2/Rivet 3.1.1 was carried out in 2020 [85] (Buckley et al) using generic model from Buchkremer et al [84], where the four VLQ states X, T, B and Y are added as new coloured spin-1/2 objects to the SM, embedded in complete $$SU(2)_L$$ representations.

The model files and example Herwig steering file are available in the VLQ_UFO directory here .

Initial studies were carried out by Bepari and Burton, supervised by Butterworth, Huang and Waugh, as UCL final year undergraduate projects.