T Quark Analysis from Generated Data

Names: Cole Brabec, Olathe Northwest High School

Research Teacher Mentor: James Deane, Ottawa High School, Ottawa, KS

Research Mentor: Prof. Philip Baringer, University of Kansas, Lawrence, KS

Purpose: The Purpose of this research is to investigate the possible existence of a fourth generation of quarks, specifically the T quark. This quark has many applications in modern physics such as solving the Hierarchy Problem or explaining the low Higgs Mass.

Note: The T quark is the particle formerly known as the t’ quark.

Methods: We used C++ and the software framework ROOT to analyze Monte Carlo files generated from MadGraph. We used these files to investigate the characteristics exhibited by the particles such as their phi, eta and transverse momentum. In order to determine what cut would maximize the data included from the signal file while minimizing the data included from the background file, we created a macro to calculate the figure of merit using the function FoM = S/Bk, where S is the amount of points within in the cuts from the signal file, B  is the amount of points within the cuts from the background file and k is a scaling factor. The scaling factor was calculated using the relative sizes and probabilities of decay between the background and signal file; for these files it had a value of 802. The optimal cut would be used to determine which data received from the CMS exhibited signs of T quark decay

We also had to analyze the properties of the forward jet; the light quarks generated external to the T quark decay chain. This was difficult at first as in ROOT it is not possible to check for the grandparent or great-grandparent of a particle. To solve this issue,  we looked at light quarks whose parents were other light quarks; this occurred only in the forward jet.

We had issues attempting to create cuts for both the Z boson and the forward jet, as these were not present in the background file. To work around this issue, we treated every light quark in the background file as the “forward jet”. For the Z boson, we were unable to develop a method to accurately imitate a presence of Z bosons in the background file and thus we were not able to generate meaningful cuts for them.

Results: Analyzing our cuts, it appears that the optimal cuts arePT > 410 GeVand < 2.4 for the top;HT > 1100; and PT < 570 and < 2.4for the Forward Jet at T quark mass 1 TeV. Cuts for other T quark masses were also generated and are available on a spreadsheet. We were also able to develop a piece of software to quickly and efficiently calculate the optimum cuts for different background and signal files.

Meaning to Larger Project: These cuts help refine the search range for finding the T quark. It will help us when analyzing real data to more quickly find the signs of a T quark. This data will also be used to help publish a paper about the T quark.

Future Research: The next step is analyze data directly from the CMS within our given cuts to see if it lines up with our predictions for the T quark. We also need a background file with Z bosons to better refine our cuts.


  • Zachary Flowers: Undergraduate Student, University of Kansas, Lawrence, KS

  • Emily Smith: Undergraduate Student, University of Kansas, Lawrence, KS

  • Dr. Alice Bean: Professor, University of Kansas, Lawrence, KS