Searching for Evidence of a 4th Generation Quark

Names: Grant Gollier, Bishop Seabury Academy, Lawrence, KS

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

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

Purpose: We are looking for evidence of a fourth generation quark which could help answer the hierarchy problem and specifically the odd discontinuity of mass.

Methods: I started by learning CERN’s ROOT data analysis framework. I used an online tutorial from Nevis Laboratories at Columbia University and help from fellow student researchers. I began by using demo files from the Nevis tutorial then proceeded to using ‘real’ files, plotting simple variables. In order to solve many of the problems I faced, I turned to both the ROOT documentation and the ROOT Talk forum. In addition to the learning curve of ROOT, I was new to C++ as well and had to learn the basic syntax and style of C++ as I went. After this introductory phase I began to look at two different decay modes for T (WbT and ZtT), plotting R, , Ht, and ptin one and two dimensional histograms. I then looked at these plots and decided upon cuts to maximize SB*k where S is the number of signal events, B is the number of background events, and k is the scale factor. This scale factor was necessary because I was only looking at one or two decay modes for as opposed to all possible decays. This scale factor accounts for the different probabilities/branching ratios.

Results: I developed multiple different scripts for processing these cuts. I looked at multiple T masses ranging from 800 GeV to 2.5 TeV. I then processed all the mass files with these cuts and passed the remaining events to plot , Ht, and pt.

Meaning to Larger Project: The hypothetical T quark offers a solution to the Hierarchy problem, which the solution to and discovery of this T would be pushing the boundaries of what is currently known in particle physics. Specifically, the cuts I was looking at would improve the quality of data I am gathering.

Future Research: As I ran short on time towards the end, I would like to spend more time analyzing the cuts I made and look for other ways to improve them. Also, following the use of these cuts more analysis would be needed to then identify the T and prove its existence.

Acknowledgements:

Without the help of many of the following people this project would not have been possible

• Zach Flowers, Student, University of Kansas

• Emily Smith, Student, University of Kansas

• Prof. Alice Bean, University of Kansas

[Link #1:  http://www.nevis.columbia.edu/~seligman/root-class/