Belle Electron-Positron Annihilation Analysis: A Search for a Dark Photon

Belle Electron-Positron Annihilation Analysis: A Search for a Dark Photon

Name: Margaret Lockwood, Lawrence High School
Research Teacher Mentor: James Deane, Ottawa High School, Ottawa, KS
Research Mentor: Prof. Dave Besson, University of Kansas, Lawrence, KS

Purpose: Analyzing positron-electron annihilations that result in either a positron-electron pair or two positron-electron pairs could provide support the theorized dark photon or other dark sector particles giving evidence for physics beyond the current standard model.

Methods: I first applied for and eventually received an account to access the Belle ( ) KEKB server. The data from the Belle asymmetric B factory collider in Japan provided me with data I could run scripts on to generate histograms of the invariant mass of collisions of interest. Any narrow spikes in the invariant mass histograms could indicate interesting physics, and potentially a dark photon. I installed a virtualbox to run Linux on my computer in order to become familiar with Linux commands. Waiting for my application approval, I started to become familiar with ROOT by following tutorials found on the internet and provided by other students. I learned more about the Belle collider in order to understand how and why the data I will be analyzing is produced. Once I gained access to the Belle server I ran a job using code a graduate student, Steven Prochyra, had created to start analyzing data. I used the generated data and information from Belle to become more familiar with the Belle framework. I started making histograms of the invariant mass from the data generated. I am starting to modify the macro that I used to analyze the data so that I can analyze different aspects of the data.

Results:  I started editing the macro Steven Prochyra made to look at positron-positron and electron-electron collisions in order to use this data as background noise to compare to the electron-positron collisions. I made some invariant mass histograms electron-positron collisions, but it is difficult to know if I did these correctly or if the plots indicate anything interesting until I create more plots.

Meaning to Larger Project:  Analyzing data from Asymmetric B Factories has led to evidence of CP (charge-parity) violations, information about rare decays, and can potentially provide support for new particles that may be a part of the dark sector. Finding a dark photon could lead to information about dark matter, the earliest moments of the Universe, new forces and other new particles outside of the standard model.

Future Research: I am going to continue to work on this project because I have only been working on getting over the Belle framework learning curve. The Belle data is a valuable resource that can be used for a vast amount of research projects regarding different decays. I will start creating my own macros to analyze different aspects of the data and continue to look for new physics including hints of the hidden sector.


  • Steven Prochyra, Graduate Student, University of Kansas