My project was to test criteria developed to detect muons in a simulated Doubly-Charged Higgs decay for use in the search for Doubly-Charged Higgs. I used tight, medium, and loose Muon identification criteria and Particle Flow Isolation IDs to do this.

The Doubly-Charged Higgs is a part of the Type II Seesaw Leptogenesis Mechanism that extends the Standard Model in order to account for neutrino masses (the current Standard Model doesn’t do this) [1]. The DCH would be paired with another DCH in order to remain neutral, as each DCH would be either “doubly-charged” positive or negative. The DCH would decay into any combination of electrons, muons, and taus; of which there would be four total, with two positive and two negative.

My work was focused on finding the best criteria I could for detecting muons produced by a DCH decay.

I created 9 different IDs using the different combinations of the previous criteria and Particle Flow Isolation criteria to do this. Using these IDs, I counted how many of each grouping of muons (m, mm, mmm, mmmm) I got from the Monte Carlo simulation data and plotted them to a histogram. I ran the given signal and background data through these IDs and recorded my results.

Fig. 1: Signal-Loose ID with Iso1-3

Fig. 2: Signal-Medium IDs with Iso1-3

Fig. 3: Signal-Tight IDs with Iso1-3

Background Data

Fig. 4: Background-Loose IDs with Iso-1-3

Fig. 5: Background-Medium IDs with Iso1-3

Fig. 6: Background-Tight IDs with Iso1-3

 

Using these results I calculated the expected number of 4 muon events for the signal and the background.

Fig. 7: Signal Data Table

Fig. 8: Background Data Table

 

The signal is only expected to produce around 3 mmmm events and the background is expected to produce around 25. This presents a problem because any signal produced 4 muon events would be within the margin of error for background produced 4 muon events.

By measuring the transverse momentum (pT) of the muons in the 4 muon events (3 for background), I was able to find a possible place to put a pT cut in order to help this problem. The cut would be making sure that the muons have pTs of below 200 GeV, where the most overlap in the pTs of the signal muons and the background muons occur.

Fig. 9: Signal pT plot

Fig. 10: Background pT plot

 

I believe that the loose ID with loose PF Isolation is the best criteria for the identification, but that the mentioned 200 GeV pT cut should be implemented in order to see if it improves the likelihood of detecting a 4 muon event from the signal.

Acknowledgments

Dr. Andrew Ivanov Kim Coy, Dr. Loren Greenman, Dr. JT Laverty This material is based upon work supported by the National Science Foundation under Grant No. #2244539. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.

References

1. Sánchez Villamizar, Yozara. (2019)

Final Presentation