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Undergraduate Researchers

David Sweigart

David Sweigart, Physics and Mathematics

“Study of Single and Diboson Z Production at the LHC”

This year, the Large Hadron Collider (LHC) at CERN has been running exceptionally well with pp collisions at a center-of-mass energy √s of 7 TeV. This has led to an unprecedented amount of data collection by the ATLAS experiment with an integrated luminosity of roughly 0.84 fb-1 after selections to require data quality sufficient for physics analysis. The aim of my project was to acquire an understanding of how data analysis is used in high energy physics. To do this, I implemented a cut-based technique using the needed Monte Carlo (MC) corrections to search for single and diboson Z production. In the Z→μμ channel, I discovered a distinct peak of the invariant mass signal against the background at 91 GeV which indicates the production of Z bosons. Furthermore, by implementing a cut on the ETMISS,Ax, I started to determine how to separate the ZZ process from the rest of the background in the ZZ→μμνν decay channel. This cut may prove to be a powerful tool for future diboson Z production studies. Future work on this project will need to include applying additional MC corrections that were not considered and calculating the corresponding cross-sections for both single and diboson Z production. Comparison of these results with theory could serve as a stringent test of the Standard Model and potentially indicate the presence of new physics.

Where did you do your research this summer? When were you there?

I conducted research at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland as a summer student. I was part of the University of Michigan (UM) Research Experience for Undergraduates (REU) program which is funded by the National Science Foundation (NSF). My stay at CERN was for a total of 9 weeks starting in mid-June.

How did you learn that physics students could do research away from UMBC in the summer?

Before attending UMBC, I had two summer internships at the U.S. Food and Drug Administration researching implant materials for medical devices. Therefore, I already knew that research opportunities existed away from UMBC, but I did not learn about the REU programs until my freshman year from one of my professors.

Did you already know that undergraduates could work at a place like CERN? How did you find out?

I had no idea that undergraduates could work at CERN until I saw the UM REU program on the NSF’s website. The UM REU program is in fact the only program that allows Americans to be official CERN summer students. This is because the United States is not a Member State of CERN.

What did you do at CERN?

In the mornings, I attended a series of lectures specially designed to teach us about a wide range of topics in theoretical and experimental particle physics. In the afternoons, I worked on my summer-long project to study single and diboson Z production at the Large Hadron Collider (LHC) using data collected from the ATLAS detector. To do this, I ended up spending most of my time writing code in a programming language called ROOT. The goal of my project was to understand how data analysis is used in high energy physics.

Did everyone speak English?

Geneva is in the French-speaking part of Switzerland. However, everyone at CERN spoke English except for the workers in the restaurants. I do not speak any French, but I still found it easy to get around and order food by just learning a few useful phrases.

Where did you live while you were there?

I lived in one of the CERN hostels. This was very convenient for me because it was located close to most of the main facilities including the building where I worked as well as the restaurant.

Did you have time to travel in Switzerland or around Europe during your program?

Yes! While the program did not organize any traveling, the summer students formed groups to go places each weekend. Being my first time in Europe, I was very adventurous and went on a tour of Europe. In Switzerland, I visited Geneva, Zermatt, and Bern which were all very beautiful places. I also traveled to Paris and Lyon in France as well as other large cities including Barcelona, London, Rome, and Berlin.

What experience did you have before you went?

I have actually never taken a course in particle physics since one is not offered at UMBC. Before going to CERN, I only had a junior-level knowledge of general physics. However, I was able to learn everything that I needed to know for my project with the help of my supervisors.

Were there other undergraduates at CERN? How many?

The UM REU program was composed of 15 undergraduates including myself, but the entire CERN summer student program was made up of over 200 undergraduates from all over Europe.

Who did you work with most directly? Other students? Full-time researchers?

I worked each day at a table with other summer students, and we would frequently help each other debug our code or talk out any problems we had. I met with my supervisors only once or twice a week to discuss the progress of my project, but we would still correspond often via e-mail.

Was it expensive to do this?

The UM REU program covered the cost of my plane tickets and my travel insurance. I also received a per diem of 90 CHF to pay for my hostel and food which turned out to be more than enough. Furthermore, the program gave me a stipend of $2,500 which I used to help pay for all of my traveling.

Do you want to go back?

Yes! It was amazing to participate in our universal quest for knowledge during these very exciting times at CERN, especially with the first of many results now coming from the LHC. This experience has extremely enriched my cultural and academic knowledge!

What are your goals after UMBC?

After graduating from UMBC, I plan to attend graduate school for a Ph.D. in physics with the ultimate goal of becoming a research scientist. However, I am still keeping my options open regarding my specific sub-field of concentration. Who knows? I might even find myself back at CERN one day!

What should other UMBC students know about summer research opportunities?

There are plenty of research opportunities in all different fields if you know where to look for them. The NSF maintains an updated list of their REU programs which can be accessed by going to their web site: National Science Foundation. These programs offer an incredible chance to experience the day-to-day work of research groups across the United States and abroad. I strongly encourage applying to anyone thinking about going to graduate school.