– By Adam DeAbreu, TRIUMF High School Fellowship Student
“Oh my god”, “it was so crazy”, “it was nuts” – that’s about all I was able to say during my interview with the North Shore News after I found out I had won the TRIUMF Fellowship. Even now [at the end of the work-term], those same emotions still stand – I’m still amazed that I was able to work at TRIUMF, work with particle physicists, work with data from the ATLAS detector – that after reading the sign saying, “TRIUMF employees only past this point”, I could walk right past it.
Before I even knew what happened my first day had come, I arrived at TRIUMF and sat down in the lobby and just about died from anticipation and anxiousness. That first day I knew I was working with Dr. Oliver
Stelzer-Chilton and the ATLAS group, but I didn’t have a clue as to what my project was going to be. The constant whirlwind of butterflies in my stomach calmed as Oliver and I talked about possible projects, areas of research, and tools that I would be using. The decision came down to working with data from the ATLAS detector or using the program Pythia to simulate collisions of particles. The answer came easy to me – if I had the chance to work with data from ATLAS, from the LHC, from CERN, then there wouldn’t be much that would persuade me to choose otherwise.
And so my learning/research project/adventure began. All the data was of sets of two muons that ATLAS had detected and that had decayed from a Z boson. The simulated data is run through a detector resolution smearing equation because there are thousands of events that have to be sorted depending on where in the detector the muons went. This equation uses two parameters, S1 and S2, with ranges that the program incrementally goes through to create templates with a range of resolutions; from very high, being a very skinny histogram, to low, being a wider histogram. These templates are then used as a structure to fit the data from ATLAS.
The first part of my project was to rewrite the code with only one resolution parameter, S1, and have the second resolution parameter, S2, that had a different momentum dependence fixed. By doing this and removing the S2 variable, we could see how much additional scaling was needed for the fits. As well, we were able to measure the Z boson mass and compare it to the world’s average value of 91.187 +-0.002 GeV.
I’d like to say that I just jumped right into the project and finished it within a day. However, when I looked at Oliver’s code it looked as though it was in a completely different language and to an extent, it was. I had to learn the C++ it was written in and the usage of the program ROOT, which created and manipulated all the histograms and data. I am not the most tech savvy person and getting my head into the programing was hard; however, it helped that I had a goal – that my programing was helping Oliver with his report: “Search for High-Mass Dilepton Resonances in pp Collisions at √(s) = 7 TeV”. Just knowing that was what my work was related to would have kept me going for months. As well, I took solace in something Oliver had said during the first days of my fellowship, “Use the code, and the programs and the language as tools. I became a physicist and if I’m not careful with all the coding around me I may end up a computer scientist.”
Finally I began what would inevitably be my last project during my fellowship. I had to create another program that would take the same data set, but include the second resolution term S2 and produce templates with one dimensionality higher. We split the data and simulation depending on the muon’s momentum. In the equation used for the resolution of the detector, the S1 and S2 terms have a different dependence on the momentum value, so it’s important to split the data in this fashion. With the Z boson mass distribution split according to momentum the motivation was that we would be able to simultaneously constrain S1 and S2. If both could be constrained, this would allow for an independent measure of S2 that currently can only be obtained from an external input. As well, this would allow both resolution parameters to be measured from the Z boson sample, which is an important calibration sample when searching for new particles at high mass.
Despite really enjoying all that I was learning, I was still thankful that the entirety of the six weeks wasn’t constant coding and compiling. No, there was a lot more to the six weeks than just that; I met great people, attended lectures, seminars and workshops. There’s a very strange feeling I got when, after hearing all these people talk about their work during lectures or in the lunchroom or the office with such passion and insight and knowledge, and to know that not long ago they were in my position – gearing up to take the first step in an education of physics. In just the six short weeks I’ve been at TRIUMF my comprehension of everything particle physics related has grown so much. And it was a great feeling when I saw that it wouldn’t be long before I would be neck deep in the physics.
Then there was the BBQ, I won’t say that I’m surprised but I was definitely pleased to see so many physicists being able to put their work aside to relax and have a great time. To see someone, one day talking about the applications of particle physics, now desperately trying to bite a hanging donut from a string, was definitely a great way to take a break, laugh and relax.
In the end I went from being completely overwhelmed by just the thought of working at TRIUMF – nevertheless actually working with particle physicists and using the same tools and data that they use – to having a handle on ROOT, C ++, and the manipulation of data and histograms. This fellowship has jump-started my learning, and my career. One last quote from Oliver: “there’s so much out there, at a certain point you go from learning it all, as in elementary and high school, to having to narrow your scope – to choose what it is you want to learn”. I’ve narrowed my scope to physics and this fellowship has given me a great experience of what it means to be a particle physicist and will undoubtedly help me when it comes time for me to narrow my scope for the next step. Until then my horizon holds all the possibilities that university physics brings with it, all rushing towards me – and I can hardly wait another minute.
