by Alexander Held

Hello there! My name is Alexander Held, and I recently joined the AMVA4NewPhysics network as an Early Stage Researcher (ESR), who will be based mostly at CERN in Geneva. Before we get to any details regarding my work here in the following two years, I am going to take this opportunity to briefly introduce myself.

Me in front of the ATLAS detector (you can only see a small part of it in the background, the full detector is huge!)

I was born and raised in Germany. My first proper particle physics experience was a two-week internship at CERN during my time in high school, where I was working on silicon detector calibration. This was right around when the Large Hadron Collider was starting to deliver proton beams at 7 TeV, and I distinctively remember that there seemed to be an aura of excitement everywhere. Physicists were of course hoping to see signs of a Higgs boson (thought it took some more time for that to really happen), but were also curious as to what other unexpected phenomena might maybe appear.

In my time as an undergraduate, I wanted to give some other fields of physics a try. An internship at the Max Planck Institute for Radio Astronomy in Bonn showed me how much I enjoy working on large scale data analysis. I analysed telescope data of star-forming regions, with the goal to better understand the physical conditions in these clouds. In order to extract parameters like temperature and composition, I automated a fitting procedure of spectral line data.

For my undergraduate thesis, I worked on a topic in theoretical quantum mechanics. Compared to some of these other fields of physics, the description of particle physics actually seemed less elegant and more convoluted to me. This was great motivation for me to learn more about it!

Two years ago I started in the graduate physics program at the University of British Columbia in Vancouver, where I am now a Ph.D. candidate. I am a member of the ATLAS collaboration, and in my research I analyse data from this detector to search for collisions involving Higgs bosons and top quarks (a process also called ttH). Specifically, I am focusing on the Matrix Element Method (MEM), which Alessia has already briefly described here.

I am going to describe my research in more detail at some point in the future, but for now only a very brief motivation for my work: even though there was already the 2013 nobel prize awarded to François Englert and Peter W. Higgs for their prediction of the Higgs mechanism, this does not mean that we have already confirmed all predictions experimentally.

Most notably, there are four major ways of producing Higgs bosons. The ATLAS and CMS collaborations are examining all these different production mechanisms, but some, like the ttH process, are very rare and tricky to measure. We thus have no conclusive measurements of this process yet. Such measurements could either confirm yet another aspect of the predictions by the Standard Model of particle physics, or give us clues of new physics phenomena. I am involved in the analysis of ATLAS data in order to see which case it will be.

So how did I end up in the AMVA4NewPhysics network? While spending some time at CERN earlier this summer, I found out that there was a posting looking for an ESR to work on MEM in ttH. I had been working on exactly that topic for two years already, and the position would have allowed me to continue doing research towards my Ph.D., while simultaneously offering additional benefits. I applied and was accepted!

Living in Vancouver was great (I highly recommend a visit if you have the chance!), but for now I am back in Europe. One thing I will certainly not miss is attending video conference meetings at four in the morning (they typically take place in Geneva, and the nine-hour time difference to the North American west coast is not exactly convenient). Now I can attend these meetings in person at much more pleasant times of the day.

I am looking forward to the upcoming two years in the network and working together with the other members to achieve our common goals. You can stay up to date with our progress by following this blog. Talk to you soon!