An interview with Dr. Andreas Crivellin, theoretical physicist at the Paul Scherrer Institute (PSI) in Villigen (Switzerland)
What are the typical questions theoretical particle physicists look at? What are their tools of the trade and how important are creativity and lateral thinking in theoretical physics? These and further questions were posed to Dr. Andreas Crivellin for TRANSFER by the Steinbeiser Ute Villing.
Hello, Dr. Crivellin, you deal with the mathematical description of the fundamental building blocks and interactions of matter. Can you briefly summarize the current state of knowledge?
The standard model (SM) of particle physics states that the matter all around us consists of fundamental building blocks and that interactions also originate from the exchange of particles. I’m sure you know the concept of atoms from school or university – that they consist of protons and neutrons in the nucleus and that they orbit around electrons, or rather there’s a kind of cloud of electrons around them. There’s a force holding the atoms together called electromagnetic interaction. As far as we can say today, the electrons really are fundamental particles and in terms of their mathematical description they’re like little dots. Protons and neutrons on the other hand aren’t elementary; they’re composed of individual building blocks. These building blocks – quarks – are held together by powerful interaction, which has a somewhat surprising property: As the distances between particles increase, the interactions increase rather than decrease. As a result, you can’t observe individual quarks, you can only indirectly deduce their existence. The third and last interaction with the SM is a weak interaction which appears to be extremely exotic and only occurs in “everyday life” during radioactive decay. Last but not least, there is the famous Higgs boson particle, which was discovered in 2012 in the Large Hadron Collider (LHC) at CERN in Geneva. This particle not only lends mass to other elementary particles, it also gives itself mass.
The red ellipses show the preferred area where measurements combine. As the diagram indicates, there are no overlaps between this area and the origin of the coordinate system, which corresponds to the standard model value. The analysis therefore suggests the existence of a new kind of physics. Source: Patterns of New Physics in bsℓ+ℓ− transitions in the light of recent data Autoren: Bernat Capdevila, Andreas Crivellin, Sébastien Descotes-on, Joaquim Matias, Javier Virto
So that’s what’s happening in terms of secured know-how in particle physics. But what questions does that leave open – the things people are still looking into?
Since the discovery of the Higgs boson – which is sadly and wrongly sometimes called the God Particle, even though it’s just a particle – the SM of particle physics is now complete. We now have our eyes peeled for the existence of new, unknown particles, which are so heavy that they couldn’t even be identified until now. Directly searching for these particles is the main remit of the LHC at CERN. But it’s also possible to search indirectly for new particles using precision experimentation. The reason this is feasible is that Heisenberg’s principle of uncertainty means that even heavy particles can be produced in a vacuum for a short period of time and then they can be destroyed again. Such experiments are carried out at the PSI, among others. For example, lots – lots and lots – of muons are produced and measured as they disintegrate. Searching directly for heavy particles in the LHC hasn’t unearthed any indication of their existence until now and most of the precision measurements that have been taken tally with the standard model. Despite this, some deviations have been noticed recently in B meson decay, which I find highly interesting.
What’s the connection between your theoretical research and the experimentation that is going on at the moment?
I’m looking at the design of new theoretical models, which serve to extend the SM. These models include new particles which can be important for direct searches and indirect measurements. My role in this is to calculate the predictions for these models. In particular, I’m trying to develop models that can explain the aforementioned deviations in the decay of B mesons and any potential correlations with other possible measurements.
What structure does your research follow, and how important is creativity and unorthodox thinking?
In theoretical particle physics we mainly work in small groups, usually just two, three, or four people. I supervise a doctoral student at the PSI who I’m conducting research with. I’m also working with other scientists in a theory group at the PSI, though I do have lots of other contacts to physicists across the globe, some of which are quite close, and I do work such as writing publications with them. It’s important in this respect to present your research findings at international conferences and talk in seminars at universities and research institutions. So I tend to travel a lot to keep my research network up to date and expand my scientific network.
With model-building, by which I mean designing models for new physics, creativity has an important role to play. Work’s been going on in this area for decades and it’s not easy coming up with new ideas that nobody’s looked into yet. That said, perseverance is an extremely important attribute in this respect. You need it in research because of course not all models you think up actually work, so you have to be able to deal with setbacks. One thing you really have to stay focused on is that even if lots of models appear consistent, there’s only one actually in place in nature, so there’s very little likelihood of hitting the jackpot.
But unconventional thinking – i.e., exploring new territory – also has its benefits. For example, we’ve not found a single experimental indication of a model that can be described as interesting from a mathematical point of view and has already been extensively investigated in the past. There are also indications that there are models that most physicists would not consider “natural.” Of course one has to adhere to “norms,” in the sense that a model is not self-contradictory and that the calculations have to be right, but one thing I value about the area I work in is that people are generally quite open and tolerant – not just regarding new things and unorthodox concepts, but also when it comes to extraordinary people. Overall, it would be safe to say that you need a lot of perseverance and creativity, but also unconventional thinking to track down the fundamental laws of nature.
Contact
Dr. Andreas Crivellin is a theoretical particle physicist at the Paul Scherrer Institute in Villigen (Switzerland). He studied at the Karlsruhe Institute of Technology (KIT) and currently works at the University of Bern and at the European Organization for Nuclear Research (CERN) in Geneva. Crivellin is currently looking at the mathematical description of the fundamental building blocks and interactions of matter. His particular area of expertise lies in expanding the standard model of particle physics, which involves investigating the influence of new and previously undiscovered particles on the decay of heavy mesons (quark bonding states). As part of his studies, Crivellin will be giving a talk on the topics touched on in this interview on January 29, 2018 in Rottweil.
Ute Villing is a project manager at the Steinbeis Transfer Institute Business School Alb-Schwarzwald, which belongs to Steinbeis University Berlin. The school has been offering management degree programs since 2004 with an emphasis on people already in employment (and future managers). The Steinbeis Enterprise also offers a selection of university- standard training courses and a variety of networking options.
Dr. Andreas Crivellin
Paul Scherrer Institut (Villigen (CH))
Ute Villing
Steinbeis-Transfer-Institut Business School Alb-Schwarzwald (Berlin/Gosheim)