Profile

I completed my PhD last year, and am currently an experimental particle physicist.  I work on the Large Hadron Collider (LHC) which in general attempts to probe how the universe works at the smallest distances, and what the universe was like a fraction of a second after the big bang.

Specifically I’m attempting to find out how gravity works on the atomic scale. Gravity is extremely well understood at large scales (where ‘large’ is pretty much anything bigger than 1 mm).  We know that general relativity, the best theory we have for explaining gravity, completely fails when you get down to the size of an atom.  Several theories attempt to explain how gravity works at these small distances.  Most of these predict the existence of particles called gravitons, which I’m attempting to find.

In the LHC, protons are given large amounts of kinetic energy, accelerating them around a circular track until they are close to the speed of light.  These are subsequently collided head on with each other. The large amount of energy they contain can then be converted into a flurry of particles.  What particles are created in a collision cannot be controlled. and many particles that are created we are already familiar with.  On very rare instances it is possible for an exotic particle that’s never before been seen to be created.

The collisions occur inside the ATLAS detector, which is essentially a six storeys tall camera. Shaped like a cylinder, protons enter from both ends, collide in the centre, and a 3D picture is captured of the new particles flying out of the centre and through the detector.

By looking at the flurry of particles that pass through the detector it is possible to partially reconstruct what happened in the collision event.  By looking at huge numbers of these events it is possible to infer whether a new particle exists or not.

To generate the huge number of collisions needed, the LHC collides protons 40 million times per second.  To analyse this huge dataset physicists spend their days programming their own software to filter out the events that we already understand.  Then more code needs to be written to perform the analysis of the selected events to determine the validity of the theories being tested.

I’ve not found anything yet, but by not finding anything I have succeeded in ruling out some theories.

In the past I was living near Geneva, and working on site at CERN.  However presently I work from Manchester and can access the computers and datasets remotely.

Arriving in the office inevitably leads to the consumption of a cup of coffee.  I share my office with two other people working on the same experiment, but we all work on different analyses.  I am the only person in the UK working on my specific analysis, with my half dozen collaborators living in France and the US.  The day’s first cup of coffee is sufficient to fuel me through the night’s emails which arrived in from the different time zones.  If there is anything requiring more discussion with people in France, I’d at this point fire up skype to have a quick chat.

With the emails sorted it’s time to look over the mass of post-it notes covering the wall behind my chair.  Each detailing a different task that I’m currently working on.  It’s usually programming related.

Almost every facet of physics analysis is programming.  Performing a simulation? Need to write the code to perform it. Looking at data? Need to write some code to filter the events. Analysing data? Need to write the code to perform the statistical analysis. Most of my day is spent typing in C++ and Python.

After an hour or so of coding it’s time for the morning coffee break.  At this point the entire particle physics department pours into the coffee area.  We have quite a large department in Manchester, so usually someone will be celebrating a birthday, or arriving back from a conference or holiday.  All of these events require the provision of cake/chocolate/sweets.

Once full of caffeine and sugar it’s time to get back to coding for a few hours before lunch.  After lunch is the prime time for video meetings to be scheduled, as this suits the most time zones.  These meetings can vary from tens of minutes with only a handful of collaborators discussing the week’s progress, to multiple hours long with upward of a hundred people listening in.

Mid afternoon calls for another coffee break, mirroring the morning’s gathering.

Back to coding for a few hours before heading home and playing ukulele / going climbing / jogging / hanging out at a friend’s. Or invite some friends over and fire up the home made laser obstacle course.