Beam in LHCb

Its been a long time coming but sometime late on Friday evening, the first beam from the LHC passed through LHCb, one of the four LHC experiments. This was a big moment for all the members of the LHCb collaboration, some of which have been hard at work on the experiment for many years. There was much excitement when the first tracks were seen in the VELO sub-detector (see picture from our eLog by Malcolm John).



The LHC accelerator is a complex beast and so it must be coaxed into life slowly, one step at a time. Eventually there will be two proton beams counter-rotating and then colliding in the center of each of the experiments. That is probably several weeks (or months) away. In the mean time, the two proton beams are being injected into the LHC and then dumped on large metal targets after they have passed through LHCb or Alice (one of the other experiments). These beams are of much lower energy than those which will eventually be circulating, but they are still useful for testing both the LHC and LHCb.

Its now 3am and I'm on shift in the LHCb control room. We are waiting for a problem with the accelerator to be sorted out so that we can continue to test the radiation monitoring system. The control room is stuffed full of computers and screens showing all kind of information on the state of both the accelerator and the experiment. I've attached a picture showing the current state of the beam. The beam spot can clearly be seen.



I'm glad I am here at the beginning of running. We all hope that the next few years at CERN will provide lots of interesting discoveries about our world. That feels inspiring, even when stuck in an uncomfortable chair in the middle of the night somewhere close to a hypermarket in France.

I've got a fair few more shifts to do over the next few months, so I will try and post an update on how the commissioning of LHCb comes along.


Update:

The CERN press office has published an article on the tests discussed above. You can find the article here.

I thought, as I'm on night shift again, that I'd add a little explanation of what the picture of the tracks in the Velo actually shows. LHCb has been specifically designed to study the decays of so called B mesons - relatively heavy bound states which include a bottom quark. These systems are an interesting place to look for deviations from the Standard Model and to really test our understanding of nature.

The Bs have a relatively long lifetime and so we can watch them decay after they are produced. The Velo is the LHCb sub-detector designed specially for this task. You can find lots of glossy pictures of it here. It consists of a set of CD sized disks of Silicon which react when charged particles travel through them. The lines shown in the first tracks picture above show the trajectory as a group of particles traveled through the detector. These tracks are made by taking all of the points at which a particle passes through a disk and then trying to draw a line through all of the points. As we are still in the early stages of commissioning, parts of the Velo were switched off, which is why not all of the disks show up as the particles pass through them.