On March 30, the Large Hadron Collider, the world’s largest particle collider, set a new world record by smashing two 3.5 trillion electron volt (TeV) proton beams to produce a 7 TeV collision. The $9 billion project — part of the European Organization for Nuclear Research (CERN) — is part of a global effort to better understand the universe and its origins, as well as a search for the Higgs boson, also known as the “God particle,” which is an elementary particle that is theorized to be what gives objects mass.
Joe Incandela, a UCSB physics professor and deputy spokesman for the Compact Muon Solenoid project at the LHC, maintained correspondence with the Nexus and answered some questions about the recent developments at the facility and what they mean for the future of physics.
Congratulations on the 7 TeV collision record. With the beam now operating over three times the previous record, what is the next step for the program, and what do the scientists hope to see in the next few months?
The beams are at record high energy, but still somewhat low intensity as [the scientists] learn to operate the LHC. Higher intensities increase the rates of proton-proton collisions, and the processes we want to study are very rare processes, so we need high collision rates. The thing to watch now is how quickly [the scientists] can achieve stable operation with high intensity beams. Right now we are being told that there are some very large steps up in intensity coming very soon. If all goes reasonably well, we should have very nice results for somewhat rare but known processes by the summer, and we could start to have sensitivity to hypothetical new physics processes by the end of 2010.
How are researchers and others from UCSB continuing to contribute to the project? How is the Compact Muon Solenoid project coming along?
Professors [Claudio] Campagnari, [Jeff] Richman, [David] Stuart and I, together with our post-docs and students, are all involved in searches for new physics, like evidence of dark matter and other new heavy particles. Some of the students and post-docs are stationed at CERN. Others work from UCSB and come to CERN periodically.
As for the experiment, CMS has 98 to 99 percent of its [approximately] 76 million channels functioning extremely well right now. We are very pleased but still working to improve things all the time.
The sheer amount of data the LHC collects is immense. How is the data from a machine that can collide millions of beams an hour collected and stored?
The collisions will eventually reach rates of millions [of collisions] per second. Right now we are seeing tens of thousands per second and our systems have the ability to read and store around 300 events per second, each of which is about 0.5 megabytes of raw data. We have to do a quick analysis of each collision to pick the fraction of interesting ones we can keep. The data is reconstructed (turning raw information into physics quantities like energy) at CERN on a farm of thousands of processors and then shipped out, eventually distributed over [about] 50 large computing centers worldwide where physicists can work with the data. We will eventually be producing more than 10 million gigabytes of data per year in our experiment. It is a major challenge to process and store these data, but we have prepared the system over many years and it works very well now.
Would we be able to theoretically begin to detect the Higgs boson soon? If not, what more needs to be done to reach the levels necessary to start possibly seeing it?
In the Standard Model of particle physics — which is the theoretical framework people refer to the most when they talk about the Higgs — the Higgs is still produced very rarely at the [conditions in the] LHC, and the signatures we can use to detect it are not unlike those of other more mundane processes. This means we have to gather lots of data to see a statistically significant signal over backgrounds. We will definitely start to cover some of the mass range where it could exist in the next one to two years, but we will not cover the whole range until perhaps end of 2013 or 2014 when the beam energies and intensities increase substantially.
If it isn’t detected, what kind of implications would that have for physicists?
If it is not detected, then this would be quite interesting. Some major new physics could then be required at a bit [of a] higher energy scale that we could also eventually study at the LHC.
What are some of the other experiments being done and how are they progressing so far?
The A.T.L.A.S. experiment is the other big multipurpose experiment like CMS. It is doing very well also which is great. Two other experiments are very specialized and are also doing very well: LHCb studies production of particles containing b-quarks to further understand things like predominance of matter over antimatter in the universe and [A Large Ion Collision Experiment] A.L.I.C.E. will study collisions of heavy ions such as lead on lead collisions to understand the conditions in the early universe at a time when it was something of a soup of quarks and gluons. A.T.L.A.S. and CMS will … study b-particles and heavy ion collisions, but they are not designed specifically for these things.
Has there been any particularly interesting data from the machines?
The data obtained so far with low intensity beams does not include rare processes or new physics but it is very useful to compare with what we expect from predictions of the Standard Model and this helps us to understand our complicated detectors. So far things look extremely good — better than any of us expected.
The LHC project has scientists and researchers from all around the world working on it. What is the social environment at CERN like, and does the process of creating something that has never been done before and using it to try to answer fundamental questions within nature create an interesting social dynamic among the people at CERN and international groups involved in the project?
The global nature of these experiments is a very interesting aspect of what we are doing. In the CMS experiment that includes our UCSB group, there are about 2,000 physicists from around 180 institutions in 38 countries. We work together incredibly well. I have seen zero racism and very nearly zero nationalism — except perhaps during World Cup soccer.
It is very heartening. The global spread can be frustrating at times but it can also be a lot of fun. We sometimes pass urgent tasks from one major region of the world to the next so that people can be working on them 24 hours per day without anyone having to stay up late. We have some pretty good tools that allow us to video conference hundreds of people at one time. But communication is a challenge.
What is in store for the future?
There are reasons to believe the LHC will produce new particles like those that make up the dark matter detected around galaxies, the Higgs particle or many other possible new particles. Dark matter is the most exciting because we already know that it is five times more prevalent than normal matter in the universe but we really don’t know what it is. If we could make it on earth with the LHC, we could begin to understand it in more detail and this would be a major achievement.