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Techmology and Scientism / News from the LHC
« on: December 13, 2011, 03:28:04 pm »
The Large Hadron Collider shut off for the winter a few days ago, and there was a conference announcing their most recent results today.
(This is a link to the liveblog of it that I was following)
The conference was almost entirely to do with the Higg's boson. So here's a quick reminder of why it is so difficult to find:
First, it is only detectable at high energies. This is why we need such a powerful machine to look for it.
Second, the theoretical results that predict the existence of the Higgs do not predict its mass. So we do not know at exactly what energy to start looking. This makes things more difficult when combined with the next point.
Third, it does not exist for long. The LHC produces new particles by smashing old ones together very fast. The new high-mass particles do not exist long enough for the detectors to register them. What they do register are the results of how the high-mass particles decay. The decay modes of the Higgs are very well-understood, so they know what to look for. For example; two high energy photons moving in opposite directions perpendicular to the proton beam. The problem then, is that these photons may also have arisen from other "background" effects from normal Standard Model processes. The scientists deal with this by using a lot of statistical analysis. Fortunately, they have vast amounts of data to work with. The LHC can produce 40,000 collisions per second.
So what have they found this year? The conference presented results from the two main detectors; CMS and ATLAS. They both narrowed down the energy range at which the Higgs may be found.
ATLAS has excluded 112.7-115.5GeV and 131-453GeV. (GeV stands for Giga-electronvolt, which is a unit of energy) This leaves a gap between 115.5 and 131GeV The current theoretical prediction for the Higgs is between 114 and 149GeV, so this is in line with what was expected.
So that's where the Higgs isn't. What's more tantalising is an indication that there may be something at an energy of 126GeV. Because of all the statistical analysis necessary to come to this result, this is very much not an announcement that the Higgs has been found. But it is a definite sign that this energy should be probed much more next year. (The 126GeV measurement has an excess of 3.6 sigma)
CMS has excluded energies from 129-238GeV and has seen a small excess at around 125GeV, with a lower confidence of 2.6 sigma. The fact that the two detectors are seeing the same small bulge in their graphs is obviously very exciting, and it is becoming much more likely with these results that the Higgs exists. It seems very likely that more definite results will confirm these preliminary findings next year.
(This is a link to the liveblog of it that I was following)
The conference was almost entirely to do with the Higg's boson. So here's a quick reminder of why it is so difficult to find:
First, it is only detectable at high energies. This is why we need such a powerful machine to look for it.
Second, the theoretical results that predict the existence of the Higgs do not predict its mass. So we do not know at exactly what energy to start looking. This makes things more difficult when combined with the next point.
Third, it does not exist for long. The LHC produces new particles by smashing old ones together very fast. The new high-mass particles do not exist long enough for the detectors to register them. What they do register are the results of how the high-mass particles decay. The decay modes of the Higgs are very well-understood, so they know what to look for. For example; two high energy photons moving in opposite directions perpendicular to the proton beam. The problem then, is that these photons may also have arisen from other "background" effects from normal Standard Model processes. The scientists deal with this by using a lot of statistical analysis. Fortunately, they have vast amounts of data to work with. The LHC can produce 40,000 collisions per second.
So what have they found this year? The conference presented results from the two main detectors; CMS and ATLAS. They both narrowed down the energy range at which the Higgs may be found.
ATLAS has excluded 112.7-115.5GeV and 131-453GeV. (GeV stands for Giga-electronvolt, which is a unit of energy) This leaves a gap between 115.5 and 131GeV The current theoretical prediction for the Higgs is between 114 and 149GeV, so this is in line with what was expected.
So that's where the Higgs isn't. What's more tantalising is an indication that there may be something at an energy of 126GeV. Because of all the statistical analysis necessary to come to this result, this is very much not an announcement that the Higgs has been found. But it is a definite sign that this energy should be probed much more next year. (The 126GeV measurement has an excess of 3.6 sigma)
CMS has excluded energies from 129-238GeV and has seen a small excess at around 125GeV, with a lower confidence of 2.6 sigma. The fact that the two detectors are seeing the same small bulge in their graphs is obviously very exciting, and it is becoming much more likely with these results that the Higgs exists. It seems very likely that more definite results will confirm these preliminary findings next year.