In my previous post I linked to a talk I presented at the 2012 Annual Conference of the American Translators Association on the so-called “God Particle”, Dark Matter, and All That.
Since I unfortunately won’t be able to attend the 2013 ATA conference, I won’t be able to present an update on the particle physics frontier. Therefore, I am summarizing the latest news below, under the assumption that the reader has either read the previous post and material or is familiar with the general topic.
The LHC, the collider where the Higgs boson was discovered last year, was shut down earlier this year for repairs and upgrades and is expected to begin operations again in 2015. However, that does not mean that there are no new results. On the contrary, scientists are quite busy analyzing all the data that were collected. These analyses have meanwhile confirmed that the particle whose discovery was announced last July really has all the right properties to be the Higgs (or one of the Higgses). The discovered “Higgs-like” particle has therefore been relabeled as (one of) the Higgs boson(s) (see e.g. the CERN press release from March 14th, 2013 here). I added the plural in parentheses, because there are a host of particle physics models, which attempt to explain the origin and composition of dark matter and include more than one of the particles like the one predicted by Peter Higgs in 1964.
Another exciting and related update comes from the astrophysics front, more precisely from the aptly named Planck space telescope, which measures–among other things–the composition of the universe. The findings are summarized in the pie charts below:
Composition of the Universe before and after Planck (Source: ESA and the Planck Collaboration)
You may also have read or seen about the latest results of the Alpha Magnetic Spectrometer (AMS) announced very recently, that claims to provide direct evidence of dark matter. To be precise, what was measured was an excess in a certain type of radiation that can (among other things) be attributed to annihilation of dark matter particles. Annihilation means roughly speaking that 2 particles combine, are converted into energy and thus cease to exist as particles. Now, what was measured by the AMS is an excess in the expected amount of radiation. This may (or may not) be due to dark matter. Unfortunately we can’t just fly out there and search for the source, be it dark matter or not. So this is another strong hint at the existence of dark matter and indeed also constrains some theoretical models, but unfortunately it does not provide a direct clue.
In summary, existing theories have been confirmed and refined by new experimental data, and no new particles have been found. This may sound disappointing, but even a null result means progress, because the absence of new particles helps constrain various models that could have explained the existence of dark matter. A lot of these models or at least a large parameter space of these models has been ruled out since the first collision at the LHC. Furthermore, the large amount of data has yet to be analyzed from all angles, as does the amount of data of the aforementioned astrophysics experiments. Who knows, maybe there are some new insights hiding in these data? Stay tuned, subscribe to this blog, and find out!