Saturday, April 30, 2011

Connecting the dark with the light

Just this month, the CDF experiment at Fermilab saw a bump in their data at an energy of 140-150 GeV suggesting that they had seen a new type of particle. But does it really exist and, if so, what is it?

The result was at the 3.2 sigma level, which in statistics means that it is about three standard deviations away from the null hypothesis--or about a 6 in 10,000 chance that the signal is just a statistical fluctuation. That's a small chance but particle physicists have high standards when it comes to this sort of thing.

In particle physics, a 3 sigma result is often described as "evidence" for something but it takes a 5 sigma result to claim "discovery." The trouble is, there are lots of 3 sigma results in particle physics that go away with more data, usually because of some unsuspected systematic error. That doesn't change the likelihood that this result is correct but says that 3 sigma is not actually a discovery, just a promising hint.

[Photo courtesy of Echo Romeo.]

So now we've dealt with the idea that this might not be anything, let's play with a fun speculation advanced by Fermilab's Dan Hooper at today's plenary session at the American Physical Society April meeting.

One thing that physicists know is that it isn't the Higgs particle. But Hooper suggested that the bump could be a new particle representing a new type of force. The particle would generally be described as a Z' (pronounced Z prime) or, equivalently, the force could be called a fifth force, different from electromagnetism, gravity, the weak force, or the strong force.

To make sense, the particle must interact modestly with quarks and extremely weakly with leptons--a so-called leptophobic Z'. But if that is the case, it needs a bunch of other exotic particles to exist or else the Standard Model of particle physics goes haywire. One of those particles would have the properties of a dark matter particle. Furthermore, it would have a mass and cross section just where a bunch of other experiments hint (see our previous story about this).

One role for this Z' could be to mediate between dark matter and the matter we can see--between the dark and the light, so to speak. And that opens up a whole new world of exploration.

Remember that this is just speculation about what the particle could be if it exists but that isn't guaranteed. Expected at the end of the summer is a new analysis that will include about four times the amount of data and that should make the situation much clearer. But wouldn't it be cool if we found a gateway to dark matter in the final year of running of the Tevatron?

1 comment:

  1. Well, the discovery of gravity’s exact mechanism along with that of dark matter has already taken place, way back in autumn 2010. I know from my theoretical understanding that it is impossible to find any traces of Higgs boson as a quantum particle in the Hadron collider, neither can it show the existence of dark matter. The details of my discovery of how gravitation exactly works, http://www.anadish.com/ , and how it is produced in the framework of quantum mechanics are lying in wraps with the USPTO and I can only make it entirely public after there is clarity on how the USPTO is going to settle the issue of secrecy on my application. I consciously did not report to any peer-reviewed journal, fearing discrimination, because of my non-institutional status as a researcher; I was right; two days back, Nature Physics out rightly rejected to even consider a short communication submission on the subject, most of the journal did not respond, only one paid but peer-reviwed journal has agreed to consider. However, if the USPTO also continues with their non-committal secrecy review under LARS Level 2 (find the PDF of Private PAIR of the USPTO on my site), then, anyway, my discovery may not get published for a long time to come, in spite of me having filed the US patent application (US 13/045,558) on March 11, 2011, after filing a mandatory Indian patent application on January 11, 2011. Till, I decide to consciously jump out of government regulations, unless, of course, the USPTO decides to put it out of secrecy.

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