The big news in physics in 2012 was the official discovery of the Higgs boson, which was actually all but certain a year ago. Now that the dust is settled, the details are being examined and an interesting nuance has come up.
There are two experiments at the Large Hadron Collider (LHC) that have looked for and found the Higgs boson. One is called CMS, and the other is called ATLAS.
The various means of detecting a Higgs boson at CMS has produced mass estimates for the Higgs boson that are consistent with each other.
But, at ATLAS, the mass determined by some methods is a bit more than two standard deviations different than the mass determined by other methods used at the experiment. The high number at ATLAS (from diphoton measurements) is 126.6 GeV. The low number from ZZ decays is 123.5 GeV. A combined number that is the best fit to the combined data is about 125 GeV. The measured value of the signal strength of the Higgs boson evidence at ATLAS is also about 80% higher (about two standard deviations) than the expected value, although this may be due in part to systemic measurement errors and biases in the mass fitting formula used.
By comparison at CMS the mass estimate based on ZZ decays are at 126.2 +/- .6 GeV, and the mass estimate based on gamma gamma decays is around 125 GeV. So the CMS masses are compatible with and in the middle between the two extreme ATLAS values, and a best fit to the combined CMS data is between 125 GeV and 126 GeV.
In all likelihood, the discrepency seen at ATLAS is simply a matter of measurement error and, in fact, there is just one Higgs boson with a mass of something like 125 GeV (a crude average of the four measurements would be 125.3 GeV, and where there are good reasons that a more sophisticated combination of the four measurements are more technically correct, this isn't far from the mark of what makes sense). This would be consistent with both of the ATLAS measurements and the CMS measurement at about the two standard deviation level. (For comparison, estimates from four and a half months ago are summarized here.)
But, there is another possibility. There are well motivated beyond the standard model theories in which there is more than one neutral charge, spin zero Higgs boson, and if there were, there could be two such Higgs bosons similar in mass to each other and that would also produce a greater than otherwise expected Higgs boson signal. This is the case in almost all SUSY models.
While signal strengths after new data are mostly migrating towards the Standard Model expected strength, the diphoton data remain stronger than expected at both ATLAS and CMS even as new data come in. So this is looking more like the stronger than expected signal in the diphoton channel could have real physical meaning, rather than simply being a fluke.
I don't think that the LHC is really seeing two different Higgs bosons, and neither do lots of other people who nevertheless have duly noted the possibilty. But, it is the most interesting story from the LHC results at the moment, so it deserves a mention. The existence of two neutral Higgs bosons, rather than just one, would revolutionize physics, would be the only beyond the standard model experimental result other than neutrino oscillation in the last half a century, and would dramatically tip the balance in the SUSY v. no SUSY determination.
Another interesting new little tidbit is that further analysis of the data has determined that the Higgs boson has even parity and spin-zero, rather than spin-2 or odd parity, at a 90% confidence level, as expected.