I mentioned during a particle physics lecture today that sometimes big results grow from small statistical indications, but more often than not these turn out to be false detections. I wonder what this will turn out to be?
The CDF Collaboration released this plot today (arXiv:1104.0699, 6-April-2011): The blue peak at MJJ = 145 GeV is not predicted by the standard model, of course. The CDF paper is very clear and sober, and it is good that the collaboration reported these results. Let me outline the analysis in a few paragraphs. Th … Read More
via Collider Blog
This entry was posted on April 13, 2011 at 12:19 pm and is filed under The Universe and Stuff with tags Particle Physics, Tevatron. You can follow any responses to this entry through the RSS 2.0 feed.
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In the Dark 
April 13, 2011 at 12:54 pm
I’m surprised that the energy calibration explanation hasn’t been mentioned more widely .. look at this
this is what happens with a slight change (3-4%) in the dijet energy measure – the bump entirely disappears! (The discrepancy at the very lowest energies is an artefact of the cuts used before doing the rescaling.)
Here’s the discussion – http://www.science20.com/quantum_diaries_survivor/blog/jet_energy_scale_explanation_cdf_signal-77886
the ‘maybe’ is turning into a ‘nope’ very quickly and one has to wonder what the experiment was doing even publishing something so prone to small miscalibration.
Never mind the statistical significance, feel the systematic error.
May 1, 2011 at 5:08 pm
@stringph – I suggest you read this http://arxiv.org/abs/hep-ex/0510047 before commenting on CDF energy scale uncertainties. The lovely animated gif was done by someone on CMS with no knowledge of CDF and who mindlessly doubled a systematic error for cheap publicity and in fact the effect on the significance cannot even be got by doing this. PRL
http://prl.aps.org/abstract/PRL/v106/i17/e171801
didn’t feel the need to double the systematic error – I’m all in favour of skeptical critique of papers but I’d tend to favour reading the peer reviewed papers ahead of blogs. The systematic errors in the paper are conservative.
There are certainly things from the CDF analysis that one could take issue with (and I say that as someone on CDF) for instance ALPGEN doesn’t do a particularly good job and in fact we get the best description of the data with the default Q2 scale doubled and the default ALPGEN doesn’t describe the dR(jj) distribution particularly well. The methodology of reweighting the dR(jj) has issues (and hence is used as a cross-check) but if you reweight from two different control regions then the significance can decrease to 2 sigma or increase to 4 sigma. This spread of +/- 1 sigma is in my opinion indicative of how robust the W+jets prediction is and e.g. the W(jj) peak is also not perfect. To suggest the energy scale uncertainty is wrong by 100% is complete nonsense.