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Speaking of http://www.nature.com/news/lhc-sees-hint-of-boson-heavier-than-higgs-1.19036. I understand that such a bump can be a statistical fluctuation. What troubles me is that the bump has been seen in two completely disconnected and independent experiments. How can this happen by chance? Is there some systematic error that has been overlooked by both of them? Is there any common mistake in background subtraction?

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  • $\begingroup$ There is no reason to be troubled. Just be patient and the statistics issue will be resolved with the next set of data. As you said, that still leaves the worry about systematic errors. While the two experiments are similar, they still use a lot of the same principles and the data analysis is aided by similar (and sometimes the same) algorithms and code, so it's not totally impossible to have a subtle mistake cause havoc in both data sets. Having said that... I would be more than happy to see something. If LHC could find nothing but a standard Higgs, how boring would that be? $\endgroup$ – CuriousOne Jan 3 '16 at 20:59
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    $\begingroup$ Are you familiar with the "opps-Leon" particle? With the reason particle physics looks for five-sigma before taking claims of "discovery" seriously? $\endgroup$ – dmckee Jan 4 '16 at 0:53
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I rolled two sixes in a row when I sat down once and rolled a six sided die five times. Same thing happened to my friend once! Instead of asking how that can be, you can just ask about the chance of that happening.

When the chance gets too small you are starting to get good evidence that something is going on. When the chance is too high, you have to accept that these things literally happen every so often.

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    $\begingroup$ In this case it seems to me that the probability that a bump at 750 GeV occurs to two "friends" entirely by chance is pretty close to zero! $\endgroup$ – Arnaldo Maccarone Jan 3 '16 at 21:10
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    $\begingroup$ @ArnaldoMaccarone I'm literally not impressed by you ask "how it can be" instead of computing the chance. Seeing two 1 sigma events is not the same as seeing a single 2 sigma event. I still can't tell if you are literally asking how to compute a probability. We have actual standards about how close to zero you need to be. We don't announce discoveries based on "pretty close to zero." $\endgroup$ – Timaeus Jan 3 '16 at 21:17
  • $\begingroup$ you are perfectly right. I am not a professional in experimental particle physics and thought that an heuristic explanation were available. If the answer is "shut up and calculate" (cit.) you have won! Thank you for your time! $\endgroup$ – Arnaldo Maccarone Jan 3 '16 at 21:27
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    $\begingroup$ Short comment: you could improve your answer by implementing the look-elsewhere-effect into your roll-the-dice analogy. $\endgroup$ – Hans Moleman Jan 3 '16 at 22:39
  • $\begingroup$ @HansMoleman I started with bump searches way back in the seventies, and was in an experiment where a four sigma mu pi resonance was seen in antineutrino scattering. At that time there was no knowledge of the "look elsewhere" effect and the whole colaboration, all 50 of us , were quite excited until a similar experiment in the US saw nothing ( they had gone directly to the mu pi channel). As far as I am concerned the 5 sigma requirement is really necessary, plus the two experiments. $\endgroup$ – anna v Mar 19 '16 at 13:37

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