{"id":3820,"date":"2012-09-21T19:58:28","date_gmt":"2012-09-21T23:58:28","guid":{"rendered":"http:\/\/spinor.info\/weblog\/?p=3820"},"modified":"2014-11-06T10:04:10","modified_gmt":"2014-11-06T15:04:10","slug":"e38-a-new-boson-or-a-statistical-fluke","status":"publish","type":"post","link":"https:\/\/spinor.info\/weblog\/?p=3820","title":{"rendered":"E(38): A new boson or a statistical fluke?"},"content":{"rendered":"

I am reading about a new boson<\/a>.<\/p>\n

No, not the (presumed) Higgs boson with a mass of about 126 GeV.<\/p>\n

I am reading about a lightweight boson, with a mass of only about 38 MeV, supposedly found at the onetime pride of Soviet science, the Dubna accelerator.<\/p>\n

Now Dubna may not have the raw power of the LHC, but the good folks at Dubna are no fools. So if they announce what appears to be a 5-sigma result, one can’t just not pay attention.<\/p>\n

\"\"<\/a>

The PHOTON-2 setup. S1 and S2 are scintillation counters. From arXiv:1208.3829<\/a>.<\/p><\/div>\n

But a 38 MeV boson? That’s not light, that’s almost featherweight. It’s only about 75 times the mass of the electron, for crying out loud. Less than 4% of the weight of the proton.<\/p>\n

The discovery of such a lightweight boson would be truly momentous. It would certainly turn the Standard Model upside down. Whether it is a new elementary particle or some kind of bound state, it is not something that can be fit easily (if at all) within the confines of the Standard Model.<\/p>\n

Which is one reason why many are skeptical. This discover is, after all, not unlike that of the presumed Higgs boson, is really just the discovery of a small bump on top of a powerful background of essentially random noise. The statistical significance (or lack thereof) of the bump depends fundamentally on our understanding and accurate modeling of that background.<\/p>\n

And it is on the modeling of the background that this recent Dubna announcement has been most severely criticized.<\/p>\n

Indeed, in his blog Tommaso Dorigo<\/a> makes a very strong point of this; he also suggests that the authors’ decision to include far too many decimal digits in error terms is a disturbing sign. Who in his right mind writes 38.4935\u00a0\u00b1 1.02639 as opposed to, say, 38.49\u00a0\u00b1 1.03?<\/p>\n

To this criticism, I would like to offer my own. I am strongly disturbed by the notion of a statistical analysis described by an expression of the type model<\/em> = data<\/em>\u00a0\u2212 background<\/em>. What we should be modeling is not data minus some theoretical background, but the data, period. So the right thing to do is to create a revised model that also includes the background and fit that to the data: model’<\/em> = model<\/em> + background<\/em> = data<\/em>. When we do things this way, it is quite possible that the fits are a lot less tight than anticipated, and the apparent statistical significance of a result just vanishes. This is a point I raised a while back<\/a> in a completely different context: in a paper with John Moffat about the statistical analysis of host vs. satellite galaxies in a large galactic sample.<\/p>\n<\/fb:like>","protected":false},"excerpt":{"rendered":"

I am reading about a new boson. No, not the (presumed) Higgs boson with a mass of about 126 GeV. I am reading about a lightweight boson, with a mass of only about 38 MeV, supposedly found at the onetime pride of Soviet science, the Dubna accelerator. Now Dubna may not have the raw power […]<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20,3],"tags":[],"class_list":["post-3820","post","type-post","status-publish","format-standard","hentry","category-astronomy","category-physics","category-20-id","category-3-id","post-seq-1","post-parity-odd","meta-position-corners","fix"],"_links":{"self":[{"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=\/wp\/v2\/posts\/3820","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3820"}],"version-history":[{"count":18,"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=\/wp\/v2\/posts\/3820\/revisions"}],"predecessor-version":[{"id":6374,"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=\/wp\/v2\/posts\/3820\/revisions\/6374"}],"wp:attachment":[{"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3820"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3820"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spinor.info\/weblog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3820"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}