Bump Hunting (Redux)

By John Conway | October 22, 2007 8:44 pm

Last January, in my blogger-virginity-losing post to CV, and a follow-up post, I wrote about the experience of “opening the box” on a never-before-seen sample of data from the CDF experiment at Fermilab and being perhaps the first human to see what nature had to tell CDF in the search for the Higgs boson predicted by supersymmetry with the then-current data sample. What we’d seen was a small excess that might have in fact been the first experimental glimpse of a Higgs boson with a mass of around 160 GeV, or 170 times the mass of a proton. Or, it could have been a statistical fluctuation, or an artifact of the detector or analysis. It was excitng, but as scientists we had to keep our heads on straight.

There is basically nothing we can do about a statistical fluctuation – you get what you get. What keeps us awake at night is the prospect that we had made a mistake, or overlooked some detail. And so for months now, we (and when I say “we” I mostly mean Anton Anastassov, a postdoc at Rutgers, and my student Cris Cuenca) worked very hard to make sure that we hadn’t missed anything.

As far as we could tell, we hadn’t missed any problems, and so by late summer we decided to “open the box” again on a sample with 1.8 times more data (but containing the original sample). So it was not totally new data, but a sample with 80% more statistics. Was the bump still there? Would we see an even more significant excess?

We already kind of knew, given that the D0 experiment had not seen a similar excess, that we might not see the bump. So finally, after we had dotted the i’s and crossed the t’s, we took a look and there it was:

Higgs to tau pairs in CDF with 1.8 fb-1

Gone! The data points all fell within an error bar or so of every bin…no excess, no bump, no Higgs… I am sure you are thinking “no tickets to Stockholm” too. Were we suprised? No. Once you’ve been working in this field awhile you realize that this is what happens with two-standard-deviation effects very often: they go away with more data. If you want all the gory details you can find them here.

If you do go back and read the original posts, you’ll find that we assumed that a statistical fluctuation was one very possible explanation. Unless we had auxiliary information that said that there should be a Higgs at that mass with that production rate, etc., it was much more likely than not to have been a statistical fluctuation. And in the end that is what it was…even with a probability of 1 in 50 or so. It happens.

So the quest for this beast continues. Mother Nature is a big fat tease!

Now, gentle readers, one thing we’ve learned is that among you are many science journalists who use blogs as a means to catch wind of breaking news. You all have to have an angle, and a story to tell (sell). In the past, our field has been treated to stories of the ilk “300 Physicists Fail to Find Supersymmetry” with the subtitle “Study Illustrates the Risks of Big Science”. (New York Times, 1993). I sincerely hope that’s not your angle here, science writers! Our favorite put-down of that is to ask whether there should have been an 1888 story titled “Physicists Fail to Find Ether in Vacuum” about the Michelson and Morley null result. But okay, we’re nerds.

Of all the stories that appeared this past year about the quest for the Higgs I think that the one that got it right was Dennis Overbye’s in the New York Times. He captured the true spirit of this hunt without hitting false notes about blogging and science, or trying to make it look like some sort of last-chance desperate ploy by an accelerator nearing the end of its useful life, or trying to foment some non-existent controversy. I challenge you journalists out there to tell it like it is: this is a great human adventure, with all the twists and turns any good adventure has. And someday, maybe soon, if not at the Tevatron then at the LHC, there it will be…but will it be what we expect?

CATEGORIZED UNDER: Science, Science and the Media

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