D0 Decides to be Debbie Downers

By Sean Carroll | June 10, 2011 9:40 am

Alliterative title stolen shamelessly from the lovely and understanding Jennifer Ouellette, who blogs background about the hunt for new particles at Discovery News.

So here we have science, marching on. Just last week we heard that CDF, one of the big experiments at the Tevatron at Fermilab, had collected more data relevant to a mysterious bump they had previously reported around 150 GeV in collisions that produced a W boson and two jets. The new data (7.3 inverse femtobarns, up from 4.3 fb-1 previously) made the bump look even more prominent, rather than watching it regress back down to the mean. The discrepancy is now more than 4 sigma, giving license to get just a wee bit excited that new physics might be on the loose.

Now D0, the other big experiment at the Tevatron, is ready to weigh in — and the “D” stands for “damper,” it appears. Here’s a blog post at symmetry, a link to the technical paper, and a webcast for a talk that will happen this afternoon at 4:00pm Central Time. You knew that Jester would be on the case, and he is.

But this picture tells you all you need to know.

With 4.3 fb-1 of data analyzed, the CDF bump should be just barely visible, as indicated by the dotted line labeled “Gaussian.” But there doesn’t seem to be anything there. And it’s not just you; the collaboration estimates that the probability that there is really a bump there is less than 10-5. Not very encouraging, really.

But still — it does seem to be there in the CDF data. So what’s going on? At this point, it’s not clear. Both experiments are extremely mature and well-understood, and the collaborations are good at what they do, so it is likely to be something very subtle at work. It still could be new physics, that is somehow playing games with us, but certainly the prospects don’t look as good today as they did yesterday. Look like science is going to have to march on a bit more before everything is clear.


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Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] cosmicvariance.com .


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