Most Wanted Particle by Jon Butterworth

Author:Jon Butterworth
Language: eng
Format: epub, pdf
Publisher: The Experiment

5.2 Crying Wolf

The Large Electron–Positron Collider (LEP) ran from 1989 to 2000 in the tunnel now occupied by the LHC. The LEP experiments made many of the measurements that established the Standard Model as a precise theory; amongst these were measurements that, when fed through the precise calculation framework of the Standard Model, indicated roughly what the Standard Model Higgs boson mass had to be (if it existed). Towards the end of the run, there was one of those heated decision points in particle physics: should the machine be turned off as planned, to start construction of the LHC, or should it run a bit longer at maximum energy to see if the Higgs boson popped up, right about the limit of sensitivity?

Extending the run would have cost a lot of money and would have delayed the LHC. But there were hints (how I hate hints) that the Higgs boson might be there, at a mass of about 115 GeV. The hints were just a few suggestive collision events, but a one-month extension was granted to see if more showed up. None did, so the machine was turned off. Several LEP physicists remained utterly convinced they had seen the Higgs and that its mass was 115 GeV. I have a colleague who bet several bottles of champagne on this, and another who gave a talk a year later in which he claimed they really had seen the Higgs already – and wasn’t entirely joking.86 Passions ran high.

86. He later became a leading Higgs physicist at the LHC, so obviously – and very sensibly – recanted. Perhaps it shouldn’t have been a surprise, then, that as the data were accumulating and we were all obsessing about the latest distributions (especially the two-photon mass I talked about in the previous section), a group of ATLAS physicists, amongst them some of the leading proponents of the 115 GeV ‘LEP Higgs’, got a rush of blood to the head – or some part of their anatomy – when for a while the data showed a small excess around the 115 GeV mass bin. An internal note making extravagant claims was distributed very widely within the ATLAS collaboration. It was clearly an overstated claim and in my opinion showed a lack of objectivity.

These are easy mistakes to make, but not so easy to email to thousands of colleagues. It should still have remained a slip-up between friends, part of the internal process by which ATLAS discusses such things and filters out those that aren’t robust. Unfortunately, someone chose to breach collaboration confidentiality and post the title and abstract (and the internal author list, naming those would-be Nobel Prize winners who had beaten all their colleagues to the punch) on a blog . . .

The upshot was that many of us on the ATLAS experiment at CERN were a little busier than we anticipated over the Easter break.

The level of public and media interest in the Higgs search was high. The fear was that if too

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