Archive for December 24, 2008

How many times do we have to discover the Higgs boson?

Readers of physics blogs may notice that collider physicists seem to want to find the Higgs over and over again… Some time ago, Tommaso Dorigo mounted a very challenging strategy of using the ttH channel in hadronic mode (ie, the Higgs is produced in association with a top and anti-top quark). In fact, he even issued an open invitation to come up with useful kinematic quantities.  More recently, he discussed looking for Higgs bosons in a variant of the so-called golden mode, in which the Higgs boson decays to four leptons through a pair of intermediate Z bosons.  Tommaso and his group plan to look for the Higgs in the more challenging di-lepton and di-b-jet channel.

Why not just focus on one, promising channel? Why pursue the more difficult ones?

The standard model of particle physics predicts unambiguously the properties of the Higgs boson (its decays and production cross section) for any assumed value of its mass. Theories of physics beyond the standard model (supersymmetry, little Higgs models, extra-dimensional theories, etc.) predict deviations from those standard model values. So the pat answer to those questions above is: we want to know whether the Higgs boson that we discover (if we discover) is exactly like the standard model version, or some other version, and the only way to know is to look for deviations from the standard model predictions. Since we don’t know where those deviations will/might occur, we need to look everywhere.

But for an experimenter, there is an almost crude reason for wanting to discover the Higgs boson in several channels. We need to know that the signal is real. We do not want to report a statistical fluctuation – or worse, a defective analysis. It is important to be skeptical. But sometimes this translates into a reluctance to report results, or even a suppression of unexpected (or unwelcome) results, and I think this is wrong. If something is a true signal, then repeated, related analyses will prove it more definitely than one single, over-done piece of work.

Inside the internal world of experimental collider physics, I am happy to see people attack the difficult channels, and to try to think of new ones.  (I am doing this, too.)  For the outside world of interested educated people, please understand that finding the Higgs several different ways is plain good science.  Let’s hope that, one or at most two years from now, bloggers like Tommaso, Gordon, colleagues at the US-LHC blog site and at Cosmic Variance among others, will be debating explanations and hypotheses of real Higgs signals, plural.


December 24, 2008 at 11:23 am Leave a comment

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