## Archive for January 1, 2008

### What is the value of measurement?

I was happy to see that Evolving Thoughts picked up the discussion of judging experiments based on concepts taken from information theory. Apparently these ideas are not new and show the fault lines between the statistics community and certain scientific groups, including HEP.

Today I would like to iterate an earlier point: **what is the value of measurement?** (in the context of judging experiments)

The use of “surprisals” and the like limit the scope to discoveries only, with the idea that more surprising discoveries are worth more than “ordinary” discoveries. (One goes on from there to develop the notion that an experiment, or analysis, which is better directed toward making a surprising discoveries is inherently worth more than one which makes “expected” discoveries – the problems in this formulation seem pretty clear when stated this way…) But this overlooks completely one of the main roles of experiment, which is *to measure.* We know that the standard model is successful not only because someone discovered the W and the Z bosons, the top quark, etc., but also because a host of precision measurements when taken together conform to the expectations of the standard model. No one would argue that experimental (or theoretical) particle physics would be just fine without this corpus of measurements, and I doubt that many people would say that looking for new physics beyond the standard model doesn’t need concrete and precise knowledge of standard model particle properties and interactions. After all, we know in which range the mass of the standard model Higgs boson must lie, and some people are enthusiastic about supersymmetry because of the way it conforms to measurements of precision electroweak observables. What situation would we be in today if we lacked those measurements, or they were considered unimportant? (Another example might be the current empirical knowledge of CP violation, culminating in the beautiful sets constraints on the CKM matrix and the unitarity triangle, but I am more familiar with electroweak physics, myself.)

(The top quark mass plot comes from the Tevatron Electroweak Working Group, and the “blue-band” Higgs mass plot comes from the LEP Electroweak working group.)

Of course I hope for a surprising discovery from the LHC or Tevatron data, one which is *not foreseen* by theorists. And I would be happy for clear signs of new physics even if it corresponds to one of the many available excellent theoretical ideas. But if people like the idea of judging experiments in some semi-quantitative way, how might one incorporate the value of measurement? Any ideas?