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February 18, 2005

Comments

Ben

Congratulations! Could you tell us more about the larger significance of the result (i.e., what it tells us about the Z boson, b quarks and the Standard Model?) Thanks!

Tommaso Dorigo

Well, the answer is really simple. It does not tell us anything that we do not as of yet know about the physics. It instead speaks volumes about a hadron collider experiment actually being able to reconstruct hadronically decaying heavy objects, such as is the Z boson. This is not easy due to the limited resolution of the typical detectors to hadronic jets, and due to the typically huge backgrounds due to non-resonant production of jets.
The whole business of the Higgs hunt at the Tevatron revolves around the assumption that we can see a tiny bump on top of a large background - not unlike the one in the plot. The Higgs boson decays to pairs of b quarks with large probability if the Higgs mass is not too large. We hope that we can find it that way, but it will require the hell of a lot of data and the most cunning ideas on our side.

T.

Ben

Thank you for the information, and I am enjoying your other posts too! Congratulations again on what sounds like a fantastic technical and intellectual achievement. However, I wanted to ask why you and fellow particle physicists don't (at least publicly) get discouraged that experiments like this don't yield physics information that wasn't already known. It sounds as if you're finding an already known needle in a large haystack, in order to gain the skills to find a yet-unobserved needle. In this World Year of Physics, I have to ask: Didn't you and your particle physics colleagues--among the brightest, hardest-working, most mathematically talented scientists--go into physics to discover more new things than this? From my (uninformed!) point of view, it seems that particle physicists are celebrating very incremental steps like these, rather than worrying that the return of truly significant, worldview-altering scientific knowledge appears to be very low at this point (with no real guarantees that there will be much huger payoffs even with the LHC). Please comment!

Tommaso Dorigo

Hi Ben,

I always reply in my blog to people's comments, even the least interesting, but your answer is indeed very interesting and I will paste it to an independent post tomorrow. For now, I answer below.

1) Thanks for your appreciation of this blog and of the results shown above!

2) You are right when you say that we (I am extrapolating other colleague's feelings here, but I am confident on it) study Particle Physics to hit on big new things, which can bring sudden advances to our field and to science in general. However, there are then several constraints. First of all, one is not always free to pick the kind of research one thinks is the most interesting, the most useful, or the most likely to produce a Nobel prize. To first order, after a PhD all but the very brightest (who are able to pick exactly what they want) are typically just happy to be able to stay in the business, and will conform to the research program of the University or Institute that hires them. After a few years, one gets to a tenured position and can then have more freedom to choose... But will one then be still able to have the energy and the stimulus to do groundbreaking research ? Not easy!
The other constraints come from one's background. It is hard to leave one's specific expertise (which is a valuable asset) to move to another more promising research. Finally, the most promising things are the ones where there is more competition, and one cannot always afford to have to fight.
3) Most of the big advancements in Physics, and I would say in Science in general, are indeed pictured as quantum leaps, but are rather the result of the collection of a mass of independent, smallish pieces of information. Then there is a stroke of genius, sure. But if you look closely, the genius was first of all a very well informed person! And without all the work of obscure colleagues, even a Planck would not have figured out how to fit a power spectrum the right way. In order to have the need of hypothesizing a quantization of energy Planck needed a very precise measurement of the emission spectrum of a blackbody to have to fit: and the higher precision of that measurement was - one could argue - a very incremental step from less precise measurements available at that time, to use your words. Another instance of that mechanism is the discovery of parity violation. Lee and Yang produced a earthquake when they speculated that Weak Interaction did not conserve the Parity symmetry, in a paper in 1956. But that paper was just a very detailed, precise and methodical review of all data available to that point: small experiments, tiny bits of information, sometimes imprecise, sometimes incomplete. Incremental steps!

So, am I worried by doing my tiny little bit of Science instead than concentrating on the big issues ? No. I am a soldier, not a general. Maybe one day I will be a general, but I have the feeling I will enjoy Particle Physics less then!

Cheers,
T.

Ben

Thank you so much, Tommaso! I look forward to your further posts! As a science writer (whose beat does not currently include particle physics), I've always been very interested in these issues--and you've shed a lot of light on them for me!

And you know what, I think that LHC WILL probably yield lots of great info--I guess I was just feeling that the Standard Model has been so surprisingly unyielding against many of the best experimental tests in recent times! Anyway, thanks for helping me to appreciate and celebrate the importance of "incremental steps"--physics and the public are very lucky to have "soldiers" like you!
Ben

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