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Will it really take ATLAS 3 years to see 5 sigma Higgs? August 20, 2008

Posted by gordonwatts in ATLAS, CERN, D0, Fermilab.

Probably (for ATLAS new predictions on this should be released in a few months). But in the context of the Tevatron and the LHC Higgs search that isn’t really what is important.

The ATLAS prediction that it might take 3 years to reach the 5 sigma level for a low mass Higgs discovery got a lot of airplay. It got me to thinking. Lets say the two accelerators are in close competition for the Higgs. The Tevatron can really only speak to the 3 sigma level. It isn’t ever going to get to the 5 sigma level. Further, at the Tevatron the CDF and DZERO experiments will have to combine their results to even reach this 3 sigma level. So, I find it highly unlikely that the LHC will sit back and let the Tevatron get away with this. I certainly wouldn’t (and I’m on a LHC experiment). So what to do? Obvious – beat the Tevatron at its own game: combine results from CMS and ATLAS and the 3 sigma level will be obtained much more quickly. At that point the LHC has stolen the thunder from the Tevatron and CMS and ATLAS can now race each other to individual discoveries of the Higgs at the 5 sigma level.

I don’t expect the experiments to combine for the 5 sigma discovery (I could well be wrong, of course – I know of no plans to not do this or to do this!). There are many forces at play that are driving each experiment to make the first paper submission of a 5 sigma signal. This may, indeed, be what gives the Tevatron space to slip in with a 3 sigma evidence paper. And in the grand scheme of things – the Tevatron goes out with a 3 sigma evidence and the LHC with a 5 sigma discovery – that doesn’t seem like a bad “split”. But who has ever heard of the free market working like that!?

As a member of DZERO I want to push as hard as possible to nail a low mass Higgs. As a member of ATLAS, I want the experiment to scramble as fast as possible to get the Higgs – evidence and discovery. After all, that is one of the LHC’s main points.



1. Kevin - August 20, 2008

As a scientist its hard not to take the position that the science should be solid and quick regardless if its the Tevatron or the LHC.

As a matter of personal bias it would be a bit of disaster for me if the Tevatron scoops the LHC on EWSB. What happens to me? Do I take up professional fly fishing? Search for black holes? Drive a delorean at 88 mph and tell my past self to take a Tevatron post-doc?

2. gordonwatts - August 20, 2008

And Kevin, this is exactly the reason why I think if the LHC folks think the Tevatron is going to “scoop” them they will do everything they can to make sure that isn’t the case! It will be a little weird, of course, because just about every member of the Tevatron is also a member of the LHC. So collaborations and people will have to tread carefully there…

And I wouldn’t worry about it – fly fishing is not in your future (unless you so choose — but do take it up as a hobby, not full time!). Even if the Tevatron hits it at 3 sigma, the LHC will get the 5 sigma, and there will be a lot of press about “LHC discoveres it” and the only place the Tevatron will get mentioned will be something like “finishing the job the Tevatron was too weak to finish!” or something like that… And after that… well, the winners get to write history…

3. Ben Lillie - August 21, 2008

How well do the detectors need to be understood to do this kind of combination? I was under the impression it took CDF and D0 a while to do this; never been sure if the issues were technical or sociological though.

4. gordonwatts - August 21, 2008

Ben — I think this is one of the major issues that controls the size of the “window” that the Tevatron has. From D0’s point of view, I think I can stay we are still understanding our detectors. Each time we try to go to a new level of precision, we learn something new about our 20 year old + hardware.

In the case of the LHC, they will not have to understand our detectors as well as we understand ours to gain the same results for the Higgs results. This is one of the big advantages that 14 TeV gives you (vs. the Tevatron’s 2 TeV). So it is a race – and it isn’t obvious which horse is going to win at this point. Once colliding beams are delivered at the LHC we’ll know a lot more about what shape the detectors are in.

If I remember correctly, it took CDF about a year to publish the W when their detector was new (short run, sort of like the fall 2008 LHC run). I don’t remember how long it took D0 when it first ran.

5. Joe - August 23, 2008

Cern and others should take as long as needed to confirm the Higgs. If that is five years so be it.

6. Gordon Watts - August 24, 2008

Joe — I’m sure no one will release results before they are ready. But the idea of sitting back and doing it slowly when there is competition… that is what I don’t think will happen.

7. Joe - August 28, 2008

Which competiton? CERN vs Fermi or Higgs vs. BE vs GHK? Much more concerned about the later competition. Higgs, Brout and Englert are getting a great pass by the physics community – led by folks such as Veltman and ‘t Hooft. GHK seems to be getting cut out due to numbers and not being European even though they had the better paper, better careers, and can claim they were further along earlier on the boson. Not sure how this happened – but it has. Time can only help the Rochester/Brown/IC London team.

8. gordonwatts - August 28, 2008

Joe — the former is what I’m talking about.

I expect to see more stories about the latter when we actually see something. I’m curious to see how that plays out – but the science — the Higgs (or whatever you want to call it) should be the main news. Hopefully scientific politics won’t drown that out.

9. Kea - August 28, 2008

Correction: If you actually see something.

10. gordonwatts - August 28, 2008

Yes, “if” – it would be great if we see something else. Actually, lets say we see it as we think we will. Even in that case it will take a while longer before we are sure we have seen what we think we have seen. Everyone will assume that it is the Standard Model higgs (which will be a fairly safe assumption), but, scientifically, it will take us a bunch of time before we are sure.

11. Joe - August 28, 2008

Gordon – thanks. Good post and I agree. However, the scientific politics seems to get a good run also from such publications as The Economist and The London Times. As always, time will tell.

12. gordonwatts - August 28, 2008

True — but that is, perhaps, because politics is about humans. There are always two sides to science — the actual science and the people. Both are fascinating and I do hope that news papers, etc., pay attention to both. 🙂 And in this particular story there is a kernal of how actual science works. Many years were spent putting together the ground work that allowed someone to posit the Higgs… it wasn’t that a single person was thinking about it for years and years and came up with the idea. It was definately a leap – but it wasn’t a leap that came out of the blue without supporting infrastructure.

13. Anonymous - November 23, 2008

Im really new in this high energy/colliders subject. But, why competing? science should not be a competition, but a matter of creating knowledge, if you let me put it that way. Why not joining “forces” of ATLAS and CMS for the 5 sigma signal as well? whats the problem with that? I’d appreciate an answer on this, thanks.

14. Gordon Watts - November 24, 2008

Each experiment has invested 20 some-odd years in getting their detector ready. If they can, they’d like to be first to declare that they have found the Higgs. It is a huge prize. It will generate an amazing amount of press. If one experiments does it and the other doesn’t, it will do all sorts of things – for example, good funding is more likely to flow to the winner.

In-and-of-itself, competition isn’t a bad thing. First of all, it keeps everyone honest: everyone is checking each others work. Second, it limits the amount of useless work that is being done – useless work is wasted time!

Science is like any other field that involves humans. A bit of competition can really improve the way it works. However, as we’ve seen in the past, it can be taken too far: falsifying data, for example. So there are certianly limits.

15. Anonymous - November 25, 2008

So, would you agree that the problem are the humans? hehe. Well, we could say that on an hipothetical society where people is honest (Asimov’s foundation jumps right into my head) there wouldnt be trouble in joining forces of ATLAS ans CMS? Sorry to insist, but Im just wondering if this is a matter of “making money” and “press” or there are other more fundamental reasons why they (ATLAS and CMS) shouldnt join (besides hat honesty one, consider he hipothetical society)? Thanks for the response.

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