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12:00 pm
Fri December 16, 2011

Physicists Find 'Hints' of Elusive Higgs Boson

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IRA FLATOW, HOST:

This is SCIENCE FRIDAY. I'm Ira Flatow. Scientists have been searching for decades for a subatomic particle called the Higgs Boson. You've heard about it. It's been in the news, and you know, in theory, it explains why and how objects have mass.

But for more than 40 years, after it was first posited, the Higgs Boson remains elusive. This week, two teams of researchers studying trillions of proton-proton collisions at the Large Hadron Collider say they've made progress in the hunt for the Higgs. In fact, CERN's director general, Rolf Heuer, said that while the evidence was not definitive, two teams of scientists have narrowed down the Higgs' hiding spot.

ROLF HEUER: I think we have made extremely good process by closing in the window of the allowed mass range of the Higgs Boson, but it's still alive inside, and we saw some tantalizing hints today.

FLATOW: And Joe Incandela joins us from CERN in Geneva to help sift through the data and talk about those tantalizing hints that Rolf Heuer was talking about. Mr. Incandela is currently the deputy spokesman for the CMS experiment at CERN, and beginning in January 1, he's going to be the spokesperson for the experiment. He's also physic professor at the University of California Santa Barbara. Welcome to SCIENCE FRIDAY, Dr. Incandela.

JOE INCANDELA: Well, thank you, it's my pleasure to be here.

FLATOW: Tell us exactly, you know, sometimes the announcement reminds me of a phrase that someone is a little bit pregnant, you know. He's saying yes and no at the same time.

INCANDELA: Well, it's - it really comes down to statistics, and the fact that we're at a stage where we're sensitive, fairly sensitive, to begin looking for the Higgs in many areas, but we're not quite at the point where we have enough data to really nail it.

And sometimes I give the analogy of looking through binoculars. We're somewhere between out of focus and completely in focus, you know, that range where things are a little blurry, and you can kind of imagine you see things, but you're not sure exactly what they are.

FLATOW: So what - as a scientist, what did they actually see? They saw some evidence of a mass at a certain energy level.

INCANDELA: Well, what we were looking for, yes, is let me just say this: We had a range of Higgs masses that we think are possible. We don't know - if we don't know if the Higgs exists, but if it exists, it has to exist in a certain range of masses. And we use the units of the proton mass.

So somewhere between roughly 114 and 600 times the proton mass was open, except for about 20 units around 160 that was ruled out by Ferme Lab in Chicago. So we started looking there. And depending where you're looking, the Higgs kind of manifests itself in different ways, by what it decays to. And so we looked for those kinds of events that looked like Higgs decays, and remarkably, in just one year, that whole 500 GEV range, that 500 times the proton mass range, we've narrowed it down to just 14, 13 or 14 units now.

FLATOW: Right, and so you saw evidence of what would be a photon decay there or a photon?

INCANDELA: Well, we see - we definitely see - one of the things the Higgs can do in the range where we haven't sort of - let me say this: We haven't really ruled it out of everywhere else in this big range, but we have - it's become somewhat less probable or possible that we'd expect to see it there. We still have a lot of work, even in this big range, to really rule it out to a very high degree.

But in this range that's still kind of really very possible, this 15 GEV range or 14 GEV range, that's just right where the Higgs tends to want to decay in the most interesting ways, in many different ways. And one way is to two photons, very energetic photons.

FLATOW: Right. And so you saw that?

INCANDELA: We see that, but there are many...

FLATOW: But that's not convincing - that's not convincing evidence enough? As you say, there are many ways you could get there.

INCANDELA: Well, there are many other things that can actually produce two photons, as well.

FLATOW: So you need to run more experiments?

INCANDELA: Well, we need to get more data, and we're going to do that next year. We'll get about maybe five times the data. And then we'll be able to be, I think, much more certain. On the other hand we do see interesting events that could be candidates for the Higgs, and in some cases it's to two photons, sometimes to two Z-particles that then decay to electrons or muons.

And these are rather clean events. And they're quite interesting, for sure.

FLATOW: But they could be caused by something natural, also, something...?

INCANDELA: That's right. That's right. So what we have to do is look for the signal over a background, just signal over noise is really the issue. So we need larger statistics to see that what we're seeing is really statistically significant, and we're tantalizingly close to being there. Within the next year, we'll be there.

FLATOW: So you run the Large Hadron Collider all winter long, and you collect data?

INCANDELA: Well, this winter - we're off right now.

FLATOW: You shut down for the winter?

INCANDELA: We shut down for much of the winter, and we'll come back up, I think they start re-commissioning the machine in February. We'll go, very likely but not for sure, it'll be decided in January, we'll go up a little bit of a step in energy, and we'll go to more intense beams. And this makes more collisions per unit time.

And so where hoping that whereas this year in some sense we - each experiment had something like 350 trillion proton-proton collisions, next year we'll have something like four or five times that many. And so we should make more of these Higgs, and if there's something there, it will become statistically significant.

FLATOW: So why not wait until it was statistically significant? Why come out with this tantalizing little hint? Is it something to tide us over the wintertime so we can wait for it to power up again in February?

INCANDELA: Well, it's actually the way we do things at some level. There's a - whenever the machine goes down - or actually more generally, about two times per year, we like to go through our data and understand it as well as we can and present it publicly. And so this is sort of a normal process.

This is a little earlier than usual, it's normally in February or March, but because of the excitement over this search, it was of great interest for us to do this now. And the fact that we narrowed down this range that I told you about, that we've kind of begun to eliminate 490 units of the 500 units of this range, is a huge achievement, actually.

You have to realize that for 30 or 40 years, we've been looking, and it's - you know, we were moving at a snail's pace. But this machine is so fantastic, it allowed us to really make great progress in just one year, and I think the community at large was very excited to see that we've made such progress.

FLATOW: But it's possible you could never get past this stage of - you can continue to run and not come up with anything more statistically significant and not find the Higgs Boson?

INCANDELA: No, we will definitely come up with something more statistically significant. We're very confident of that. Now, the thing is that there's a possibility that we don't see it, it's just not there, and the theories are wrong, or at least the standard model version of the Higgs theory is wrong, and it has to be something else.

FLATOW: That would be good, too.

INCANDELA: That would be good, too, because, you know, we - we're here as experimentalists. Our job is to really view nature. We're not making any prejudgments about it.

FLATOW: I think Steven Weinberg once said our job is not to make physicists happy, or nature is not here to make physicists happy.

INCANDELA: That's right, that's right, and that's why we need these experiments.

FLATOW: OK, well, when do you think we'll get the first data coming in, or we'll have something where you'll be jumping up and down, again, you know, maybe next spring, or will it be another year from now?

INCANDELA: Well, we're tentatively targeting having additional results in the summer, probably in July, and we're hoping by that time to have maybe twice as much data as we have now. And then by the end of the year, and perhaps right at the end of the year or shortly thereafter, we'll have another doubling.

So we'll go to four times the data that we have right now, roughly speaking, and at that point we are pretty confident that we'll be able to really focus in on this thing.

FLATOW: All right. OK, Joe, thank you very much, and good luck to you.

INCANDELA: Thank you very much.

FLATOW: We hope to have you back with some more results next year. Have a happy holiday.

INCANDELA: All right, same to you.

FLATOW: Joe Incandela is - he joined us from CERN in Geneva. He will become, in January, the official spokesman for the experiment over there. He's also a physics professor at the University of California at Santa Barbara Transcript provided by NPR, Copyright National Public Radio.