Tevatron experiments close in on favored Higgs mass range

Jul 21, 2011

(PhysOrg.com) -- Experiments at the Department of Energy’s Fermilab are close to reaching the critical sensitivity that is necessary to look for the existence of a light Higgs particle. Scientists from both the CDF and DZero collider experiments at Fermilab will present their new Higgs search results at the EPS High-Energy Physics conference, held in Grenoble, France, from July 21-27.

The Higgs particle, if it exists, most likely has a mass between 114-137 GeV/c2, about 100 times the mass of a proton. This predicted mass range is based on stringent constraints established by earlier measurements, including the highest precision measurements of the top quark and W boson masses, made by Tevatron experiments. If the Higgs particle does not exist, Fermilab’s Tevatron experiments are on track to rule out this Higgs mass range in 2012.

If the Higgs particle does exist, then the Tevatron experiments may soon begin to find an excess of Higgs-like decay events. With the number of collisions recorded to date, the Tevatron experiments are currently unique in their ability to study the decays of Higgs particles into bottom quarks. This signature is crucial for understanding the nature and behavior of the Higgs particle.

“Both the DZero and CDF experiments have now analyzed about two-thirds of the data that we expect to have at the end of the Tevatron run on September 30,” said Stefan Soldner-Rembold, co-spokesperson of the DZero experiment. “In the coming months, we will continue to improve our analysis methods and continue to analyze our full data sets. The search for the Higgs boson is entering its most exciting, final stage.”

For the first time, the CDF and DZero collaborations have successfully applied well-established techniques used to search for the Higgs boson to observe extremely rare collisions that produce pairs of heavy bosons (WW or WZ) that decay into heavy quarks. This well-known process closely mimics the production of a W boson and a Higgs particle, with the Higgs decaying into a bottom quark and antiquark pair—the main signature that both Tevatron experiments currently use to search for a Higgs particle. This is another milestone in a years-long quest by both experiments to observe signatures that are increasingly rare and similar to the Higgs particle.

“This specific type of decay has never been measured before, and it gives us great confidence that our analysis works as we expect, and that we really are on the doorsteps of the Higgs particle,” said Giovanni Punzi, co-spokesperson for the CDF collaboration.

To obtain their latest Higgs search results, the CDF and DZero analysis groups separately sifted through more than 700,000 billion proton-antiproton collisions that the Tevatron has delivered to each experiment since 2001. After the two groups obtained their independent Higgs search results, they combined their results. Tevatron physicist Eric James will present the joint CDF-DZero search for the on Wednesday, July 27, at the EPS conference.

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User comments : 29

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typicalguy
1.7 / 5 (13) Jul 21, 2011
Tevatron has found nothing but is approaching the range where it might find something if predictions made by theory prove true. Wow, is this what we call 'news' these days?
jscroft
4.7 / 5 (13) Jul 21, 2011
Negative results ARE news.
thales
2.1 / 5 (15) Jul 21, 2011
It's called "defending your budget".
pauljpease
5 / 5 (11) Jul 21, 2011
If they believe they are working to discover something important, why shouldn't they defend their budget? Don't you work to keep your job too? Or do you work for free?
Corban
1 / 5 (1) Jul 21, 2011
Higgs Boson territory is like Normandy. We are in the gunboats. Get ready for the hatches to open, and be prepared.
eachus
5 / 5 (6) Jul 21, 2011
If the Higgs exists, and is found, it confirms that the standard model is correct, at least in how it accounts for mass. If the Higgs is NOT found though, that is huge news. It may be that the Higgs exists, but decays in different modes than expected, or that the Higgs has a higher mass than expected. Both of these are pretty unlikely, but the LHC can check them.

That leaves the situation where the Higgs does not exist, and new physics is needed to account for mass--and gravity. Right now if you forced physicists to bet, the result would be about 15% that Fermilab will find the Higgs, 35% that it will require the LHC at CERN, and 50% that the Higgs doesn't exist.

Well maybe not today, but by the end of next week. The EPS conference in Grenoble has started, and I would expect lots of buzz by now if someone was going to present evidence for the Higgs.

So is the news that Fermilab's two detector groups are presenting together at EPS huge news? No. Big news? Yes.
typicalguy
3 / 5 (2) Jul 21, 2011
Eachus, I thought gravity is based on the geometry of space? Didn't Einstein prove that during a solar eclipse when light from a star behind the sun was visible?
thales
5 / 5 (7) Jul 21, 2011
If they believe they are working to discover something important, why shouldn't they defend their budget? Don't you work to keep your job too? Or do you work for free?


In fact, I do think they should defend their budget. I'm happy that they came out with this during a time of budget cutting. Just thought it was worth pointing out.

If my coworkers were being laid off, I would certainly defend my worth as an employee as well. The best defense is the truth; I don't doubt that the Tevatron is valuable and worth keeping around.
Pyle
5 / 5 (2) Jul 21, 2011
new physics is needed to account for mass--and gravity
A little misleading. Einstein's gravity doesn't need a Higgs. Nor does about 99.9% of the other established physics we have.

We would need new physics to describe the mechanism that leads to mass and gravity (inertia is somewhere in there too) if the Higgs particle doesn't exist though.

There is a lot of work being done on this. A lot. Most of it is way too much for a site like this. Just a bunch of ridiculous math.

Eachus, I thought gravity is based on the geometry of space? Didn't Einstein prove that during a solar eclipse when light from a star behind the sun was visible?
Sure, something like that. But that still works if there is a Higgs boson.
thales
not rated yet Jul 21, 2011
Gravity IS based on the curvature of space. Mass curves space. Therefore mass causes gravity.
vacuum-mechanics
1 / 5 (1) Jul 21, 2011
Gravity IS based on the curvature of space. Mass curves space. Therefore mass causes gravity.


How mass curves space, and how curved space cause gravity?
Pyle
4.4 / 5 (5) Jul 21, 2011
Gravity IS based on the curvature of space. Mass curves space. Therefore mass causes gravity.
Nope. Spacetime.

And how exactly is spacetime curved? Mass just does it? Just because some equations seem to work, doesn't make it self-evident. There is something to it and we are still working on it. The Higgs field was an attempt at explanation and we're waiting to see if it proves right. If not, there are a host of alternate theories out there right now that seem promising. Loop Quantum Gravity being near the top of the list, despite no gamma polarization / granularity.
thales
5 / 5 (4) Jul 21, 2011
Fair enough, spacetime. I was jotting off a quick response to typicalguy's question and obviously wasn't thinking clearly enough.

I don't know what causes mass to curve spacetime, but whatever it is isn't the proximate cause of gravity anyway.

Why do you say Loop Quantum is near the top, despite evidence against it? I'm sure you agree at least that it's dropped down the list.
FrankHerbert
2.8 / 5 (9) Jul 21, 2011
Mass causes gravity by warping spacetime a la Einstein, but the Higgs is what (is believed to) cause(s) mass itself, correct?

It's not that the Higgs is the direct cause of gravity, it is the direct cause of mass which gravity requires.

Is this right?
ubavontuba
3 / 5 (2) Jul 21, 2011
Loop Quantum Gravity being near the top of the list, despite no gamma polarization / granularity.
Intersting, but I'm beginning to be more inclined to suspect spacetime is fundamentally different from quantized mass/energy, in a way we have yet to comprehend. That is, I'm thinking spacetime may be infinitely divisible and smooth, as opposed to mass/energy being granular/quantized. That they affect one another is evident, but that doesn't mean there isn't a fundamental and irreconcilable difference between the two.

Simpy put, spacetime could be a whole 'nuther thing, altogether.
Pete1983
5 / 5 (4) Jul 22, 2011
"Simpy put, spacetime could be a whole 'nuther thing, altogether."

I think this may be our natural tendancy, conceptually that is, simply because of the issues between quantum mechanics and general rel. I'm still rather for a holographic model, where everything is interrelated, as having 2 distinct models (if that was the ultimate result) seems a bit strange universe wise (although what I think about how the universe should act doesn't ever seem to come into play).

That being said, I still agree that spacetime may be a whole other thing. It almost seems that we've become more confused in the last 15 years, as opposed to more informed about the universe, but that's a GOOD thing. We know where the problems are, we just need another physicist to come up with the next huge idea. Ideally I hope we get somebody of the genuinely nutty variety. Another Niels Bohr type character would be fantastic.
RobertKarlStonjek
1 / 5 (3) Jul 22, 2011
I think you guys should all relax ~ if the Higgs doesn't exist we can always make some in the LHC ~ problem solved!!!
Waterdog
not rated yet Jul 22, 2011
I have read many articles and books on these anticipated new particles and their impact on the standard model over the last few years and I find it interesting that as the models evolve they seem to be converging on a concept of spacetime that is more similar to the ninetenth century concept of ether than not.
This is not a criticizism, but merely an observation. If true then I think that this could have interesting impacts on many fields of research, not least of which it could open up the possibility of reactionless space drive systems eventually
Darkboy
not rated yet Jul 22, 2011
Why does everyone only say that mass curves spacetime? Energy does this too. In fact, I don't believe that the higgs is necessary, at all, to explain gravity. The higgs explains how particles "acquire" mass, or, in other words, how energy becomes tightened up into matter.
In layman's terms, the Higgs has little to do with gravity.
gurloc
not rated yet Jul 22, 2011
You are talking about 2 different things.

What you call gravity is a bulk phenomena and general relativity is a somewhat goofy but very successful geometrical model of large scale gravity. Just as Newtonian mechanics is a crude, but very useful, approximation to quantum electrodynamics in the bulk.

What gravity actually *is* is unknown. But has to be a force which functions at the subatomic level and be quantized to reconcile with the other three forces. The Higgs does not deal with quantum gravity, it only concerns why particles have mass and why that mass differs between particles. It does not address possible forces caused by that mass.
gurloc
not rated yet Jul 22, 2011
I should also mention that although gravity will not be understood until its explained at the subatomic level (which is the scale where every since process in the universe actually takes place) it is virtually impossible to study due to its low strength.

A good example of how weak gravity is compared to the other forces is to stand on the tip of your toe. The electromagnetic interaction of atoms in 1 square cm of your skin with the atoms in 1 square cm of the floor is easily resisting the gravitational force of the entire earth on your body.
vacuum-mechanics
not rated yet Jul 22, 2011
Gravity IS based on the curvature of space. Mass curves space. Therefore mass causes gravity.
Nope. Spacetime.

And how exactly is spacetime curved? Mass just does it? Just because some equations seem to work, doesn't make it self-evident. There is something to it and we are still working on it. The Higgs field was an attempt at explanation and we're waiting to see if it proves right. If not, there are a host of alternate theories out there right now that seem promising. Loop Quantum Gravity being near the top of the list, despite no gamma polarization / granularity.

What is Higgs field, is it the same thing as the old ether ?
Darkboy
not rated yet Jul 22, 2011

What is Higgs field, is it the same thing as the old ether ?


The Higgs field is what gives particles their masses, as I have previously stated.
frajo
2 / 5 (1) Jul 23, 2011
I'm thinking spacetime may be infinitely divisible and smooth, as opposed to mass/energy being granular/quantized.

The concept of infinity should be reserved for the realm of mathematics. Even there it causes headache; see the Banach-Tarski paradox.
Mathematics is a great tool for physics but it certainly is not physic's second identity. Maybe the exclusion of infinities in physics is the most fundamental difference.
vacuum-mechanics
not rated yet Jul 23, 2011

The Higgs field is what gives particles their masses, as I have previously stated.

How the Higgs field give mass to particles?
Cynical1
not rated yet Jul 24, 2011
Like entities in our universe (regardless of size) gravitate towards others of their kind - because they CHOOSE to...
Cynical1
not rated yet Jul 24, 2011
If one planet has twice as much mass as another and a third planet is twice as massive as the second, is the gravitational effect 4 times as much in the third body than in the first?
Pete1983
5 / 5 (1) Jul 24, 2011
Hi Cynical1,

from my understanding (which is very limited), yes if you increase the mass by 4, the gravitational field would increase 4 fold. You would also get the same gravitional field strength increase by reducing your distance by half (becuase it's all relative baby!)

Kind of makes me think of the tree falling in the woods scenario... If a mass exists in it's own universe and there are no other masses to be (relativistically) attracted to, does the first mass have mass?

Ok that doesn't really make sense, but the whole relativity thing of it is incredibly cool.

Also @Waterdog -
I agree with you that conceptually it can feel like modern physics is describing an aether like spacetime, however it seems that this is quite implicitly not the case. I can't explain why this is the case, but look up "frame dragging" on wikipedia, as that is a good explanation of what at first appears to be aether-like behavior, when it is most definitely not (for confusing reasons...).
ubavontuba
1 / 5 (1) Jul 25, 2011
look up "frame dragging" on wikipedia, as that is a good explanation of what at first appears to be aether-like behavior, when it is most definitely not (for confusing reasons...).
If you aren't at least a little confused, it probably isn't relativity! LOL!

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