World's best measurement of W boson mass tests Standard Model, Higgs boson limits

Feb 23, 2012 by Tona Kunz
The new CDF result for the W boson mass, combined with the world's best value for the top quark mass, restricts the Higgs mass to the green area, requiring it to be less than 145 GeV/c2. Direct searches have narrowed the allowed Higgs mass range to 115-127 GeV/c2.

(PhysOrg.com) -- Just as firemen use different methods to narrow the location of a person trapped in a building, scientists employ two techniques to find the hiding place of the theorized Higgs particle: direct searches for Higgs interactions and precision measurements of other particles and forces.

Today, scientists from the CDF collaboration have unveiled the world's most precise measurement of the W boson , based on data gathered at the . The precision of this measurement surpasses all previous measurements combined and restricts the space in which the should reside according to the Standard Model, the theoretical framework that describes all known and forces.

The result comes at a pivotal time, just a couple of weeks before physicists from experiments at the Tevatron and the in CERN plan to present their latest direct-search results in the hunt for the Higgs at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond in Italy.

CDF collaborators have measured the mass of the W boson with a precision of 0.02 percent and found the particle's mass to be 80387 +/- 19 MeV/c2. They measured the particle's mass in six different ways, which all match and combine to produce the final result. CDF collaborator and Duke University Professor Ashutosh Kotwal will present the details of the measurement at a special seminar at Fermilab today, and additional information will be posted after the seminar on the CDF website.

Direct Higgs search limits established by the LEP experiments many years ago require the to be heavier than 114 GeV/c2. The new W mass measurement and the latest precision determination of the mass of the from Fermilab triangulate the location of the Higgs particle and restrict its mass to less than 145 GeV/c2. This is in excellent agreement with the latest direct searches at the LHC, which constrain the Higgs mass to less than 127 GeV/c2, and direct-search limits from the Tevatron, which point to a Higgs mass of less than 156 GeV/c2.

"The result couldn't align more with the direct Higgs search results than this," said CDF co-spokesman Rob Roser. "It indicates that if the Higgs boson exists, it should be right where we are looking."

The DZero collaboration at the Tevatron expects to release its updated W mass result in the next couple of weeks.

The Higgs boson is the last undiscovered component of the Standard Model and theorized to give fundamental particles mass. The upcoming results for the Higgs hunt combined with this new measurement of the W boson mass will provide the strongest test yet of the accuracy of the Standard Model.

If experimenters at the Tevatron and LHC didn't find the Higgs where the W boson mass implies it should be, it would suggest our understanding of nature as embodied in the Standard Model is wrong. It would imply the existence of other undiscovered particles or of undiscovered forces that govern how matter behaves.

"This is one of the most important of the Tevatron because it serves as a stress test for the - all sort of new physics models might in principle show up in the W mass measurement," said CDF co-spokesman Giovanni Punzi.

The CDF and DZero results for the W mass likely will be one of the long-lasting scientific legacies of the Tevatron.

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User comments : 8

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Deesky
3.9 / 5 (16) Feb 23, 2012
Things are heating up. Exciting times!
infiniteMadness
not rated yet Feb 24, 2012
I want time machines and teleportation devices :(
antialias_physorg
5 / 5 (7) Feb 24, 2012
I want time machines and teleportation devices

Go ahead: Invent/Build one.
Science is open for all. That's the beauty of it. All you need is a brain. The teaching materials are out there for free (and if you have a good idea and an exciting project you can always find a professor that will support you with equipment when you enter the experimental phase).
Things are heating up. Exciting times!

Yup. I realy don't know what would be more exciting, though: Finding the Higgs or NOT finding the Higgs. In the latter case we would see a flurry of new theories with possible radical new shifts in perspective upon the universe.
But I'm really looking forward to the Tevatron/CERN results.
Kinedryl
1 / 5 (7) Feb 24, 2012
In dense aether model the Higgs mechanism is scale invariant and it manifests at all scales like the weak attractive force, responsible for gluing of quarks (Yukawa force), nucleons (nuclear force) or even macroscopic particles (Casimir force). The upper limit of bosons mediating this force is given with upper mass particles involved, i.e. the mass of top quarks (which exhibit pairing too). The product of Yukawa coupling for the left- and right-handed top quarks have nearly the same rest mass (173.1±1.3 GeV/c2) like those Higgs boson.

In accordance with this insight, a top quark bound by to its anti-matter partner, the antitop, would act as a version of the elusive Higgs boson, conferring mass on other particles.

http://www.nature...436.html

BTW, the article mistakenly attributes the top quark condensation idea to Christopher Hill. The idea came from Nambu, Jona-Lasino 1961, Nambu 1988, Miransky et al 1989, Tanabashi and Yamawaki.
baudrunner
3 / 5 (1) Feb 25, 2012
Two unresolvable things I like to think about:

1. Why is the speed of light limited to 186,000 miles per second?
2. Why do physicists think that mass is something conferred on a particle by another particle? That's just weird.
CardacianNeverid
3.7 / 5 (6) Feb 25, 2012
1. Why is the speed of light limited to 186,000 miles per second? - baudrunner

It just is. No one knows.

2. Why do physicists think that mass is something conferred on a particle by another particle? - baudrunner

There is good theoretical reason behind it, is why. And it's more the Higgs field (a quantum field) which permeates all of spacetime rather than just a 'particle'. The Higgs boson is an excitation of the all pervasive Higgs field.
baudrunner
not rated yet Feb 26, 2012
I think that the Higgs field is bogus theory, CardacianNeverid.

I think that there does exist a photon background from which virtual particles are constantly popping in and out of existence in the only reality that can contain matter. Some get trapped and ultimately become real particles and real objects when they mutually attract one another. Electron-positron pairs are regularly seen to spontaneously create from this photon background in collider experiments.

Didn't Einstein teach us where mass comes from? Motion and velocity confer mass on particles, not some magic intermediary boson. The Higgs boson, when discovered, is just some other form of W type boson, with different specs, that's all.
CardacianNeverid
3.7 / 5 (6) Feb 27, 2012
Didn't Einstein teach us where mass comes from? -baudtripper

No. Perhaps you mean the the massenergy equivalence?

Motion and velocity confer mass on particles -baudtripper

No. There is a difference between relativistic mass and rest (invariant) mass. Since most particles have mass, your statement can be reframed as: Motion and velocity confer mass on mass - which means nothing.

...not some magic intermediary boson -baudtripper

Why is it 'magic'? It's a direct theoretical prediction based on solid physics.

The Higgs boson, when discovered, is just some other form of W type boson, with different specs, that's all. -baudtripper

Not in the least. You don't understand this stuff, but that can be cured.