Precision measurement of W boson mass portends stricter limits for Higgs particle
March 11, 2009
The Standard Model describes the interactions of the fundamental particle of the world around us. Experimental observations agree with the predictions of the Standard Model with high precision. The W boson, the carrier of the electroweak force, is a key element in these predictions. Its mass is a fundamental parameter relevant for many predictions, including the energy emitted by our sun to the mass of the elusive Standard Model Higgs boson, which provides elementary particles with mass. Credit: Fermilab
(PhysOrg.com) -- Scientists of the DZero collaboration at the Department of Energy's Fermi National Accelerator Laboratory have achieved the world's most precise measurement of the mass of the W boson by a single experiment. Combined with other measurements, the reduced uncertainty of the W boson mass will lead to stricter bounds on the mass of the elusive Higgs boson.
The W boson is a carrier of the weak nuclear force and a key element of the Standard Model of elementary particles and forces. The particle, which is about 85 times heavier than a proton, enables radioactive beta decay and makes the sun shine. The Standard Model also predicts the existence of the Higgs boson, the origin of mass for all elementary particles.
Precision measurements of the W mass provide a window on the Higgs boson and perhaps other not-yet-observed particles. The exact value of the W mass is crucial for calculations that allow scientists to estimate the likely mass of the Higgs boson by studying its subtle quantum effects on the W boson and the top quark, an elementary particle that was discovered at Fermilab in 1995.
Scientists working on the DZero experiment now have measured the mass of the W boson with a precision of 0.05 percent. The exact mass of the particle measured by DZero is 80.401 ± 0.044 GeV/c2. The collaboration presented its result at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond last Sunday.
"This beautiful measurement illustrates the power of the Tevatron as a precision instrument and means that the stress test we have ordered for the Standard Model becomes more stressful and more revealing," said Fermilab theorist Chris Quigg.
The DZero team determined the W mass by measuring the decay of W bosons to electrons and electron neutrinos.
Performing the measurement required calibrating the DZero particle detector with an accuracy around three hundredths of one percent, an arduous task that required several years of effort from a team of scientists including students.
Since its discovery at the European laboratory CERN in 1983, many experiments at Fermilab and CERN have measured the mass of the W boson with steadily increasing precision. Now DZero achieved the best precision by the painstaking analysis of a large data sample delivered by the Tevatron particle collider at Fermilab. The consistency of the DZero result with previous results speaks to the validity of the different calibration and analysis techniques used.
"This is one of the most challenging precision measurements at the Tevatron," said DZero co-spokesperson Dmitri Denisov, Fermilab "It took many years of efforts from our collaboration to build the 5,500-ton detector, collect and reconstruct the data and then perform the complex analysis to improve our knowledge of this fundamental parameter of the Standard Model."
The W mass measurement is another major result obtained by the DZero experiment this month. Less than a week ago, the DZero collaboration submitted a paper on the discovery of single top quark production at the Tevatron collider. In the last year, the collaboration has published 46 scientific papers based on measurements made with the DZero particle detector.
Provided by Fermilab
Jan 08, 2007 |
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KEEP TEVATRON ALIVE!
I can't wait for that LHC restart!
I wish they had mentioned the previous best estimate s we could see how much improvement there was.
http://www.allame...de/17469
It's a small improvement in uncertainty.
The true ingenious model is Heim's theory, which can handle these predictions in many orders of precision with using of only five constants and without using of ad hoced particles, like Higgs boson. No results from LHC could improve these calculations or to decrease the number of constants needed, the discovery of Higgs boson the less - they can just a bring a huge explosion, which can destroy our civilization - that's all.
Adding of new constants into regression can never replace the clever ab initio model - it just can prolong safe life of some scientists and companies from our taxes.
Ethelred
Not saying, the product of cosmic ray collisions always have a large speed toward Earth, while product of collider collisions can have a zero momentum toward Earth - so they have a lotta time to interact with it.
These connections are so obvious, that the every notion of cosmic rays in connection of LHC risk should be considered a naive propaganda, supposed to fool the rest of layman society. Those who spreading such "objections" are simply liars.
If our society isn't sufficiently rich to do such experiments, it simply means, it has a different priorities by now and it should invest for example into research of could fusion. Why the hell latest Arata tabletop experiments weren't replicated even after one year? The cost and practical significance of such experiments are incomparable to LHC experiments. Every year we are depleting the nonrecoverable supplies of fossil fuels, destroying life environment and risking global wars - just because we aren't able to concentrate our research to fundamental problems. The main purpose of Higgs boson research is to mask intellectual crisis of contemporary physics.
http://nextbigfut...eat.html
It's apparent, high energy physicists transformed into alchemists, looking for Philosopher's stone instead of solving practical problems - thus being separated from the rest of society. They ignoring fundamental finding, just because they don't play well with their silly theories, full of ad-hoced constants.
http://arxivblog.com/?p=664
Sheesh, you are the naive one. There is no Heim's "theory" just some pseudoscience that does not even predict the mass of the particle discussed here, the W boson. The Standard Model has very good predictions of the Higgs mass, and the improved W and top masses narrow the range of allowed masses significantly. You know nothing about high energy physics, go back to talking to your cats and making tinfoil hats.
http://en.wikiped...isbelief
At second, 8-dimensional extension of Heim theory made by Dröscher supports quarks and vector bosons and even provides some estimation of rest mass.
At third, W boson was never observed directly and while basic Heim theory predicts mass / lifetime of real, existing particles only, it doesn't need to consider ad-hoced artifacts in doing it with extremely high precision.
http://superstrun...heim.gif
Science should always follow an Occam's razor principle - and if some theory doesn't require ad-hoced artifacts for explanation of observation, it should be considered first.
Or science becomes a God based religion.
http://www.newsci...ght.html
Um, aren't stranglets a postulation of the STANDARD MODEL you reject?
Have your cake, eat it, or kindly shut the hell up...one of the three....
I've pointed out to you (or "you both"), on several occasions how by simple probability over the course of the planet's lifetime that if stranglette creation and subsequent interaction was possible through the sort of collisions taking place in the LHC and Tevatron that it would have already happened.
The comment that completely blows my mind is this:
What part of the preceding statement makes any sense?
If the US Government was aware of the risk of stranglette creation we would not have been involved in the construction of the LHC, nor would we have funded it or sat idlly by while it was built.
Also, how exactly would it be a strategic decision? By the mathematics, if a stable stranglette was created and interacted with our resident matter it would take mere minutes to completely "strange goo" the planet, I don't know what other crazy conspiracies you think the government is up to but unless they have a way to leave Earth without leaving behind so much as an atom thick trail of exhaust within seconds there is no "strategy" to be seen.
There's a few points that the Aether theorists completely discount, and this is because of the ignorance inherent in the framework on which it's based.
Atoms are not dense. Realistically you could be bombarded by strangelettes for a millenia without actually encountering or interacting with one.
Stable Strangelettes are virtually impossible within AWT due to reflexive surface tension aspect of the theory.
Stranglettes are theorized by application of the standard model, which we know to be wrong in some way, shape, or form. Any physicist will tell you it's a "sick" theory. There are too many pieces that are either missing or unaccounted for, and it's ridiculously un-elegant in application as it discounts many necessary aspects of observed physics, for example, Mass, or particle-field mass interaction.