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from the extraordinary-claims-require-extraordinary-evidence dept.
Shock result in particle experiment could spark physics revolution
Scientists just outside Chicago have found that the mass of a sub-atomic particle is not what it should be.
The measurement is the first conclusive experimental result that is at odds with one of the most important and successful theories of modern physics.
The team has found that the particle, known as a W boson, is more massive than the theories predicted.
[...] The scientists at the Fermilab Collider Detector (CDF) in Illinois have found only a tiny difference in the mass of the W Boson compared with what the theory says it should be - just 0.1%. But if confirmed by other experiments, the implications are enormous. The so-called Standard Model of particle physics has predicted the behaviour and properties of sub-atomic particles with no discrepancies whatsoever for fifty years. Until now.
CDF's other co-spokesperson, Prof Georgio Chiarelli, from INFN Sezione di Pisa, told BBC News that the research team could scarcely believe their eyes when they saw the results.
"No-one was expecting this. We thought maybe we got something wrong." But the researchers have painstakingly gone through their results and tried to look for errors. They found none.
The result, published in the journal Science, could be related to hints from other experiments at Fermilab and the Large Hadron Collider at the Swiss-French border. These, as yet unconfirmed results, also suggest deviations from the Standard Model, possibly as a result of an as yet undiscovered fifth force of nature at play.
Also at Nature and Ars Technica.
Journal Reference:
T. Aaltonen. S. Amerio. D. Amedei, et. al.,High-precision measurement of the W boson mass with the CDF II detector, Science, (DOI: https://www.science.org/doi/10.1126/science.abk1781)
(Score: 4, Insightful) by PiMuNu on Sunday April 10 2022, @04:13PM
Just to be clear, the paper is very well thought through as one might expect. The team present 6 different measurements for the W boson mass, each of which is consistent with the others. The team is using a very mature analysis toolset, which has been used in countless other papers for similar analyses and not shown any problems. It is in tension with the standard model at ~ 7 sigma and in tension with the other experiments at about 3 sigma.
The analysis studies the mass of a W boson, a particle which decays radioactively after a vanishingly short lifetime. The experiment studies the kinematics of the decay products (momentum, energy) and uses this to infer the mass of the decaying primary particle.
One might question whether there are any systematic errors that may systematically effect all of the separate analyses. For example, such an analysis may be systematically biased by decays of particles that are not W bosons but do look like W bosons. The experiment studies two different decay modes, W -> electron + neutrino and W -> muon + neutrino. It would be surprising if there was an impurity that effected both decays in the same way, and of course the paper authors have thought of this and checked. The experiment uses the kinematic properties of the decay products. Electrons and muons behave differently and it would be surprising if both were biased in the same way. The paper authors checked by calibrating their instrumentation against a known decay having a known mass (J/psi).
Of course, mistakes do occur, and we will see what the experts say. But it is beyond "guy on the internet" level dismissals. It really needs a cross check from the other experiments.