Freya Blekman Profile picture
Particle physicist - Physicist at @CMSExperiment @CERN - Lead Scientist @DESYnews & Helmholtz Distinguished Professor @UniHH - Also:Future colliders! - She/her

Apr 7, 2022, 18 tweets

Very excited about @Fermilab seminar tomorrow!

It will present a new measurement of the W boson mass to be published soon, no #openscience article yet.

There are already articles appearing, but in this thread, I try to explain why this is important with one (famous) plot

Why? Because the W boson is really important for the standard model, particularly for checking its consistency. I'm really excited!

The standard model, the physics theory that particle physics use is great at predicting things. This plot checks its internal consistency by comparing different ways to determine the mass of two particles: the W boson (connected to the weak interaction) and the top quark

The standard model is great at predicting connections between particles, this plot was made by a theory collaboration called #GFitter, which includes some @desynews colleagues. This plot has two green bands, these are the measured values of the top quark and the W boson

There is a lot more in this plot: the possible values that the standard model predicts/calculates for the W boson and top quark if everything else is perfect. This depends on the value of the mass of the Higgs boson and is represented by the diagonal lines

There also is the blue blob. This are the values that the standard model predicts if all other information in the formula is measured and filled in. The blue blob is following the known value of the Higgs boson mass at 125 GeV, but is wider as there are measurement uncertainties

And finally, the green ellipse. Which is where the green lines intersect.

I'm sure you noticed the blue and green ellipses don't perfectly overlap, and this is what this consistency check is actually looking at: two ways to measure the same thing, and they should be the same!

Measuring the W boson mass or top quark mass more accurately will affect the green ellipse... and can point to inconsistencies with the prediction. Here are some crude scenarios of what could happen (yes I'm totally into low-fi graphics ☺️😇🤓)

So it turns out that the new measurement of the W boson claims that the green ellipse should move up quite a lot. A LOT! so much that the two ellipses would definitely not be consistent, meaning that the standard model prediction is not consistent with the measurement. Exciting!

This is particularly exciting for particle physicists because now we can all do some sciencing and try to figure out if the apparent agreement can be explained by some missing measurement mistake, a miscalculation of one of the two numbers, or truly something new!

Here are some links to articles that cover this result, of various levels of detail:

Did Fermilab's new result blow a hole in the Standard Model? bigthink.com/starts-with-a-…

BBC in good british tradition goes with the drama. Happy the word boffin wasn't used.

Shock result in particle experiment could spark physics revolution

bbc.com/news/science-e…

@Fermilab The #Science paper is here:

High-precision measurement of the W boson mass with the CDF II detector science.org/doi/10.1126/sc…

Loving the commitment to #openscience !

When particle physicists publish in paywall journals we remember YOU already paid for this result (thanks!)

An article by @brunchik in Dutch broadsheet @nrc (where I have an opinion):

@brunchik @nrc And some more dutch language articles here: Natuurkundigen plaatsen potentiële bom onder ons begrip van de werkelijkheid volkskrant.nl/ts-bd5f8648 via @volkskrant

The particle physics magazine for the general public @symmetrymag (with news from all the labs in the particle physics discipline) has a nice writeup too!

If you want to read the paper: it's of course publicly available #openscience so here: inspirehep.net/literature/206… on the main particle physics find-out-everything database @inspirehep

And I am assuming by tomorrow also on more general preprint site @arxiv

If you paid attention (of course you did!) the first figure of this paper should be really really easy to understand (it's the same figure, just with some other things on there, specifically which W boson/top quark combos are consistent with SUSY (green) science.org/doi/10.1126/sc…

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