The Standard Model of Particle Physics

an explainer video by David Tong, Cambridge UK

Study matter and its motion through spacetime...

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Re: The Standard Model of Particle Physics

#21  Postby newolder » Mar 07, 2022 4:20 pm

^ I'll include both in future, felltoearth, but it'll mean more white space for some and double copies for others. Hey ho.
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Re: The Standard Model of Particle Physics

#22  Postby felltoearth » Mar 07, 2022 7:24 pm

No problem!


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Re: The Standard Model of Particle Physics

#23  Postby newolder » Apr 07, 2022 6:34 pm

New results posted today from the Collider Detector at Fermilab (CDF) show the mass of the W boson is heavier, by about 0.1%, than Standard Model calculations yield. The result: Wmass = 80,433 million electron volts (MeV), ± 9 MeV. This is 76 MeV heavier than the Standard Model predicts or, a 7-sigma discrepancy. Sheesh!

Of course, this result will have to be confirmed at the LHC and they'll get on the job soonest, no doubt.

4 write-ups:
Science by Adrian Cho
Research Article at Science by CDF COLLABORATION T. AALTONENS. AMERIOD. AMIDEIA. ANASTASSOVA. ANNOVIJ. ANTOSG. APOLLINARIJ. A. APPEL[...]S. ZUCCHELLI +389 authors
Quanta magazine by Charlie Wood
Big Think by Ethan Siegel

ETA reference and a plot of results of the W mass in MeV/c2 from various experiments with todays measurement CDF II at the Bottom. SM is the Standard Model estimate.

Image

Announcement of Fermilab seminar tomorrow but with no details, yet. Will I get to sleep tonight? :scratch:

Tweet from @Fermilab: "We don't joke about W boson mass."
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Re: The Standard Model of Particle Physics

#24  Postby Spearthrower » Apr 08, 2022 2:31 am

What's funny is that, despite there being 2 (or more) independent measurements that measure the mass in a way consistent with the standard model, physicists are almost certainly performing their little physicist prayers and beseeching the spirit of Sagan for this new measurement to be right, for the standard model to be shown wrong, and a space opened for new physics to populate.

I always love how science gets most excited when believing it can show itself wrong.
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Re: The Standard Model of Particle Physics

#25  Postby newolder » Apr 08, 2022 7:06 am

Having slept like a proverbial Hogg's Bison (i.e. very well) I woke to read a reply tweet from @Fermilab:
The seminar is at 4pm CDT tomorrow, April 8:
https://theory.fnal.gov/events/event/cdf-w-mass-2022/

That's 9pm 10PM BST for us Brits, 10pm for CET dwellers & ... so, a working day's wait reading speculations galore. :party:

The "things" about this measurement include: the CDF Collaboration is very good/top notch; the work is a decade's worth; there was as much "blindness" in the work as possible and the error bar is tiny (±9MeV, or about 0.01% FFS!) in comparison with previous studies.

I haven't tracked down the referenced SM theory calculation, yet, but I speculate that someone has a sign or a term wrong somewhere in there but it would be just great if that was not the case either.

From the Science Research Article above:
Its (the W boson) mass, one of the most important parameters in particle physics, is presently constrained by SM global fits to a relative precision of 0.01%, providing a strong motivation to test the SM by measuring the W boson mass to the same level of precision.

Later, the calculation reference is given as: Particle Data Group, Review of Particle Physics, Prog. Theor. Exp. Phys. 2020, 083C01
With another long author list and returns this from google scholar:
The Review summarizes much of particle physics and cosmology. Using data from previous
editions, plus 3,324 new measurements from 878 papers, we list, evaluate, and average
measured properties of gauge bosons and the recently discovered Higgs boson, leptons,
quarks, mesons, and baryons. We summarize searches for hypothetical particles such as
supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and
search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and …


... and a link to this pdf which is a long url & pdf - in which I do nor find a W boson mass. Grrr! Wrong link!

The Review paper - at this link - links to summaries of details of the World Average of the W boson mass from other experiments at this link: World Average W mass of 80,379 ± 12 MeV - top page 1015 - (is from experiment) and corresponds with they grey SM bar on the posted figure.

Hmmm... My spider senses are tingling now that I didn't immediately get to a theoretical calculation group or program... :coffee:




Such fun!

Edit for correction to seminar time - it starts about 1 hour from this edit time...
Last edited by newolder on Apr 08, 2022 7:57 pm, edited 1 time in total.
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Re: The Standard Model of Particle Physics

#26  Postby newolder » Apr 08, 2022 9:39 am

There's going to be much written about this so we should have the thoughts of those who know of what they speak ...

Here's a blog post from Prof. Dr. Matthias Schott wherein...
...

I started to work on the W boson mass in 2012 and it took us more than five years to publish a first measurement based on data of the ATLAS Experiment [2]. When I applied for funding for this project, one of the referees wrote that "this measurement is too complicated to be done in time and hence (s)he would not recommend funding". Luckily for me the other referees disagreed and I guess I have to thank the DFG and the Volkswagen foundation at this point that they were willing to take the risk. I have another anecdote on the W boson mass measurement, which illustrates its difficulty: We observed for quite some time some features in the our data, which we could not explain. Once one of my PhD students came into my office and told that he finally figured out this feature: the protons in the ATLAS detector do not collide heads-on but under a very small angle, allowing the not interacting protons to continue their travel through the LHC on the other side of the experiment. Indeed he was right - we have not been considering this effect in our simulations, however - after some calculations and speaking to the machine experts - it turned out that this effect induces a feature in our data, which is opposite in sign that we observe; so we have been left with an effect that was twice as large and unexplained. In the end it turned out to be caused by the deformation of the ATLAS detector by its own weight of more than 7000 tons over time. Enough of my memories - I just want to say with this that the W boson mass measurement is a difficult business.

So let's start to look at the new CDF measurement.

...continues


... and the morning-after thought of a post doc in the field... @irrediated
Sure am learning a lot today about the global electroweak fit - what gets called "the SM" on plots - from talking with my local muon g-2 lattice pals about the W boson result.

tl;dr this SM is not pure-theory, it also contains a lot of experimental results, with their own quirks
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Re: The Standard Model of Particle Physics

#27  Postby aufbahrung » Apr 08, 2022 11:10 am

It's a hard nut to crack but the standard model being basically astrology was bound to break at some point. I'm not surprised it has, only that it took so long. Then much is empty space at the subatomic level...as far as I know.
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Re: The Standard Model of Particle Physics

#28  Postby The_Piper » Apr 08, 2022 12:18 pm

Well I haven't heard of any experiments by neutral parties showing astrology to be correct. The standard model has experimental veracity to it.
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Re: The Standard Model of Particle Physics

#29  Postby aufbahrung » Apr 08, 2022 1:02 pm

The_Piper wrote:Well I haven't heard of any experiments by neutral parties showing astrology to be correct. The standard model has experimental veracity to it.


I'm sure a astrological chart can be used to prove pi via some experiment. Still a astrological chart with no reason to exist outside of itself.
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Re: The Standard Model of Particle Physics

#30  Postby The_Piper » Apr 08, 2022 1:10 pm

:lol: :lol:
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Re: The Standard Model of Particle Physics

#31  Postby Spearthrower » Apr 08, 2022 1:27 pm

aufbahrung wrote:It's a hard nut to crack but the standard model being basically astrology was bound to break at some point.


More LARPing.
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Re: The Standard Model of Particle Physics

#32  Postby Spearthrower » Apr 08, 2022 1:28 pm

aufbahrung wrote:
The_Piper wrote:Well I haven't heard of any experiments by neutral parties showing astrology to be correct. The standard model has experimental veracity to it.


I'm sure a astrological chart can be used to prove pi via some experiment. Still a astrological chart with no reason to exist outside of itself.



It's strangely satisfying to know that your understanding of astrology is equivalent to your comprehension of physics.
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Re: The Standard Model of Particle Physics

#33  Postby newolder » Apr 08, 2022 1:38 pm

Can a mod move this astrology discussion to its own pseudoscientific topic, please?
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Re: The Standard Model of Particle Physics

#34  Postby newolder » Apr 13, 2022 2:48 pm

Interesting arXiv post on "Oblique Lessons from the W Mass Measurement at CDF II" and the "swino" object where the "oblique" (higher dimensional) parameters S, T & U are investigated as explanatory for the reported largesse of the W-boson mass...

The CDF collaboration recently reported a new precise measurement of the W boson mass MW with a central value significantly larger than the SM prediction. We explore the effects of including this new measurement on a fit of the Standard Model (SM) to electroweak precision data. We characterize the tension of this new measurement with the SM and explore potential beyond the SM phenomena within the electroweak sector in terms of the oblique parameters S, T and U. We show that the large MW value can be accommodated in the fit by a large, nonzero value of U, which is difficult to construct in explicit models. Assuming U=0, the electroweak fit strongly prefers large, positive values of T. Finally, we study how the preferred values of the oblique parameters may be generated in the context of models affecting the electroweak sector at tree- and loop-level. In particular, we demonstrate that the preferred values of T and S can be generated with a real SU(2)L triplet scalar, the humble "swino," which can be heavy enough to evade current collider constraints, or by (multiple) species of a singlet-doublet fermion pair. We highlight challenges in constructing other simple models, such as a dark photon, for explaining a large MW value, and several directions for further study.

arXiv abstract link

Of relevance if the reported result stands further tests, of course.
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Re: The Standard Model of Particle Physics

#35  Postby newolder » May 26, 2022 10:11 pm

The CMS experiment at CERN's LHC provides a "refreshable" live event display to show collisions but no analysis. Just a bit of fun...
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