Wikipedia:Reference desk/Archives/Science/2021 April 28

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April 28

Does Cryoprecipitate have platelets?

Does cryoprecipitate contain platelets? --ThePupil (talk) 16:55, 28 April 2021 (UTC)

The article links to Blood plasma, which you may find helpful. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:19, 28 April 2021 (UTC)

The article Blood plasma makes clear that blood plasma does not contain blood cells, but is not explicit about the plasma not containing platelets – which are not regular cells, as they have no nucleus. The point is that plasma is pure liquid (or almost pure – there is no such thing as 100% pure plasma). It is mostly water; any other substances (such as salts and proteins) are dissolved in the water. Platelets do not dissolve in water; they are separated from the plasma in the preparation process.  --Lambiam 09:32, 29 April 2021 (UTC)

The lack of a nucleus doesn't not make something a cell. In most mammals, red blood cells lack a nucleus. Platelets also lack many of the other structures and functions of cells as well, being basically cell fragments. However, the line is rather arbitrary, as their other name (thrombocytes) literally means "clotting cell". Langauge and categorization are not always logical or consistent. <shrug>. --Jayron32 01:47, 30 April 2021 (UTC)

What part of Muon G2 results are not explained by current theories ?

Physicists discover Muon G2 results are not explained by current theories. source. So what part of Muon G2 results are not explained by current theories ? Rizosome (talk) 17:42, 28 April 2021 (UTC)

This video explains it better than I could. In a nutshell, the experiment measures how much the muon is disturbed by other particles. Each other particle a muon interacts with will alter its behavior by a measurable amount; once you account for every known particle in the standard model, there's a tiny little bit of motion that is unaccounted for. That little tiny bit of leftover disturbance can't be explained by any known part of physics, so if it is correct, then it means there is some part of physics that the Standard Model doesn't contain. You really should watch that video if you want more details, though. --Jayron32 17:47, 28 April 2021 (UTC)

The "g-2" in the name of the Muon g-2 experiment is read as "gee minus 2", where the "g-factor" is the magnetic dipole moment of the muon. In quantum field theory you treat this as a kind of series expansion (where subsequent terms contain coupling constants raised to higher and higher exponents). The first term is exactly 2. If you subtract this out, you get the anomalous magnetic dipole moment g-2. The question is whether the measured value of g-2 matches the sum of the higher terms in the series expansion given the fields and coupling constants in the standard model. Unfortunately, the standard model includes QCD, so the series expansion includes hadronic terms that can't be calculated in perturbation theory. Getting values for those terms requires a very difficult mix of theory and empirical measurement from other experiments. About 20 years ago when the Brookhaven muon g-2 experiment had a similar result, it turned out that there had been an error in these hadronic terms on the "theory" side (the same sign flip error made independently by two groups of theorists). If the new experimental results are correct, it could be that there are new terms in the series expansion (new particles and fields), or that there are corrections to be made in how the standard model terms are calculated. --Amble (talk) 20:39, 28 April 2021 (UTC)

@Amble: Our article Muon g−2 makes no mention of inadvertently flipped signs. It seems (to me) interesting enough to mention this. Do you have sources? (There is a mention of physicists at CERN having to recalculate their theoretical model because of a discrepancy, which is not unambiguously clear about the cause of the discrepancy – theoretical error, or calculation with insufficient precision.)  --Lambiam 09:09, 29 April 2021 (UTC)

@Lambiam: There’s a good writeup from 2004 by one of the g-2 collaborators here: [1]. The part of the story I was talking about starts at the end of p. 32 and continues at the top of p. 33. A similar saga played out several times where the g-2 experimenters would publish a tighter measurement about 3 sigma from the SM prediction, and each time the best SM prediction would hop to 1-2 sigma from the experimental result. It would be great to add some of this to our articles. —-Amble (talk) 11:46, 29 April 2021 (UTC)

Thanks, maybe later; this requires careful reading, and I'm facing an imminent deadline absorbing my attention.  --Lambiam 13:46, 29 April 2021 (UTC)

See also Sec. 4.2.4 in the very recent, very comprehensive, very long review paper here: [2] --Amble (talk) 16:53, 29 April 2021 (UTC)

True to form, the snippet you mentioned about recalculating the theory during the CERN days isn't either of the Brookhaven-era (early 2000's) cases I had in mind, but yet another time that the same basic story played out. This one was back in the 1960's or 1970's. --Amble (talk) 17:28, 29 April 2021 (UTC)

It's shocking that we don't have anything at all on the infamous 17-keV neutrino [3]. Anybody who's looking for a new topic that needs an article could write a great one about that saga. --Amble (talk) 17:53, 29 April 2021 (UTC)

@Amble: It's looks like everybody posting their edits in too technical manner. I want simple English edits. Rizosome (talk) 17:12, 30 April 2021 (UTC)

There is a kind of particle called a muon. We make lots of muons. We put the muons close to a big magnet. The magnet makes the muons turn. Every kind of particle helps the magnet turn the muons. Photons help the magnet turn the muons. Electrons help the magnet turn the muons. Protons and neutrons help the magnet turn the muons. Maybe there are other kinds of particles that we don't know about. The new particles might help the magnet turn the muons. We watch the muons turn because we want to find out about new particles. A lot of muons went by the magnet. We measured how much the muons turned. They turned a little more than we expected. Maybe there is a new particle! --Amble (talk) 18:12, 30 April 2021 (UTC)

Didn't I say basically exactly that, in that level of English, in the first answer? --Jayron32 18:44, 30 April 2021 (UTC)

Your answer seems clear (and entirely correct) to me! I'm not really sure what OP is looking for, so I can only say what I was aiming to add. My first answer was mainly to explain why the theory value has been a moving target. After the subsequent request for simple English, I wanted to convey what physical quantity is measured, without using words like theory, standard model, interact, disturb, and field. --Amble (talk) 19:03, 30 April 2021 (UTC)