Standard model; 3 neutrinos, could there be four? (Introduction)

by David Turell @, Sunday, January 13, 2019, 05:26 (7 days ago) @ David Turell

Fast moving, very fast through everything. tiny mass and always associated to other particles:

"Every single second of every single day, you are being bombarded by trillions upon trillions of subatomic particles, showering down from the depths of space. They blow through you with the strength of a cosmic hurricane, blasting in at nearly the speed of light. They're coming from all over the sky, at all times of the day and night. They penetrate the Earth's magnetic field and our protective atmosphere like so much butter.


"These tiny little bullets are called neutrinos, a term coined in 1934 by the brilliant physicist Enrico Fermi. The word is vaguely Italian for "little neutral one," and their existence was hypothesized to explain a very curious nuclear reaction.


"Physicists noticed that decay reactions that suggested the existence of the neutrino always had an electron pop out, and never a muon. In other reactions, muons would pop out, and not electrons. To explain these findings, they reasoned that neutrinos always matched up with electrons in these decay reactions (and not any other kind of neutrino), while electron, the muon must pair with an as-yet undiscovered type of neutrino.. After all, the electron-friendly neutrino wouldn't be able to explain the observations from the muon events.

"And so the hunt went on. And on. And on. It wasn't until 1962 that physicists finally got a lock on the second kind of neutrino. It was originally dubbed the "neutretto," but more rational heads prevailed with the scheme of calling it the muon-neutrino, since it always paired itself in reactions with the muon.

"Okay, so two confirmed neutrinos. Did nature have more in store for us? In 1975, researchers at the Stanford Linear Accelerator Center bravely sifted through mountains of monotonous data to reveal the existence of an even heavier sibling to the nimble electron and hefty muon: the hulking tau, clocking in at a whopping 3,500 times the mass of the electron. That's a big particle!

"So immediately the question became: If there's a family of three particles, the electron, the muon and the tau … could there be a third neutrino, to pair with this newfound creature?
Maybe, maybe not. Maybe there are just the two neutrinos. Maybe there are four. Maybe 17. Nature hasn't exactly met our expectations before, so no reason to start now.

"Skipping over a lot of gruesome details, over the decades, physicists convinced themselves using a variety of experiments and observations that a third neutrino ought to exist. But it wasn't until the edge of the millennium, in 2000, that a specifically designed experiment at Fermilab (called humorously the DONUT experiment, for Direct Observation of the NU Tau, and no, I'm not making that up) finally got enough confirmed sightings to rightly claim a detection.


"The reason is that neutrinos continue to live outside our expectations. For a long time, we weren't even sure they existed. For a long time, we were convinced they were completely massless, until experiments annoyingly discovered that they must have mass. Exactly "how much" remains a modern problem. And neutrinos have this annoying habit of changing character as they travel. That's right, as a neutrino travels in flight, it can switch masks among the three flavors.

"There might even still be an additional neutrino out there that doesn't partake in any usual interactions — something known as the sterile neutrino, that physicists are hungrily hunting for."

Comment: particle physics finds these weird things, identifies them, but there is no theory to explain why they are what they are. No more explanation as in quantum theory which no one can explain why it is the way it is. So we describe but don't understand the underlying plan or reason. God may not be revealed, but His plan isn't either.

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