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Hints Of New Physics At The Lhc?

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jim360 | 22:12 Tue 23rd Mar 2021 | News
29 Answers
I'm posting this in news for two reasons:

1. Maximum attention to one of the day's more interesting stories.

2. Just because it has a science bent doesn't mean it didn't pick up interest from multiple sources. Mentioned on Today on Radio 4, for example, as well as articles in the Guardian, Express, Telegraph etc.

I suppose a third reason is that this is more or less exactly related to the areas of physics I specialise in. (Proof: four of the papers cited in this piece of research were co-written by my PhD supervisor.) For those who are interested, I'm offering this as an opportunity to ask a specialist questions about niche physics.

(The Telegraph's headline is overselling things rather, in my opinion, but there we are)

Original paper pre-print, awaiting peer review:


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Thanks! Very disappointed that this won't allow the Vulcans to make first contact ...
23:27 Tue 23rd Mar 2021
Jim, have you finished your PhD? If so are you doing work connected to your studies? You were in Scotland?
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I finished my PhD in 2018. As to what I'm doing next, I'll leave that for a separate thread in due course. For now I wanted to focus on this specific news item, no problem with your asking though!
That was the phrase I was looking for. I read the reports on a couple of sites and it made me think ... wow. The phrase was "Beauty Quark".
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Who ever claimed there was? :P

It is quite fascinating, for sure, although as most of the news reports are obliged to type, this is not an announcement of a new discovery: merely a hint. What I suspect has got scientists excited is that it isn't the only such hint in this sector of particle physics. Earlier results from 2013-2016 found similar hints in related decays. Depending on whom you ask, this is either a sign of new physics, or a sign that we haven't understood the current picture well enough, or a sign that there's something weird going on with the LHCb experiment itself.
I love the way scientists love to find something unexpected which throws their previous ideas into doubt and opens up new and exciting future developments. Not the same as religious people, who seem to dislike and dismiss any new ideas. Hopefully, they won't be attracted to this thread. Jim; I haven't had time to study the links - is there a very succinct summary you could provide?
OK here goes, Jim. If this area of physics is wrong, is there any chance we'll discover time travel and/or the ability to travel vast distances across the universe to meet alien species? Or vice versa.
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I'll do my best!

Just to set the scene briefly: all known material stuff in the Universe is made of chemical elements, all elements are made of atoms, all atoms are made of protons, neutrons and electrons, and all protons and neutrons are made of quarks (specifically, one proton = two up quarks plus one down, and one neutron = one up plus two down). Particle Physics tries to explain how quarks and leptons behave and interact with each other.

For the purposes of understanding this result, there are six particles we need to know about:

1. The electron, easily the most familiar to most people, as this is what carries electric current.

2. The muon: possibly the first truly weird particle to be discovered. It's essentially just an electron but about 200 times heavier.

3. The strange quark: another weirdo, first seen in so-called "strange" particles, because at the time scientists didn't understand their behaviour.

4. The bottom or "beauty" quark, which is again effectively just a heavier version of the strange quark.

5. The K meson, which contains exactly one strange quark.

6. The B meson, which contains exactly one bottom quark.

That's a lot of scene-setting, but hopefully it all makes sense.

* * * * *

Next, there's a basic rule in particle physics that heavy stuff decays into lighter stuff. In particular, the B meson is the heaviest thing I have mentioned so far, and it's allowed to decay, among other things, into:

1. a K meson plus two electrons, or
2. a K meson plus two muons

These decays don't happen that often, because they involve a bottom quark turning into a strange quark, a process that the Standard Model says can't happen easily. On the other hand, processes that are expected to not happen very often are the most interesting, because if anything new happens it is likely to make the decay more common! That's why physicists have been looking at this process in particular, it's been on the radar for some time.

* * * * *

The final thing to know is that, other than the muon being 200 times heavier than an electron, there is supposed to be no difference between an electron and muon: the Standard Model treats them as the same thing in all other respects. Therefore, the two decays above *should* behave in more or less the same way, and in particular there should be the same number of each. To make things easier, physicists therefore defined the ratio:

R_K = (number of times B decays to K plus two muons) divided by (number of times B decays to K plus two electrons).

The prediction is that R_K = 1. This experiment has shown that R_K = 0.85, which is (a) not 1, and (b) far enough away that it seems to be a genuine result, rather than just experimental error.

I haven't proofread this, but I hope it's clear and that it helps. If it isn't clear, hopefully it is at least enough to guide further questions.
You gave the quarks a bit of an intro, but just threw the leptons into the middle of the party.
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// OK here goes, Jim. If this area of physics is wrong, is there any chance we'll discover time travel and/or the ability to travel vast distances across the universe to meet alien species? Or vice versa. //

Based on this? Probably not. Time travel and interstellar travel feel to me too related to General Relativity, as opposed to particle physics, where the usual assumption is that Gravity can be safely ignored. I wouldn't want to rule it out entirely, but it just feels that the fix here won't touch on anything so exotic. Still, anything that advances our understanding of how the Universe works is bound to have a payoff sooner or later.
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// You gave the quarks a bit of an intro, but just threw the leptons into the middle of the party. //

Whoops! Leptons = electrons, muons, and neutrinos.

Very disappointed that this won't allow the Vulcans to make first contact ...
I can understand how heartening it must be when your specialism is featured in the mainstream news. It was on the main BBC news today, and there's a good explanation for the layman of what it's about on their website:

For some reason, as soon as I hear 'beauty quark' I immediately think University Challenge, as questions around the subject seem to have become very popular recently. Some very arcane science stuff last night, and well done Warwick for beating the science specialists Imperial - not once, but twice!
Thanks for the thread Jim :-) Absolutely fascinating, though way over my head once the maths shows up.

Nice mundane, non-niche Q's for you - have you been to the LHC? If not, do you want to go & when do you think you might get there (pandemic allowing...)?
Little graphic that groups the different particles.
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LIK: I was lucky enough to visit in 2017, a friend took me on a behind-the-scenes tour, although at the time the main facility was closed for I think some tech upgrades, so I didn't get to see the detectors themselves.
Ta Jim, I just wondered :-)
manyt hanks Jim
I er 'read' and reached eek at around p 6

astounded that the journos understand particle physics better than virology ( = nil really)
Well there’s a surprise! Who’d a thunk? ...
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Oh, do go on... what's a surprise?

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