[HN Gopher] Result from LHCb experiment challenges the Standard ...
___________________________________________________________________
Result from LHCb experiment challenges the Standard Model
Author : Kaibeezy
Score : 203 points
Date : 2021-03-23 08:17 UTC (14 hours ago)
(HTM) web link (www.bbc.co.uk)
(TXT) w3m dump (www.bbc.co.uk)
| jokoon wrote:
| Nice to see the LHC can still be useful to make discoveries.
| Cthulhu_ wrote:
| It'll be in operations for years if not decades to come still.
| They're working on an upgrade to increase the 'luminosity'
| (dunno what that means yet) by a factor 10 as we speak, slated
| to be finished in 2027 (see https://en.wikipedia.org/wiki/High_
| Luminosity_Large_Hadron_C...)
| ShinyRice wrote:
| Luminosity is the number of particles (in the LHC's case,
| protons) flowing per unit area and unit time.
|
| Additionally, integrated luminosity is luminosity integrated
| over time, and is just the number of _events_ produced per
| unit area. It is the main metric used when CERN releases data
| and shares just how many events are in a given data set; this
| is done such that you can take the cross section of a given
| event (like Higgs production), multiply it by this value, and
| get how many events of that type happen (how many Higgs were
| produced).
| nabla9 wrote:
| CERN: https://home.cern/news/news/physics/intriguing-new-result-
| lh...
|
| Video News release : : https://videos.cern.ch/record/2758757
|
| LHCb article : https://lhcb-
| public.web.cern.ch/Welcome.html#RK2021
|
| LHCb paper : https://arxiv.org/abs/2103.11769
| JosephRedfern wrote:
| The title of the submission no longer seems to refer directly to
| the content of the article. If the feeling is that the article is
| dumbed down too much (as some of the comments suggest), could the
| URL also be changed? Maybe the UKRI press release, or CERN
| update? https://www.ukri.org/news/result-from-lhcb-experiment-
| challe... https://lhcb-public.web.cern.ch/Welcome.html#RK2021
| DJBunnies wrote:
| Biggest pet peeve of this place, editorializing.
| jackweirdy wrote:
| It's very common for BBC headlines to change 3-5 times after
| being posted. I don't know whether they are A-B testing or
| just twitchy, but it's annoying for sharing new articles
| mamon wrote:
| I think it is a clickbait - you see new title on their main
| page and click only to realize that you've read that
| before.
| BelenusMordred wrote:
| > I don't know whether they are A-B testing or just twitchy
|
| Have worked in the dark basements for a news company, it's
| A-Z testing for some online pieces to see what gets more
| fish on the hook. They'll use wildly different headlines
| without changing a single word in the article.
| Kaibeezy wrote:
| FTR, OP here. I didn't change the title. Perhaps HN will
| comment. In my experience their reasoning is typically solid.
|
| When I posted, I believe it was "LHC machine finds
| tantalising hints of new physics". I remember that seemed
| oddly redundant, like an "ATM machine". Current title for the
| article is showing as "Machine finds tantalising hints of new
| physics", but a search is also coming up "LHC machine
| challenges leading theory of physics".
| dukwon wrote:
| I guess the logic of the headline was that LHCb is one of
| the "machines" at the LHC.
|
| Unfortunately in LHC jargon, "the machine" is the collider
| itself rather than the detectors.
| rrmm wrote:
| The result is three-sigma, so not yet there (5 sigma). As usual,
| interesting if true.
| whatshisface wrote:
| I will give you $999 if it's just noise in exchange for $1 if
| it's not.
| lainga wrote:
| Looks like some people didn't like you putting the concept in
| more accessible terms. "Three sigma" has a real
| interpretation, it's not just a little score where you pull
| out LaTeX when it reaches 6.
| rrmm wrote:
| But LaTeX seems to take a whole lot longer to run when it's
| 6 sigma than when it's 3.
| mlyle wrote:
| Of course, to perform any valid statistical reasoning, you
| need to consider the prior. The standard model has held up
| very well, and we do a _lot_ of experiments-- any of which
| has a small chance of popping out a result that looks
| highly significant by chance. There 's a reason why 6 sigma
| is the line to take things super seriously (in fundamental
| physics).
| rrmm wrote:
| Plenty of 3 sigma results have come and gone, (there's
| obviously an xkcd for this about doing a whole lot of
| experiments). It's certainly something to watch and I would
| personally be stoked for some new physics.
|
| I only posted because it was the first thing I wanted to
| know, and I had to dig around in the article for a bit before
| I found it at the end.
| hardtke wrote:
| My mentor once said "3 sigma effects happen in physics a
| lot more often than they should." I've since come to
| realize that we should do a multiple-hypothesis testing
| correction on all such results, where the number of
| hypotheses tested is approximately equal to the number of
| Ph.D.s granted in particle physics.
| rrrrrrrrrrrryan wrote:
| Break-even for three sigma would be 997:1, so the parent
| should actually take this bet.
| whatshisface wrote:
| The result was past three sigma, not exactly at three
| sigma. But good point, because if it was exactly at three
| sigma I would have snookered myself. :)
| prof-dr-ir wrote:
| You are joking, right? The experiments around the LHC have
| produced a handful of three-sigma "non-standard-model"
| results already. So far they have all gone away.
|
| This is not a bad thing, by the way - just an inevitable
| consequence of doing many searches.
| TrispusAttucks wrote:
| Yes. I think it's a joke.
|
| As in 3-sigma ~= 1/1000
| sunpar wrote:
| Yes but he brings up a good point. They are more likely
| to talk about a 3 sigma result that challenges the
| standard model than one that doesn't yield anything
| special. So given you know a 3 sigma result is being
| discussed, the probability that it's a false result at
| higher sigma is more than 1/1000.
| alkonaut wrote:
| Shouldn't there just be around 1 in 1000 experiments the
| state reach 3 sigma for a result which then turn out to be
| noise?
|
| I guess that only applies if there are no mistakes or
| biases at all?
| unchocked wrote:
| The model indicates 1000:1, but it may not capture all
| aspects (i.e. correlations) in the system. So what seems like
| excessive sigmas is also margin for those unknown-unknowns.
| whatshisface wrote:
| Hence the qualifier "if it's just noise," ruling out other
| falsifications.
| WhompingWindows wrote:
| How about 999 subscriptions to Penthouse in exchange for 1
| subscription to Private Eye?
| geuis wrote:
| Jeebus, another frustrating air-filled article to up the word
| count.
|
| Meat:
|
| > The LHCb produces sub-atomic particles called "beauty quarks",
| which are not usually found in nature but are produced at the
| LHC. Sub-atomic particles undergo a process known as decay, where
| one particle transforms into several, less massive ones.
| According to the Standard Model, beauty quarks should decay into
| equal numbers of electron and muon particles. Instead, the
| process yields more electrons than muons. One possible
| explanation is that an as-yet undiscovered particle known as a
| leptoquark was involved in the decay process and made it easier
| to produce electrons.
| mellosouls wrote:
| More in depth, but plain English summary from the researchers
| here:
|
| https://theconversation.com/amp/evidence-of-brand-new-physic...
| xenophonf wrote:
| Non-AMP link:
|
| https://theconversation.com/evidence-of-brand-new-physics-at...
| mellosouls wrote:
| Yeah I normally take it out, just forgot this time. I don't
| mind it myself, but try and default to neutral.
| random5634 wrote:
| This is interesting - normally AMP is great and I'm (generally)
| a fan of it. But somehow they messed up AMP here - I've not
| seen that before. The AMP page is really poor (third party
| blocking, time to paint, even JANK is here - shift after load).
|
| The non AMP page is 1.4MB and 45 requests, the AMP page is
| 400KB and 16 requests - normally this means AMP just blows
| everything out of the water (despite HN hate). Something is
| messed up here that AMP is so poor, initial server response is
| terrible.
| shmageggy wrote:
| > _which ultimately could allow us to unravel any number of
| established mysteries. These include the nature of the invisible
| dark matter that fills the universe, or the nature of the Higgs
| boson. It could even help theorists unify the fundamental
| particles and forces..._
|
| To this non-physicist, it's not clear at all how this potential
| discovery might do any of that. From here, it looks like a
| mininally consequential addendum to the standard model, almost
| like a single epicycle to a geocentric cosmology. The effect only
| shifts by a few percent the chance of some obscure and rare
| interaction. Is it really plausible that it could have such grand
| implications?
| ISL wrote:
| To continue the epicycle analogy:
|
| The problem in modern physics is that the epicycles work too
| well. There are some big obvious mysteries and an incredibly-
| successful epicycle-based theory. Essentially everyone expects
| that the epicycles are not the truly fundamental theory of
| things.
|
| So, physicists keep comparing the predictions of the "epicycle-
| theory" with reality in new ways, ways where a deviation from
| the prediction would be an unambiguous signpost pointing a
| direction toward which one might be able to address a big
| mystery. As those tests become established, they are then
| performed with higher and higher precision.
|
| The signal potentially seen with LHCb is, if it persists,
| important. In a nutshell, electrons are, in this particular
| way, predicted to act _exactly_ like muons. No ifs, ands, or
| buts. What they see is that electrons and muons might be acting
| slightly differently. If so, some new physics (or a major error
| in our understanding of the epicycles -- I 'm looking at you,
| loops) must be at work. If this result persists, it is
| guaranteed that we will learn something.
|
| Too convoluted? Here is a different analogy:
|
| You're pretty sure someone is embezzling from your company.
|
| You look at your bank account, and you have ~95% less money
| than you thought you should. Really. Oh, no.
|
| You check the summary budgets, they're balanced. So you do this
| for all the company's divisions. Yep. Still balanced. You get
| paranoid. You do this for decades -- the books balance, but at
| the end of the day? 5%.
|
| Then an employee runs up to you and says, "Shmageggy! We're not
| sure yet, but it looks like one of our most-trusted partners,
| whom the firm has worked with since 1936, transferred thirty-
| seven cents to an account in the Cayman Islands!"
|
| Until we find the embezzler, that's what every one of these
| precision physics tests that makes the news is all about.
| DavidSJ wrote:
| _The measurement from LHCb is three-sigma - meaning there is
| roughly a one in 1,000 chance that the measurement is a
| statistical coincidence._
|
| No, that's not what this means. But this is about one in 1,000
| BBC Science articles that have repeated this confusion.
|
| Edited to add:
|
| What this actually means is that, conditional on the null
| hypothesis (that there is nothing there to find), there is a one
| out of 1,000 chance of seeing an observation such as this by
| chance.
|
| But the BBC article has inverted this. Rather than giving you the
| probability of the data given the hypothesis, they're purporting
| to give you the probability of the hypothesis given the data
| (which in general cannot be objectively stated; this is a
| standard difficulty in the philosophy of science and statistics):
| "there is roughly a one in 1,000 chance that the measurement is a
| statistical coincidence [i.e. the null hypothesis is true and
| there's nothing to see here]". They make it sound like the
| scientists are virtually certain that they've found something
| here, when in reality this is probably nothing (although that's a
| matter of opinion).
| simiones wrote:
| Even after you explain it, I can barely grasp the significance.
| Given the expected level of understanding of someone reading a
| BBC article about this topic, I don't think they are wrong at
| all in explaining it that way - that is, I don't think their
| intended audience would take the message differently to any
| extent whatsoever if they had explained the way you do.
|
| To be more specific, to the average BBC reader, the phrases
|
| _The measurement from LHCb is three-sigma - meaning there is
| roughly a one in 1,000 chance that the measurement is a
| statistical coincidence._
|
| and
|
| _The measurement from LHCb is three-sigma - meaning there is
| roughly a one in 1,000 chance to have seen this data even if
| the particle doesn 't exist._
|
| convey the exact same message, the first one just uses fewer
| words.
| DavidSJ wrote:
| Look, that may be so, but if it is, then they should either
| omit such a line entirely so as not to mislead their readers,
| select better language so that we don't collapse concepts
| which are fundamentally, completely, different from each
| other, or they could try to educate the public on a
| distinction which is fundamental to science.
|
| I mean, we might as well say that the BBC should just use the
| words "million" and "billion" interchangeably because most
| readers have no sense of scale.
|
| Bottom line: thanks to this line, the reader is likely to
| think that new physics has very likely been discovered, when
| the opposite is the case.
| simiones wrote:
| I don't agree. The whole paragraph makes that clear - 1 in
| 1000 is actually pretty good odds that this is just a
| coincidence, and most people should know this intuitively.
|
| > The measurement from LHCb is three-sigma - meaning there
| is roughly a one in 1,000 chance that the measurement is a
| statistical coincidence. _So people should not get carried
| away by these findings, according to team leader Prof Chris
| Parkes, from the University of Manchester._
| davrosthedalek wrote:
| The problem with it is that layman people believe that both
| of these statements are equal to "it's a 999/1000 chance that
| it was something else". Which is not true.
|
| The difference in these two formulations is that for b) it's
| explicit wrong, for a) this is arguably what the article says
| (which is not what the scientists say)
| simiones wrote:
| The article can be read as "there is a 999/1000 chance that
| this is not a coincidence". This is strictly speaking
| correct, because it doesn't specify what the coincidence
| would be.
|
| The correct interpretation is "there is a 999/1000 chance
| that you wouldn't see this data if the particle didn't
| exist" / "there is a 1/1000 chance that you would see this
| data if the particle didn't exist".
|
| The wrong interpretation that still agrees with the
| statement is "there is a 999/1000 chance that the particle
| exists given that we have seen this data" / "there is a
| 1/1000 chance that the particle doesn't exist given that we
| have seen this data".
|
| P(data | no particle) = P (no particle | data) * P (data) /
| P (no particle). As a layman, I have no idea what P(data)
| is, and I think no one can give a convincing estimate for
| P(no particle).
|
| Since P(data | no particle) and P(no particle | data) are
| in fact proportional, the only thing I should really care
| about as a layman is the value of any one of them. I any
| way can't evaluate myself what would be a convincing
| probability, since I don't have any proper priors.
| davrosthedalek wrote:
| No, not quite. The probability that this is not a
| coincidence is unknown. The probability that you SAW the
| data if the particle didn't exist is 100%. The
| probability that you will not see it /again/ is 999/1000.
|
| The probabilities 1/1000 (or 999/1000) are only meaningul
| probabilites for something in the world where in fact it
| was a coincidence. In any other world, they are not. So
| saying "there is a 999/1000 chance that this is not a
| coincidence" isn't true, as the calculation of 999/1000
| must assume that it fact it IS a coincidence.
| flukus wrote:
| How many iterations that could create this result do they run?
| 1 in 1000 sounds unlikely, but for all I know they have run
| this experiment 50,000 times.
| dalewe wrote:
| Not sure I entirely understand your question but I'll try to
| explain a bit anyway: they're using a dataset of 9fb^-1. That
| means it includes 9 events for a crosssection of 1fb
| (femtobarn). Now the paper doesn't seem to include what
| crosssection their events have but if we assume something of
| the order of magnitude of 1pb then the dataset would contain
| around 9000 events of interest.
|
| Now all that doesn't really matter as this is already
| factored into the standard deviation of their result. They
| have enough data to say it's a 3 sigma (being the standard
| deviation) deviation from the standard model. Now this "1 in
| 1000" really just means that the null hypothesis (the
| Standard Model) says there's a 0.1% chance for that result to
| happen. Of course it could also be that they forgot to factor
| in some uncertainty of their measurements and their sigma is
| actually much bigger. But it surely won't be the size of
| their dataset as this is quite obvious and easy to take into
| account.
| DavidSJ wrote:
| I would guess there are many more than thousands of such
| experiments that have been run, testing all the various
| permutations of dozens (or more) of different beyond Standard
| Model physical theories.
| dukwon wrote:
| Testing different models is done in the analysis of the
| data, not in running the experiment differently.
|
| The "experiment" (colliding protons together) has been
| repeated quadrillions of times at the LHC. But there are
| only a few parameters you can change about it, namely the
| energy and how focused the beams are. Altering the
| detectors to change/improve how data is collected is an
| expensive and slow process.
| DavidSJ wrote:
| Fair enough; what I meant is "multiple testing" in the
| context of a single overarching experiment, which is I
| believe what the comment I was replying to was getting at
| as well.
| davrosthedalek wrote:
| In any case, you have a point. Whether multiple analysis,
| multiple channels or multiple experiments, you have a
| look-elsewhere effect, and that can easily knock off one
| or two sigmas. If you look at a 10000 possibilities, you
| will a couple with 3 sigma difference, just by chance.
|
| LHC looks at MANY possibilities. For a while, they tried
| to keep track to quantify the look-elsewhere effect. I
| think they have given up on that.
| dataflow wrote:
| I don't see how the BBC's statement can translate into
| P(hypothesis|data). To me it's P(data|H0).
|
| Consider this simpler example: _" Scientists always assumed
| their coin was fair. Well, they flipped it 10 times, and it
| came up heads every time. This is a 3-sigmal result. There's a
| 1 in 1024 chance of this measurement being a statistical
| coincidence."_
|
| The reader would take this "1 in 1024 chance of coincidence" to
| mean "if the coin was fair, they'd have a 1 in 1024 chance of
| seeing this event occur". That's P(data|fair) = P(10
| heads|fair) = 1/1024.
|
| I don't see how you read that and translate it into P(fair|10
| heads).
| davrosthedalek wrote:
| It's like this: The chance to get 10 heads with a fair coin
| is <1/1000. I.e., if you use the same coin many-many times,
| <1/1000 of these 10-throw runs will have all heads, on
| average.
|
| This does not mean that, if you get 10 heads, it's a fair
| coin with 1/1000 probability. In the strongest sense, without
| further information, one can not make any statement about
| that probability.
| dataflow wrote:
| I don't think either of us disagrees with this. We're not
| debating what is mathematically true. We're debating what
| the BBC wrote.
| davrosthedalek wrote:
| Yeah. My point is this "There's a 1 in 1024 chance of
| this measurement being a statistical coincidence." I
| understand this as "There is a 1:1024 chance that a
| statistical coincidence is the cause of this result".
|
| But that's wrong, the statement must be: If it is a
| statistical coincidence, it had a probability of 1:1024
| of occurring. But then the probability that it was cause
| by a statistical fluctuation is 100% -- It's assumed to
| be true.
| DavidSJ wrote:
| If I say: "there's a 25% chance that Pat is from North
| Dakota", I'm taking as a given that there is a person named
| Pat, and I'm talking about the chance that Pat, whom we know
| to exist, is from North Dakota.
|
| In this case, grammatically, they're talking about the chance
| that the measurement (data) is a statistical coincidence, as
| opposed to not being a statistical coincidence. They're not
| talking about the chance that the data exists, as opposed to
| not existing.
| dataflow wrote:
| > If I say: "there's a 25% chance that Pat is from North
| Dakota", I'm taking as a given that there is a person named
| Pat, and I'm talking about the chance that Pat, whom we
| know to exist, is from North Dakota.
|
| Yes, and if I say "there's a 0.001% chance that these coin
| flip observations were coincidental", I'm taking it as a
| given that there were coin flips observed (indeed, there
| were!) I'm talking about the chance that the observations,
| which we (indeed) know to exist, were coincidental.
|
| That is... literally P(observations | null hypothesis) =
| P(10 heads | fair). It's clearly not P(null hypothesis |
| observations) = P(fair | 10 heads)...
|
| > In this case, grammatically, they're talking about the
| chance that the measurement (data) is a statistical
| coincidence, as opposed to not being a statistical
| coincidence. They're not talking about the chance that the
| data exists, as opposed to not existing.
|
| Which is... perfectly fine. The data clearly _does_ exist
| (as would the coin flips in my example), so the chance of
| the data existing is 100%... there 's nothing interesting
| to talk about there. But the chance of it having been
| coincidental is 0.001%.
|
| This all seems correct to me...
| DavidSJ wrote:
| There's been a misunderstanding between us. To clarify,
| I'm not saying we know _some_ data exists (that 's of
| course true, since an experiment was done). I'm saying we
| know _this_ data exists. Grammatically, they 've worded
| it so that the question is whether _this particular data
| that we have seen_ (as opposed to other data we could
| have seen) _was in fact_ produced by chance or not.
|
| The difference between the data being a statistical
| coincidence and the data not being a statistical
| coincidence is precisely the difference between the null
| hypothesis being true and the null hypothesis not being
| true. So they're making a claim about the probability of
| a hypothesis.
| dataflow wrote:
| > There's been a misunderstanding between us. To clarify,
| I'm not saying we know some data exists (that's of course
| true, since an experiment was done). I'm saying we know
| _this_ data exists.
|
| But that's exactly what I'm saying too? When I flip 10
| coins and see 10 heads, _that is the data_ , and it _very
| much exists_. _Nobody_ is talking about any data except
| that one. Not me, not you, not BBC.
|
| > Grammatically, they've worded it so that the question
| is whether _this particular data that we have seen_ (as
| opposed to other data we could have seen) was _in fact_
| produced by chance or not.
|
| Yes, and as I see it _this is 100% correct_. Like in my
| example where I saw 10 heads ( _that is the one and only
| dataset we know exists_ ), and I'm wondering if they were
| produced by chance or not. That is _precisely_ P(10 heads
| | fair coin) = P(observations | H0).
|
| > The difference between the data being a statistical
| coincidence and the data not being a statistical
| coincidence is precisely the difference between the null
| hypothesis being true and the null hypothesis not being
| true.
|
| Maybe your English analogy is the source of the confusion
| here? I don't know what rigorous definition you might
| have for "the difference" here(?), but whatever it is,
| "10 heads have a 0.001% chance with a fair coin" doesn't
| imply "10 heads have a 99.999% chance under an unfair
| coin"... right? Even though the former assumes H0 and the
| latter assumes !H0.
|
| Or to put it another way, just because H0 is true in one
| statement and false in another, that doesn't mean we're
| talking about the probability of H0 being true in one
| statement and the probability of H0 being false in
| another.
| DavidSJ wrote:
| The original wording is: "there is roughly a one in 1,000
| chance that the measurement is a statistical
| coincidence".
|
| By definition, "the measurement is a statistical
| coincidence" means the same thing as "the null hypothesis
| is true". That's literally just how we define
| "statistical coincidence".
|
| So the sentence might as well be worded: "there is
| roughly a one in 1,000 chance that the null hypothesis is
| true".
| davrosthedalek wrote:
| The point is that, from the measurement alone, you cannot
| make a statement of whether the null hypothesis is true.
| You can only make a statement how likely the observed
| outcome was /if/ the null hypothesis is true.
|
| (edit: I realize that you mean this. I just wanted to
| make it clearer. The article should have said: It's a
| 1/1000 chance that a measured difference of this or
| larger magnitude occurs as a statistical fluctuation
| assuming the SM)
| dataflow wrote:
| > By definition, "the measurement is a statistical
| coincidence" means the same thing as "the null hypothesis
| is true".
|
| OK, now I see what you're saying. I'm not sure that's how
| people interpret it in plain English though. I feel like
| people would interpret "is a coincidence" to mean
| "occurred coincidentally", aka "occurred naturally [by
| chance]". It might be kind of like arguing that "ladies
| and gentlemen" refers to their intersection rather than
| union. Mathematically it does, but English is another
| matter...
|
| Maybe the only way to settle this is to actually go do an
| experiment on people. I could be wrong, but I feel like
| if you go up to people and say "I think these 2 dice are
| fair, and I got two 6's when I tossed them; what are the
| chances this is a coincidence?" you'd get back "1/36"
| from most people. (Assuming they remember basic
| probability at all. You can filter against that by first
| asking them something more obvious, like maybe "what are
| the chances of getting 2 heads in a row with a fair coin"
| and making sure they tell you 1/4 before you proceed.)
| DavidSJ wrote:
| I consider "occurred coincidentally", "is a coincidence",
| and "occurred by chance" interchangeable. They are all
| equivalent to the null hypothesis.
|
| If my dice are loaded then the two 6's _weren't_ a
| coincidence. They were guaranteed. So to say they
| happened by coincidence is to say the dice are fair (the
| null hypothesis is true).
|
| Consider a typical English sentence: "was it just a
| coincidence that I saw Frank in town, or was he following
| me?" They are two alternative hypotheses to explain the
| same observation: In the first scenario, we assume that
| Frank was going about his business and just happened by
| chance to be in the same place as I. In the second, we
| assume Frank was following me and that's why he was in
| the same place. The question is about the hypothesis
| invoked to explain the observation. "Coincidence" is a
| (null) hypothesis.
| davrosthedalek wrote:
| Again, the chance that the ten heads occurred "by
| chance", "occurred coincidentally" or "is a coincidence"
| is not 1/1000. IF they occurred by chance, the
| probability for such a thing to occur (again) is 1/1000.
|
| 1/36 is the wrong answer for the question "what are
| chances this is a coincidence?". That probability is
| unknown, because it depends on whether the dice are
| actually fair, and what other dice are there. For
| example, if you have to discriminate between fair dice
| and unfair dice with only 2s on them, a 12 would indicate
| that with 100%, it was a coincidence.
|
| You might ask differently though: "What WAS the
| probability to throw a 12 with two fair dice?". But that
| probability collapsed to 100% when you actually throw
| them and got the result.
| lovemenot wrote:
| Since neither heads nor tails bias had been hypothesised,
| 1/512 rather than 1/1024.
| choeger wrote:
| I did not even see this at first. But they _did_ really write
| that the chance of "no new physics" is 1:1000, right? So they
| gave "there is new physics" interpretation a huge probability.
|
| Seriously, I completely glanced over this. Slightly
| embarrassing.
|
| In any case, if the LHC runs thousands of such experiments, we
| _do_ expect such signals, right?
| skissane wrote:
| I believe you that isn't what it means, but for those (like
| myself) who have limited familiarity with this topic, could you
| please explain what it actually means.
| Mordisquitos wrote:
| In case it helps, following that logic, green jelly beans
| could cause acne and there would be _" roughly a 5% chance
| that the measurement is a statistical coincidence"_:
| https://xkcd.com/882/
| mhh__ wrote:
| The p-value of a physics experiment isn't the probability of
| the result coming from thin air but rather than the
| probability of a result as or more extreme under the
| assumption of the null hypothesis (i.e. the effect we are
| looking for doesn't exist). The rub is that the design of the
| experiment and thus the hypothesis test is all dependent on
| various subjective factors, especially the people designing
| the experiment themselves.
|
| I'm not statistician however so presumably I'm just as wrong
| Kaibeezy wrote:
| Good explanation of sigmas here:
| https://news.mit.edu/2012/explained-sigma-0209
|
| I'm thinking it would be more accurate (by being less
| precise) for BBC to describe the 1:1000 possibility as just
| coincidence rather than "statistical" coincidence.
| spuz wrote:
| This article seems to agree that 3 sigma simply means "1 in
| 1000 possibility the result is a coincidence". I'm not sure
| what difference removing the word "statistical" makes here
| or why the BBC explanation is wrong.
| Kaibeezy wrote:
| Yeah, I'm not exactly getting why BBC is wrong either.
|
| Re "statistical", to me, it sort of implies all sources
| of error or variability were _provably_ not present
| (prove a negative) and the _only_ reason for a
| coincidental result was a statistical anomaly. What's got
| to be far more likely is some unaccounted-for variable
| produced the coincidental result.
| trehalose wrote:
| The article _does_ seem to agree, and it 's wrong just
| like the BBC article.
|
| Here's an old article from the time of the Higgs Boson
| discovery that had a great explanation:
|
| https://blogs.scientificamerican.com/observations/five-
| sigma...
|
| > Chances are, you heard this month about the discovery
| of a tiny fundamental physics particle that may be the
| long-sought Higgs boson. The phrase five-sigma was tossed
| about by scientists to describe the strength of the
| discovery. So, what does five-sigma mean?
|
| > In short, five-sigma corresponds to a p-value, or
| probability, of 3x10-7, or about 1 in 3.5 million. This
| is not the probability that the Higgs boson does or
| doesn't exist; rather, it is the probability that if the
| particle does not exist, the data that CERN scientists
| collected in Geneva, Switzerland, would be at least as
| extreme as what they observed. "The reason that it's so
| annoying is that people want to hear declarative
| statements, like 'The probability that there's a Higgs is
| 99.9 percent,' but the real statement has an 'if' in
| there. There's a conditional. There's no way to remove
| the conditional," says Kyle Cranmer, a physicist at New
| York University and member of the ATLAS team, one of the
| two groups that announced the new particle results in
| Geneva on July 4.
| spuz wrote:
| Thanks - I think that does explain some of the potential
| area of confusion. However, I don't agree that the BBC's
| explanation differs from what the true meaning is
| according to this Scientific American article says.
|
| The BBC article says:
|
| > The measurement from LHCb is three-sigma - meaning
| there is roughly a one in 1,000 chance that the
| measurement is a statistical coincidence
|
| My interpretation of this is "If there was no new
| physics, then there is a 1/1000 chance the same result
| could be measured by coincidence."
|
| I understand why some people may interpret this as "There
| is a 1/1000 chance that there is no new physics" though.
| DavidSJ wrote:
| "There is a one in 1,000 chance that the measurement _is_
| a statistical coincidence ", grammatically, presumes the
| measurement which did in fact occur and says something
| about the chance that a statistical coincidence did, in
| fact, happen. It's P(hypothesis | data). This is a
| classic no-no in science writing.
|
| "There is a one in 1,000 chance that the measurement
| _would arise by_ statistical coincidence " uses the
| conditional, (implicitly) presuming a hypothesis and
| saying something about the chance that, under that
| hypothesis, such a measurement as occurred would occur.
| It's P(data | hypothesis).
| cycomanic wrote:
| I agree, I understand the difference between the
| conditionals, but was trying to get what the OP was
| criticising. I think this is much more a interpretation
| of language issue than a correct/incorrect in the formal
| sense issue.
| cycomanic wrote:
| >"There is a one in 1,000 chance that the measurement is
| a statistical coincidence", grammatically, presumes the
| measurement which did in fact occur and says something
| about the chance that a statistical coincidence did, in
| fact, happen. It's P(hypothesis | data). This is a
| classic no-no in science writing. >"There is a one in
| 1,000 chance that the measurement would arise by
| statistical coincidence" uses the subjunctive,
| (implicitly) presuming a hypothesis and saying something
| about the chance that, under that hypothesis, such a
| measurement as occurred would occur. It's P(data |
| hypothesis).
|
| I now see your criticism and I agree the subjunctive is
| much clearer. I guess my brain just converts the other
| wording into yours whenever I read text like that.
| Asraelite wrote:
| Your point still stands, but technically that's not the
| subjunctive, it's the conditional.
|
| Actual subjunctives are only rarely used in English and
| often sound clunky. If you did use it it would be "There
| is a one in a 1,000 chance that the measurement arise by
| statistical coincidence". Note that it must be "arise",
| not "arises".
| exo-pla-net wrote:
| Subjunctives aren't rare. They arise whenever we
| speculate or wish for something.
|
| "I don't think he'd appreciate you stealing his spotlight
| on grammatical minutia."
|
| "I wouldn't bet on it."
| Asraelite wrote:
| Again, both of those examples you have given are the
| conditional, not the subjunctive. If the clause uses
| "would" with its main verb, it's not the subjunctive
| mood.
|
| You can read more about it here:
| https://en.wikipedia.org/wiki/English_subjunctive
|
| Also note that I'm specifically referring to the plain
| subjunctive. There is also something sometimes referred
| to as the "past/imperfect subjunctive" which is something
| different entirely.
| exo-pla-net wrote:
| I think "subjunctive" is used loosely. I think that I'm
| right in terms of descriptive diction; anything irrealis
| is often (typically?) called subjunctive in English,
| since we only use distinct verbs for indicative,
| imperative, and subjunctive moods.
|
| I think, however, that I prefer your rigorous
| distinctions. Moods seem to be important to human
| language, even if they're atrophied in English. So
| keeping the gate on the subjunctive vs conditional
| distinction points people toward a deeper understanding
| of how language works.
| DavidSJ wrote:
| Thank you, good point. My statistics is better than my
| linguistics. ;)
|
| I'll correct it in my comment (you're replying to someone
| quoting me).
| DavidSJ wrote:
| My brain does too, but I fear the average layperson won't
| know to do this and will come away from the article
| thinking there's been a real discovery here.
| DavidSJ wrote:
| The issue is not the word "statistical". It's the inversion
| of P(data | hypothesis) into P(hypothesis | data). I
| updated my comment to clarify.
| stdbrouw wrote:
| The probability of winning the lottery if you're a cheater is
| high, but the probability of being a cheater if you win the
| lottery is low. More generally, the probability of A
| conditional on B is not the same as the probability of B
| conditional on A. Sometimes they're similar, but it depends
| on the pre-existing odds of A and B.
| asplake wrote:
| Any clues as to what new physics might be out there if this gets
| confirmed?
| dalewe wrote:
| The paper mentions leptoquarks (particles that interact with
| leptons and quarks with potentially different coupling
| strengths for different leptons therefore breaking lepton
| universality) or some unknown heavy (didn't look into it any
| further but I guess the heavy requirement is there because
| otherwise we would already have observed its effects, I don't
| think it's necessary for this particular observation) neutral
| boson that would for example allow flavor changing of leptons
| ("flavor" means whether it is an electron, muon our tau
| lepton).
|
| Edit: https://arxiv.org/pdf/2103.11769.pdf - references 54 to
| 90 are about potential new physics models.
| [deleted]
| debacle wrote:
| The current standard model is slowly getting messier and
| messier. At some point we will make a discovery that adds some
| degree of elegance into our understanding of these
| interactions.
| albertTJames wrote:
| Its surprising that a 3sigma results is promoted in such a way.
| It is not psychology.. in Physics we usually expect a 5sigma.
| amadsen wrote:
| 3 sigma is termed "evidence" in particle physcis (while
| "discovery" is reserved for 5 sigma) and is often enough to get
| people interested. Keep in mind that these are just numbers and
| must be interpreted in context. There have been tensions in
| various heavy flavour measurements for a looong time and across
| multiple experiments. It is very plausible that this is where
| we'll finally see new physics at the LHC. So it is worth
| serious consideration.
|
| The super-luminous neutrinos had 6 sigma significance and still
| no one took it seriously because it was simply such a
| ridiculous claim. Obviously the number of zeros in your p-value
| don't mean a damn if you haven't plugged in your equipment
| correctly!
| morbia wrote:
| Indeed, there have been 3sigma deviations before (e.g. the
| diphoton resonance) which attracted a lot of attention and
| turned out to be nothing.
|
| I'd encourage people to read up on the Look-elsewhere Effect
| when you see something like this:
|
| https://en.wikipedia.org/wiki/Look-elsewhere_effect
|
| I'm not saying this isn't potentially an interesting result,
| but 3sigma deviations when your parameter space is so large is
| actually not a big deal.
| rocqua wrote:
| 3 Sigma seems like it is very much worthy of more research,
| though not necessarily cause to say this is the new truth.
| dukwon wrote:
| Unlike that 750 GeV lump, there are other observables in this
| case which build a consistent picture. Some fits to Wilson
| coefficients in b->sll were at almost 7s even before this new
| result.
| FinanceAnon wrote:
| I don't know much about physics (I am trying to learn more), but
| does anyone else find the idea that the universe is made of
| "little balls" fundamentally wrong? It just feels like it will
| never end. First, we thought that atom is fundamental. Then
| electrons, protons and neutrons were discovered. Then, we
| discovered that there are smaller particles. Are we ever going to
| discover a fundamental particle that cannot be broken up? What
| would it be made of? How much space would it take up? Just some
| armchair philosophy.
| vesinisa wrote:
| Do not think about "little balls". It's a fundamentally broken
| mental image that everyone was taught in high school chemistry.
| Already at atomic level things are adequedly expressed only as
| wave functions. Matter is not little balls made up of even
| tinier balls, but something altogether stranger - recall that
| matter and energy are interchangeable. I like to imagine the
| subatomic particles (like neutrons and protons) as beautiful
| rays of energy only temporarily trapped in particle form as
| ugly matter.
| shadowofneptune wrote:
| It gets worse when you consider that they are also equally
| valid as waves.
| humanistbot wrote:
| Step one in learning subatomic physics is to completely
| disregard your intuitions about what feels right or what seems
| to make sense.
| davrosthedalek wrote:
| As far as we know, leptons are not composite. They might be
| able to decay, but a muon or electron is fundamental. It's not
| made up from something else. Quarks seem to be fundamental too.
| Same for photons.
|
| We are pretty confident of this, because the theory describing
| them is so precise -- QED is the best tested theory of all, to
| about 14 digits IIRC. In fact, a big factor in the discovery
| that a proton is a composite system was that it could not be
| described by QED, it has a anomalous magnetic moment.
| endisneigh wrote:
| I know nothing of physics, but I'm just curious - could you
| explain in layman's terms how one could say an electron is
| fundamental without infinitely precise measurement tools?
| whatshisface wrote:
| You can't. It's a universal philosophical limitation on
| science. One humorous way to phrase it would be, "there
| could always be a gnome hiding behind the camera."
|
| You have got to see the implicit, unspoken qualifiers that
| are on all statements like that. "It would be counter to
| all known patterns if...", "it would have to be
| extraordinarily small, beyond unimaginable sensitivities,
| if..." and "we can't imagine any practical distinction
| between what it seems like and what it might be," are all
| reasonable interpretations of the statement "it isn't." The
| only unreasonable interpretation would be the literal one.
|
| (P.S. It is not actually fundamental, it is made up of
| right-electrons and left-electrons, coupled together.)
| gus_massa wrote:
| 100% sure is not possible, but there is some good
| circumstantial reasons.
|
| Let's use the bad model that an electron is a small ball
| made of some magic material. And that the material inside
| it is even, there are not more dense parts. Also the charge
| is distributed evenly, it's not concentrated in some parts.
|
| The electron is spinning, so you imagine that the ball is
| spinning. So you can calculate the angular momentum of the
| electron, assuming it's an even ball of a magical material.
| The angular momentum can be measured experimentally, so you
| can calculate how fast the electron is spinning, assuming
| it's an even ball of a magical material.
|
| It has charge, and the charge is moving, so it is like a
| small magnet. You have calculated how fast it is spinning,
| and you can calculate the magnetic moment of the electron,
| assuming it's an even ball of a magical material.
|
| Now you go to the lab and measure the real magnetic moment
| of the electron and it is twice the value of the number you
| got assuming it's an even ball of a magical material. This
| number is called g, so for an electron g=2 (actually almost
| 2).
|
| You can repeat the same calculation for protons, and the g
| of the proton is g~=1.410606...
|
| For an elementary particle, there are theoretical reasons
| to be sure that g=2. So the conclusion is that the electron
| is an elementary particle and the proton is a composite
| particle.
|
| ---
|
| Bonus: Actually, you can get a perfectly isolated electron
| alone, because there are nasty virtual particles floating
| around. You can't see the virtual particles, but they cause
| small corrections in the experiments with high energy
| particles. In particular, the g of the electron is not
| exactly 2 because these virtual particles cause a small
| correction. The value is approximately
| g=2.00231930436182(52)
| https://en.wikipedia.org/wiki/Electron_magnetic_moment
|
| If it smell to much hand waving, don't worry. There are
| very good models for all the nasty virtual particles, and
| you can make a long calculation of the effect of them, and
| calculate these correction. You can make the theoretical
| calculation and the experimental measure and they agree
| with 10 significant figures. They prefer to publish
| a=(g-2)/2 and a_thoretical =
| 0.001159652181643(764) a_experimental =
| 0.00115965218073(28)
|
| So the model of a electron as an elementary particle with
| some virtual particles floating around is quite accurate.
| kosh2 wrote:
| I would say it is filled with not made out of. The emptiness of
| space is not made out of particles.
| pixl97 wrote:
| The emptiness of space is filled with fields.
| kosh2 wrote:
| Yes. But as far as I know, space itself is not made out of
| particles.
| reedf1 wrote:
| This really grinds my gears, we purposefully moved away from
| "beauty quark" as it was a bit too whimsical (at the expense of
| descriptiveness), now science communicators keep using it as it
| seems to capture the imagination of non-sci readers. So please,
| as an informed individual, replace "beauty quark" with "bottom
| quark" every time you see it in this piece.
| amadsen wrote:
| I'm a physicist who spent seven years working at the LHC and
| I've never heard of a "purposeful" move away from the term
| beauty quark. It just fell out of favor but some, including
| myself, still like to use that name on occasion, personally I
| like it much better.
|
| The particle does _not_ have a name in the official (PDG)
| listing, only a symbol "b". The "bottom" quantum number is
| universally called as such so one talks of "bottom hadrons" and
| so on. On the other hand the general area of research is called
| "b-physics" or "beauty physics", LHCb is the LHC-beauty
| experiment and so on. It makes perfect sense that this article
| uses "beauty" throughout for consistency.
|
| At the end of the day its just a name and this particle happens
| to have more than one (as does the J/psi and others) and
| neither is more whimsical than the other. Physicists tend to be
| quite whimsical anyway, particle physicists perhaps especially
| so.
| goldenkey wrote:
| In any case, which authority told /u/reedf1 that studying the
| universe should be barred from being whimsical? Alan Watts
| would be laughing. So would the Joker. The universe is not
| meant to be taken so seriously. It is whimsical. And that is
| part of its beauty ;-)
| reedf1 wrote:
| I have absolutely no problem with it being whimsical.
| Actually I would like it to be as whimsical as possible,
| while still being easy and consistent to learn that is.
| reedf1 wrote:
| I was given the impression by my professors that it was a
| purposeful move, maybe it was just in teaching and not
| research. I'll defer to you, the actual particle physicist.
| goldenkey wrote:
| How can something you wear so light on your sleeve cause
| you such angst that it "grinds your gears." Though you may
| have resigned in this tumult, I believe you still need to
| resolve something far deeper in your perspective on
| knowledge with regard to yourself and others.
| chriswarbo wrote:
| > How can something you wear so light on your sleeve
| cause you such angst that it "grinds your gears."
|
| They revised their perspective in light of new
| information.
|
| That seems preferable to _not_ revising their perspective
| ( 'wearing it heavy on their sleeve'?).
| minitoar wrote:
| This may just be a language subtlety. I've frequently
| heard "grinds my gears" used as a synonym for "a pet
| peeve of mine".
| reedf1 wrote:
| Make no mistake, I think they should teach the b-quark as
| "bottom quark" to the general public and students. What
| particle physicist actually choose to use should be done
| at their own whimsy. I appreciate your diagnosis though,
| always feel I could be a bit more introspective.
| soulofmischief wrote:
| Sounds like you got triggered as well into making a
| comment? Maybe it's best to give OP the benefit of the
| doubt.
| Method5440 wrote:
| I'd also heard something like this during my physics
| education - you're not alone apparently. One name was
| apparently more 'respectable' than the other. Lol
| cabaalis wrote:
| An example of how the educators drive the narrative for
| the future.
| patcon wrote:
| heh there's a deep irony here, in a story about "how
| science communicators [supposedly] ditched the term
| favoured for _capturing the public imagination_ , in
| order to instead favour a more descriptive factual
| term"...
|
| ...of which the story itself is an overly neat
| simplification that has spread by better capturing the
| imagination of descriptive-minded physics students, in
| the teachers' _own_ science communicating :)
| reasonabl_human wrote:
| What do you do now? Is there a demand for CS skills at the
| LHC, and was it a fulfilling place to work in general?
| Presumably you lived in the UK that whole time?
| amadsen wrote:
| The LHC is in Switzerland (not the UK) and in fact I'm
| still here. I was a data scientist for while. These days
| I'm back in research, but in a different field.
|
| There is a huge demand for CS skills of all kinds. CERN has
| one of the largest SCADA installations in the world, runs
| its own internet exchange point, operates a network of
| computing centers with a million cpu and hundreds of PB of
| data, and maintains many many millions of lines of code of
| specialized software, just to give you an idea.
|
| It is a fantastic place to work, the level of expertise and
| dedication among the people there (scientists and engineers
| alike) is very very high.
| tsimionescu wrote:
| They have also shown an impressive 1000-machine
| kubernetes cluster running on GCP for analyzing data
| (they did a live demo at KubeCon in 2018 I believe where
| they ran the Higgs boson data analysis during a panel).
| andrewflnr wrote:
| I kind of don't believe there is such a thing as "just a
| name". People persistently confuse names with the thing
| named. If you want to communicate truthfully, you have to
| take into account the psychology of your audience. So "it's
| just a name" is not a good reason for misleading names.
|
| I realize this isn't a big deal for quarks, but it's been on
| my mind a lot. The application to politics is left as an
| exercise for the reader.
| lovemenot wrote:
| I'd heard of bottom quark before. Never beauty.
|
| Does top quark have its antecedent too?
| reedf1 wrote:
| Yes, "Truth quark". Because they don't exist naturally it
| lead my physics prof to say "There is no truth in the
| universe".
|
| Also, Some physicists call the fourth, fifth, and sixth
| derivative of position, "snap, crackle, and pop"
| respectively. Physicists are a fun lot aren't they?
| DrBazza wrote:
| > Physicists are a fun lot aren't they?
|
| Atomic cross section is measured in barns. As in "you
| couldn't hit a barn door".
| quchen wrote:
| In particle physics a barn is a huge area though, so the
| joke kind of makes sense there.
| lovemenot wrote:
| T and B retained. They clearly like symmetry, even through
| terminological adjustments.
|
| Not defending BBC's using non-prescribed terms, but quarks
| were always named whimsically. The word quark itself having
| been taken from Ulysses.
|
| It's hard to argue with snap following jerk, then
| acceleration then velocity. The next two follow snap, if
| not physically then at least historically.
| lovemenot wrote:
| @rocqua Your explanation is interesting, but seems to
| omit the third derivative "jerk" - not intended as a
| slur.
| speakeron wrote:
| Quark is from Finnegans Wake, not Ulysses.
| lovemenot wrote:
| Thanks. That is correct.
| jcims wrote:
| Also jounce, flounce and pounce lol
|
| https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_deri
| v...
|
| I thought were all useless terms but apparently snap is
| quite commonly used in quadrotor motion control.
| ragebol wrote:
| Not just quadrotor motion control, it applies to
| precision machinery as well. Eg. it's used in those big
| ASML wafer stepper machines that help power Moores Law
| for example, but also 3D printers etc. Low values for
| these derivatives help reduce vibrations in the machines
| IIRC.
| rocqua wrote:
| Snap is that feeling you get when a train is braking and
| comes to a halt. The breaking force suddenly falls of,
| which is noticeable. In general, snap shows how smoothly
| the acceleration occurs. This allows anything that flexes
| (like flesh) to slowly take-up the slack.
|
| I've also heard this is important for self-driving
| convoys. You want the cars in the convoy to all
| accelerate and brake smoothly rather than jostle all the
| things inside them.
| b3orn wrote:
| > In general, snap shows how smoothly the acceleration
| occurs.
|
| That's third derivative of position and called jerk.
| rocqua wrote:
| Dang you are right. My bad
| dataflow wrote:
| I think they're distinguishing between "how quickly
| acceleration changes" and "how smoothly acceleration
| changes".
| rocqua wrote:
| Nope, I confused Jerk and Snap
| [deleted]
| [deleted]
| isaacg wrote:
| The official name of the LHCb experiment is the "Large Hadron
| Collider beauty" experiment, as named by the scientists
| themselves. So "beauty quark" is more correct in this context.
|
| https://home.cern/science/experiments/lhcb
|
| Moreover, the paper that describes the result that this article
| is discussing has "beauty quark" in the name:
| https://arxiv.org/abs/2103.11769
| pmontra wrote:
| And "b is for beauty" https://lhcb-
| public.web.cern.ch/en/Physics/Beauty-en.html
| reedf1 wrote:
| And I wish they wouldn't have, for the sake of scientific
| clarity.
| jjk166 wrote:
| I would actually say that beauty is more scientifically
| clear.
|
| The various quantum numbers of the quarks are real physical
| quantities, but not ones for which we have a good way of
| conceptualizing in classical, macroscopic life. The up and
| down quarks aren't actually spinning, but they do kind of
| behave as if they were spinning, so their names make sense,
| but for the others there isn't even an analogue. Luckily no
| one expects to be able to visualize strangeness, and
| likewise charm and beauty convey quite well that the naming
| is arbitrary. Top and bottom on the other hand sound like
| they could refer to a "real" property, or perhaps represent
| two ends of a spectrum. While I've seen no evidence that
| confusion is rampant, it would be easy to see how confusion
| could arise. If anything, the Top quark should be renamed
| to something more whimsical, or both should be renamed to
| something more clearly arbitrary like heads and tails.
| irjustin wrote:
| Yea scientists are up there in terms of the people with the
| worst ability to name things.
|
| Right there with developers but our terrible naming
| conventions don't really make it to publications.
| andrewinardeer wrote:
| Spaghettification
| twic wrote:
| _Drosophila geneticists have entered the chat_
| aYsY4dDQ2NrcNzA wrote:
| Explain?
| klyrs wrote:
| I'd guess this is a dig at biology's naming tradition,
| for the purpose of showing that scientists as a whole
| aren't great at naming either. Or maybe people in general
| -- check out the wikipedia page for Mohammadabad: looks
| like there are hundreds of places with that name in Iran
| d_theorist wrote:
| Why though? What's wrong with being whimsical and capturing
| people's imagination?
| reedf1 wrote:
| Well because you can encode intuition in names. e.g. Quarks
| come in pairs, and each pair has one quark with +2/3e charge
| and one with -1/3e. The names can give you intuition for
| their charge, i.e. Up quark is +2/3e Down quark is -1/3e. And
| if you give names that give you intuition for the charge it
| is considerably easier to remember (as a former undergrad
| physicist trust me you need assistance here). The name name
| "top" allows you to immediately think "up" and +2/3e and
| "bottom" allows you to immediately think "down" and -1/3e.
| shawnz wrote:
| What is intuitive about the up quark and down quark
| charges?
|
| The fact that "up" is associated with positivity is totally
| arbitrary, and even the fact that positive charges are
| called positive is totally arbitrary.
| stan_rogers wrote:
| And the pair, in this case, is _truth_ and _beauty_. Are
| you saying that _strange_ and _charm_ give you an intuitive
| feel for the charge number?
| [deleted]
| [deleted]
| goldenkey wrote:
| What you are describing is association, not intuition. It
| is not the responsibility of scientific laborers to name
| and structure things in order to create convenient
| associations for cramming physics undergrads. Intuition
| involves a deep understanding of the objects and processes,
| a lot more harrowing than memorizing charges..
| [deleted]
| Kaibeezy wrote:
| Maybe because it misleads people into an inaccurate
| anthropomorphic impression of what these cute little nippers
| are up to, undermining this-is-serious science. See also: Sea
| Monkeys.
| Kaibeezy wrote:
| How do you/scientists feel about _strange_ and _charm_?
|
| I've seen "sideways" sub for strange, which actually seems to
| fit the mnemonic better anyway. Why not "curly" or something
| instead of charm?
| chriswarbo wrote:
| 'Strange' predates the quark/parton model, and was a
| placeholder name for a particular unexplained phenomenon;
| similar to how the prefix 'dark' gets used.
|
| In particular, collider experiments were giving rise to a
| 'particle zoo' of pions, kaons, lambdas, etc. all of which
| were assumed to be fundamental. Some of these lasted much
| longer than expected, and were called "strange".
|
| It turned out that these could be modelled by giving
| fundamental particles a new property, which got the name
| "strangeness". Similar to how particles can have "charge",
| which is zero for neutral particles; non-strange particles
| have zero strangeness. Their long lifetime was explained due
| to the strong force conserving strangeness: collisions
| between non-strange particles can make pairs of particles
| with positive/negative strangeness (as long as it sums to
| zero); but once those individual particles have separated
| they can no longer decay via the strong force; they have to
| wait for the weak force, which gives them a longer half-life.
|
| It was only later, once the quark model became more accepted,
| that these particles were no longer considered fundamental,
| and "strangeness" could be explained as "containing strange
| quarks".
|
| On the other hand charm, beauty/bottom and truth/top seem to
| all be built on the quark model from the start; which makes
| the whimsy in their names more deliberate.
|
| ---
|
| FYI the BBC's Horizon did an episode in the 60s called
| "Strangeness Minus Three" (
| https://www.bbc.co.uk/programmes/p01z4p1j ) which is
| interesting to watch in hindsight, now that we have quarks
| and the standard model; and makes a nice comparison to the
| more recent search for the Higgs boson.
|
| ---
|
| Tangentially this idea, of a new property whose conservation
| prevents massive particles from decaying, also arises in
| supersymmetric models of dark matter. There, supersymmetric
| particles have a different "R parity" to normal particles,
| which prevents them decaying even if they're very massive;
| such particles are a candidate for dark matter.
| ars wrote:
| Isospin is another property that has been explained better
| in a new way.
|
| They still teach it for some reason though.
| [deleted]
| burundi_coffee wrote:
| Are there any primary sources for this?
| mhh__ wrote:
| I had a look and I couldn't immediately see any papers, seems
| fresh out of the university press departments
|
| https://www.ukri.org/news/result-from-lhcb-experiment-challe...
|
| Where the universities involved are Bristol
| University of Cambridge Imperial College London.
| dukwon wrote:
| Also the University of Zurich. The Cambridge involvement is
| just because someone from Imperial moved there.
| nabla9 wrote:
| CERN: https://home.cern/news/news/physics/intriguing-new-
| result-lh...
|
| LHCb article : https://lhcb-
| public.web.cern.ch/Welcome.html#RK2021
|
| VNR : https://videos.cern.ch/record/2758757
|
| LHCb paper : https://arxiv.org/abs/2103.11769
| isaacg wrote:
| I believe this is the relevant arxiv preprint:
| https://arxiv.org/abs/2103.11769
|
| And here is a post by some of the main authors describing their
| findings: https://theconversation.com/evidence-of-brand-new-
| physics-at...
| lutorm wrote:
| "858 additional authors not shown."
|
| Particle physics, the field where you can make a
| difference... ;-)
| dylan604 wrote:
| If only movie/game credits were like this.
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