
Neutrino experiment reveals inconsistency in how matter and antimatter behave - okket
https://www.quantamagazine.org/neutrinos-suggest-solution-to-mystery-of-universes-existence-20171212/
======
ianai
1999 article talking a little about historical results and projections for CP
violation
[http://cerncourier.com/cws/article/cern/28092](http://cerncourier.com/cws/article/cern/28092)

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laretluval
Oof, p value misinterpretation:

> That result got the community excited — although most physicists were quick
> to point out that with such a small sample size, there was still a 10
> percent chance that the difference was merely a random fluctuation. (By
> comparison, the 2012 Higgs boson discovery had less than a 1-in-1 million
> probability that the signal was due to chance.)

~~~
nonbel
Yep. When reading the actual papers from the LHC, LIGO, etc groups the
p-value/significance aspect seems nearly irrelevant though.

My impression is usually they have some set of possible theories that predict
the exact result observed, then go on to do more experiments to distinguish
between the predictions of those.

Really they should just drop the significance testing because it adds nothing
and they don't seem any better at interpreting those tests than other fields.
If I am wrong about all this and that aspect actually is crucial, then physics
is in trouble...

~~~
QAPereo
In HEP, it’s more that the bar is so damned high, and your n equals something
in the billions or trillions, _and_ oversight from the community is extreme.
The confidence required for example, to make people feel generally positive
about the discovery of the Higgs boson, was in the realm of billions to one.
Generally there is a model, and dats needs to fit that model to what would be
an insane degree of confidence in most other fields.

There is a bit more to it than just pure sigma values; it is also a matter of
how closely the data fits the model overall, a lack of competing hypotheses to
explain said data, and to what degree other evidence exists to support the
model. Of course, if the theory being confirmed is complementary to existing
physics, that also helps a lot. Having said that, 3 sigma is about when people
started to get excited about the Higgs, and 5 sigma was confirmation.

~~~
nonbel
The problem is that the sigma calculation is only about rejecting the null
model (ie, the model of "background noise"). That number is calculated without
including info about any theory/evidence regarding the Higgs boson.

So, all of the confidence and confirmation _regarding the Higg 's boson_
better actually be coming from "how closely the data fits the model overall, a
lack of competing hypotheses to explain said data, and to what degree other
evidence exists to support the model".

As an example, I'd imagine detecting the Higgs boson at 1 eV energy levels is
theoretically predicted to be even less likely than billions/trillions to one
odds, therefore detector noise would be a more likely explanation for such
results, despite the low p-value.

~~~
mattheww
>That number is calculated without including info about any theory/evidence
regarding the Higg's [sic] boson.

That's not true. You can see plots in the 2011 and 2012 papers that give these
calculations as a function of mass. It's basically impossible to make a mass-
independent calculation. (Not withstanding the fact that there's no Higgsless
theory to do calculations for the background).

>As an example, I'd imagine detecting the Higg's [sic] boson at 1 eV energy
levels is theoretically predicted to be even less likely than
billions/trillions to one odds, therefore detector noise would be a more
likely explanation for such results, despite the low p-value.

You're right, the p-value is much lower. Previous experiments have long since
excluded such a low Higgs mass. Also, if the Higgs mass were so low, we
probably wouldn't exist.

~~~
nonbel
1) Typos fixed.

2) "That's not true. You can see plots in the 2011 and 2012 papers that give
these calculations as a function of mass."

\- Can you explain what you mean via figure 1 in this paper:
[https://arxiv.org/abs/1207.7235](https://arxiv.org/abs/1207.7235) ?

\- I don't see the relevance of calculating p-values as a function of mass to
my comment

3) "Not withstanding the fact that there's no Higgsless theory to do
calculations for the background"

\- Then what model did they use to calculate the p-values? (I do not know the
details but am fairly certain it is one where there is no Higgs boson at any
given mass)

4) "Also, if the Higgs mass were so low, we probably wouldn't exist."

\- Ok, but I've also read headlines like "CERN proves the universe shouldn't
exist", clearly this is just because their model of the universe is wrong. I'm
sure in a pinch people could come up with some kind of balancing out of
whatever problems would arise from such a small Higgs mass. The point was that
_assuming the current theory is correct_ , the Higgs would be a much worse
explanation than detector noise.

~~~
mattheww
RE 2: What I mean is that "N-sigma" and local p-value are being used
interchangeably, which you can see from this plot. There's no "number ...
calculated without including info about any theory/evidence regarding the
Higgs boson".

RE 3: The model used to calculate the background are unphysical in the sense
that they set the Higgs production cross section to zero without changing
anything else. There's no physical Higgsless theory.

RE 4: I was agreeing with you and adding some facts.

~~~
nonbel
>'What I mean is that "N-sigma" and local p-value are being used
interchangeably, which you can see from this plot. There's no "number ...
calculated without including info about any theory/evidence regarding the
Higgs boson".'

Sorry, I still don't see what information is being used that requires
theory/evidence regarding the Higgs boson. Whether or not anyone knows about
the Higgs boson they could be plotting p-value by mass for these experiments.

>"The model used to calculate the background are unphysical in the sense that
they set the Higgs production cross section to zero without changing anything
else. There's no physical Higgsless theory."

So they actually change their model to be surely false, then go on to prove
the known false model they just created... is false. This is pointless.

~~~
posterboy
> they could be plotting ... by mass

he was saying, the mass calculation depends on the theory about the higgs?
they can't just put it on a scale :)

~~~
nonbel
You may be right on that point. For some reason I was thinking they just
summed up the velocities, etc from whatever hits the detector. Perhaps
somewhere they assume something about the Higgs boson though.

This makes the significance testing they do even more ridiculous though. At
first I thought the model of background noise was simply not providing much
info about the topic of interest: the existence and mass of the Higgs.

According to what I have learned here, it is much worse. Not only are they
testing a purposefully rendered false model (and taking rejection of that
known-false model as evidence for the Higgs), but they are also assuming the
Higgs exists (and has whatever properties you all are referring to) as part of
this process. As a result, the Higgs exists either way (whether background
model is rejected or not) according to this process.

Doing this test sounds pretty meaningless to me.

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scotty79
How can they know they detect their neutrinos not the neutrinos travelling
through space and passing earth as if it wasn't there?

Sine we are living in matter dominated region of space it would stand to
reason that most stellar neutrinos that pass through us are matter neutrinos.

~~~
danharaj
They can infer the momentum of a detected neutrino from the detector data,
which lets them statistically distinguish neutrinos coming from the beam they
control (controlled direction and energy) from background noise (e.g.
neutrinos from the sun).

~~~
scotty79
What about neutrinos from outside of the solar system?

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danharaj
I don't know what biases there are in the distribution of such neutrinos, but
the basic idea still holds, which is that they have a specific source of
neutrinos they're looking out for and neutrinos of other origins will only
look like they're from that source very seldom. They can infer the origin of
the neutrinos based on the direction from which they entered the detector and
how energetic they are.

~~~
raattgift
The Super-Kamiokande detector is useful for neutrino detections generally, and
they calibrate it from time to time using various devices, and have been for
decades (!).

[https://arxiv.org/abs/hep-ex/9807027v1](https://arxiv.org/abs/hep-
ex/9807027v1) [1998]

The T2K experiment is in a way essentially another calibration system. It of
course has its own overview page at
[http://t2k-experiment.org/t2k/](http://t2k-experiment.org/t2k/)

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thriftwy
"Experts believe that neutrinos and anti-neutrinos have super heavy
counterparts" \- is this one about supersymmetry?

Then, "some experts" not "[all] experts" since supersymmetry is not
universally accepted with its lack of evidence.

~~~
QAPereo
Definitely. ADMX for example, is searching for axions, under the assumption
that WIMPs or sterile-heavy neutrinos are he wrong bet. Having said that, SUSY
is still very popular, albeit unsupported by evidence. Critically for
proponents of supersymmetric theories, they have also not been ruled out, and
nothing else has been ruled definitely in.

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csomar
Maybe to lower down expectations we should have two names: Universe existence
and Universe formation.

Universe formation is how the universe "formed".

Universe existence is how the universe come to exist out of nothing.

The article and neutrino experiment talk about the former. The latter is more
interesting, though.

~~~
QAPereo
The latter feels like a classic case of questions for which the answer is
unhelpfully, 42. That is to say, do we even know what the question is? We have
no real reason to believe that the universe came from nothing, or that nothing
exists in a way that isn’t purely Conceptual. Certainly all of our
explorations into the nature of nature indicate complete absence of
nothingness, which may go someway to explaining the popularity of theories
which don’t require it. Cyclic universes, cyclic ekpyrotic universes,
multiverses and more all essentially attempt to reframe the question on
nature’s terms, not ours.

So it’s interesting to think about, but there are reasons to believe that
humans will always lack the tools to find the answers. Imo that makes it feel
like questions about the existence of god, or an afterlife. They are important
and have massive bearing on our existence, but I doubt in our ability to
answer them, or even to ask the right questions in the first place. In that
sense, they’re less interesting than questions we can actually formulate and
hope to answer, like the “hows” rather than the “whys” of existence.

~~~
csomar
Nothing is a concept; therefore it should exist, no? The only possible
exception I can think of is if concepts are actually physical the way physical
reality is.

~~~
renox
In classic physic, nothing is a concept true, in quantum physic with the foam
of virtual particles coming from the void (see casimir effect) 'nothing' is a
much nebulous concept!

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scotty79
How do they produce exactly same number and energy distribution of muon
neutrinos and antineutrinos?

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nsxwolf
What a terrible headline.

~~~
kowdermeister
Why? It sums up perfectly the article. The existence of the Universe IS a
mystery. And the article is about neutrinos.

~~~
nsxwolf
There are mysteries in the universe that may be solved through a discovery
about neutrinos. But the mystery of the _very existence_ of the universe
itself cannot be solved by appealing to the existence of some other contingent
object within the universe.

~~~
kowdermeister
Let's go one step at time. Matter and antimatter should be created in equal
way and they annihilate once they bump into each other. This very fact should
raise an eyebrow that no matter should exists, but clearly does. If we solve
this mystery then we can go further another step.

~~~
duderific
If they would simply be annihilated after being created, why be created at
all?

I feel like somehow, we are way off in our understanding of the universe and
how it works. There are so many unanswered questions, such as:

1) If the big bang created space and time as we know it, what was there before
that?

2) Why did the big bang suddenly occur 14 billion or so years ago? Why not a
couple billion years before or after that?

I know that the steady state theory of the universe has fallen out of favor,
but I wonder if some appeal could be made to some kind of fundamental force
that has always existed and always will, which behaves with fluid dynamics,
and the "islands" of matter that we experience are actually some kind of
fluctuations in that fluid.

~~~
posterboy
1) The canonical answer is: there was no before, the singularity happened at
delta_t=0. It is a mathematical construct resulting from extrapolating a
physical model backwards in time which somehow converges. I'm not sure its not
just convention. The big bang didn't create space time. It _is_ space-time
indeed and we know nothing (absolutely nothing, I believe!) about an object
that has no spacial or temporal extend. All they are interested in is a few
seconds after.

And the other big point is that our concept of time might be flawed. Maybe in
relativistic terms, from our point of view it was a few seconds, but it
actually took an eternity and you could keep observing closer and closer to
the origin (in the diagrammatic sense) but never reach it, so who even cares,
still? So, in a way more easily grasped by humans, it would be more apt to
say, there is no _after_ , because we will possibly never get _behind_ it in
our way forward. Does that seem sensible to you?

2) Because that's when the size of the universe in the calculation reaches
plank scale? I'd like some correction because I have read before that plank
scale is not actually a hard physical boundary, but I believe we just don't
have the tools to say anything about that time with any certainty. And don't
be mistaken, there are loads of competing theories and all have warts,
paradoxes and open questions. Such is life, ironically, which I still think is
a comfortable closure.

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scotty79
Can nothing influence rate of oscilations of neutrinos?

I have trouble accepting CP symmetry violations.

~~~
vardump
> I have trouble accepting CP symmetry violations.

Universe does seem to exist, though, doesn't it?

How would you explain that without CP symmetry violation?

~~~
scotty79
> How would you explain that without CP symmetry violation?

My preferred explanation is that areas dominated by matter and anti-matter got
pushed away far apart by the energy of annihilation between them, universe is
much larger than observable universe and our galaxy, neighbouring galaxies,
possibly even whole observable universe belongs to region that was dominated
by matter that is now separated from anti-matter dominated ones with
sufficiently large and empty void.

I don't exactly buy the idea that all of the matter was at the beginning in
one geometrical point, and exactly uniform. Background radiation is not
exactly uniform so imho not all places in space had exactly the same amounts
of matter and anti-matter either.

~~~
sethrin
The geometrical point you refer to is a projection, not an empirical fact. PBS
has an excellent YouTube series called _Space Time_ , which describes the Big
Bang cosmology in some detail, in several episodes. I'm not exactly sure which
ones, but I could track them down if you like. However, I might recommend the
entire series; you might be able to refine your speculation somewhat.

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saalweachter
My impression as a layman is that quantamagazine.org is leaking a lot of ...
ambitious ... physics headlines into HN; I've kind of stopped clicking on them
after the first few.

Physicists in the audience, is that an accurate assessment or should I go back
to excitedly clicking through when I see them?

~~~
specialp
I work for a physics journal and when we make articles for the public to
describe findings we have the opposite problem when it comes to authors.
Scientists especially in theory are reluctant to ascribe much at all to their
research other than the phenomenon shown. In research this is a good thing,
but when we want to show the public what these very theoretical or specialist
discoveries mean to our total understanding of physics it is not as helpful.
Just getting anyone to speculate what a finding means is hard.

In this case, this is something that might explain a CP violation that can
explain why we exist in a universe of matter. To a physicist, explaining it is
a CP violation is grandiose enough. But in reality the title is not at all
misleading as CP parity is one of the biggest unsolved problems in physics,
and yes it is a mystery as to why we have a universe of matter that exists. So
while it may seem ambitious to a person in the field, it is indeed truthful
and exciting research.

~~~
yk
Quite simply, when the specialist tell you that it is not news worthy, then it
is probably not news worthy. Otherwise we get all these new particle
discovered clickbait, where the journalists just neglect to mention that the
"particle" in question is a compound state that was well studied in the 60ies
or that the particle in question is just an oscillation mode of a crystal. (I
am not joking, both are examples that were well upvoted on HN.)

And that is just the ideal case, where journalists report on experiments. In
theory most articles are just as interesting as someone created a branch on a
github project, that is the very first step towards something that may develop
into something interesting, or it may not.

So yeah, "just getting anyone to speculate what a finding means is hard,"
because everybody knows that science journalists try to feed the public
bullshit. Seriously, every single climate change denier I ever discussed with
has given me page after page of links to popular science reporting where the
entire problem was, that the journalist found someone who was willing to
speculate and these speculations turned out to be wrong.

