9 ms·

Neutrino experiment reveals inconsistency in how matter and antimatter behave

127 points by okket 9y ago

laretluval 9y ago
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 9y ago
  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 9y ago
    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.
    - sandworm101 9y ago
      5-sigma is a ridiculous level. Im not that confident of my own name, which i spell incorrectly on at least two of every billion forms i fill.
    - nonbel 9y ago
      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 9y ago
        >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 9y ago
        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.
  - haZard_OS 9y ago
    We should just drop the significance testing/reporting period. The ASA's recent statement on p-values is spot on: http://www.amstat.org/asa/files/pdfs/P-ValueStatement.pdf http://www.amstat.org/asa/files/pdfs/P-ValueStatement.pdf
    - nonbel 9y ago
      Significance testing is probably fine as long as you put your theoretical prediction as the null hypothesis.
  - posterboy 9y ago
    Measurements are inherently probabilistic. If there was no trouble, there would be no physics.
thriftwy 9y ago
"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 9y ago
  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.
- T-A 9y ago
  > is this one about supersymmetry? Not necessarily. The seesaw mechanism [1] itself does not require supersymmetry, it's quite generic. [1] https://en.wikipedia.org/wiki/Seesaw_mechanism https://en.wikipedia.org/wiki/Seesaw_mechanism
- cozzyd 9y ago
  Maybe more precise would be to say "might have"
- posterboy 9y ago
  It's a false scottsman, those other experts aren't true experts.
saalweachter 9y ago
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?
- rf15 9y ago
  I am just into physics as a hobby as well, but yes, the site is a somewhat extreme variant of soft/popular science. (maybe extreme isn't the right word, but it's very much inside this category with all the enthusiasm that comes with it)
- QAPereo 9y ago
  I’d call it... aspirational. It’s not there yet, but it’s almost always an interesting discussion. Typically for pop-sci it oversells the matter, but it feels more enthusiastic than deluded or dumb. Just my gut though, as a dilettante.
- nyc111 9y ago
  I like their biology, natural sciences and mathematics articles. They are usually an interview with the researcher and a video.
- kowdermeister 9y ago
  > leaking a lot of ... ambitious ... physics headlines into HN QuantaMagazine is a very good bridge between cutting edge research and layman. What does leak even mean? They don't write titles to be "hackernewsed". This headline in question is also totally normal, not sure why you have a problem with it.
  - SubiculumCode 9y ago
    The title suggests that a discovery had been made that explains why the universe exists. Can you come up with a more grandiose title?
scotty79 9y ago
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 9y ago
  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).
  - ianai 9y ago
    They’re also talking about low numbers. It’s bad for statistical noise but helps to distinguish generated from background.
  - scotty79 9y ago
    What about neutrinos from outside of the solar system?
    - danharaj 9y ago
      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.
      - scotty79 9y ago
        I highly doubt they can rule out other sources with total observations counted in single or double digits especially that they can detect just one in bazzzilion of neutrinos that go through the detector. But I guess you are right. I just read that in case of some more energetic neutrinos interaction can create electron muon or tau dependant on neutrino flavor.
ianai 9y ago
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
nsxwolf 9y ago
What a terrible headline.
- kowdermeister 9y ago
  Why? It sums up perfectly the article. The existence of the Universe IS a mystery. And the article is about neutrinos.
  - nsxwolf 9y ago
    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 9y ago
      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 9y ago
        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.
csomar 9y ago
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.
- deleted 9y ago
  [deleted]
- QAPereo 9y ago
  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 9y ago
    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.
    - QAPereo 9y ago
      We can’t even imagine nothing though... it’s just a word we use to describe a state which may not and may never have existed.
scotty79 9y ago
How do they produce exactly same number and energy distribution of muon neutrinos and antineutrinos?
scotty79 9y ago
Can nothing influence rate of oscilations of neutrinos? I have trouble accepting CP symmetry violations.
- vardump 9y ago
  > 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 9y ago
    > 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 9y ago
      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.

127 points by okket 9y ago

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 9y ago
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 9y ago
  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.
  - sandworm101 9y ago
    5-sigma is a ridiculous level. Im not that confident of my own name, which i spell incorrectly on at least two of every billion forms i fill.
  - nonbel 9y ago
    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 9y ago
      >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 9y ago
        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.
- haZard_OS 9y ago
  We should just drop the significance testing/reporting period. The ASA's recent statement on p-values is spot on: http://www.amstat.org/asa/files/pdfs/P-ValueStatement.pdf http://www.amstat.org/asa/files/pdfs/P-ValueStatement.pdf
  - nonbel 9y ago
    Significance testing is probably fine as long as you put your theoretical prediction as the null hypothesis.
- posterboy 9y ago
  Measurements are inherently probabilistic. If there was no trouble, there would be no physics.

thriftwy 9y ago

"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 9y ago
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.
T-A 9y ago
> is this one about supersymmetry? Not necessarily. The seesaw mechanism [1] itself does not require supersymmetry, it's quite generic. [1] https://en.wikipedia.org/wiki/Seesaw_mechanism https://en.wikipedia.org/wiki/Seesaw_mechanism
cozzyd 9y ago
Maybe more precise would be to say "might have"
posterboy 9y ago
It's a false scottsman, those other experts aren't true experts.

saalweachter 9y ago

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?

rf15 9y ago
I am just into physics as a hobby as well, but yes, the site is a somewhat extreme variant of soft/popular science. (maybe extreme isn't the right word, but it's very much inside this category with all the enthusiasm that comes with it)
QAPereo 9y ago
I’d call it... aspirational. It’s not there yet, but it’s almost always an interesting discussion. Typically for pop-sci it oversells the matter, but it feels more enthusiastic than deluded or dumb. Just my gut though, as a dilettante.
nyc111 9y ago
I like their biology, natural sciences and mathematics articles. They are usually an interview with the researcher and a video.
kowdermeister 9y ago
> leaking a lot of ... ambitious ... physics headlines into HN QuantaMagazine is a very good bridge between cutting edge research and layman. What does leak even mean? They don't write titles to be "hackernewsed". This headline in question is also totally normal, not sure why you have a problem with it.
- SubiculumCode 9y ago
  The title suggests that a discovery had been made that explains why the universe exists. Can you come up with a more grandiose title?

scotty79 9y ago

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 9y ago
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).
- ianai 9y ago
  They’re also talking about low numbers. It’s bad for statistical noise but helps to distinguish generated from background.
- scotty79 9y ago
  What about neutrinos from outside of the solar system?
  - danharaj 9y ago
    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.
    - scotty79 9y ago
      I highly doubt they can rule out other sources with total observations counted in single or double digits especially that they can detect just one in bazzzilion of neutrinos that go through the detector. But I guess you are right. I just read that in case of some more energetic neutrinos interaction can create electron muon or tau dependant on neutrino flavor.

ianai 9y ago

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

nsxwolf 9y ago

What a terrible headline.

kowdermeister 9y ago
Why? It sums up perfectly the article. The existence of the Universe IS a mystery. And the article is about neutrinos.
- nsxwolf 9y ago
  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 9y ago
    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 9y ago
      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.

csomar 9y ago

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.

deleted 9y ago
[deleted]
QAPereo 9y ago
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 9y ago
  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.
  - QAPereo 9y ago
    We can’t even imagine nothing though... it’s just a word we use to describe a state which may not and may never have existed.

scotty79 9y ago

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

scotty79 9y ago

Can nothing influence rate of oscilations of neutrinos? I have trouble accepting CP symmetry violations.

vardump 9y ago
> 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 9y ago
  > 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 9y ago
    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.