[HN Gopher] Physicists detect signs of neutrinos at Large Hadron...
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Physicists detect signs of neutrinos at Large Hadron Collider
Author : pseudolus
Score : 150 points
Date : 2021-11-26 12:03 UTC (10 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| photochemsyn wrote:
| Rather amusingly this article is presently right below one on the
| arXiv project, but the phys.org article doesn't link to the arXiv
| version, so:
|
| https://arxiv.org/abs/2105.06197
| kordlessagain wrote:
| It's always bugged me that science claims there are trillions of
| neutrinos going through me, yet can hardly detect them with a
| nearly trillion dollar machine and a doctorate. Then there's dark
| energy, which just seems like a lame excuse for saying "we don't
| know".
|
| Nobody says what goes through my body but me!
|
| (I'm being funny, y'all! Happy holidays!)
| sleepysysadmin wrote:
| >Nobody says what goes through my body but me!
|
| That's selfish! Mandatory trip to Chernobyl!
| canjobear wrote:
| > seems like a lame excuse for saying "we don't know".
|
| Dark matter/energy aren't excuses, they're labels for things
| that behave like matter and energy but whose nature is unknown.
| macintux wrote:
| Well, dark matter at least to this layperson's eye a label
| for observations that are most easily explained by matter,
| which is not quite the same as a "thing that behaves like
| matter".
| aardvark179 wrote:
| Not exactly. Dark matter might reasonably considered a
| label for observations that are most easily explained by
| matter that only interacts with anything gravitationally.
| That's really a quite strange property compared to all the
| other matter we see, but it does seem to explain a lot of
| things rather well.
| hluska wrote:
| Just for the record, I'm not trying to be a jerk - I'm a
| layperson too. However, in science, it's important to
| understand that some of the "I don't know"s are so
| incredibly precise they're not intended for the layperson.
| Rather, many are precise models used to help experts
| communicate.
| pvg wrote:
| John Updike wrote a poem about the crassness of neutrinos:
|
| http://www.physics.mcgill.ca/~crawford/PSG/PSG21/204_97_L21....
| JProthero wrote:
| Excellent. I give this 10^14 / 10^14.
|
| The pedant in me wants to point out that they are now known
| to have some mass and do interact _a bit_ , but this was
| written in 1960.
| [deleted]
| lookatme wrote:
| In all seriousness, I found myself wondering about those
| numbers before; but consider that there's on the order of 10^27
| atoms in your body. So, if we assume a trillion neutrinos in
| your body, that indicates that for each neutrino in your body,
| there are 10^15 atoms - that's one part per quadrillion! A
| machine capable of detecting neutrinos in your body would need
| to be _unimaginably_ sensitive, before even considering the
| intrinsic difficulty in detecting them due to low mass and
| neutral charge.
| jiggawatts wrote:
| Look at it this way: Solar neutrinos carry away approximately
| 1% of the total fusion power output of the Sun. This works
| out to about 14 Watts per square meter at the distance of the
| Earth. The area of a human adult body front-on is about a
| square meter.
|
| It's pretty easy to detect 14 W of typical forms of radiation
| at those scales! If it were light, it would be equivalent to
| the light put out by something like a laptop screen, spread
| out just a bit. You can see something like that with your
| eyes from a kilometer away!
| JProthero wrote:
| This is a great analogy, I'd never seen it translated into
| tangible terms like that before.
|
| I remember reading that, at close enough range, the
| neutrino emissions from a supernova would be intense enough
| to be dangerous to structures made of ordinary matter,
| despite the weakness of their interactions, and that they
| would reach an observer earlier than other forms of
| radiation due to their ability to escape the collapsing
| star relatively unimpeded. Neutrinos would be the least of
| your problems if you were the observer of course.
|
| As I was trying to find a source for this, I discovered
| there is a unit [1] for the amount of energy released by a
| supernova called the Foe, which seems apt (it's an acronym
| derived from 'ten to the power of Fifty-One-Ergs').
|
| [1] https://en.wikipedia.org/wiki/Foe_(unit)
| gus_massa wrote:
| Perhaps " _Lethal Neutrinos_ " https://what-
| if.xkcd.com/73/
| cshimmin wrote:
| The trillions of neutrinos going through you are low energy
| neutrinos from the sun. We've been able to detect those for
| decades, and with only moderately pricey technology.
|
| The neutrinos in the article are high energy ones produced from
| proton collisions at the LHC. Although we have ways of
| producing neutrino beams from accelerators, the LHC is not set
| up for that, and these neutrinos are sparsely produced,
| incidentally to the high energy hadron collisions being
| produced there.
|
| In any case, the LHC cost at least an order of magnitude less
| than a trillion dollars. And the FASER experiment in particular
| which runs parasitically on existing LHC infrastructure runs on
| a shoestring budget, largely privately funded.
| Noobquestion wrote:
| Noob qestion, but I am interested: _um_ "So why the _heck_
| they doesn 't 'fusion'-react their stuff in a _hu_ liquid? ",
| and why isn't there an energy-surplus gotten from 'friction'
| ?
|
| And yes, way back i read something about the (reversed)
| bernoulli-effect.
|
| Any help ?
| cshimmin wrote:
| Hmmm... in good faith I'm not able to parse your question.
| I don't know what _hu_ liquid is, or what you mean by
| "their stuff". Maybe you could try again.
| magicalhippo wrote:
| I had similar issues parsing the question.
|
| I've noticed a marked uptick in almost-but-not-quite
| comprehensible questions in the last few months in
| various internet venues, like Discord and Slack.
|
| Having run my own MegaHAL[1] on IRC back in the days, it
| made me think about if someone is having fun with a new
| generation AI chat bots...
|
| Not saying that is the case here though.
|
| [1]: https://en.wikipedia.org/wiki/MegaHAL
| aardvark179 wrote:
| It's interesting that you class dark energy (the thing
| accelerating universal expansion) as, "We don't know," but
| don't put gravity into that same category. They are both
| aspects of general relativity that we have failed to integrate
| with our other most successful fundamental theories, but if you
| asked an average person on the street I'm sure they'd put them
| in very different categories of understanding, as you did.
| Ma8ee wrote:
| The thing with gravity is that it is kind of easy to detect,
| even for a layperson, while dark energy and dark matter
| haven't been detected at all, by anyone, but only used as
| mathematical devices to make indirect measurements of large
| scale structures align with our models.
|
| So, it isn't only the "average man on the street" that thinks
| there are good reasons to put them in very different
| categories of understanding.
| mnw21cam wrote:
| Relevant xkcd: https://xkcd.com/1489/
|
| The mouseover-text is the important bit: "Of these four
| forces, there's one we don't really understand." "Is it the
| weak force or the strong--" "It's gravity."
|
| That's even though it's the one with the simplest
| equations.
| tsimionescu wrote:
| > That's even though [gravity]'s the one with the
| simplest equations.
|
| Aren't the equations for gravity non-linear, while the
| other 3 are linear?
| whatshisface wrote:
| They're linear to the first-order, but everything is
| linear to first order by the definition of first order.
| Ma8ee wrote:
| Is that an attempt to appeal to authority?
| whatshisface wrote:
| Curiously... In the way dark matter has never been detected
| (no particle has been found), gravity has never been
| detected, and in the way gravity has been detected (through
| its influence on the trajectories of detectable matter),
| dark matter has been as well.
| vkazanov wrote:
| Well, scientists would argue that general relativity
| (I.e. gravity the way we understand it now) does predict
| a lot of things really well.
|
| Now, the problem is that its predictions fall apart at
| quantum scale and cosmological scale. Dark thingies are
| just a way to make the equations work at cosmological
| scale.
|
| There's always modified gravity, which takes an
| alternative approach by changing the equations.
|
| That's how they taught me 15 years ago, so give or
| take:-)
| Ma8ee wrote:
| It's a rather novel and very strange to say that
| something hasn't been detected because you haven't found
| a particle responsible for it, even though our whole
| existence and all our everyday experiences are grounded
| in it.
|
| Gravity is the effect. It's there. Whether you explain it
| with force carrying particles or the geometry of space
| time won't change it.
|
| Dark matter is one hypothetical explanation of an effect
| (or rather several). It's possible to find another
| explanation for the same phenomena without changing the
| phenomena.
|
| In other words, gravity and dark matter have very
| different ontological status.
| whatshisface wrote:
| > _In other words, gravity and dark matter have very
| different ontological status._
|
| I get what you're saying, but you can make them the same
| again by transposing Dark Matter to Dark Matitation, by
| analogy to Gravitons->Gravitation.
| spodek wrote:
| If you think science has you stomach untenable ideas, it's got
| nothing on what a lack of science will stick you with.
| neom wrote:
| I didn't really know what a neutrino is but I watched this and
| now I know, it was good:
|
| The physics anomaly no one talks about: What's up with those
| neutrinos?
|
| https://www.youtube.com/watch?v=p118YbxFtGg (Sept 2021, 12
| minutes)
| EMM_386 wrote:
| More information about FASER here:
|
| https://faser.web.cern.ch/about-the-experiment/detector-desi...
| jkaplan wrote:
| The sophons are here
| xwdv wrote:
| What happens if a neutrino interacts with something?
| flatiron wrote:
| You can tell the tale. It has happened to you!
|
| That pesky sun doing it's pesky fusion.
| lnauta wrote:
| That depends on the energy of the neutrino, for lower energies
| there will be some momentum exchange, but since neutrinos are
| extremely light, this may be neglected depending on your
| experimental setup.
|
| At higher energies (>GeV) depending on the interaction type
| (whether a W-boson or a Z-boson is exchanged), a charged lepton
| comes out, which can be an electron, muon or tau (the tau
| decays very fast) and this is the same as the neutrino flavor.
| Or a hadronic shower if a nucleon is hit.
|
| Of course it's always more complicated than that: for lower
| energies (sub-GeV) you get resonance scattering, where the
| nucleus will emit a meson (quark-anti-quark particle), or deep-
| inelastic scattering, where the nucleus is broken up and
| hadronic particles create a cascade of more particles.
|
| Edit: see https://en.wikipedia.org/wiki/Particle_shower for
| more on these cascades. It's a bit bare-bone, I don't have a
| nice reference right now.
| hinkley wrote:
| Do we calculate the weight of all neutrinos in the Known mass
| of the universe? Or is that part of Dark Matter?
|
| What is the mass of all the neutrinos in a cubic meter of
| "vacuum"?
| adrian_b wrote:
| Usually the neutrino will interact with a nucleus and what
| happens is the reverse of a beta decay, i.e. either a proton
| will be changed into a neutron or a neutron into a proton, with
| the emission of an electron or a positron.
|
| So one atom will be converted into an atom of another element,
| which is a neighbor to it in the periodic table.
|
| Because one neutral lepton goes in and one charged lepton goes
| out, you might say that the neutrino snatches an electric
| charge from a nucleus, transmuting it into the nucleus of
| another element. However this interaction happens extremely
| seldom. In most cases the neutrino passes by without any
| effects.
|
| Nevertheless, there has been a proposal to generate extremely
| powerful neutrino beams, with which to destroy any hidden
| nuclear weapons.
| xwdv wrote:
| So if we could force neutrino interactions at scale we could
| make any element we want in large quantities?
| adrian_b wrote:
| Using neutrinos is far less efficient than using gamma
| radiation or neutrons or high energy electrons or ions for
| transmutations.
|
| The photons/neutrons/electrons/ions have a high probability
| of interaction with the target, while the neutrinos have a
| very low probability of interaction.
|
| All the elements that do not exist in nature due to low
| lifetime have been produced by transmutation, but this can
| be done only for very small quantities at huge prices.
| JProthero wrote:
| Thanks for a great couple of replies. I'd just add that
| there are almost certainly more superheavy elements not
| thought to exist in nature which have yet to be produced
| artificially, but probably will be at some point.
| koheripbal wrote:
| ... but which instantly decay. So not interesting.
| dmurray wrote:
| There are definitely unstable superheavy elements that
| have never yet been produced, or at least detected, but
| the interesting prediction (widely accepted, but far from
| proven) is that there are some stable ones.
|
| [0] https://en.wikipedia.org/wiki/Island_of_stability
| blablabla123 wrote:
| In some sense this is how particle collisions works. You
| collide something and with certain probability you get
| something else at the other end under the physical
| constraints. Probably you want to use bigger particles and
| lower energy though to go from subatomic to
| atomic/molecular scale. The laser ignition fusion
| experiments would be closer to that. (Mind the costs though
| :))
|
| https://en.wikipedia.org/wiki/Stellar_nucleosynthesis
| LegitShady wrote:
| I imagine like a lot of the nuclear alchemy the cost is
| much higher than just getting the existing material you
| want.
| xwdv wrote:
| But for something like a kardashev type 2 or 3
| civilization with abundant energy, it would be trivial
| and saves time searching for and accumulating the
| material? It would also be conflict free.
| hinkley wrote:
| Maybe we could start with processing nuclear waste though.
| koheripbal wrote:
| Having a big pile of random heavy elements can be a worse
| environmental issue.
| [deleted]
| [deleted]
| idontwantthis wrote:
| Would there be any good reason or theoretically practical way to
| use neutrinos for communication?
|
| Asking because in 3 Body Problem it's seen as a "civilized" way
| to communicate compared to radio waves.
| themodelplumber wrote:
| I've wondered the same about gravitons. Notwithstanding the
| need for likely-huge sensing equipment for the first N years of
| development...
| LegitShady wrote:
| It's not yet clear if gravitons exist at all.
| koheripbal wrote:
| Isn't that what the higgs is?
| LegitShady wrote:
| No. The higgs is a field that gives some elementary
| particles themselves (the W and Z bosons) mass, but
| doesn't necessarily say anything about gravity or how
| gravitic 'force' is transferred.
|
| There was a lot of media hype about 'the god particle'
| that doesn't really translate into reality. I've said
| this in another comment, but if you add up the mass of
| the constituent quarks of a neutron, you get
| approximately 1% of a neutron's mass. The majority of the
| mass comes from interactions with strong nuclear force
| which are mediated by gluons, which are themselves
| massless.
|
| There is no current agreed upon understanding of quantum
| gravity or if gravitons exist. I think the big contenders
| right now are String Theory (which seems to be having
| issues progressing in a way that is useful) and loop
| quantum gravity, but there are a lot more theories than
| that.
| Koshkin wrote:
| I have a hard time imagining a particle associated with the
| curvature of spacetime.
| LegitShady wrote:
| the inability of current science to square relativity and
| its predictions of space-time with quantum mechanics is
| exactly the reason why we aren't sure, and one of the
| biggest open questions in physics.
|
| I mean it could all be strings, or quantum gravity, or
| Wolfram's crazy graph theory automatons, or maybe
| something else entirely.
|
| We don't know.
| dr_dshiv wrote:
| I had a really hard time imagining a particle associated
| with mass (Higgs boson)
| Koshkin wrote:
| Doesn't this simply follow from the mass-energy
| equivalence (the energy being that of interaction with
| the Higgs in this case)? Not to say that said equivalence
| is intuitively obvious, of course.
| LegitShady wrote:
| note that the Higgs is not responsible for all mass as is
| understood by a layperson. The Higgs field gives mass to
| subatomic particles but it doesn't translate directly
| into the mass of objects as we know them.
|
| The mass of the three quarks (one up quark and two down
| quarks) making up a neutron is only about 1% of the mass
| of a neutron. The rest of the mass comes from strong
| nuclear force interactions via gluons which are
| themselves massless.
| ForHackernews wrote:
| There have been (theoretical) proposals to use them to
| communicate with submarines:
| http://www.physics.ucla.edu/~hauser/neutrino_communication_p...
|
| > Neutrinos have many properties that would make them superior
| even to the extremely low radio frequencies. Because neutrinos
| are nearly unaffected by matter, a neutrino beam could traverse
| directly through the earth from the transmission site to the
| submarine. A directional beam would allow confidential
| information to be passed only to the intended recipient.
| Neutrino communications would also be totally jam-proof. As an
| additional benefit, a neutrino message could be received in the
| deepest of waters, leaving a submarine less vulnerable to enemy
| attacks.
| jahnu wrote:
| We can collect enough over hundred of days to make a picture of
| the sun*. Bear in mind the absolutely unimaginable quantities
| of neutrinos the sun is producing every femtosecond just in our
| direction and we can barely detect them with a giant apparatus.
|
| https://apod.nasa.gov/apod/ap980605.html
| DrBazza wrote:
| The 'good reason' to use them for communication, if it were
| practical, is that they interact so weakly, you don't have to
| worry about pesky things like planets or stars getting in the
| way of your signal (though gravity is still a thing).
| hn_throwaway_99 wrote:
| Neutrinos are produced by radioactive decay, and they interact
| very weakly with ordinary matter, making them extremely
| difficult to detect.
|
| Seems like the exact opposite qualities of something you'd want
| to use for communication.
| WitCanStain wrote:
| If there were a way to reliably detect neutrinos in
| sufficient quantities they'd be ideal since you could send
| messages through the earth and at near light speed, I
| suppose.
| R0b0t1 wrote:
| Just generate inordinate amounts of neutrinos. Doable for
| something akin to a undersea cable. If we could focus the
| output of the reaction then I see this being feasible,
| otherwise maybe not.
| hungryforcodes wrote:
| As opposed to how we communicate now globally?
| zodiac wrote:
| Communication via EM waves travel around the earth, not
| through it. (eg radio waves, fibre optic cables,
| satellite...)
| dclowd9901 wrote:
| This is important because... line of sight has somehow
| stymied us?
|
| I feel like quantum entangled communication would be a
| better direction to head. Not that they're mutually
| exclusive development paths.
| thatcherc wrote:
| (un?)fortunately quantum entanglement cannot be used to
| send information any faster than classical
| communications. Entanglement is a good way to share bits
| for encrypting secrets, but you still need to be send
| entangled photons over a <c channel like a fiber optic or
| microwave cable.
| dmitrybrant wrote:
| While neutrinos are not very difficult to generate, they are
| extremely, astoundingly difficult to detect. Unless we discover
| a new type of matter that interacts more strongly with
| neutrinos, we're stuck with cavern-sized detectors that can
| detect single-digit numbers of neutrinos (out of many
| trillions), unreliably.
| chasil wrote:
| From the article:
|
| "Casper said that there have only been about 10 observations
| of tau neutrinos in all of human history but that he expects
| his team will be able to double or triple that number over
| the next three years."
| misnome wrote:
| Tau neutrinos, yes, but electron and muon neutrinos are
| significantly easier to identify - the problem with tau
| neutrinos is that when they interact, they produce a tauon,
| which very, very quickly decays so it's hard to know if it
| was a tauon decaying to, say, a muon or electron - which
| look identical to their respective neutrino flavours, or
| one of those neutrinos to begin with.
|
| This is not to say that it's _easy_ to detect the other
| kinds, you still need a large number of neutrinos and a
| large volume for detection. The example that always comes
| up is submarine communication - which has two problems -
| detecting a sparse and intermittent signal to get a useful
| bitrate out, and generating a beam of sufficient intensity
| to begin with, let alone a beam that is steerable!
| make3 wrote:
| so 30
| mrfusion wrote:
| I guess if we found a way to provide say a trillion times
| more neutrinos than normal we could detect that more easily.
| YakBizzarro wrote:
| your "opponent" is the sun that is bombarding us with tons
| of neutrinos. your SNR would be probably bad
| retrac wrote:
| The same problem is faced by optical communication during
| the day with the sensors exposed to sunlight. SNR can be
| increased a fair bit with even slight directionality. If
| sensitivity of detection is one day high enough, I think
| it would be theoretically possible to obtain directional
| information about neutrinos, by building a whole network
| of sensors and synthesizing an aperture.
| CamperBob2 wrote:
| For conventional electronic and optical purposes this
| isn't a huge deal. You "just" modulate the signal to be
| transmitted onto a fixed-frequency carrier, and have the
| receiver ignore everything that's not a sideband of that
| particular carrier frequency.
|
| It's one of those cases where "just" really does apply.
| IR remote controls work this way, using a slow bitstream
| to key a 40 kHz carrier that drives the IR LED.
| Scientific applications that need even greater
| sensitivity can take advantage of the fact that the
| expected phase of the carrier is known as well as its
| frequency. Devices called lock-in amplifiers are used to
| run a wide variety of experiments and processes using
| that principle.
|
| Doing this stuff with neutrinos rather than photons,
| however, is one of those * * * * * exercises that the
| textbook authors put in as a joke.
| tehsauce wrote:
| I think this would be impossible without truly alien
| materials.
| wyldfire wrote:
| Really? Seems like if we were motivated to do it, we
| could have a network of Earth satellite detectors in ~a
| century or so.
| nine_k wrote:
| We need to put a few kilotons of extremely pure water (or
| maybe other transparent substance) into each satellite.
|
| Not impossible, but likely this amount of orbital lift
| capacity is better used for other projects.
| retrac wrote:
| "If the sensitivity gets high enough" is the big if to my
| conjecture. We may never be able to detect enough
| neutrinos to be reliably detect multiple coming from the
| same source passing through multiple detectors.
| ericbarrett wrote:
| Yea, this. 100,000,000,000 solar neutrinos pass through
| your thumbnail every second. This number is not
| substantially different at night, either.
| scythe wrote:
| https://www.nature.com/articles/s41567-018-0319-1
| devoutsalsa wrote:
| Unless I orient the thin edge of my thumbnail so I'm
| presenting the smallest possible cross section towards
| the sun!
| thelittleone wrote:
| I'm not embarrassed to admit I just tried this. I will
| walk around with thumbnail oriented thusly and make my
| observations. Perhaps the origin of the thumbs up? If
| anyone asks I will casually explain that I'm reducing my
| thumbail cross section to minimise the unknown effects of
| solar neutrinos.
| devoutsalsa wrote:
| If you can detect neutrinos below your thumb, I'm
| officially impressed!
| postalrat wrote:
| Not so bad if your detector can detect the direction the
| neutrino came from.
| rowanG077 wrote:
| As long as you have multiple detectors and a neutrino
| stream crosses them you can obtain the direction. I
| assume this is what the poster meant.
| traeregan wrote:
| > _Unless we discover a new type of matter that interacts
| more strongly with neutrinos_
|
| How about astrophage? :)
| [deleted]
| booleandilemma wrote:
| Amaze.
| Faaak wrote:
| Fore those that haven't read it, "Hail Mary" from Andy Weir
| is a quite good book IMHO. It reads quite rapidly and it's
| very enjoying
| [deleted]
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