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Neutrino Mass Confirmed
biohack writes "BBC News reports that results from the MINOS experiment have confirmed that neutrinos have mass. To look for neutrino oscillations, scientists created muon neutrinos in a particle accelerator at the Fermi National Accelerator Laboratory (Fermilab). After passing through a particle detector at Fermilab, a high intensity beam of neutrinos travelled to another particle detector 724km (450 miles) away in a disused mine in Soudan, US. The set up established that fewer particles were being detected at the Soudan site than had been sent from Fermilab, which confirmed that some neutrinos changed their flavor on the way - an effect called neutrino flavor oscillation, which requires them to have mass. 'To put it simply, if they are heavy, it means that there is a lot more mass in the Universe than we thought there was,' said Professor Jenny Thomas from University College London."
I've actually seen the detector at the Soudan Mine. Pretty impressive. Kinda hard to get to (300 mile drive into the middle of nowhere followed by a half mile trip underground).
Thats is sloppy on the BBC's part, they should have put the State in there. In this case it is Minnesota.
e rground_mine/physicslab.html
http://www.dnr.state.mn.us/state_parks/soudan_und
You know you are a serious geek when you read the headline and say 'YES!' out loud.
Would slashdot also be interested in posting my own confirmations that light has a finite speed?
When things get complex, multiply by the complex conjugate.
Minos? Muons? Soudan? They're just making stuff up! This article just reeks of April Fools!! /Peter Griffin Voice
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
SNO Detector.
This was proven in the late 90's in a Japanese lab. The experiment was similar and involved muon neutrinos changing flavors to electron neutrinos in a large particle accelerator. The real question is how many eV are the combined masses of the three flavors? The answer to that question portends much for the state of the universe.
Making you think you're crazy is a billion dollar industry.
New evidence has confirmed that the Universe does in fact have mass. Science advisor for the Bush administration was quick to point out that this is a theory and there was still no hard evidence. "The Bible makes no mention of the Universe having mass so we'll have to wait until a method is devised for weighing the Universe. We don't want any more psedoscience like that Darwin character was spreading."
Could these particles having mass explain the "missing matter" that scientists formerly attributed to dark matter? I wonder what other particles are there taking up space that we never thought had mass, either.
today is spelling optional day.
Although the article implies that the Standard Model will have to be revised as a result of this experiment, this result does not really change the Standard Model all that much. The theoretical method used to establish neutrino mass, ie- that neutrino oscillations imply neutrino mass, is itself a Standard Model prediction. Rather the results fixes some of the unbound parameters of the theory. In other words, the arguments are better known now, but the method signatures remian the same.
- Matter has mass and is made of particles.
- Light has no mass and is made of waves.
Nowadays it's more like this:- Fermions are wave-particles that have half-integer spin. Atoms are made of fermions.
- Bosons are wave-particles that have integer spins. Bosons are the things that carry forces.
All the familiar, everyday fermions have nonzero rest mass, and the only familiar, everyday boson -- the photon -- has zero rest mass. However, there are bosons that have nonzero rest mass (e.g., gluons), and it's also possible that there are fermions that have zero rest mass. (Experiments so far only measure the differences between masses of different types of neutrinos, so it's still possible that the electron's neutrino has zero mass.)Find free books.
We'll have to wait and see, but for anyone who would like more information, Fermilab's website has an article about the discovery.
There is a large bit of hand waving here. Why are neutrino oscillations and neutrino mass inseparable?
I hate when people act as if a complicated issue is simply true. So, as a public service to the Slashdot community:
Here is a site that attempts to explain it.
My quantum physics knowledge isn't teriffic. Any particle physicists know of a better source?
Um, no, you're just completely wrong here.
Neutrinos are also very important in understanding the mechanics of radioactive decay. Remember, the entire premise from which neutrinos came from was that decay needed a massless particle that could carry with it rotational momentum. Since neutrinos have M amount of mass, then the sum of all other actual and effective masses being emitted must be reduced by M, for the calculations to still balance out.
No, the mass/energy scale -- eV -- is wrong for it to have any significant effect on nuclear beta decay, where the mass/energy scale is MeV.
Find free books.
I joined the experiment in 1995 soon after the collaboration came together and created the proposal. In that time I've written simulation ("Monte Carlo"), reconstruction and framework code for the experiment. It's been a pretty exciting 10 years. The push to get everything together this last month has been exhausting. But after presenting the results on Thursday do we physicists take a well deserved break and party like 1999? Well, noooo. We spend Friday, Saturday and Sunday IN MEETINGS! Today (Saturday) we were there from 8:30am to 7:00pm discussing how further to proceed. We've got 50% more data "in the can" that we didn't yet present (cross checks to perform, fits to perform). Plus plans for more data taking after the accelerator comes up again in June. Plus other physics results we're still trying to extract. Plus more improved simulations to do in order to yield improved limits. Such is the life of a physicist.
is this an April fools joke I'm too dumb to understand?
Neutrinos have mass? I didn't even know they were Catholic!
This may be one of the last discoveries at Fermilab. As it stands now, Fermilab, SLAC, and Brookhaven's future is in severe doubt.
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http://www.sciam.com/article.cfm?chanID=sa006&art
"To those who are overly cautious, everything is impossible. "
Neutrino? What, Is that like the new Pentium or something?
"To put it simply, if they are heavy, it means that there is a lot more mass in the Universe than we thought there was..."
So what this means is that people are really a lot fatter than what they think they are.
How I am a going to explain to my wife tomorrow when I say "Yes" to her saying "Am I fatter today?" - I'll pack my bags now and save myself some time. ummm, I may want to book a room too!
Never try to beat a professional at his own game!
Bosons don't necessarily carry forces; in fact not all atoms are fermions. For example, the Helium-4 and Carbon-12 nuclei is a boson. See wikipedia. Bosons are best defined as having integer spin and being capable of sharing the same quantum state while fermions have half-integer spin and obey the Pauil Exclusion Principle (cannot share the same quantum state). A composite particle of an even number of fermions (2 protons + 2 neutrons) is a boson (helium nucleus) but an odd number of fermions is always a fermion.
I also believe that physicists have determined that the electron neutrino has a mass of about 1meV-1eV (from a slide I saw in lecture a couple days ago).
In addition, physicists divide fermions into quarks and leptons, which are supersets of the elementary particles that make up nucleons and electrons.
Not only is neutrino mass important, it will make (IMHO) a fundamental change to the way in which we analyse cosmology. Although IANAP (I Am Not A Physicist) I would be more that interested to learn how this affects the concepts of dark matter, gravitational irregularity (deviations from the inverse-square law that have been suggested), and the neccesity for the existence of Black Holes to explain invisible mass and the motion of galaxies. Does the non-zero mass of neutrinos wipe out all of these uncomfortable irregularities in physics? I don't know - but I do hope so!
"Rafiniert ist der Herrgott, aber boshaft ist er nicht."
Ian D. K. Kelly
idkk Consultancy Ltd.
"Quality through Thought"
That was discovered back in Stardate 43349.2 when Wesley was tinkering with his Neutrino pulse beacon. Don't you guys watch TV?
There are 10 types of people in the world; those who can read binary, and those who can't.
have a look at this. it's the transcript from the BBC's recent "horizon" show, called "project poltergeist", which is on precisely this topic (neutrinos having mass). very neatly explains to a lay audience what the mystery is, and also answers exactly your specific question. it's not a long read, maybe 10mins max, and as it's the transcript to the show it leads you through the topic in a well thought out manner http://www.bbc.co.uk/science/horizon/2004/polterge isttrans.shtml
and the short answer to your question is as follows: in order to undergo neutrino oscillation, the neutrino must be capable of change. to be capable of change it must experience a personal sense of time. if it was travelling at the speed of light, it would have no sense of time. objects with mass cannot travel at the speed of light (infinite energy required for objects with mass to do this). therefore, as we experimentally can confirm neutrino oscillation, we are also confirming that neutrinos have a sense of time, which implies they are not travelling at the speed of light, which implies they have mass.
hope that clears it up -- on a side-note my first degree was actually in astrophysics, at University College London (UCL), where the article's quoted scientist comes from... didn't have her for any of my lecures though ;)
I'm glad to see people excited about this result! Super-K and others had discovered neutrino masses first, but this was the most controlled experiment to date - they made the neutrinos, examined them when they left the accelerator, and examined them again 700 km away. Any modifications to the Standard Model are very exciting.
One thing I feel obligated to point out, however: this has nothing to do with string theory. String theory is a framework for thinking about how to unify the known Standard Model with general relativity. It's incredibly interesting, both from a physics point of view and as a purely mathematical construct. However, it has no prediction about neutrino mass, or indeed about anything remotely accessible to experiment (except, perhaps, that supersymmetry should be true at some level), and has little prospect of making such predictions anytime soon.
Many posters seem to jump to the conclusion that if something is new in physics (whether it be neutrino mass or supersolids) then it MUST somehow be confirming string theory. String theory is very pretty and I hope it's true, but not everything in physics points back to it.
Sorry for the physicists' rant, no offense intended.
Dark matter (mass we can't see) has several components: ordinary (protons, neutrons, electrons) matter we happen to be unable to see, exotic matter that we do understand, and exotic matter that we don't understand. You could go into a Rumsfeld-esque discussion of "known unknowns" and "unknown unknowns" at this point.
When people talk about dark matter, they usually mean the exotic stuff, since there is a lot of evidence that the bulk of the universe's matter is exotic (look up "big bang nucleosynthesis" for details).
Neutrinos make up some of the exotic stuff, and how much depends on their mass. It turns out that they can't make up nearly enough of it, however. Furthermore, neutrinos are light particles which move at speeds near that of light. This means they don't clump together under their own gravity very easily, and tend to disrupt the formation of galaxy clusters. From looking at the distribution of galaxies in the universe, we can argue that most of the exotic dark matter must be slow-moving and "clumpable". The bulk of what people mean by dark matter is this stuff, which can't be neutrinos.
A massless particle (like the photon) should move at exactly the speed of light, while a massive particle should always move slower than light. We always used to say that neutrinos move at the speed of light because we assumed they had no mass. Now that we know they are massive, they must be moving slower. They are so incredibly light, however, that we expect them to be moving extremely close to that speed - it takes very little force to accelerate them, so anything energetic enough to make them would make them go very fast.
If photons (quanta of light) had mass, the world around us would be very different. Photons mediate the electromagnetic force, which is responsible for light, the pull of magnets, the fact that electrons stay in their orbits, etc. If the photon were massive this force would become short-range - its strength would decay exponentially with distance (like the weak nuclear force), rather than as an inverse-square law. We have done ridiculously precise tests of the inverse-square law, which translates into very tight constraints on photon mass.