Slashdot Mirror
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).
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.
I mean, String Theory, not Wikipedia, sorry about that (forgot to include the title of the article, silly me).
AFAIK, light doesn't have a reference frame. Likewise, nothing can travel at a velocity of light and have a reference frame.
By relativity, the velocity of light in all reference frames is equal/constant. Therefore, if you were in light's reference frame, then light would be moving past you at c. However, you are in light's reference frame, so you are moving with the light and the light is not moving past you. Contradiction.
Of course, I'm not an actual physicist, so take this with a grain of salt.
Ewige Blumenkraft.
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.
And you know you are a sceptic when your next thought is,"hold on, they sent these particle's through an object they know next to nothing about and then use the fact that some of them didn't turn up as proof".
Then you read more and you get,"Of course, most of them travel right through our detectors as well, but once in a blue moon one of them will interact - about one or so per day."
I suppose I am being pedantic, but can anybody explain to me why I should believe their explanation that their not turning up in such large numbers is proof?
/. bug #926803 - Why I can post.
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"
But it is natural to ask: what if states of definite flavor and states of definite mass are NOT the same? And which are we measuring in the lab? If they are not the same state, then flavor (the thing we apparently measure in the lab) will change in time and you get "flavor oscillations".
You might ask why normal electrons don't change into muons. This is because for electrons and muons, it appears that states of definite flavor and states of definite mass ARE the same. Not true for neutrinos.
i\hbar\dot{\psi}=\hat{H}\psi
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.
Not quite - the SK result has been confirmed several times (to less precision) by other atmospheric neutrino experiments.
And once before by the K2K accelerator experiment, which was (like MINOS) a controlled, make-your-own-neutrinos, measured-before-and-after sort of experiment. Although one might argue since that used SK as a far detector that it might not be as independant a confirmation as you might like.
The MINOS result is nice because in the first 6 months of a multi-year run, we already have the precision of the K2K results, and that all the experiments point to a similar number. Which makes us feel good that after a few more years work we'll have accomplished the goal of measuring these oscillations way more precisely than ever before, and will have a shot at uncovering more subtle things going on with the neutrinos.
But, that doesn't make good headlines, so you won't read that take on things in the popular press. Same reason as we get a rash of "black holes finally discovered" articles every six months when someone presents some new black hole observations at an AAS meeting.
Fox News had a fun headline though, something like "Feds lose neutrinos, gain knowledge".
PS - note that I'm on both Super-K and MINOS, in fact I created my slashdot account in 1998 to respond to comments about that first SK result. It's pretty neat that doing the experiment a completely different way still shows the same thing happening - so Mother Nature must be up to something real here.
PPS - if you're up in Northern MN for some reason (likely canoeing or fishing) do stop by the Soudan Underground State Park on your way to Ely to take a tour of our lab (and the historic mine). Add a proper geeky component to your otherwise dangerously outdoorsy vacation.
Super-Kamiokande showed that neutrinos have mass if our models about solar neutrino production are correct. (There was a slight day/night shift observed too, but that's statistically weaker). SNO-ball provided strong supporting evidence too, by which point pretty much everyone agreed neutrino mass was right theory, but there's still the question of exactly what the solar neutrino flux is made up of.
MINOS showed the same thing (neutrion oscillations), but this time with a direct measurement of the source neutrino flux and not a model-dependent estimate of the flux. There's really no way to argue with this result, only with the exact mechanism for neutrino oscillation.
-JS
Vanity of vanities, all is vanity...