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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).
You know you are a serious geek when you read the headline and say 'YES!' out loud.
... as claimed in 1998 Scientific American article
--- Attorneys Assisting Citizen-Soldiers & Families -
http://en.wikipedia.org/wiki/Dark_Matter#Compositi on
...short answer is: yes it has been considered, but current models of neutrino formation suggest they can't account for all dark matter (or even a significant component of it).
http://en.wikipedia.org/wiki/Hot_dark_matter
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.
The experiment was similar and involved muon neutrinos changing flavors to electron neutrinos in a large particle accelerator.
No, it wasn't an accelerator, and the experiment wasn't similar.
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.
No, not really. Not unless the mass of the electron's neutrino is surprisingly large compared to the mass differences among the different types of neutrinos.
Find free books.
Okay, as a particle physicist, I learned about this in terms of the Hamiltonian evolution of a wavefunction, and some analogy to neutral kaons, and a page of math. But thats not what you wanted to hear.
A physicist on the recent Nova special "The Ghost Particle" (Maybe it was Boris Kayser) had a nice explanation. If neutrinos have no mass, then they travel at the speed of light. If they travel at the speed of light, then they would not experience "time". Since changing flavor is a process that takes time, or duration, or something like that (this previous clause is maybe a non-trivial thing to say), then if neutrinos change flavor, they must experience time, so they must travel slower than the speed of light, so they must have some mass.
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.
The US is a federation of 50 sovereign states (each with the size and economy to match), and saying "Foo City, US" would be like saying "Foo City, EU" (though Europe has the advantage of many languages to broaden the name space).
While this is true, it's somewhat misleading, especially to those will limited knowledge of U.S. history or government. Even many Americans don't understand the difference between as state and a province.
State governments in the U.S. function approximately equally to provincial governments in countries that are not federations. Most of them were not originally independant countries, but were instead provinces and territories that were sponsored into statehood.
A significant fraction of the United States were indeed independant countries at one point. ALL U.S. states have significantly more rights than any given province. Each has its own constitution and government, and, contrary to popular opinion, the states elect the President and Senators. The U.S. president is *not* elected by a popular vote. (Although there have been calls to change this.) A few, most notably Texas, still claim the right to secede from the Union, although no state has really had this right since the end of the American Civil War in the late 1800s.
The U.S. constitution sets up the states as individual entities, unlike provinces. They can each impose their own taxes and own laws. In fact, this is one of the major contentions in our government to this day. States can theoretically impose any law that the constitution doesn't reserve for the Federal government. This causes a lot of conflict and consternation since States are also required to respect contracts formed in other states, frequently under a different set of laws and regulations.
The conflict over gay marriage contracts is one of the more recent flaps this has caused.
States can also each maintain their own militias. Many states have 'State Troopers', who usually do the same kind of jobs as normal policemen, albeit with greatly expanded jurisdiction. A few states have 'State Guards', although they usually don't server a military purpose. They usually come to the fore during natural disasters and the like.
While the U.S. is an extremely tight federation-- the word 'Union' is very accurate-- it is still a federation. Each state is indeed its own nation.
The next Slashdot story will be ready soon, but subscribers can beat the rush and slashdot the links early!
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. "
Thats is sloppy on the BBC's part, they should have put the State in there.
Why? They don't care anymore than we (Americans) care that Tijuana, Mexico is more appropriately, "Tijuana, BC, Mexico".
To us, the state is important, but to the British, it's really not that pertinent. The point is that the detector is in the US, not what particular state it's in.
Given how awful most Americans are at geography, your complaint comes off trite and arrogant, sort of like you require people to call you by your full name and title, yet you don't really care whether you get anyone else's name right at all.
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 ;)
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.