> 1. If an electron neutrino can spontaneously transform to a tau neutrino with higher mass, where exactly does the required energy come from? Alternatively, when a tau neutrino transforms to an electron neutrino, where does the extra energy disappear?
It is not yet known which neutrino has the higher mass. Also, when we say electron-, muon- or tau-neutrino we are speaking of weak-eigenstates, something that is well defined at the point of interaction (only). These do not even have a definite mass (they are not mass eigenstates) although they do have a mass expectation value (average, expected mass). Instead they are a super-position of the 3 mass eigenstates. This superposition changes as the neutrino wave packet propagates. This is because each mass eigenstate propagates independently and since energy must must be conserved, each mass eigenstate will travel at different speeds. This propagation then leads to oscillations, or the mixing of weak eigenstates. If the neutrino wave package is detected later, one may see an outgoing electron, muon or tau even if one starts, in the case of OPERA, with a muon-neutrino (and the neutrino energy is at least high enough to produce the outgoing lepton mass).
> 2. If neutrinos have mass, then they are restricted to speeds below c. If they are accelerated to near c, then according to the relativistic energy-momentum equations they should have colossal mass, not miniscule (just like electrons, for example). Is there any evidence of observing neutrinos with huge energies?
Well, particle masses do not change with speed. One can couch relativistic equations into an effective mass, which does increase with speed. But, in any case, only (rest) mass differences matter in neutrino oscillations (differences of squares of masses, actually).
Experiments like IceCube look for and see incredibly and not fully explainable high energy neutrino interactions.
Your questions are not well addressed by the press release. There are two items that are missing: There are no tau neutrinos in the beam to begin with so any that are found are best explained by oscillation. The signature for a tau neutrino interaction, in this case, is a "kink" in the track produced from the outgoing tau traveling for some distance and then decaying to a muon. This signature reduces the background to negligent levels. And, yes, if background is small enough then even a single event is statistically significant.
for information on an effort to make a coincidence trigger from the many large neutrino detectors around the world. This is in order to reduce the number of false positives to one per century.
That exploit returns an assuring null, at
least on firmware 1.42.7, Apr 23 2002. BTW,
the code on the netstumbler site has large
chunks of it eaten by html-izing it. The original
can be found in this PDF file.
here
For a very long time, Ray Davis stood alone in saying there was a deficit of electron type neutrinos coming from the sun, despite criticisms that his experiment must be wrong.
Koshiba started Kamiokande which begat Super-Kamiokande, which (along with IMB) confirmed Ray's results but also showed oscillations in atmospheric neutrinos and pushed proton decay lifetime limits further than any other experiment.
These experiments fundamentally changed our view of neutrinos. So, yes, I think their originators each deserve a Nobel of their own, let alone 1/4 of one.
Wasn't it done by Super Kamiokande experiment back in 1998?
This was the anouncement of the atmospheric neutrino results which pinned down neutrino mixing between muon and tau nus better than ever before.
SK also sees solar nus but only the electron neutrinos. In addition to the electron neutrino, SNO can also see the sum of all solar neutrino types (ie, the electron type as well as other types that the e-type may have oscillated to). Their first result relied on SK's measurement of the electron type nus because SNO has a smaller mass, thus lower count. The latest announcement appears to be stating that they have collected enough events that they can have a similar result as before but with out relying on some of SK's data.
The report says that workers, with little or no protection against hazardous materials, burned plastics and circuit boards or poured acid on electronic parts to extract silver and gold.
The effect was to fill the air with carcinogenic smoke and pollute the water, said the report.
I guess my point is really that there is no guarantee that a volunteer effort will embrace uninformed questions and that a project like mplayer isn't the place for newbies to cut their teeth.
Thankfully, most free software groups are not like the MPlayer group in that they are more tolerant of newbies asking beginner questions. Also, when I say I understand their actions, doesn't mean I condone them.
As for the non-free aspect, this refers mostly to the codecs I guess? For the code part, they say "[they] are still developing towards GPL", whatever that means. It seems their development model is "grab whatever is out there and make it work", one seen in other projects. This makes it hard to keep licences compatible but will hopefully be worked out in the end. (If not, surely RMS will come to the rescue!). This sort-of-non-free state of affairs is unfortunate and one of those ideals/practicality trade offs. I am just glad I don't *need* to view DVDs and video downloads so I don't feel I am selling my soul for shiny baubles (well, I am, but they are disposable baubles).
And I can confirm that the latest mplayer won't play Vendetta_Part_2.mov.
As for this <whine>MPlayer group isn't nice to me</whine>. Whatever. I just went through the process of reinstalling the latested version from CVS and I found that their DOCS had all the info needed. It wasn't easy to install correctly, sure, but what you need to know to do it is clearly spelled out in the volumnious docs. It is an intricate and complicated install process due to all the wide ranging things needed (kernel, X11, dri, etc) things that have to be set up. But, the problem mplayer solves is not a simple so (at this stage) one shouldn't expect simplicity. I can understand how they don't want to be bothered by clueless newbies so that they can instead spend more of their time hacking on this *GPL*ed program.
Sure, maybe it would be nice if they had more tact, but, come one, get over it, they are *volunteers*!
wu-ftpd runs chrooted (for anonftp) so normally you can only see what is in the ~ftp/ dir by default. Besides openning up all files to an anonftp user is also allows the running of arbitrary code on the server, so full root shell is possible.
The main page, www-sk.icrr.u-tokyo.ac.jp has some
"press" sized pics, last I checked. Yes, here:
http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/photo/hi gh.html
Well, at least hydrostatics doesn't, which is the useful discipline in expressing water pressure as a function of depth.
You are both half wrong/right. The pressure at a certain depth is hydrostatic, but the implosion cascade is a hydrodynamic effect caused by the pressure wave from the first imploded PMT producing a pressure differential (and thus a net force) across the neighbor PMTs. If we assume a pressure differential of 1 atmoshphere, this translates more than 2 tons of net force (not balanced hydrostaic force) on the PMT. Those PMTs are extreamly strong, but drop a car on one and they will break.
That's the purpose of reducing the amount of sensors in the array. Increasing the spacing will reduce the chances of another chain reaction.
The reason for reducing the PMT coverage is simply the lack of 50 cm PMTs this world has. The added spacing that results may, as you say, reduce the chance of another cascade implosion, but it needs to be check that it will reduce it enough to be safe.
(The strength of the shock wave falls off according to the square power law. (IIRC))
I haven't checked, but there probably is indeed a 1/r^2 falloff. But there will be another component of the fall off because the wave will disapate. Think of the first moment of implosion, the pressure wave is vacuum on one side and 3 to 4 atmosphere on the other. By the time the pressure front reaches the neighbor PMT the pressure gradient must be something less than a step function.
The tank would have been closed durring filling, so nothing could have dropped in. The fill rate would certainly be close to the same as the first time it was filled (where no damage occured) and since the tank was more than half filled already when the event happened, I can't see how the fill rate would even come to play in this mystery.
The "cascade of implosions" was tested years ago, (but not in exactly the PMT configuration used in SK proper) and the neighboring PMTs were found to survive.
Slashdot Mirror
With Monte Carlo simulations the background has been estimated (http://arxiv.org/abs/0910.3468) to be 10%.
> 1. If an electron neutrino can spontaneously transform to a tau neutrino with higher mass, where exactly does the required energy come from? Alternatively, when a tau neutrino transforms to an electron neutrino, where does the extra energy disappear?
It is not yet known which neutrino has the higher mass. Also, when we say electron-, muon- or tau-neutrino we are speaking of weak-eigenstates, something that is well defined at the point of interaction (only). These do not even have a definite mass (they are not mass eigenstates) although they do have a mass expectation value (average, expected mass). Instead they are a super-position of the 3 mass eigenstates. This superposition changes as the neutrino wave packet propagates. This is because each mass eigenstate propagates independently and since energy must must be conserved, each mass eigenstate will travel at different speeds. This propagation then leads to oscillations, or the mixing of weak eigenstates. If the neutrino wave package is detected later, one may see an outgoing electron, muon or tau even if one starts, in the case of OPERA, with a muon-neutrino (and the neutrino energy is at least high enough to produce the outgoing lepton mass).
> 2. If neutrinos have mass, then they are restricted to speeds below c. If they are accelerated to near c, then according to the relativistic energy-momentum equations they should have colossal mass, not miniscule (just like electrons, for example). Is there any evidence of observing neutrinos with huge energies?
Well, particle masses do not change with speed. One can couch relativistic equations into an effective mass, which does increase with speed. But, in any case, only (rest) mass differences matter in neutrino oscillations (differences of squares of masses, actually).
Experiments like IceCube look for and see incredibly and not fully explainable high energy neutrino interactions.
Your questions are not well addressed by the press release. There are two items that are missing: There are no tau neutrinos in the beam to begin with so any that are found are best explained by oscillation. The signature for a tau neutrino interaction, in this case, is a "kink" in the track produced from the outgoing tau traveling for some distance and then decaying to a muon. This signature reduces the background to negligent levels. And, yes, if background is small enough then even a single event is statistically significant.
> Please forgive me in advance for asking, but why is this important?
Because it confirms part of our understanding of our universe. What more is there?
3.5 works fine when explicitly installed under WINE. I did that today. The face recognition is pretty cool.
So, then I guess this is a dead link: http://picasa.google.com/linux/
Most recently: Having to click on the comments link instead of the "Read more..." as the latter took me to a blank page.
In general there have been several times where I had to actually edit someones source code and recompile to work around some bug. Unbelievable!
See
http://snews.bnl.gov/
for information on an effort to make a coincidence trigger from the many large neutrino detectors around the world. This is in order to reduce the number of false positives to one per century.
Read it at: http://www.howtobrew.com/intro.html
WTF?! Have you looked at tax returns recently? Are you wealthy?
That exploit returns an assuring null, at least on firmware 1.42.7, Apr 23 2002. BTW, the code on the netstumbler site has large chunks of it eaten by html-izing it. The original can be found in this PDF file. here
For a very long time, Ray Davis stood alone in saying there was a deficit of electron type neutrinos coming from the sun, despite criticisms that his experiment must be wrong.
Koshiba started Kamiokande which begat Super-Kamiokande, which (along with IMB) confirmed Ray's results but also showed oscillations in atmospheric neutrinos and pushed proton decay lifetime limits further than any other experiment.
These experiments fundamentally changed our view of neutrinos. So, yes, I think their originators each deserve a Nobel of their own, let alone 1/4 of one.
What is the most expensive meal you did on TV, not
including the travel, just ingredients?
When will you have the Amber Waves of Grain show?
You need to kick "The Thirsty Traveler" off !!!
This was the anouncement of the atmospheric neutrino results which pinned down neutrino mixing between muon and tau nus better than ever before.
SK also sees solar nus but only the electron neutrinos. In addition to the electron neutrino, SNO can also see the sum of all solar neutrino types (ie, the electron type as well as other types that the e-type may have oscillated to). Their first result relied on SK's measurement of the electron type nus because SNO has a smaller mass, thus lower count. The latest announcement appears to be stating that they have collected enough events that they can have a similar result as before but with out relying on some of SK's data.
Stars stop burning at iron not helium.
Patient: "Hey, Doctor, it hurts when I do this!"
Doctor: "Don't do that."
Thankfully, most free software groups are not like the MPlayer group in that they are more tolerant of newbies asking beginner questions. Also, when I say I understand their actions, doesn't mean I condone them.
As for the non-free aspect, this refers mostly to the codecs I guess? For the code part, they say "[they] are still developing towards GPL", whatever that means. It seems their development model is "grab whatever is out there and make it work", one seen in other projects. This makes it hard to keep licences compatible but will hopefully be worked out in the end. (If not, surely RMS will come to the rescue!). This sort-of-non-free state of affairs is unfortunate and one of those ideals/practicality trade offs. I am just glad I don't *need* to view DVDs and video downloads so I don't feel I am selling my soul for shiny baubles (well, I am, but they are disposable baubles).
And I can confirm that the latest mplayer won't play Vendetta_Part_2.mov.
As for this <whine>MPlayer group isn't nice to me</whine>. Whatever. I just went through the process of reinstalling the latested version from CVS and I found that their DOCS had all the info needed. It wasn't easy to install correctly, sure, but what you need to know to do it is clearly spelled out in the volumnious docs. It is an intricate and complicated install process due to all the wide ranging things needed (kernel, X11, dri, etc) things that have to be set up. But, the problem mplayer solves is not a simple so (at this stage) one shouldn't expect simplicity. I can understand how they don't want to be bothered by clueless newbies so that they can instead spend more of their time hacking on this *GPL*ed program.
Sure, maybe it would be nice if they had more tact, but, come one, get over it, they are *volunteers*!
wu-ftpd runs chrooted (for anonftp) so normally you can only see what is in the ~ftp/ dir by default. Besides openning up all files to an anonftp user is also allows the running of arbitrary code on the server, so full root shell is possible.
s/don't/do/
The main page, www-sk.icrr.u-tokyo.ac.jp has somei gh .html
"press" sized pics, last I checked. Yes, here:
http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/photo/h
You are both half wrong/right. The pressure at a certain depth is hydrostatic, but the implosion cascade is a hydrodynamic effect caused by the pressure wave from the first imploded PMT producing a pressure differential (and thus a net force) across the neighbor PMTs. If we assume a pressure differential of 1 atmoshphere, this translates more than 2 tons of net force (not balanced hydrostaic force) on the PMT. Those PMTs are extreamly strong, but drop a car on one and they will break.
The reason for reducing the PMT coverage is simply the lack of 50 cm PMTs this world has. The added spacing that results may, as you say, reduce the chance of another cascade implosion, but it needs to be check that it will reduce it enough to be safe.
(The strength of the shock wave falls off according to the square power law. (IIRC))
I haven't checked, but there probably is indeed a 1/r^2 falloff. But there will be another component of the fall off because the wave will disapate. Think of the first moment of implosion, the pressure wave is vacuum on one side and 3 to 4 atmosphere on the other. By the time the pressure front reaches the neighbor PMT the pressure gradient must be something less than a step function.
The tank would have been closed durring filling, so nothing could have dropped in. The fill rate would certainly be close to the same as the first time it was filled (where no damage occured) and since the tank was more than half filled already when the event happened, I can't see how the fill rate would even come to play in this mystery.
The "cascade of implosions" was tested years ago, (but not in exactly the PMT configuration used in SK proper) and the neighboring PMTs were found to survive.