[WARNING: This entry is filled with science geekiness. Turn away now, or I cannot be responsible for the consequences!]
Looking at my calendar this morning, I noticed that February seems to be almost over. Surely this cannot be right! Where did all the time go?
One of the things that the impending Marchness means is that I have two lectures coming up fast -- one in March (Cosmic Rays: Messengers from the Extreme Universe at the Cody Astronomy Society monthly meeting) and one in April (Neutrino Astronomy at the Oxford University Annual Astronomy Weekend).
I am not particularly nervous about the first... as I will essentially recycle a lecture that I gave twice last year. All I really need to do is update with the latest results from the Pierre Auger Observatory, presented at the 2009 International Cosmic Ray Conference. Shouldn't take too long.
Although more interesting to me, preparing the Neutrino Astronomy lecture will take considerably more time. I will, of course, speak about the detection of neutrinos from a supernova burst, the search for relic neutrinos from supernovae in the early universe[*], solar neutrino measurements, searches for correlations with gamma ray bursts, and attempts to detect astrophysical point sources of neutrinos. Some of the cutting edge work here, particularly on the first topics that I mentioned, comes from the Super-Kamiokande experiment... and so I am well acquainted with the state of the art. For other topics, particularly the latter ones on my list, the Ice Cube neutrino telescope -- located at the South Pole -- is really the global leader. This means that I had best find some time soon to catch up on what the Ice Cube people have been doing! Should be rather interesting, if I can only find that magic wand to wave to create the time!
Most of you can stop reading now -- assuming that you have not already! For those who still want more, however, please see the question that I was recently asked the following by my old friend
blaisepascal:
My response -- which began life as an LJ comment but has now risen in the world to the front page -- follows:
That's an interesting question... and I'm not 100% sure about the answer! I would venture, as an educated guess, that Kamiokande was stopped in 1996, because they would not have ceased operations Kamiokande until Super-Kamiokande was running, thus ensuring that neutrinos from a supernova would not be missed. SK began taking data in the halcyon days of April 1996, so I imagine that the original "K" was shut down soon after. To back this up with second-hand anecdotal evidence, I recall hearing that early Super-Kamiokande shift work involved checking in on Kamiokande to make certain that it was still running smoothly.
What I do know is that a colleague who joined Super-K in 1997 got to see a [non-functional] Kamiokande... whereas I, joining in 1998, did not. By that time, the detector had been dismantled and the site was being prepared for construction of the KamLAND detector.
As far as proton decay goes, you may wish to see the following paper from last year: arXiv:0903.0676. This paper reports the latest limits on the lifetime of a proton decaying to a positron plus a neutral pion, as well as the mode where the proton decays to an mu+ and a neutral pion. Alas, I wish the actual limits were so good as yours! The current limit on p -> e+ π0 is 8.2 x 1033 years. That's over an order of magnitude less than your estimate!
One thing that you should know is that the total mass of Super-Kamiokande is 50 kt... but the fiducial mass used for analysis is 22.5 kt. Some of the water is in the outer detector, which serves as a passive shield and an active veto. The inner detector, instrumented for precision neutrino analysis, only contains about 32.5 kt. However, events occurring within two meters of the walls are also disregarded, as the reconstruction for such events is poor[**] and, at the lowest energies, there is a high background. Still the reduction from 30 kt to 22.5 kt would only worsen your limit by 25%... not an order of magnitude. I'm guessing that the main difference is in detection efficiency -- you probably assume a 100% efficiency, whereas the actual detector would not perform so well. Still, take a look at the paper that I linked to and let me know!
So, class..... any questions?
[*] The leading work on this topic was done by your Friendly Neighborhood Nomad, which earned him his PhD.
[**] One of the main projects that I, and two of my Imperial College students, are involved with for T2K is enlarging the volume that we use for analysis. It looks like we may be able to get an 18% increase in statistics... although the work is ongoing and, as such, it is too soon to say for sure.
Looking at my calendar this morning, I noticed that February seems to be almost over. Surely this cannot be right! Where did all the time go?
One of the things that the impending Marchness means is that I have two lectures coming up fast -- one in March (Cosmic Rays: Messengers from the Extreme Universe at the Cody Astronomy Society monthly meeting) and one in April (Neutrino Astronomy at the Oxford University Annual Astronomy Weekend).
I am not particularly nervous about the first... as I will essentially recycle a lecture that I gave twice last year. All I really need to do is update with the latest results from the Pierre Auger Observatory, presented at the 2009 International Cosmic Ray Conference. Shouldn't take too long.
Although more interesting to me, preparing the Neutrino Astronomy lecture will take considerably more time. I will, of course, speak about the detection of neutrinos from a supernova burst, the search for relic neutrinos from supernovae in the early universe[*], solar neutrino measurements, searches for correlations with gamma ray bursts, and attempts to detect astrophysical point sources of neutrinos. Some of the cutting edge work here, particularly on the first topics that I mentioned, comes from the Super-Kamiokande experiment... and so I am well acquainted with the state of the art. For other topics, particularly the latter ones on my list, the Ice Cube neutrino telescope -- located at the South Pole -- is really the global leader. This means that I had best find some time soon to catch up on what the Ice Cube people have been doing! Should be rather interesting, if I can only find that magic wand to wave to create the time!
Most of you can stop reading now -- assuming that you have not already! For those who still want more, however, please see the question that I was recently asked the following by my old friend
![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
Do you happen to know when KamiokaNDE was shut down for good? I was trying to demonstrate the other day how we can compute a lower-limit on the lifetime of the proton, and I couldn't find how long KamiokaNDE ran for. The Kamioka Observatory web-site doesn't have a lot of information on past experiments, and it doesn't have information on the total runtime of KamiokaNDE.
(FYI, I computed 1034/6 years for KamiokaNDE, and 1035/6 years for Super-K for a 95% confidence level. The Super-K should be higher because I simplified my math by assuming 30k tonnes of water, not 50k tonnes.)
My response -- which began life as an LJ comment but has now risen in the world to the front page -- follows:
That's an interesting question... and I'm not 100% sure about the answer! I would venture, as an educated guess, that Kamiokande was stopped in 1996, because they would not have ceased operations Kamiokande until Super-Kamiokande was running, thus ensuring that neutrinos from a supernova would not be missed. SK began taking data in the halcyon days of April 1996, so I imagine that the original "K" was shut down soon after. To back this up with second-hand anecdotal evidence, I recall hearing that early Super-Kamiokande shift work involved checking in on Kamiokande to make certain that it was still running smoothly.
What I do know is that a colleague who joined Super-K in 1997 got to see a [non-functional] Kamiokande... whereas I, joining in 1998, did not. By that time, the detector had been dismantled and the site was being prepared for construction of the KamLAND detector.
As far as proton decay goes, you may wish to see the following paper from last year: arXiv:0903.0676. This paper reports the latest limits on the lifetime of a proton decaying to a positron plus a neutral pion, as well as the mode where the proton decays to an mu+ and a neutral pion. Alas, I wish the actual limits were so good as yours! The current limit on p -> e+ π0 is 8.2 x 1033 years. That's over an order of magnitude less than your estimate!
One thing that you should know is that the total mass of Super-Kamiokande is 50 kt... but the fiducial mass used for analysis is 22.5 kt. Some of the water is in the outer detector, which serves as a passive shield and an active veto. The inner detector, instrumented for precision neutrino analysis, only contains about 32.5 kt. However, events occurring within two meters of the walls are also disregarded, as the reconstruction for such events is poor[**] and, at the lowest energies, there is a high background. Still the reduction from 30 kt to 22.5 kt would only worsen your limit by 25%... not an order of magnitude. I'm guessing that the main difference is in detection efficiency -- you probably assume a 100% efficiency, whereas the actual detector would not perform so well. Still, take a look at the paper that I linked to and let me know!
So, class..... any questions?
[*] The leading work on this topic was done by your Friendly Neighborhood Nomad, which earned him his PhD.
[**] One of the main projects that I, and two of my Imperial College students, are involved with for T2K is enlarging the volume that we use for analysis. It looks like we may be able to get an 18% increase in statistics... although the work is ongoing and, as such, it is too soon to say for sure.
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