Article

2016-02-26 Science

Reactor data hint at existence of fourth neutrino

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Posted by Sven the pelter 2016-02-26 00:00|| || Front Page|| [2 views ] Top

#1 1/R^2 bites pretty hard, though. And if you want directional answers, the resolution needs to be very good and the interaction medium density low--which makes the instrumentation more costly and the detectors even bigger.

Posted by james 2016-02-26 14:40|| http://idontknowbut.blogspot.com 2016-02-26 14:40|| Front Page Top

#2 There could be multiple detectors to allow triangulation. The more detector fluid the greater the chance of detection via a weak force interaction so a cylinder which can be rotated to point in a given direction. Low detection odds except down the length.

Just speculating.

Posted by Sven the pelter 2016-02-26 15:21|| 2016-02-26 15:21|| Front Page Top

#3 Sh*t. I hope nobody has already built one.

Posted by Sven the pelter 2016-02-26 16:20|| 2016-02-26 16:20|| Front Page Top

#4 To first order, orientation won't matter.

Posted by james 2016-02-26 18:36|| http://idontknowbut.blogspot.com 2016-02-26 18:36|| Front Page Top

#5 Why do you say that? Given a cylinder the path along the length would traverse the most fluid and would have the highest probability of triggering a detection event. If the cylinder's width was small when compared to its length a transverse path perpendicular to the length would encounter far less fluid and hence would have a much smaller chance of triggering a detection event. Since you would be getting many events from a pile of refined uranium/plutonium you could orient the cylinder to maximize the number of hits per unit time. The research instruments are spherical/cubist, i.e. symmetrical so they wouldn't have a preferred direction.

Posted by Sven the pelter 2016-02-26 19:10|| 2016-02-26 19:10|| Front Page Top

#6 The cross section sideways is greater, though. The integral of the area by depth is the volume.

You'd be too far away for the difference in flux between the near and far sides to matter.

You _can_ get instrumentation effects. The readout might not be so good evaluating paths on tracks that come sideways, for example.

Posted by james 2016-02-26 19:26|| http://idontknowbut.blogspot.com 2016-02-26 19:26|| Front Page Top

#7 More flux perpendicular to the length but lower detection probability per particle. I wonder if there is a minimum fluid thickness required to get a detection event?

Posted by Sven the pelter 2016-02-26 19:57|| 2016-02-26 19:57|| Front Page Top

#8 Daya Bay uses 20 ton detectors, about 2km from the reactors. If you're 200km away, make that 200,000 ton to get the same rate they do, which http://www.scholarpedia.org/article/The_Daya_Bay_Experiment says is of order 100,000/year. I don't have a good handle on how to use the spectrum to tell banned from OK materials, but I'd hope (WAG) that would be more than enough to distinguish.

FWIW, have a look a this: http://arxiv.org/abs/1510.00666

Posted by james 2016-02-26 21:23|| http://idontknowbut.blogspot.com 2016-02-26 21:23|| Front Page Top

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