Physics Of Planes

The antineutrino vanishes differently

CPT symmetry, the combination of charge conjugation, parity inversion, and time reversal, is a fundamental symmetry of particle and nuclear physics and is considered sacred. It is conserved in field theories that explain the strong, weak, and electromagnetic interactions. In the lepton sector, CPT symmetry requires that muon neutrino disappearance oscillations be identical to muon antineutrino disappearance oscillations in vacuum. A test of CPT symmetry was recently performed by the MINOS experiment at Fermilab, which, due to its magnetic field, is the first experiment to distinguish .”

What could explain this apparent difference between muon neutrino and muon antineutrino disappearance? First, it is possible that the difference is just due to a statistical fluctuation. This possibility will be tested by additional MINOS data to be taken over the next few years. If the difference is not a statistical fluctuation, then it is possible that it is due to nuclear effects [ 4 ], which can cause a difference in the energy reconstruction of neutrino events compared to antineutrino events. A large energy difference is unlikely but could arise if the hadronic energy is misreconstructed. Neutrino events have a higher fraction of hadronic energy than antineutrino events, and as the neutrino energy is needed for the determination of .

If the apparent difference between muon neutrino and muon antineutrino disappearance is not due to a statistical fluctuation or to nuclear effects, then we would have to consider new physics beyond the standard model. Indeed, global fits to the world neutrino and antineutrino oscillation data [ 5 ] encounter tension between the neutrino and antineutrino data sets and favor different neutrino and antineutrino oscillation parameters. One possible beyond the standard model solution involves nonstandard interactions [ 6 ], which would affect neutrinos and antineutrinos passing through matter (as is the case for MINOS) differently. A more extreme possibility is that Lorentz symmetry is violated [ 7 ] or CPT symmetry is violated [ 8 ], and that neutrino oscillation parameters are different from antineutrino parameters. If this were the case, then the impact on nuclear and particle physics would be profound.

Fortunately, there are several experiments that are either taking data or being constructed that will be able to test this possible difference between muon neutrino and muon antineutrino disappearance.

Physics and Focal Planes

Due to some recent discussions in another thread I’ve decided to share some fundamental physics on how lenses work, particularly with regards to sharpest focus. Hopefully a little tutorial will help you understand why your camera does what it does (or, more accurately, why your camera isn’t doing what you think it should be able to do). Many of you have heard the phrase “focal plane”. That is because lenses work on the principal that the light from one plane refocuses on a parallel plane. For the light to be focusing on your detector plane (whether it is a digital sensor or a film frame), it started in the same plane. Here is a sketch of a simple lens (more complex lenses behave essentially the same way, they’re just better at reducing aberrations): Note that there are no dimesions in this sketch. By definition a plane extends forever in two dimensions (in this sketch, up/down and in/out of the screen). With a suitably large lens and a suitably large sensor, incredibly large subjects can be captured. But more relevantly, it means that the small portion of that image plane which is your detector is focusing the light from a single plane. Whether you’re using a full-frame or a crop sensor digital camera, or 35mm or a medium- or large-format film camera, if you’re focusing on a plane, that light came from a parallel plane. Here’s an interesting illustration of the effects of parallel planes. By definition, parallel planes are the same distance from each other – go straight out from one to the other and you’ve gone the same distance. All paths marked ‘A’ in this sketch are the same length. They all start on the detector plane and end at equivalent points on the subject plane. Let’s say you want to compose your final image so that your subject (‘S’) is not centered in your frame. You turn towards ‘S’, set the focus at distance ‘D’, then turn back forward. Your camera is still focused at distance ‘D’, so anything on the plane parallel to your sensor will be in focus. You can see that your subject is now not on that plane – it is in fact at a distance ‘d’ from your sensor plane.

The Handplane Book

Physics for scientists and engineers

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Ancient And Modern Physics

Understanding physics