Slashdot Mirror
Scientists Find Long-Sought Majorana Particle
New submitter boner writes "In a follow-up to an earlier Slashdot story, scientists at the Technical University of Delft in the Netherlands yesterday published their findings that they have indeed found the Majorana particle. The announcement on the university website provides both a summary of the academic paper (PDF) and background of this groundbreaking discovery. Quoting: 'Majorana fermions are very interesting – not only because their discovery opens up a new and uncharted chapter of fundamental physics; they may also play a role in cosmology. A proposed theory assumes that the mysterious ‘dark matter, which forms the greatest part of the universe, is composed of Majorana fermions. Furthermore, scientists view the particles as fundamental building blocks for the quantum computer.'"
Or was it just me?
Please do not read this sig. Thank you.
This is not like finding the Higgs Boson. The majorana fermion they created was (hard to tell exactly how from TFA) a condensed matter excitation with the properties of a majorana fermion, not a fundamental particle. Pretty cool though.
Did I read the article correctly that this was funded by Microsoft? That's sort of coolish...
A particle that is its own anti-particle? Sounds pretty special! Of course, that would also describe photons, the commonest particle in the universe.
Come on, science reporting.
Photons are bosons. Bosons being their own antiparticle is nothing unusual. A fermion that is its own antiparticle has never been observed in nature before.
When two of them meet, they annihilate. Note from the article that there are two of these things, and they are at opposite ends of the nanowire. Presumably when you turn off the power or cooling they get together and turn back into energy.
Dark matter is suspected to be the same - when two particles meet, they annihilate, potentially giving us a signal we can measure. They don't meet very often though, because dark matter barely interacts with anything, including itself.
The summary makes it sound like there is a particle that physicists have been seeking called a Majorana particle when in fact a Majorana particle is named because of its quantum field theory behavior. In this case NO particle was discovered but an excitation of a novel condensed matter state which behaves in an analogous way to a Majorana fermion. So in conclusion this very interesting discovery was both summarized and publicized in a misleading way.
A fermion that is its own antiparticle has never been observed in nature before.
There is one possible exception, the neutrino is a half spin fermion and if it really is zero mass it would be its own anti-particle. But recent evidence suggests a tiny but non-zero mass so if that's true it's not. Maybe one experiment would be to try to observe neutrino-antineutrino annihilation, if that occurs then they are Dirac fermions http://en.wikipedia.org/wiki/Majorana_fermion
There is one possible exception, the neutrino is a half spin fermion and if it really is zero mass it would be its own anti-particle.
Actually it's the other way around: massless Fermions are Dirac, because of Chiral symmetry: in the Standard Model with massless neutrinos, all neutrinos are Dirac particles, with neutrinos being left-handed and all antineutrinos being right-handed. Mass terms break chiral symmetry, and a massive neutrino could be either Dirac or majorana depending on how the mass term is generated:
https://en.wikipedia.org/wiki/Sterile_neutrino#Majorana_or_Dirac.3F
Sometimes it looks like there's twelve.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Spin. Anti-neutrons spin the opposite way. ("Spin" here being a particle physics term--it's not the same thing as spinning in the macro world).
Actually for the Neutrinos, the question is not yet settled. That's why experimentalists are seeking for neutrino-less double-beta decay.
The Tao of math: The numbers you can count are not the real numbers.
Not a technical explanation, but a good one I heard: if you look at a Feynman diagram (they're pretty easy to understand for a layman) you'll find that you can read them in any direction - if you go "against the time arrows" you're just looking at the antiparticle versions interacting instead, it's still a valid diagram. However, the photons don't have arrows as they don't experience time, so they're identical in either time direction, and therefore their own antiparticles.
The interesting thing here is that it's a massive particle with that property, rather than a massless one.
Please consider this account deleted, I just can't be bothered with the spam anymore.
The statement is perfectly true as written. Every particle has an antiparticle, not necessarily a distinct antiparticle, and its antiparticle has the opposite charge. (Hint: zero is its own opposite.)