Editing Massless particle (section)

=== Quasiparticles ===
The [[Weyl fermion]] discovered in 2015 is also expected to be massless,<ref>
{{cite news
 |title=After 85&nbsp;year search, massless particle with promise for next-generation electronics found
 |date=16 July 2015
 |publisher=[[Princeton University]] 
 |website=phys.org
 |url=https://phys.org/news/2015-07-year-massless-particle-next-generation-electronics.html
}}
</ref><ref>
{{cite journal
 |author=Su-Yang Xu |author2=Ilya Belopolski |author3=Nasser Alidoust |author4=Madhab Neupane
 |display-authors=etal
 |date=16 July 2015
 |title=Discovery of a Weyl fermion semimetal and topological Fermi arcs
 |journal=[[Science (journal)|Science]]
 |volume=349  |issue=6248  |pages=613–617
 |publisher=[[American Association for the Advancement of Science|AAAS]]
 |doi=10.1126/science.aaa9297 |pmid=26184916 |arxiv=1502.03807 |bibcode=2015Sci...349..613X |s2cid=206636457 |url=https://www.science.org/doi/10.1126/science.aaa9297
|access-date=2023-11-14
}}
</ref> but these are not actual particles. At one time neutrinos were thought to perhaps be Weyl fermions, but when they were discovered to have mass, that left no fundamental particles of the Weyl type.

The Weyl fermions discovered in 2015 are merely ''[[quasiparticle]]s'' – composite motions found in the structure of molecular latices that have particle-like behavior, but are not themselves real particles. Weyl fermions in matter are like [[phonon]]s, which are also quasiparticles. No real particle that is a Weyl fermion has been found to exist, and there is no compelling theoretical reason that requires them to exist. 

[[Neutrino]]s were originally thought to be massless. However, because neutrinos change [[flavour (particle physics)|flavour]] as they travel, at least two of the types of neutrinos must have mass (and cannot be Weyl fermions).<ref>
{{cite news
 |first=Robert |last=Garisto
 |date=1 September 1998
 |title=Neutrinos have mass
 |series=[[Physical Review Letters]]
 |department=Focus
 |website=aps.org
 |publisher=[[American Physical Society]]
 |url=https://physics.aps.org/story/v2/st10
|access-date=2023-11-14
}}
</ref> The discovery of this phenomenon, known as [[neutrino oscillation]], led to Canadian scientist [[Arthur B. McDonald]] and Japanese scientist [[Takaaki Kajita]] sharing the 2015 [[Nobel Prize in Physics]].<ref>
{{cite news
 |first = Charles |last = Day
 |date = 2015-10-07
 |title = Takaaki Kajita and Arthur McDonald share 2015 Physics Nobel
 |magazine = [[Physics Today]]
 |issn = 0031-9228 |doi = 10.1063/PT.5.7208
}}
</ref>