Leptons are elementary fermionic particles constituting a fundamental physical system in the Standard Model, characterized by half-integer spin (spin-½), lack of color charge, and participation in electroweak but not strong interactions. They occur in three generations, each comprising a charged lepton (electron, muon, tau) and its associated neutrino, distinguished by lepton flavor quantum numbers. Leptons obey Fermi–Dirac statistics and are subject to conservation laws such as total lepton number and, to high precision, individual flavor numbers in most processes. Their dynamics are described by the electroweak sector’s SU(2)\(_L\)×U(1)\(_Y\) gauge symmetry, with mass eigenstates arising from Yukawa couplings and, for neutrinos, flavor mixing via the PMNS matrix.
Neutrinos are extremely elusive elementary particles. Day and night, 60 billion of them stream from the sun through every square centimeter of Earth every second, which is transparent to them. After the first theoretical ...
General Physics
Jul 30, 2025
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Neutrinos are subatomic particles with no charge and very little mass that are known to weakly interact with other matter in the universe. Due to their weak interactions with other particles, these particles are notoriously ...
Sharing disappointing results with a world of researchers working to find what they hope will be the "discovery of the century" isn't an easy task, but that is what Penn State theoretical physicist Zoltan Fodor and his international ...
General Physics
Jun 12, 2025
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The Higgs boson is the most intriguing and unusual object yet discovered by fundamental science. There is no higher experimental priority for particle physics than building an electron–positron collider to produce it copiously ...
General Physics
Jun 12, 2025
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Final results from a long-running U.S.-based experiment announced Tuesday show a tiny particle continues to act strangely—but that's still good news for the laws of physics as we know them.
General Physics
Jun 3, 2025
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Cosmic rays are high-energy particles from outer space that strike Earth's atmosphere, generating showers of secondary particles, such as muons, that can reach the planet's surface. In recent years, ground-based experiments ...
General Physics
Jun 2, 2025
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Muons are elementary particles that resemble electrons, but they are heavier and decay very rapidly (i.e., in just a few microseconds). Studying muons can help to test and refine the standard of particle physics, while also ...
Buried deep in the ice in the Antarctic are "eyes" that can see elementary particles called neutrinos, and what they've observed is puzzling scientists: a remarkably strong neutrino signal accompanied by a surprisingly weak ...
General Physics
May 8, 2025
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Neutrinos and antineutrinos are elementary particles with small but unknown mass. High-precision atomic mass measurements at the Accelerator Laboratory of the University of Jyväskylä, Finland, have revealed that beta decay ...
General Physics
May 6, 2025
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Neutrinos, elusive fundamental particles, can act as a window into the center of a nuclear reactor, the interior of the Earth, or some of the most dynamic objects in the universe. Their tendency to change "flavors" may provide ...
General Physics
Apr 23, 2025
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