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.
Protons and neutrons—the building blocks of matter—belong to a huge class of particles called hadrons. Hadrons are composite particles made of quarks that are bound together by the strong force. They are classified into two ...
General Physics
May 26, 2026
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While neutrinos are some of the most abundant particles in the universe, they remain among the least understood. One of the biggest puzzles is their mass: although experiments have shown that neutrinos must have some mass, ...
A tiny discrepancy in particle physics has loomed for decades as an exciting possible crack in one of science's most successful theories, hinting at unknown forces or quantum objects. Now, an international team led by a Penn ...
General Physics
Apr 22, 2026
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Recent findings from research we have been carrying out at the Large Hadron Collider (LHC) at Cern in Geneva suggest that we might be closing in on signs of undiscovered physics.
General Physics
Apr 20, 2026
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When fundamental particles are heavier or lighter than expected, physicists' understanding of the universe can tip into the unknown. A particle that is just beyond its predicted mass can unravel scientists' assumptions about ...
General Physics
Apr 8, 2026
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New research suggests that neutrinos in the early universe may have transformed into a previously unknown form of radiation. A study from Washington University in St. Louis offers a new way to explain certain puzzling observations ...
Astronomy
Apr 2, 2026
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A new independent measurement by the CMS experiment at the LHC is consistent with the existence of the most massive composite particle ever observed, the momentary union of a top quark and its antiquark
General Physics
Mar 26, 2026
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Their mass is extremely low, but how light are neutrinos really? A collaboration comprising German and international research groups has optimized its experiments to determine the mass of these "ghost particles." In doing ...
General Physics
Mar 25, 2026
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Neutrinos are extremely lightweight and electrically neutral particles that rarely interact with ordinary matter. Due to these rare interactions, neutrinos can travel across space almost entirely unaffected, carrying information ...
The NA62 Collaboration has dramatically reduced the uncertainty in its measurement of an extremely rare particle decay, in results just presented at the 2026 La Thuile conference.
General Physics
Mar 4, 2026
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