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Quarks have fractional electric charge values – either (− 1 / 3 ) or (+ 2 / 3 ) times the elementary charge (e), depending on flavor. Up, charm, and top quarks (collectively referred to as up-type quarks) have a charge of + 2 / 3 e; down, strange, and bottom quarks (down-type quarks) have a charge of − 1 / 3 e.
Each generation contains two types of leptons and two types of quarks. The two leptons may be classified into one with electric charge −1 (electron-like) and neutral (neutrino); the two quarks may be classified into one with charge − 1 ⁄ 3 (down-type) and one with charge + 2 ⁄ 3 (up-type).
Half of the fermions are leptons, three of which have an electric charge of −1 e, called the electron (e −), the muon (μ −), and the tau (τ −); the other three leptons are neutrinos (ν e, ν μ, ν τ), which are the only elementary fermions with neither electric nor color charge. The remaining six particles are quarks (discussed below).
Download as PDF; Printable version; ... Thus, there are three generations of quarks and leptons. [37] ... are free parameters, ...
τ) by the interaction eigenstate, whereas for the quarks we define the flavor (up, down, etc.) by the mass state. We can switch between these states using the CKM matrix for the quarks, or the PMNS matrix for the neutrinos (the charged leptons on the other hand are eigenstates of both mass and flavor).
In addition, leptons carry weak isospin, T 3, which is − 1 / 2 for the three charged leptons (i.e. electron, muon and tau) and + 1 / 2 for the three associated neutrinos. Each doublet of a charged lepton and a neutrino consisting of opposite T 3 are said to constitute one generation of leptons.
All quarks are assigned a baryon number of 1 / 3 . Up, charm and top quarks have an electric charge of + 2 / 3 , while the down, strange, and bottom quarks have an electric charge of − 1 / 3 . Antiquarks have the opposite quantum numbers. Quarks are spin- 1 / 2 particles, and thus fermions. Each quark or antiquark ...
Q = 2 ⁄ 3: Such a leptoquark decays into up-type quarks and neutrinos (or antineutrinos), and/or to down-type quarks (down, strange, bottom) and charged antileptons. Q = − 1 ⁄ 3: Such a leptoquark decays into down-type quarks and (anti)neutrinos, and/or to up-type quark and a charged lepton.