TY - JOUR
T1 - Mixing between ordinary and exotic fermions
AU - Langacker, Paul
AU - London, David
PY - 1988
Y1 - 1988
N2 - The results of a comprehensive analysis of the limits on mixings between ordinary fermions and possible heavy fermions with exotic SU(2)×U(1) assignments (e.g., left-handed singlets and/or right-handed doublets) are presented. A general formalism for describing such mixings is given. It is shown that a variety of constraints, including the relation between the W and Z masses and the Fermi constant, charged-current universality, limits on induced right-handed charged currents, and flavor-diagonal neutral currents suffice to limit all directions in parameter space that are not excluded by the absence of flavor-changing neutral currents. Limits on s2, the square of the mixing between ordinary and exotic fermions, are quite stringent for the L, L-, uL, and dL (s20.0020.005) if only one particle is allowed to mix at a time, but are weaker by an order of magnitude if fine-tuned cancellations between different mixings are allowed. Similar statements apply to quark mixings with heavy sequential doublets. Limits on s2 for the other light fermions (eL, eL-,eR-,R-, uR,dR) are in the range 0.020.06, while those for the s, c, b, and - are considerably weaker. Slightly stronger limits are found in specific models (e.g., E6). Implications for the masses of the heavy exotic fermions are discussed.
AB - The results of a comprehensive analysis of the limits on mixings between ordinary fermions and possible heavy fermions with exotic SU(2)×U(1) assignments (e.g., left-handed singlets and/or right-handed doublets) are presented. A general formalism for describing such mixings is given. It is shown that a variety of constraints, including the relation between the W and Z masses and the Fermi constant, charged-current universality, limits on induced right-handed charged currents, and flavor-diagonal neutral currents suffice to limit all directions in parameter space that are not excluded by the absence of flavor-changing neutral currents. Limits on s2, the square of the mixing between ordinary and exotic fermions, are quite stringent for the L, L-, uL, and dL (s20.0020.005) if only one particle is allowed to mix at a time, but are weaker by an order of magnitude if fine-tuned cancellations between different mixings are allowed. Similar statements apply to quark mixings with heavy sequential doublets. Limits on s2 for the other light fermions (eL, eL-,eR-,R-, uR,dR) are in the range 0.020.06, while those for the s, c, b, and - are considerably weaker. Slightly stronger limits are found in specific models (e.g., E6). Implications for the masses of the heavy exotic fermions are discussed.
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U2 - https://doi.org/10.1103/PhysRevD.38.886
DO - https://doi.org/10.1103/PhysRevD.38.886
M3 - Article
SN - 0380-0903
VL - 38
SP - 886
EP - 906
JO - The Journal of rheumatology. Supplement
JF - The Journal of rheumatology. Supplement
IS - 3
ER -