Goldstino

The goldstino is the Nambu−Goldstone fermion emerging in the spontaneous breaking of supersymmetry. It is the close fermionic analog of the Nambu−Goldstone bosons controlling the spontaneous breakdown of ordinary bosonic symmetries.

As in the case of Goldstone bosons, it is massless, unless there is, in addition, a small explicit supersymmetry breakdown involved, on top of the basic spontaneous breakdown; in this case it develops a small mass, analogous to that of Pseudo-Goldstone bosons of chiral symmetry breaking.

In theories where supersymmetry is a global symmetry, the goldstino is an ordinary particle (possibly the lightest supersymmetric particle, responsible for dark matter).

In theories where supersymmetry is a local symmetry, the goldstino is absorbed by the gravitino, the gauge field it couples to, becoming its longitudinal component, and giving it nonvanishing mass. This mechanism is a close analog of the way the Higgs field gives nonzero mass to the W and Z bosons.

Vestigial bosonic superpartners of the goldstinos, called sgoldstinos, might also appear, but need not, as supermultiplets have been reduced to arrays.[1][2][3] In effect, SSB of supersymmetry, by definition, implies a nonlinear realization of the supersymmetry in the Nambu−Goldstone mode, in which the goldstino couples identically to all particles in these arrays, and is thus the superpartner of all of them, equally.

## References

1. ↑ Volkov, D.V.; Akulov, V. (1973). "Is the neutrino a goldstone particle?". Physics Letters B46 (1): 109-110. doi:10.1016/0370-2693(73)90490-5. Bibcode: 1973PhLB...46..109V.
2. ↑ Salam, A. (1974). "On Goldstone Fermion". Physics Letters B49 (5): 465-467. doi:10.1016/0370-2693(74)90637-6. Bibcode: 1974PhLB...49..465S.
3. ↑ Uematsu, T.; Zachos, C. K. (1982). "Structure of phenomenological lagrangians for broken supersymmetry". Nuclear Physics B 201 (2): 250. doi:10.1016/0550-3213(82)90431-X. Bibcode: 1982NuPhB.201..250U.

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