Theory and phenomenology of exotic isosinglet quarks and squarks

Abstract

Extensions of the MSSM often predict the existence of new fermions and their scalar superpartners which are vectorlike with respect to the standard model gauge group but may be chiral under additional gauge factors. In this paper we explore the production and decay of an important example, i.e., a heavy isosinglet charge −1/3 quark and its scalar partner, using the charge assignments of a 27-plet of E6 for illustration. We emphasize that, depending on the symmetries of the low energy theory, such exotic particles may decay by the mixing of the fermion with the d, s, or b quarks; may decay by leptoquark or diquark couplings (which may nevertheless preserve a form of R-parity); or may be stable with respect to renormalizable couplings but decay by higher-dimension operators on cosmological times scales. We discuss the latter two possibilities in detail for various assumptions concerning the relative masses of the exotic fermions, scalars, and the lightest neutralino, and emphasize the necessity of considering the collider signatures in conjunction with the normal MSSM processes. Existing and projected constraints from colliders, indirect experiments, proton decay, and big bang nucleosynthesis are considered.

LHC signatures of the constrained exceptional supersymmetric standard model

“…We note that the phenomenology of D-fermions has also been discussed the general framework of E 6 models in [14], but not specifically for the cE 6 SSM which provides a more predictive framework via the use of benchmark points.…”

Survey of vector-like fermion extensions of the Standard Model and their phenomenological implications

“…Vector-like families are not motivated only by string theory considerations, but also lower energy constructions such as top-quark seesaw models [4][5][6], warped extra dimensions (see for example ref. [7] and references therein), composite Higgs [8][9][10][11][12][13], little Higgs theories [14][15][16][17], and low-scale supersymmetry [18][19][20][21][22][23][24][25][26]. Ref.…”

Modified Higgs boson phenomenology from gauge or gaugino mediation in the next-to-minimal supersymmetric standard model

“…Stable (on collider times) heavy quarks were studied recently in Ref. [59]. These can form charged exotic hadrons that punch through to the muon chamber.…”

“…Decays through the operators of Eq. (4.3) occur safely before nucleosynthesis provided the heavy mass scale suppressing them is less than about the GUT scale, M GU T ≃ 10 16 GeV [59,60].…”