New supersymmetric contributions tot→cV

Abstract

We calculate the electroweak-like one-loop supersymmetric contributions to the rare and flavor-violating decay of the top quark into a charm quark and a gauge boson: t → cV , with V = γ, Z, g. We consider loops of both charginos and down-like squarks (where we identify and correct an error in the literature) and neutralinos and up-like squarks (which have not been calculated before). We also account for left-right and generational squark mixing. Our numerical results indicate that supersymmetric contributions to t → cV can be upto 5 orders of magnitude larger than their Standard Model counterparts. However, they still fall short of the sensitivity expected at the next-generation top-quark factories.

t→cg,cγ,cZin the left-right supersymmetric model

“…In general, the neutralino contribution is bigger than the chargino contribution in the flavor diagonal scenario for t → c V (with the notable exception of the t → cZ decay mode and the t → cγ decay for certain M susy values) and this is consistent with the findings of Lopez et al [9].…”

“…t → cV (V = g, γ, Z) have also been explored in two Higgs doublet models [1,2], technicolor models [3], top-color assisted technicolor models [4], models with extra vector singlets [5] and supersymmetry with [6,7,8,9,10,11,12], and without SUSY QCD and EW contributions [6] and obtained branching ratios of 10 −6 for t → cg and 10 −8 for t → cγ, Z. Couture et al included the left-handed squark mixing in their calculation [7] and obtained branching ratios of 10 −5 for the gluon, 10 −7 for the photon and 10 −6 for the Z boson. Inclusion of the right-handed squark mixing [8], did not change branching ratios significantly.…”

Search for top quark decays t → qH with H → γγ using the ATLAS detector

“…Examples of such extensions are the quark-singlet model (QS) [18][19][20], two-Higgs-doublet models (2HDM) of type I, with explicit flavour conservation, and of type II, such as the minimal supersymmetric standard model (MSSM) [21][22][23][24][25][26][27]. In 2HDM without explicit flavour conservation (type III) [28][29][30][31][32][33][34][35][36], the tc(u)H couplings are present at tree level.…”

Collider aspects of flavor physics at high Q

“…There are however extensions of the SM, like supersymmetric models including R-parity violation [8][9][10][11][12][13][14], multi-Higgs doublet models [15][16][17] and extensions with exotic (vectorlike) quarks [18,19], which predict the presence of FCNC contributions already at the tree level and significantly enhance the FCNC decay branching ratios. The theoretical predictions for the branching ratios of top FCNC decays within the SM and some of its extensions are summarized in Table 4.…”

“…These contributions limit the FCNC decay branching ratios to extremely small values in the SM. However, there are extensions of the SM which predict the presence of FCNC contributions already at the tree level and significantly enhance the top FCNC decay branching ratios [8][9][10][11][12][13][14][15][16][17][18][19]. Also loop-induced 1 Section coordinators: G. Burdman and N. Castro.…”