Muon anomalous magnetic moment in string inspired extended family models

We propose a standard model minimal extension with two lepton weak SU(2) doublets and a scalar singlet to explain the deviation of the measured anomalous magnetic moment of the muon from the standard model expectation. This scheme can be naturally motivated in string inspired models such as E6 and AdS/CFT. E-mail: [email protected] E-mail: [email protected] 1 The recent result of the g−2 Collaboration at BNL may be the overdue first direct signal of physics beyond the standard model (SM). The data seem to indicate a 2.6 σ deviation from the theoretical expectation of the SM [1], a μ − a SM μ = 426 ± 165 · 10 . (1) Several logical possibilities have been considered [2] to explain the effect, such as supersymmetry [3], leptoquarks [4], muon substructure [5], technicolor [6], large extra dimensions [7], new interactions and fermions [8]; for a review see [2]. In this letter we propose a minimal extension of the SM, which to date has not been discussed in this context. It is sufficient to extend the second fermion family (extending the other families is optional but aesthetically appealing) by adding an extra pair of lepton doublets and a scalar singlet: