The muon magnetic moment and supersymmetry

Abstract

Abstract.The present review is devoted to the muon magnetic moment and its role in supersymmetry phenomenology. Analytical results for the leading supersymmetric one-and two-loop contributions are provided, numerical examples are given and the dominant tan β sign(µ)/M 2 SUSY behaviour is qualitatively explained. The consequences of the Brookhaven measurement are discussed. The 2σ deviation from the Standard Model prediction implies preferred ranges for supersymmetry parameters, in particular upper and lower mass bounds. Correlations with other observables from collider physics and cosmology are reviewed. We give, wherever possible, an intuitive understanding of each result before providing a detailed discussion.

Non-decoupling two-loop corrections to (g−2)μ from fermion/sfermion loops in the MSSM

“…The present theory error of the SUSY prediction has been estimated to 3 × 10 −10 [32], almost twice as large as the future experimental uncertainty.…”

“…They have been computed in the general MSSM in Ref. [33], see also [32,34]. If all relevant SUSY masses are equal to a common scale M SUSY , these contributions can be approximated by 13 × 10 −10 sgn(µ) tan β (100 GeV/M SUSY ) 2 , where µ is the Higgsino mass parameter and tan β = v u /v d is the ratio of the Higgs doublet vacuum expectation values.…”

“…However, in the general case, already the oneloop contributions have an intricate parameter dependence, as shown on an analytic level in Refs. [32][33][34][35]. We illustrate this variety of possibilities at the one-loop level by Fig.…”

“…Refs. [32,33]), the dominant contribution is the diagram with Higgsino-wino and sneutrino exchange. The result drops with increasing µ because of the Higgsino propagator.…”

“…The SUSY two-loop contributions can be grouped into two classes [32]: In class 2L(a) a pure SUSY loop (of either charginos, neutralinos, or sfermions) is inserted into a SM-like diagram; these contributions have been evaluated exactly in Refs. [37,38].…”