1-loop SQCD corrections to the decay of top-squarks to charm and neutralino in the generic MSSM

Abstract

In this article we calculate the 1-loop supersymmetric QCD (SQCD) corrections to the decay ${\tilde{u}}_1\to c{\tilde{\chi }}_1^0$ in the MSSM with generic flavour structure. This decay mode is phenomenologically important if the mass difference between the lightest squark ${\tilde{u}}_1$ (which is assumed to be mainly stop-like) and the neutralino LSP ${\tilde{\chi }}_1^0$ is smaller than the top mass. In such a scenario ${\tilde{u}}_1\to t{\tilde{\chi }}_1^0$ is kinematically not allowed and searches for ${\tilde{u}}_1\to Wb{\tilde{\chi }}_1^0$ and ${\tilde{u}}_1\to c{\tilde{\chi }}_1^0$ are performed. A large decay rate for ${\tilde{u}}_1\to c{\tilde{\chi }}_1^0$ can weaken the LHC bounds from ${\tilde{u}}_1\to Wb{\chi }_1^0$ which are usually obtained under the assumption $\mathrm{Br}[{\tilde{u}}_1\to Wb{\chi }_1^0]=100\%$. We find the SQCD corrections enhance $\Gamma [{\tilde{u}}_1\to c{\tilde{\chi }}_1^0]$ by approximately 10\% if the flavour-violation originates from bilinear terms. If flavour-violation originates from trilinear terms, the effect can be $\pm 50\%$ or more, depending on the sign of $A^t$. We note that connecting a theory of SUSY breaking to LHC observables, the shift from the $\overline{\mathrm{DR}}$ to the on-shell mass is numerically very important for light stop decays.

25 pages, 7 figures

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• Resonant Higgs pair production as a probe of stop at the LHC
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