arXiv subjects

Jason Aebischer

Publications and source records attributed to Jason Aebischer.

57 records · Page 4Linked to original sources

arXiv2017

The MSSM without Gluinos; an Effective Field Theory for the Stop Sector

In this article we study the MSSM with stops and Higgs scalars much lighter than gluinos and squarks of the first two generations. In this setup, one should use an effective field theory with partial supersymmetry in which the gluino and heavy squarks are integrated out in order to connect SUSY parameters (given at a high scale) to observables in the stop sector. In the construction of this effective theory, valid below the gluino mass scale, we take into account $O(α_3)$ and $O(Y_{t,b}^2)$ effects and calculate the matching as well as the renormalization group evolution. As a result, the running of the parameters for the stop sector is modified with respect to the full MSSM and SUSY relations between parameters are broken. We show that for some couplings sizable numerical differences exist between the effective field theory approach and the naive calculation based on the MSSM running.

hep-ph↗

arXiv2016

1-Loop Matching of gauge invariant dim-6 operators for B decays

Physics beyond the Standard Model, realized above the electroweak scale, can be incorporated in a model independent way in the Wilson coefficients of higher dimensional gauge invariant operators. In these proceedings we review the matching of the $SU(3)_C\times SU(2)_L\times U(1)_Y$ gauge invariant dimension-six operators on the effective Hamiltonian governing $b\to s$ and $b\to c$ transitions, including the leading 1-loop effects.

hep-ph↗

arXiv2014

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

In this article we calculate the 1-loop supersymmetric QCD (SQCD) corrections to the decay $\tilde u_1\to c \tildeχ^0_1$ 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 $\tilde χ^0_1$ is smaller than the top mass. In such a scenario $\tilde u_1\to t \tildeχ^0_1$ is kinematically not allowed and searches for $\tilde u_1\to W b \tildeχ^0_1$ and $\tilde u_1\to c \tildeχ^0_1$ are performed. A large decay rate for $\tilde u_1\to c \tildeχ^0_1$ can weaken the LHC bounds from $\tilde u_1\to W b χ^0_1$ which are usually obtained under the assumption ${\rm Br}[\tilde u_1\to W b χ^0_1]=100\%$. We find the SQCD corrections enhance $Γ[\tilde u_1\to c \tildeχ^0_1]$ 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 $\overline{\rm DR}$ to the on-shell mass is numerically very important for light stop decays.

hep-ph↗