Jason Aebischer

Matching of gauge invariant dimension-six operators for b → s and b → c transitions

A bstractNew physics realized above the electroweak scale can be encoded in a model independent way in the Wilson coefficients of higher dimensional operators which are in-variant under the Standard Model gauge group. In this article, we study the matching of the SU(3)C × SU(2)L × U(1)Y gauge invariant dimension-six operators on the standard B physics Hamiltonian relevant for b → s and b → c transitions. The matching is performed at the electroweak scale (after spontaneous symmetry breaking) by integrating out the top quark, W , Z and the Higgs particle. We first carry out the matching of the dimension-six operators that give a contribution at tree level to the low energy Hamiltonian. In a second step, we identify those gauge invariant operators that do not enter b → s transitions already at tree level, but can give relevant one-loop matching effects.

B physics Beyond the Standard Model at One Loop: Complete Renormalization Group Evolution below the Electroweak Scale

A bstractGeneral analyses of B-physics processes beyond the Standard Model require accounting for operator mixing in the renormalization-group evolution from the matching scale down to the typical scale of B physics. For this purpose the anomalous dimensions of the full set of local dimension-six operators beyond the Standard Model are needed. We present here for the first time a complete and non-redundant set of dimension-six operators relevant for B-meson mixing and decay, together with the complete one-loop anomalous dimensions in QCD and QED. These results are an important step towards the automation of general New Physics analyses.

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

In this article we calculate the one-loop supersymmetric QCD (SQCD) corrections to the decay u˜1→cχ˜01 in the minimal supersymmetric standard model with generic flavor structure. This decay mode is phenomenologically important if the mass difference between the lightest squark u˜1 (which is assumed to be mainly stoplike) and the neutralino lightest supersymmetric particle χ˜01 is smaller than the top mass. In such a scenario u˜1→tχ˜01 is kinematically not allowed and searches for u˜1→Wbχ˜01 and u˜1→cχ˜01 are performed. A large decay rate for u˜1→cχ˜01 can weaken the LHC bounds from u˜1→Wbχ01 which are usually obtained under the assumption Br[u˜1→Wbχ01]=100%. We find the SQCD corrections enhance Γ[u˜1→cχ˜01] by approximately 10% if the flavor violation originates from bilinear terms. If flavor violation originates from trilinear terms, the effect can be ±50% or more, depending on the sign of At. We note that connecting a theory of supersymmetry breaking to LHC observables, the shift from the DR¯¯¯¯¯ to the on-shell mass is numerically very important for light stop decays.

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

Master formula for

O(\alpha _3)

beyond the Standard Model

O(α3) and

\epsilon'/\epsilon

O(Y_{t,b}^2)