Speaker
Description
Recent reanalysis of ALEPH data on $Z\rightarrow b\bar{b} + X$ seems to indicate an existence
of the dimuon excess around 30 GeV with a branching fraction for
$Z\rightarrow b\bar{b} \mu^+ \mu^-$ around $1.1 \times10^{-5}$.
We discuss three different types of simplified models for this possible excess.
In the first class of models, we assume a new resonance couples to both $b\bar{b}$ and $\mu^+ \mu^-$.
In the second model, we assume that the 30 GeV excess is a new gauge boson $Z'$ that couples
to the SM $b$ and a new vectorlike singlet $B$ quark heavier than $Z$ and not to $b\bar{b}$.
In the third model, we consider $Z\rightarrow Z' \phi$ followed by $Z' \rightarrow \mu^+ \mu^-$ and
$\phi \rightarrow b\bar{b}$ assuming that the Higgs field for $Z'$ mass is also charged under the SM
$U(1)_Y$ gauge symmetry.
We consider constraints on the models and investigate implication of the three models at the LHC.
