Influence of $SU(2)\otimes U(1)$ singlet scalars on Higgs boson signal at LHC

We investigate a model of $SU(2)\otimes U(1)$ singlet scalars coupled to Standard Model. We point out that for the case of maximal mixing between singlet scalars and standard Higgs boson the Higgs boson production cross section is smaller than the standard Higgs boson production by factor $\frac{1}{N+1}$, where N is the number of singlet scalar scalars. For the case of big mixing Higgs boson could be nonobservable at LHC. However, there is also a possibility for the observation of scalar singlets at LHC. As a quasirealistic example we discuss a supersymmetric $SU(2)\otimes U(1)$ electroweak model with an additional gauge singlet chiral superfield.