Why do we consider higher dimensional operators in the search for new physics?

[shakeel]

I am confuse about the dimension of an operator? Why we need an operator of Dim six or greater for new physics?

 

[DimReg]

It's a little unclear how/what you don't understand.

Dimension 6 or greater operators are non renormalizable, so traditionally we don't write them down. But experience with the renormalization group tells us that we should consider those terms as well, so sometimes when we look for "new physics" we do it by considering higher dimensional operators. However, I believe this isn't necessary for new physics, for example supersymmetric extensions of the standard model contain new renormalizable terms, so these terms are of dimension 4 but aren't in the standard model.

Maybe you can elaborate a little bit more about what you know about physics (specifically quantum field theory)?