geometric reflections and cayley graph-reflections (type a1)

In this work, we consider geometric reflections based on elementsof a reflectable base of an extended affine root system r, and prove that intype a1, any geometric reflection of a reflectable base is a cayley graph-reflection if and only if the nullity of r is less than or equal one. also weshow that any extended affine root system r, is a union of extended affineroot systems of type a1 with the same nullities as the nullity of r.