Xperia Z1 C6902 Lollipop 5.1.1- Root Methods?

How can Root Xperia Z1 C6902 Lollipop 5.1.1 without pre-rooted rom. Is there other methods to root my Xperia Z1 C6902 Lollipop 5.1.1 . My xperia is installed with orginal Lollipop 5.1.1 stock rom. I want to root it. But i don't need Pre-rooted Rom, is there any method for rooting it. And also i don't want to downgrade it for rooting.