lightning:tree handling onselect

lightning:tree component displays visualization of a structural hierarchy, such as a sitemap for a website or a role hierarchy in an organization. Items are displayed as hyperlinks and items in the hierarchy can be nested. Items with nested items are also known as branches.In this example , we will be handling on select event on any structural hierarchy .On click of the structural hierarchy item we will be opening in the new window .

Apex Class 

Lightning Component 

Now with the above code, you can able to click on any structural hierarchy name it will be able to open the record in the new tab.