... Declaring new groups . ... Index type is defined by two keywords 1 : group name and representation name . Thus, color triplet index type color c3 has group name color and representation name c3 . ... So, three index types can be used: color c3, color c3b, color c8 . ... Array, i.e. the object with explicit components, can also have the user-defined type of index. ... If itype is omitted LanHEP uses default group name wild and index type wild N , where N is a number of components in the array. ...