Let $f$ be a primitive form of an even weight $k$ for the full modular group and let $L(Sym^rf,s)$ be the symmetric $r$th $(r\geq 2)$ power $L$-function associated to $f.$ I have three questions related to the function $L(Sym^rf,s):$
1) Is the function $L(Sym^rf,s)$ holomorphic on the whole real line?
2) Has it infinitely many real zeros?
3) What is its domain of convergence?
Many thanks, Khadija