On the number of zeros of $L-$functions attached to cusp forms of half-integral weight

Meher et al. [Proc. Amer. Math. Soc. 147 (2019)] have recently established that $L-$functions attached to certain cusp forms of half-integral weight have infinitely many zeros on the critical line. Kim [J. Numb. Th. 253 (2023)] obtained analogous results for $L-$functions attached to cusp forms twisted by an additive character $e\left(\frac{p}{q}n\right)$, $\frac{p}{q}\in \mathbb{Q}$. We extend the results of these authors by giving a lower bound for the number of such zeros. We start by developing a variant of a method of de la Valée Poussin which seems to have interest as it avoids the evaluation of exponential sums. We finish the paper with an improvement of our first estimate by using Lekkerkerker’s variant of the Hardy-Littlewood method.