Short-interval prime upper bound from a smooth divisor weight
= Short-interval prime upper bound from a smooth divisor weight
For $Y\geq X\geq2$, a smooth Selberg divisor weight of level $D=X^{1/10}$ equals one on every prime in $(Y,Y+X]$. Its second moment can be expressed through an Euler product $H$ whose zeta-factor bound contributes $O(1/\log D)$ after integration against rapidly decreasing Fourier transforms. Consequently
$$
\pi(Y+X)-\pi(Y)\ll\frac X{\log X}.
$$