Riemann Hypothesis: Is $1/2$ of critical line same as the $1/2$ of square-root accurately of error term of prime number theorem?

Here is a question about Riemann Hypothesis:

Is $1/2$ of critical line same as the $1/2$ of square-root accurately of error term of prime number theorem $?$

In other words, (just for some brain exercise), let's assume that critical line is at $x=3/4$, does this mean that the error term in prime number theorem will be proportional to the power of $3/4$ $?$ So $|\pi(x) - Li(x) |$ would be bounded by $x^{(3/4)}$ $?$

Which book has a simple proof of this $?$

Thank you.

• Yes, this is standard. This is probably somewhere in Montgomery and Vaughan, or in Iwaniec and Kowalski. Note that if $\zeta(s)$ has no zeroes to the right of the line $\Re(s) = \Theta$, then $|\pi(x) - \mathrm{Li}(x)| \ll_{\varepsilon} x^{\Theta + \varepsilon}$ for all $\varepsilon > 0$, but one cannot remove the $\varepsilon$. – Peter Humphries Sep 25 '15 at 19:58

Ingham, The Distribution of Prime Numbers, contains a proof that the lower bound $\Theta_1$ of numbers $\alpha$ for which it is true that
$$\psi(x)-x = O(x^{\alpha})$$
is equal to the upper bound $\Theta_2$ of the real parts of the zeros of $\zeta(s).$