I Particle on a cylinder with harmonic oscillator along z-axis

Salmone
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I need to know if I have solved the following problem well:

A spin-less particle of mass m is confined to move on the surface of a cylinder of infinite height with a harmonic potential on the z-axis and Hamiltonian ##H=\frac{p_z^2}{2m}+\frac{L_z^2}{2mR^2}+\frac{1}{2}m\omega^2z^2## and I need to calculate its eigenvalues and eigenvectors.
I thought of separating the Hamiltonian as it is written in the text, and find the Hamiltonian of a particle on a ring and a harmonic oscillator along the z-axis with eigenfunctions of the type ##|\psi\rangle=|m\rangle|n\rangle## where ##m## are the eigenvalues of ##L_z## equal to ##\frac{1}{\sqrt{2\pi}}e^{im\phi}## and ##n## are the eigenvalues of the harmonic oscillator. For the eigenvalues I had thought they were ##E=\frac{n^2\hbar^2}{2mR^2}+\hbar\omega(n+1/2)##. Is this right?
Also, if I had a perturbation like ##\epsilon cos(\phi)## to calculate on the fundamental level I could say by eye that its effect is zero since in the fundamental level there is no angular momentum?
 
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You have to write ##\mu## for the mass to distnguish if from the eigenvalue of ##\hat{L}_z##, ##m \hbar##. Then ##E_{mn}=m^2\hbar^2/(2\mu R^2)+\hbar \omega (n+1/2)##, where ##m \in \mathbb{Z}##, ##n \in \mathbb{N}_0##.
 
Thank you @vanhees71 for the answer, so the eigenvalues are correct, what about the total Hamiltonian eigenvectors? Are they correct? And the perturbation?
 
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