  Measurements at RHIC have established the creation of a Quark Gluon Plasma
(QGP) in most central heavy-ion collisions. An important tool to understand
properties of the QGP is study of the spectral shapes of low-mass vector mesons
(LVM's), $\rho$, $\omega$ and $\phi$, which can be modified in the medium by
partial restoration of chiral symmetry. This modification may be accessed
directly by measuring low-momentum LVM's via their decays into lepton pairs
inside the hot matter. Since leptons are not subject to the strong interaction,
they do not rescatter on their way out of the medium. The PHENIX experiment at
RHIC has measured LVM production at mid-rapidity in $p$ + $p$, $d$+Au and Au+Au
collisions at $\sqrt{s_{\rm NN}}$ = 200<EMAIL_ADDRESS>Mass peaks for the LVM's have
been observed in the di-electron invariant mass spectra with a resolution of 10
MeV/$c^2$ in all of the three collision systems. The extracted spectra, mass
and width of $\omega$ and $\phi$ in $p$ + $p$, $d$+Au and Au+Au, in the
leptonic and hadronic decay channels are reviewed. As the widths of the mesons
may be affected in the medium, the branching ratios of various decay modes may
also be modified from the values in vacuum. The relative branching ratio is
compared between $\phi\to e^+e^-$ and $\phi\to K^+K^-$, which may be sensitive
to the mass modification due to the small Q-value of $\phi\to K^+K^-$.
