  We use near infrared integral field unit (IFU) spectroscopy to search for
H$\alpha$ emission associated with star formation in a sample of 28 heavily
reddened ($E(B-V)\simeq$0.5-1.9), hyperluminous
($log(L_{bol}/ergs^{-1})\simeq$47-48) broad-line quasars at $z\simeq$1.4-2.7.
Sixteen of the 28 quasars show evidence for star formation with an average
extinction-corrected star formation rate (SFR) of 320$\pm$70M$_\odot$yr$^{-1}$.
A stacked spectrum of the detections shows weak [NII], consistent with star
formation as the origin of the narrow H$\alpha$ emission. The star-forming
regions are spatially unresolved in 11 of the 16 detections and constrained to
lie within $\sim$6kpc of the quasar emission. In the five resolved detections
we find the star-forming regions are extended on scales of $\sim$8kpc around
the quasar emission. The prevalence of high SFRs is consistent with the
identification of the heavily reddened quasar population as representing a
transitional phase from apparent `starburst galaxies' to optically-luminous
quasars. Upper limits are determined for 10 quasars in which star formation is
undetected. In two of the quasars the SFR is constrained to be relatively
modest, $<$50M$_\odot$yr$^{-1}$, but significantly higher levels of star
formation could be present in the other eight quasars. The combination of the
16 strong star formation detections and the eight high SFR limits means that
high levels of star formation may be present in the majority of the sample.
Higher spatial resolution data, of multiple emission lines, will allow us to
better understand the interplay between star formation and Active Galactic
Nucleus (AGN) activity in these transitioning quasars.
