  Using the observations recorded by Atmospheric Imaging Assembly (AIA)
on-board the Solar Dynamics Observatory (SDO), the Interface Region Imaging
Spectrograph (IRIS) and the Extreme-ultraviolet Imaging Spectrometer (EIS) and
X-Ray Telescope (XRT) both on-board Hinode, we present the evidence of
chromospheric evaporation in a coronal loop after the occurrence of two active
region transient brightenings (ARTBs) at the two footpoints. The chromospheric
evaporation started nearly simultaneously in all the three hot channels of AIA
such as 131~{\AA}, 94~{\AA} and 335~{\AA}, which was observed to be temperature
dependent, being fastest in the highest temperature channel. The whole loop
became fully brightened following the ARTBs after $\approx25$~s in 131~{\AA},
$\approx 40$~s in 94~{\AA}, and $\approx 6.5$~min in 335~{\AA}. The DEM
measurements at the two footpoints (i.e., of two ARTBs) and the loop-top
suggest that the plasma attained a maximum temperature of $\sim$10~MK at all
these locations. The spectroscopic observations from IRIS revealed the presence
of redshifted emission of $\sim$20~km~s$^{-1}$ in cooler lines like \ion{C}{2}
and \ion{Si}{4} during the ARTBs that was co-temporal with the evaporation flow
at the footpoint of the loop. During the ARTBs, the line width of \ion{C}{2}
and \ion{Si}{4} increased nearly by a factor of two during the peak emission.
Moreover, enhancement in the line width preceded that in the Doppler shift
which again preceded enhancement in the intensity. The observed results were
qualitatively reproduced by 1-D hydrodynamic simulations where energy was
deposited at both the footpoints of a monolithic coronal loop that mimicked the
ARTBs identified in the observations.
