Multiple populations revealed in globular clusters ( GCs ) are important windows to the formation and evolution of these stellar systems .
The metal-rich GCs in the Galactic bulge are an indispensable part of this picture , but the high optical extinction in this region has prevented extensive research .
In this work , we use the high resolution near-infrared ( NIR ) spectroscopic data from APOGEE to study the chemical abundances of NGC 6553 , which is one of the most metal-rich bulge GCs .
We identify ten red giants as cluster members using their positions , radial velocities , iron abundances , and NIR photometry .
Our sample stars show a mean radial velocity of -0.14 \pm 5.47 km s ^ { -1 } , and a mean [ Fe/H ] of -0.15 \pm 0.05 .
We clearly separate two populations of stars in C and N in this GC for the first time .
NGC 6553 is the most metal-rich GC where the multiple stellar population phenomenon is found until now .
Substantial chemical variations are also found in Na , O , and Al .
However , the two populations show similar Si , Ca , and iron-peak element abundances .
Therefore , we infer that the CNO , NeNa , and MgAl cycles have been activated , but the MgAl cycle is too weak to show its effect on Mg .
Type Ia and Type II supernovae do not seem to have significantly polluted the second generation stars .
Comparing with other GC studies , NGC 6553 shows similar chemical variations as other relatively metal-rich GCs .
We also confront current GC formation theories with our results , and suggest possible avenues for improvement in the models .