Strangeness Enhancement in Small System at LHCb

The enhanced production of strangeness was first proposed as a signature of the quark gluon plasma creation in heavy ion collisions. Recently, increased strangeness production is also observed experimentally in high multiplicity small systems such as pp and pPb collisions, where formation of QGP is not expected. In this study, production of prompt $D^+$ and $D^+_s$ in pPb collisions is measured with the LHCb detector at center-of-mass energy $\sqrt{sNN}=8.16$ TeV. LHCb's unique forward coverage together with its precise tracking and vertexing provides the possibility to measure the charm hadrons at very low transverse momentum with high accuracy. In addition to the recent results of prompt $D^+$ and $D^+_s$ production, we will also present $D^+_s$ to $D^+$ production ratio as a function of multiplicity and its comparisons to theoretical models.