Estudo de Estranheza em Colisões próton-próton no LHC

In this work, we study the production of strange hadrons in proton-proton (pp) collisions at energies of $\sqrt{s}=7~TeV$ measured by the ALICE experiment at the LHC. We present the first measurements of particle yields at central rapidities for the $K^{0}_{S}$ meson as well as for the $\Lambda$, $\Xi^{-}$ and $\Omega^{-}$ baryons and their antiparticles. Total particle production rates exceed predictions by models that use Perturbative Quantum Chromodynamics (pQCD). In particular, we compare our measurements to predictions by the PYTHIA event generator and find that predictions agree with data only at transverse momenta (pt) higher than $6-7~GeV/c$. This result indicates that the leading order processes implemented in PYTHIA are well adjusted, but the implementation of a calculation that describes the data at low $p_{t}$ is still an open issue. The results presented here should contribute to improve our understanding of particle production mechanisms at low $p_{t}$. Proton-proton collisions are also used as a reference for nuclear collisions of different multiplicities in the study of Quark-Gluon Plasma (QGP) formation. The increase of strangeness production is considered an important observable of the QGP. In this context, we study the dependence of strange particle production with charged particle multiplicity and find that there is no indication of an increase strangeness production rate in pp collisions. This is an important result that contributes to the studies that consider the possibility of QGP formation in pp collisions.