Exclusive production in $pp$ and PbPb collisions at the LHCb experiment

The LHCb experiment is one of the four main detectors installed around the points where beams collide after accelerated by LHC. Initially the LHCb was designed to study $B$ and $D$ mesons in order to elucidate the $CP$ violation mechanism. However, this detector turned out fairly effective to study central exclusive production (CEP). Two cross-section measurements performed using the data collected during the years of 2011, 2012 and 2015 are described in this thesis. The cross-section of dimuon electromagnetic production is performed with $pp$ collisions at two center-of-mass energies: $\sqrt{s} = 7\,{\rm TeV}$ with 2011 data and $\sqrt{s} = 8\,{\rm TeV}$ with 2012 data. The study of coherent photonuclear production of $J/\psi$ at a nucleon-nucleon center-of-mass energy $\sqrt{s_{NN}} = 5 \,{\rm TeV}$ is performed with PbPb collisions collected during November and December of 2015.