Experiments over the last decade at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory have yielded evidence for the formation of the new state of matter called the quark-gluon plasma (QGP). Normally, quarks (and their associated gluons) are found only in colorless doublets (mesons) or triplets (baryons), but when raised above the cross-over threshold at a temperature of ∼ 175 MeV, a strongly-coupled partonic medium of asymptotically free quarks and gluons is expected to form. The focus of heavy-ion physics at both the RHIC and Large Hadron Collider (LHC) experiments has been to study physical processes that allow for a better grasp of the properties of this medium. Because of the large center-of-mass energy per nucleon pair ([squareroot]s(NN)) of 2.76 TeV in Pb+Pb collisions at the LHC and substantial delivered integrated luminosities, the study of new processes in nucleus-nucleus collisions has become possible. One of those processes is Z-boson production, which due to it not interacting strongly, being produced in hard collisions and having a decay channel that does not interact with the QGP, can act as a control in understanding the cold nuclear matter effects present in heavy-ion collisions. This dissertation presents the measurement of the production of Z bosons in the dimuon and dielectron decay channels in Pb+Pb and p+p collisions at [squareroot]s(NN) of 2.76 TeV obtained by the CMS experiment at the LHC. The analysis is based on the data sample collected during the Pb+Pb run in 2011, which corresponds to an integrated luminosity of 150 [mu]b−1 and on the p+p data sample collected in 2013, at the same center-of-mass energy, with an integrated luminosity of 5.4 pb−1. The ratio of Pb+Pb to p+p yields, scaled by the number of incoherent nucleon-nucleon collisions, R(AA), is expected to be equal to unity if there are no nuclear effects modifying the production of the Z boson in the Pb+Pb collisions. The R(AA) for centrality-integrated Z-boson production is found to be 1.06 ± 0.05 (stat) ± 0.08 (syst) in the dimuon channel and 1.02 ± 0.08 (stat) ± 0.15 (syst) in the dielectron channel, and shows no nuclear modification across the rapidity, transverse momentum and centrality bins measured. This result demonstrates that the binary-collision scaling is seen to hold in the kinematic region studied, which is expected for a colorless probe that is unaffected by a deconfined QGP. It also opens avenues to study processes that are strongly modified by the QGP, by using Z production as a control.

The production of Z bosons in pPb collisions at √sNN = 5.02TeV is studied by the CMS experiment via the electron and muon decay channels. The inclusive cross section is compared to pp collision predictions, and found to scale with the number of elementary nucleon-nucleon collisions. The differential cross sections as a function of the Z boson rapidity and transverse momentum are measured. Though they are found to be consistent within uncertainty with theoretical predictions both with and without nuclear effects, the forward-backward asymmetry suggests the presence of nuclear effects at large rapidities. These results provide new data for constraining nuclear parton distribution functions.

With this research, the ATLAS Collaboration measures the inclusive production of Z bosons via their decays into electron and muon pairs in p + Pb collisions at \(\sqrt{s_{\mathrm{NN}}} = 5.02\) TeV at the Large Hadron Collider. The measurements are made using data corresponding to integrated luminosities of 29.4 and 28.1 nb-1 for Z → ee and Z → [mu][mu], respectively. The results from the two channels are consistent and combined to obtain a cross section times the Z → ll branching ratio, integrated over the rapidity region

The production of Z bosons is studied in the dimuon and dielectron decay channels in PbPb and pp collisions at [arrow]"NN = 2.76 TeV, using data collected by the CMS experiment at the LHC. The PbPb data sample corresponds to an integrated luminosity of about 166 [mu]b-1, while the pp data sample collected in 2013 at the same nucleon-nucleon centre-of-mass energy has an integrated luminosity of 5.4 pb-1. The Z boson yield is measured as a function of rapidity, transverse momentum, and collision centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic nucleon-nucleon collisions, is found to be 1.06 " 0.05 (stat) " 0.08 (syst) in the dimuon channel and 1.02 " 0.08 (stat) " 0.15 (syst) in the dielectron channel, for centrality-integrated Z boson production. This binary collision scaling is seen to hold in the entire kinematic region studied, as expected for a colourless probe that is unaffected by the hot and dense QCD medium produced in heavy ion collisions.

A search for Z bosons in the mu+̂mu-̂ decay channel has been performed in PbPb collisions at a nucleon-nucleon centre of mass energy = 2.76 TeV with the CMS detector at the LHC, in a 7.2 inverse microbarn data sample. The number of opposite-sign muon pairs observed in the 60--120 GeV/c2̂ invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of (33.8 +/- 5.5 (stat) +/- 4.4 (syst)) 10{̂-8}, in the.

High-precision measurements are made of Z boson production in proton-antiproton collisions at √s = 1.96 TeV recorded by the Collider Detector at Fermilab, using the electron decay channel. The cross-section times branching ratio is measured to be ?Z · Br(Z → e+e-) = (255.7 ± 2.4stat ± 5.2sys ± 15.2lum)pb in a dataset of 194 pb-1 collected between March 2002 and June 2003. This agrees well with theoretical predictions. The cross-section for W boson production in the electron channel has also been measured in the subset of this dataset of 72 pb-1 collected up until January 2003. Using this smaller dataset the ratio of cross-sections is determined to be R ≡ ?W · Br(W → e?)/?Z · Br(Z → ee) = 10.82 ± 0.18stat ± 0.16sys. Combining these results with measurements made in the muon channel gives R = 10.92 ± 0.15stat ± 0.14sys (e + ? channels), from which the branching ratio of the W to electrons and muons, and the total width of the W, have been extracted: Br(W → l?) = 0.1089 ± 0.0022 (l = e,?); ?(W) = 2078.8 ± 41.4 MeV, which are in good agreement with the Standard Model values and with other measurements. The CKM quark mixing matrix element.