Measurement of associated Z plus charm production in proton-proton collisions at root s=8TeV

• Main Authors: Sirunyan, A. M., Tumasyan, A. R., Adam, Wolfgang, Ambrogi, Federico, Asilar, Ece, Md. Ali, Mohd. Adli
• Format: Article
• Language: English; English
• Published: Springer Verlag 2018
• Subjects: Q Science (General); QC Physics
• Online Access: http://irep.iium.edu.my/70402/1/70402_Measurement%20of%20associated%20Z%20%2B%20charm%20production_new.pdf; http://irep.iium.edu.my/70402/7/70402_Measurement%20of%20associated%20Z%20plus%20charm%20production_wos.pdf; http://irep.iium.edu.my/70402/; https://helda.helsinki.fi//bitstream/handle/10138/235488/10.1140_epjc_s10052_018_5752_x.pdf?sequence=1

A study of the associated production of a Z boson and a charm quark jet (Z + c), and a comparison to production with a b quark jet (Z + b), in pp collisions at a centre-of-mass energy of 8 TeV are presented. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 fb−1, collected with the CMS detector at the CERN LHC. The Z boson candidates are identified through their decays into pairs of electrons or muons. Jets originating from heavy flavour quarks are identified using semileptonic decays of c or b flavoured hadrons and hadronic decays of charm hadrons. The measurements are performed in the kinematic region with two leptons with p T > 20 GeV, |η| < 2.1, 71 < m < 111 GeV, and heavy flavour jets with p jet T > 25 GeV and |ηjet| < 2.5. The Z + c production cross section is measured to be σ (pp → Z + c + X)B(Z → +−) = 8.8±0.5 (stat)±0.6 (syst) pb. The ratio of the Z+c and Z+b production cross sections is measured to be σ (pp → Z+c+X)/σ (pp → Z+b+X) = 2.0±0.2 (stat)±0.2 (syst). The Z+c production cross section and the cross section ratio are also measured as a function of the transverse momentum of the Z boson and of the heavy flavour jet. The measurements are compared with theoretical predictions.