Abstract

The LHCb Electroweak Physics Working Group has an ongoing program of measurements of the inclusive W , Z, and Z+jets cross-sections and of the charge asymmetry in W production. Measurements of W → μν_μ and Z → μμ(ee) have been carried out at 7 and 8 TeV. The 2011 dataset has been used to measure cross-sections of Z production in association with a D meson, inclusive Z → μμ , Z → μμ+jets, and Z+b-jets. Work on W → eν_e and W (Z) → μν_μ (μμ)+jets at 8 TeV is ongoing. Measurements of these decay channels at 13 TeV are also in progress. Recently, the forward-backward asymmetry in Z → μμ decays was used to extract the effective weak mixing angle – a fundamental parameter of the SM. Also, a first observation of top quark production in the forward region was made with a significance of 5.4 sigma.

The precision measurements of W/Z production performed at LHCb act as tests of QCD and electroweak theory in unprobed regions of x-Q² phase space. The LHCb detector is unique in the angular coverage of some of its subdetectors and is, therefore, complementary to the general purpose detectors, ATLAS and CMS . The current work thus gives crucial knowledge and experience, acting as a proof of principle for these measurements and prospective new physics searches in the forward region. Since the detector has high precision tracking, calorimetry, and a muon system close to the beamline, measurements extend up to boson rapidities of 4.5. Consequently, partons with extremely low (x≈10^-4 ) and high (x≈0.1) momentum fractions are probed. This enables these measurements to be used in constraining PDF sets, which has an indirect impact on all measurements made at the LHC .