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This dissertation describes a measurement of the forward-backward asymmetry(A{sub FB}) in p{bar p} → Z/[gamma]* → ee events using 5.0 fb−1 data collected by the D0 detector at the Fermilab Tevatron. The AFB is measured as a function of the invariant mass of the electron-positron pair. Along with obtaining normalized differential cross section 1/[sigma] x d[sigma]/dM and Z to light quark couplings, we measured the Standard Model(SM) fundamental parameter, the effective weak mixing angle sin2 [theta]{sub eff}{sup lept}, with an unprecedented precise in light quark sector, namely the single D0 measurement has surpassed the LEP combination of four experiment results of inclusive hadronic charge asymmetry.
We present a measurement of the forward-backward charge asymmetry (A{sub FB}) in p{bar p} 2!Z/[gamma]* + X 2!ee− + X events at a center-of-mass energy of 1.96 TeV using 1.1 fb−1 of data collected with the D0 detector at the Fermilab Tevatron collider. A{sub FB} is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the A{sub FB} measurement to extract the effective weak mixing angle sin2 [theta]{sub W}{sup eff} = 0.2327 ± 0.0018 (stat.) ± 0.0006 (syst.).
We present a direct measurement of the parity-violating parameter A{sub b} by analyzing the left-right forward-backward asymmetry of b quarks in ee− --> Z{sup o} --> b{bar b}. The SLD experiment observes hadronic decays of Z{sup o} bosons produced at resonance in collisions of longitudinally polarized electrons and unpolarized positrons at the SLC. Heavy flavor decays of the Z{sup o} are identified by taking advantage of the long lifetime of B hadrons, the small, stable SLC beam spot, and precise tracking from SLD. The asymmetry A{sub b} is measured with a self-calibrating technique employing momentum-weighted track charge from both hemispheres in the tagged events. From our 1994--1995 sample of 3.6 pb−1 of ee− annihilation data with a luminosity-weighted average e− polarization of 77.3%, and our 1993 sample of 1.8 pb−1 with a luminosity-weighted polarization of 63.1%, we obtain A{sub b}(preliminary) = 0.843 " 0.046(stat.) " 0.051(syst.).
The forward-backward asymmetry parameter ($A_{\rm FB}$) as a function of dilepton invariant mass in $Z / \gamma^* \rightarrow l^+l^-$ ($l$=$e$ or $\mu$) at $\sqrt{s}$=7 TeV is measured using 2.2 fb$^{-1}$ of $pp$ collision data in 2011. The uncorrected (raw) $A_{\rm FB}$ and the corrected (unfolded) $A_{\rm FB}$ is performed in a wide mass range between 40 GeV/$c^{2}$ to 1000 GeV/$c^{2}$, and comparative studies and correction techniques with simulation are described in detail. We measure raw $A_{\rm FB}$ for the first time in a large rapidity range of 3 $>
The authors describe a measurement of the charge asymmetry of electrons from W{sup {+-}} boson decays using p{bar p} {yields} W {yields} e{nu} events. They also present a measurement of the forward-backward charge asymmetry of electron-positron pairs resulting from the process p{bar p} {yields} Z{sup 0}/{gamma}* {yields} e{sup +}e{sup -}, from which they extract the Z{sup 0}-quark and Z{sup 0}-electron coupling constants and measure the sensitivity of the CDF experiment to these couplings. These analyses use integrated luminosities of 170 pb{sup -1} and 72 pb{sup -1}, respectively, of data collected by the CDF Run II detector at the Fermilab Tevatron.
The charge asymmetry in $t \bar t$ events is measured using dilepton final states produced in pp collisions at the LHC at √s = 8 TeV. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.5 fb-1. The measurements are performed using events with two oppositely charged leptons (electrons or muons) and two or more jets, where at least one of the jets is identified as originating from a bottom quark. The charge asymmetry is measured from differences in kinematic distributions, unfolded to the parton level, of positively and negatively charged top quarks and leptons. The $t \bar t$ and leptonic charge asymmetries are found to be 0.011 ± 0.011 (stat) ± 0.007 (syst) and 0.003 ± 0.006 (stat) ± 0.003 (syst), respectively. Lastly, These results, as well as charge asymmetry measurements made as a function of $t \bar t$ system kinematic properties, are in agreement with predictions of the standard model.