We present measurements of the forward-backward asymmetry in the angular distribution of leptons from decays of top quarks and antiquarks produced in proton-antiproton collisions. We consider the final state containing a lepton and at least three jets. The entire sample of data collected by the D0 experiment during Run II of the Fermilab Tevatron Collider, corresponding to 9.7 inverse fb of integrated luminosity, is used. The asymmetry measured for reconstructed leptons is $A_{FB}^l = \big(2.9 \pm 2.1(stat.) ^{+1.5}_{-1.7}(syst.) \big)$%. When corrected for efficiency and resolution effects within the lepton rapidity coverage of $|y_l|<1.5$, the asymmetry is found to be $A_{FB}^l = \big(4.2 \pm 2.3(stat.) ^{+1.7}_{-2.0}(syst.) \big)$%. Combination with the asymmetry measured in the dilepton final state yields $A_{FB}^l = \big(4.2 \pm 2.0(stat.) \pm 1.4(syst.) \big)$%. We examine the dependence of $A_{FB}^l$ on the transverse momentum and rapidity of the lepton. The results are in agreement with predictions from the next-to-leading-order QCD generator \mcatnlo, which predicts an asymmetry of $A_{FB}^l = 2.0$% for $|y_l|<1.5$.
Observed ASYMFB(LEPTON) as a function of PT(LEPTON) at reconstruction level.
Observed production-level ASYMFB(LEPTON) as a function of PT(LEPTON).
Observed production-level ASYMFB(LEPTON) as a function of ABS(YRAP(LEPTON)).
We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.
CP-folded electron charge asymmetry for data with $E_T^{e} > 25$ GeV multiplied by 100. $\langle|\eta^e|\rangle$ is the cross section weighted average of electron pseudorapidity in each bin from RESBOS with PHOTOS.
CP-folded electron charge asymmetry for data with $25 < E_T^{e} < 35$ GeV multiplied by 100. $\langle|\eta^e|\rangle$ is the cross section weighted average of electron pseudorapidity in each bin from RESBOS with PHOTOS.
CP-folded electron charge asymmetry for data with $E_T^{e} > 35$ GeV multiplied by 100. $\langle|\eta^e|\rangle$ is the cross section weighted average of electron pseudorapidity in each bin from RESBOS with PHOTOS.
We present a measurement of the $W$ boson production charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center of mass energy of 1.96 TeV, using 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum is determined using a neutrino weighting method, and the asymmetry is measured as a function of the $W$ boson rapidity. The measurement extends over wider electron pseudorapidity region than previous results, and is the most precise to date, allowing for precise determination of proton parton distribution functions in global fits.
${\it CP}$-folded $W$ charge asymmetry for data and predictions from MC@NLO using NNPDF2.3 PDFs tabulated in percent (%) for each $|y_W|$ bin. The $\langle|y_W|\rangle$ is calculated as the cross section weighted average of $y_W$ in each bin from RESBOS with photos. For data, the first uncertainty is statistical and the second is systematic. The uncertainties on the prediction come from both the PDF uncertainties and $\alpha_s$ uncertainties. The numbers in this table are the revised data published on 10th December 2014 (after the journal publication).
Correlation coefficients between central values of asymmetry in different $|y_W|$ bins.
A search is conducted for non-resonant new phenomena in dielectron and dimuon final states, originating from either contact interactions or large extra spatial dimensions. The LHC 2012 proton-proton collision dataset recorded by the ATLAS detector is used, corresponding to 20 fb$^{-1}$ at $\sqrt{s}$ = 8 TeV. The dilepton invariant mass spectrum is a discriminating variable in both searches, with the contact interaction search additionally utilizing the dilepton forward-backward asymmetry. No significant deviations from the Standard Model expectation are observed. Lower limits are set on the $\ell\ell q q$ contact interaction scale $\Lambda$ between 15.4 TeV and 26.3 TeV, at the 95% credibility level. For large extra spatial dimensions, lower limits are set on the string scale $M_{S}$ between 3.2 TeV to 5.0 TeV.
Reconstructed $A_{\rm FB}$ distributions for data and the SM background estimate as a function of dielectron mass.
Reconstructed $A_{\rm FB}$ distributions for data and the SM background estimate as a function of dimuon mass.
This final analysis of hadronic and leptonic cross-sections and of leptonic forward-backward asymmetries in e+e- collisions with the OPAL detector makes use of the full LEP1 data sample comprising 161 pb^-1 of integrated luminosity and 4.5 x 10^6 selected Z decays. An interpretation of the data in terms of contributions from pure Z exchange and from Z-gamma interference allows the parameters of the Z resonance to be determined in a model-independent way. Our results are in good agreement with lepton universality and consistent with the vector and axial-vector couplings predicted in the Standard Model. A fit to the complete dataset yields the fundamental Z resonance parameters: mZ = 91.1852 +- 0.0030 GeV, GZ = 2.4948 +- 0.0041 GeV, s0h = 41.501 +- 0.055 nb, Rl = 20.823 +- 0.044, and Afb0l = 0.0145 +- 0.0017. Transforming these parameters gives a measurement of the ratio between the decay width into invisible particles and the width to a single species of charged lepton, Ginv/Gl = 5.942 +- 0.027. Attributing the entire invisible width to neutrino decays and assuming the Standard Model couplings for neutrinos, this translates into a measurement of the effective number of light neutrino species, N_nu = 2.984 +- 0.013. Interpreting the data within the context of the Standard Model allows the mass of the top quark, mt = 162 +29-16 GeV, to be determined through its influence on radiative corrections. Alternatively, utilising the direct external measurement of mt as an additional constraint leads to a measurement of the strong coupling constant and the mass of the Higgs boson: alfa_s(mZ) = 0.127 +- 0.005 and mH = 390 +750-280 GeV.
The forward-backward charge asymmetry in E+ E- --> MU+ MU- production corrected to the simple kinematic acceptance region ABS(COS(THETA(P=5))) < 0.95 and THETA(C=ACOL) < 15 degrees, and the energy of each fermion required to be greaterthan 6 GeV. Statistical errors only are shown. Also given are the asymmetries a fter correction for the beam energy spread to correspond to the physical asymmetry at the central value of SQRT(S).
The forward-backward charge asymmetry in E+ E- --> TAU+ TAU- production corrected to the simple kinematic acceptance region ABS(COS(THETA(P=5))) < 0.90 andTHETA(C=ACOL) < 15 degrees, and the energy of each fermion required to be great er than 6 GeV. Statistical errors only are shown. Also given are the asymmetriesafter correction for the beam energy spread to correspond to the physical asymm etry at the central value of SQRT(S).
The forward-backward charge asymmetry in E+ E- --> E+ E- production corrected to the simple kinematic acceptance region ABS(COS(THETA(P=5))) < 0.70 and THETA(C=ACOL) < 10 degrees, and the energy of each fermion required to be greater than 6 GeV. Statistical errors only are shown. Also given are the asymmetries after correction for the beam energy spread to correspond to the physical asymmetryat the central value of SQRT(S).
We present a measurement of the forward-backward charge asymmetry ($A_{FB}$) in $p\bar{p} \to Z/\gamma^{*}+X \to e^+e^-+X$ 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. $A_{FB}$ 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 $A_{FB}$ measurement to extract the effective weak mixing angle sin$^2\Theta^{eff}_W = 0.2327 \pm 0.0018 (stat.) \pm 0.0006 (syst.)$.
Unfolded forward-backward asymmetry as a function of the di-electron mass.
A measurement of the electron charge asymmetry in inclusive pp to W + X to e nu + X production at sqrt(s) = 7 TeV is presented based on data recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 840 inverse picobarns. The electron charge asymmetry reflects the unequal production of positive and negative W bosons in pp collisions. The electron charge asymmetry is measured in bins of absolute value of electron pseudorapidity in the range of abs(eta) < 2.4. The asymmetry rises from about 0.1 to 0.2 as a function of the pseudorapidity and is measured with a relative precision better than 7%. This measurement provides new stringent constraints for parton distribution functions.
Summary of the measured charge asymmetry results. The first uncertainty is statistical and the second is systematic. The theoretical predictions are obtained using MCFM interfaced with four different PDF models. The PDF uncertainties are estimated using the PDF reweighting technique. All values are in units of $10^{-3}$.
Covariance matrix for the systematic uncertainties on the asymmetry. All values are given in units of $10^{-6}$.
A measurement of the forward-backward asymmetry (A[FB]) of Drell-Yan lepton pairs in pp collisions at sqrt(s) = 7 TeV is presented. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 5 inverse femtobarns. The asymmetry is measured as a function of dilepton mass and rapidity in the dielectron and dimuon channels. Combined results from the two channels are also presented. The A[FB] measurement in the dimuon channel and the combination of the two channels are the first such results obtained at a hadron collider. The measured asymmetries are consistent with the standard model predictions.
The unfolded mu+mu- measurement of AFB at the Born level in four rapidity bins. The errors on data are statistical only.
The unfolded e+e- measurement of AFB at the Born level in four rapidity bins. The errors on data are statistical only.
Unfolded combined measurements of AFB in each M-|y| bin (mu+mu- and e+e- combined).
Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The measurements are used to determine the electromagnetic coupling constant alphaem at LEP2 energies. In addition, the results are used together with OPAL measurements at 91-183 GeV within the S-matrix formalism to determine the gamma-Z interference term and to make an almost model-independent measurement of the Z mass. Limits on extensions to the Standard Model described by effective four-fermion contact interactions or the addition of a heavy Z boson are also presented.
Measured forward backward asymmetries for MU+ MU- production. The data are corrected to no interference between initial and final state radiation.
Measured forward backward asymmetries for TAU+ TAU- production. The data are corrected to no interference between initial and final state radiation.
Measured forward backward asymmetries for E+ E- production.
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