This letter reports a measurement of the muon charge asymmetry from W Boson produced in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS experiment at the LHC. The asymmetry is measured in the W Boson to muon decay mode as a function of the muon pseudorapidity using a data sample corresponding to a total integrated luminosity of 31 pb-1. The results are compared to predictions based on next-to-leading order calculations with various parton distribution functions. This measurement provides information on the u and d quark momentum fractions in the proton.
The muon charge asymmetry from $W$-boson decays in bins of absolute pseudorapidity. Note that these numbers are taken from the journal version which differ slightly from those in the archive version 1.
A measurement of the energy asymmetry in jet-associated top-quark pair production is presented using 139 $\mathrm{fb}^{-1}$ of data collected by the ATLAS detector at the Large Hadron Collider during $pp$ collisions at $\sqrt{s}=13$ TeV. The observable measures the different probability of top and antitop quarks to have the higher energy as a function of the jet scattering angle with respect to the beam axis. The energy asymmetry is measured in the semileptonic $t\bar{t}$ decay channel, and the hadronically decaying top quark must have transverse momentum above $350$ GeV. The results are corrected for detector effects to particle level in three bins of the scattering angle of the associated jet. The measurement agrees with the SM prediction at next-to-leading-order accuracy in quantum chromodynamics in all three bins. In the bin with the largest expected asymmetry, where the jet is emitted perpendicular to the beam, the energy asymmetry is measured to be $-0.043\pm0.020$, in agreement with the SM prediction of $-0.037\pm0.003$. Interpreting this result in the framework of the Standard Model effective field theory (SMEFT), it is shown that the energy asymmetry is sensitive to the top-quark chirality in four-quark operators and is therefore a valuable new observable in global SMEFT fits.
Data measurements and predictions of the energy asymmetry in three bins of the jet angle $\theta_j$. The SM prediction was obtained from simulations of $t\bar{t}j$ events with MadGraph5_aMC@NLO + Pythia 8 at NLO in QCD for $t\bar{t}j$ + PS, including MC statistical and scale uncertainties.
Data Measurements and predictions of the energy asymmetry in three bins of the jet angle $\theta_j$. The SM prediction was obtained from simulations of $t\bar{t}j$ events with MadGraph5_aMC@NLO + Pythia 8 at NLO in QCD for $t\bar{t}j$ + PS, including MC statistical and scale uncertainties.
Correlation coefficients $\rho_{i,j}$ for the statistical and systematic uncertainties between the $i$-th and $j$-th bin of the differential $A_E$ measurement as a function of the jet scattering angle $\theta_j$
A search for the leptonic charge asymmetry ($A_\text{c}^{\ell}$) of top-quark$-$antiquark pair production in association with a $W$ boson ($t\bar{t}W$) is presented. The search is performed using final states with exactly three charged light leptons (electrons or muons) and is based on $\sqrt{s} = 13$ TeV proton$-$proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN during the years 2015$-$2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. A profile-likelihood fit to the event yields in multiple regions corresponding to positive and negative differences between the pseudorapidities of the charged leptons from top-quark and top-antiquark decays is used to extract the charge asymmetry. At reconstruction level, the asymmetry is found to be $-0.123 \pm 0.136$ (stat.) $\pm \, 0.051$ (syst.). An unfolding procedure is applied to convert the result at reconstruction level into a charge-asymmetry value in a fiducial volume at particle level with the result of $-0.112 \pm 0.170$ (stat.) $\pm \, 0.054$ (syst.). The Standard Model expectations for these two observables are calculated using Monte Carlo simulations with next-to-leading-order plus parton shower precision in quantum chromodynamics and including next-to-leading-order electroweak corrections. They are $-0.084 \, ^{+0.005}_{-0.003}$ (scale) $\pm\, 0.006$ (MC stat.) and $-0.063 \, ^{+0.007}_{-0.004}$ (scale) $\pm\, 0.004$ (MC stat.) respectively, and in agreement with the measurements.
Measured values of the leptonic charge asymmetry ($A_c^{\ell}$) in ttW production in the three lepton channel. Results are given at reconstruction level and at particle level. Expected values are obtained using the Sherpa MC generator.
We study $\Lambda$ and $\bar{\Lambda}$ production asymmetries in $p \bar{p} \rightarrow \Lambda (\bar{\Lambda}) X$, $p \bar{p} \rightarrow J/\psi \Lambda (\bar{\Lambda}) X$, and $p \bar{p} \rightarrow \mu^\pm \Lambda (\bar{\Lambda}) X$ events recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV. We find an excess of $\Lambda$'s ($\bar{\Lambda}$'s) produced in the proton (antiproton) direction. This forward-backward asymmetry is measured as a function of rapidity. We confirm that the $\bar{\Lambda}/\Lambda$ production ratio, measured by several experiments with various targets and a wide range of energies, is a universal function of "rapidity loss", i.e., the rapidity difference of the beam proton and the lambda.
Forward-backward asymmetry $A_{FB}$ of $\Lambda$ and $\bar{\Lambda}$ with $p_T > 2.0$ GeV in minimum bias events $p \bar{p} \rightarrow \Lambda (\bar{\Lambda}) X$, events $p \bar{p} \rightarrow J/\psi \Lambda (\bar{\Lambda}) X$, and events $p \bar{p} \rightarrow \mu^\pm \Lambda (\bar{\Lambda}) X$.
Forward-backward asymmetry $A_{FB}$ of $\Lambda$ and $\bar{\Lambda}$ in bins of $p_T$ in events $p \bar{p} \rightarrow \mu^\pm \Lambda (\bar{\Lambda}) X$.
We measure the forward-backward asymmetries $A_{\rm FB}$ of charged $\Xi$ and $\Omega$ baryons produced in $p \bar{p}$ collisions recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV as a function of the baryon rapidity $y$. We find that the asymmetries $A_{\rm FB}$ for charged $\Xi$ and $\Omega$ baryons are consistent with zero within statistical uncertainties.
Forward-backward asymmetry $A_{\rm FB}$ of $\Xi^\mp$ baryons with $p_T > 2$ GeV in minimum bias events, $p\bar{p} \rightarrow \Xi^\mp X$, and muon events $p \bar{p} \rightarrow \mu \Xi^\mp X$, and $A_{\rm FB}$ of $\Omega^-$ and $\Omega^+$ baryons with $p_T > 2$ GeV in muon events $p \bar{p} \rightarrow \mu \Omega^\mp X$. The first uncertainty is statistical, the second is systematic due to the detector asymmetry $A'_{\rm NS} A'_\Xi$.
We present a measurement of the forward--backward asymmetry in top quark-antiquark production using the full Tevatron Run II dataset collected by the D0 experiment at Fermilab. The measurement is performed in lepton+jets final states using a new kinematic fitting algorithm for events with four or more jets and a new partial reconstruction algorithm for events with only three jets. Corrected for detector acceptance and resolution effects, the asymmetry is evaluated to be 10.6+-3.0 %. Results are consistent with the standard model predictions which range from 5.0% to 8.8%. We also present the dependence of the asymmetry on the invariant mass of the top quark--antiquark system and the difference in rapidities of top quark and antiquark.
Production-level forward-backward asymmetry as a function of the absolute difference in rapidity of the top quark and antiquark. The measured values are calibrated and listed with their total uncertainties. The theoretical predictions are based on MC@NLO simulation.
Production-level forward-backward asymmetry as a function of the invariant mass of the top quark-antiquark system. The measured values are calibrated and listed with their total uncertainties. The theoretical predictions are based on MC@NLO simulation.
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 muon charge asymmetry from the decay of the $W$ boson via W to mu nu using 7.3 fb^{-1} of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider at sqrt{s} = 1.96 TeV. The muon charge asymmetry is presented in two kinematic regions in muon transverse momentum and event missing transverse energy: (p^{\mu}_{T} > 25 GeV, \met > 25 GeV) and (p^{\mu}_{T} > 35 GeV, \met > 35 GeV). The measured asymmetries are compared with theory predictions made using three parton distribution function sets. The predictions do not describe the data well for p^{\mu}_{T} > 35 GeV, \met > 35 GeV, and larger values of muon pseudorapidity.
Muon charge asymmetry for data and predictions from RESBOS+PHOTOS using the CTEQ6.6 PDFs. The measurement is shown with statistical uncertainties followed by systematic uncertainties. The uncertainties for the predictions are only from the PDFs.
Contributions from individual sources of systematic uncertainty for the ($p^{\mu}_{T} > 25$, $E_T^{missing} > 25$) GeV kinematic region. All uncertainty values are multiplied by 100. The columns (1-7) correspond to: 1.0 = Electro-Weak background 2.0 = Multi-Jet background 3.0 = Charge mis-identification 4.0 = Relative charge efficiency 5.0 = Magnet polarity weighting 6.0 = Momentum/$E_T^{missing}$ resolution 7.0 = Trigger isolation.
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)).
The production cross sections of the inclusive Drell-Yan processes W to l nu and Z/gamma to ll (l=e,mu) are measured in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector. The cross sections are reported integrated over a fiducial kinematic range, extrapolated to the full range and also evaluated differentially as a function of the W decay lepton pseudorapidity and the Z boson rapidity, respectively. Based on an integrated luminosity of about 35 pb^-1 collected in 2010, the precision of these measurements reaches a few per cent. The integrated and the differential W+- and Z/gamma cross sections in the e and mu channels are combined, and compared with perturbative QCD calculations, based on a number of different parton distribution sets available at NNLO.
Combined lepton charge asymmetry from W boson decays.
Fiducial cross sections of Z0 versus W+ from fitting the combined electron and muon decay data sets. The table shows the fitted ellipse centre in Z0 W+ space plus the ellipse radii and angle using the total uncertainties and only the experimental uncertainties.
Fiducial cross sections of Z0 versus W- from fitting the combined electron and muon decay data sets. The table shows the fitted ellipse centre in Z0 W- space plus the ellipse radii and angle using the total uncertainties and only the experimental uncertainties.