Inclusive and differential measurements of the top-antitop ($t\bar{t}$) charge asymmetry $A_\text{C}^{t\bar{t}}$ and the leptonic asymmetry $A_\text{C}^{\ell\bar{\ell}}$ are presented in proton-proton collisions at $\sqrt{s} = 13$ TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb$^{-1}$, combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive $t\bar{t}$ charge asymmetry is measured to be $A_\text{C}^{t\bar{t}} = 0.0068 \pm 0.0015$, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the $t\bar{t}$ system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients.
The unfolded inclusive charge asymmetry. The measured values are given with statistical and systematic uncertainties. The SM theory predictions calculated at NNLO in QCD and NLO in EW theory are listed, and the impact of the linear term of the Wilson coefficient on the $A_C^{t\bar{t}}$ prediction is shown for two different values. The scale uncertainty is obtained by varying renormalisation and factorisation scales independently by a factor of 2 or 0.5 around $\mu_0$ to calculate the maximum and minimum value of the asymmetry, respectively. The nominal value $\mu_0$ is chosen as $H_T/4$. The variations in which one scale is multiplied by 2 while the other scale is divided by 2 are excluded. Finally, the scale and MC integration uncertainties are added in quadrature.
The unfolded differential charge asymmetry as a function of the invariant mass of the top pair system. The measured values are given with statistical and systematic uncertainties. The SM theory predictions calculated at NNLO in QCD and NLO in EW theory are listed, and the impact of the linear term of the Wilson coefficient on the $A_C^{t\bar{t}}$ prediction is shown for two different values. The scale uncertainty is obtained by varying renormalisation and factorisation scales independently by a factor of 2 or 0.5 around $\mu_0$ to calculate the maximum and minimum value of the asymmetry, respectively. The nominal value $\mu_0$ is chosen as $H_T/4$. The variations in which one scale is multiplied by 2 while the other scale is divided by 2 are excluded. Finally, the scale and MC integration uncertainties are added in quadrature.
The unfolded differential charge asymmetry as a function of the transverse momentum of the top pair system. The measured values are given with statistical and systematic uncertainties. The SM theory predictions calculated at NNLO in QCD and NLO in EW theory are listed. The scale uncertainty is obtained by varying renormalisation and factorisation scales independently by a factor of 2 or 0.5 around $\mu_0$ to calculate the maximum and minimum value of the asymmetry, respectively. The nominal value $\mu_0$ is chosen as $H_T/4$. The variations in which one scale is multiplied by 2 while the other scale is divided by 2 are excluded. Finally, the scale and MC integration uncertainties are added in quadrature.
The energy and centrality dependence of local particle pseudorapidity densities as well as validity of various parametrizations of the distributions are examined. The dispersion, σ, of the rapidity density distribution of produced particles varies slowly with centrality and is 0.80, 0.98, 1.21 and 1.41 for central interactions at 3.7, 14.6, 60 and 200A GeV incident energy, respectively, σ is found to be independent of the size of the interacting system at fixed energy. A novel way of representing the window dependence of the multiplicity as normalized variance versus inverse average multiplicity is outlined.
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NUCLEUS IS AGBR, CENTRAL EVENTS.
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We present a measurement of the top quark pair ttbar production cross section in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1} of data collected by the DO detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the ttbar content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1} (syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.
TTBAR production cross section from the combined electron+jet and muon+jet channels.
In this letter the distribution of slow target associated particles emitted in Au + Emulsion interactions at 11.6 A GeV/ c is studied. The three models RQMD, FRITIOF and VENUS are used for comparisons and especially their treatment of rescattering is investigated.
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PROJECTILE ASSOCIATED HE-FRAGMENTS.
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The isoscalar structure functions xF_3 and F_2 are measured as functions of x averaged over all Q~2 permissible for the range 6 to 28 GeV of incident (anti)neutrino energy. With the measured values of xF_3, the value of the Gross-Llewellyn Smith sum rule is found to be $\int_{0}~{1}{F_3 dx} = 2.13\pm0.38 (stat)\pm 0.26 (syst)$. The QCD analysis of xF_3 provides $\Lambda_{\overline{MS}} =358 \pm 59 MeV$ . The obtained value of the strong interaction constant $\alpha_S (M_Z)=0.120~{+3}_{-4}$ is larger than most of the deep inelastic scattering results.
The value of F2 is extracted with R = 0. The difference F2(C=R=.1)-F2(C=R=0.) is also presented.
In an experiment on K--proton interactions in a hydrogen bubble chamber, the cross sections and angular distributions have been studied for elastic and charge-exchange scattering, and charged sigma hyperon production in the momentum range 90-300 MeV/c. Good agreement is found with previous cross sections except for the charge-exchange channel where the new values are 60% larger. The production distributions of the charged sigma hyperons and the polarisation of the Sigma + hyperon clearly indicate that P waves are present down to about 150 MeV/c, much lower than previously reported.
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A change in estimated integrated luminosity (from 226 pb$^{-1} to 257 pb$^{-1}$ leads to a corrected value for ${\sigma (p \bar p \to Z) \cdot}$Br${(Z \to \tau \tau)}$ of $209\pm13(stat.)\pm16(syst.)\pm13(lum) pb.
Total cross section for W boson pair production. The second systematic (DSYS) error is due to the uncertainty in the luminosity.
Results are presented on π + p and K + p elastic scattering at 250 GeV/ c , the highest momentum so far reached for positive meson beams. The experiment (NA22) was performed with the european hybrid spectrometer. The π + p elastic cross section stays constant with energy while the K + p cross section increases.
No description provided.
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ERRORS IN ELASTIC CROSS SECTIONS INCLUDE SYSTEMATIC ERRORS.
Pseudorapidity distributions of relativistic singly charged particles in oxygen-induced emulsion interactions at 14.6, 60, and 200 GeV/nucleon are studied. Limiting fragmentation behavior is observed in both the target and projectile fragmentation regions for a central as well as for a minimum-bias sample. Comparisons with the fritiof model reveal that the picture of fragmenting strings successfully describes the observed data.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
The inclusive production of vector mesons (charged ρ(770), ω(783), ϕ(1020) and neutralK*(892)) in π−p interactions at 360 GeV/c is studied. The data are based on 160 000 reconstructed events recorded in the NA 27 Experiment using the LEBC-EHS facility at CERN. The production cross sections in the forward hemisphere in c.m.s. and the longitudinal momentum distributions are determined. The results are compared with data obtained at lower energies.
No description provided.
Upper limits of cross sections.
Cross sections extrapolated to x > 0.