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).
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 $10^{-6}$.
The cross-sections and the forward-backward charge asymmetries of muon and tau pairs produced ine+e− collisions at\(\sqrt s= 35 GeV\) have been measured by the JADE Collaboration. The cross-sections,\(\sigma _\mu(\sqrt s= GeV) = 69.79 \pm 1.35 \pm 1.40 pb\) and\(\sigma _\mu(\sqrt s= GeV) = 71.72 \pm 1.48 \pm 1.61 pb\), are in agreement with the QED α3 prediction. The charge asymmetries areAμ=−(9.9±1.5±0.5)% andAτ=−(8.1±2.0±0.6)% in agreement with the value −9.2% predicted by the standard model, usingMZ=91.0 GeV and sin2θW=0.230.
No description provided.
We report on a measurement of the forward-backward charge asymmetry in e+e−→qq¯ at KEK TRISTAN, where the asymmetry is near maximum. We sum over all flavors and measure the asymmetry by determining the charge of the quark jets. In addition we exploit flavor dependencies in the jet charge determination to enhance the contributions of certain flavors. This provides a check on the asymmetries of individual flavors. The measurement agrees with the standard model expectations.
Forward--backward asymmetry summed over all flavours of quarks.
At the tagged photon facility PHOENICS at the Bonn accelerator ELSA a measurement of the target asymmetry of the reaction γp→pη from threshold to 1150 MeV has been performed. Simultaneously the reaction γp→pπ0 has been measured in the first resonance region. Results are presented for both reactions. The target asymmetry data are suited to put considerable constraints on the model parameters used for the theoretical description of meson photoproduction.
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
Spin asymmetries for the 16O(γ→,pπ−) reaction are reported for incident photon energies of 293 ± 20 MeV, proton angles ranging from 28° to 140° (lab), and pion angles of 35° to 115°. The data are compared with calculations in a quasifree plane-wave impulse approximation model. This model is in good agreement with the data at small momentum transfer q, but does not follow the trend of the data at large q. Sensitivity to the Δ-nucleus potential and to modification of the Δ lifetime from nuclear medium effects are explored using a simple modification of the Δ propagator in the calculations.
The data are extracted from the figures by S.Slabospitsky. ASYM is the spin asymmetry. It is the ratio of the difference to the sum of the cross sections with the photon's linear polarization oriented parallel or perpendicular to the scattering plane.
The data are extracted from the figures by S.Slabospitsky. ASYM is the spin asymmetry. It is the ratio of the difference to the sum of the cross sections with the photon's linear polarization oriented parallel or perpendicular to the scattering plane.
The data are extracted from the figures by S.Slabospitsky. ASYM is the spin asymmetry. It is the ratio of the difference to the sum of the cross sections with the photon's linear polarization oriented parallel or perpendicular to the scattering plane.
A leading charm meson is one with longitudinal momentum fraction, xF>0, whose light quark (or antiquark) is of the same type as one of the quarks in the beam particles. We report on the production asymmetry, A=[σ(leading-σ(nonleading)]/[σ(leading)+σ(nonleading)] as a function of xF. The data consist of 1500 fully reconstructed D± and D*± decays in Fermilab experiment E 769. We find a significant asymmetry for the production of charm quarks is not expected in perturbative quantum chromodynamics.
Asymmetry as function of XL.
Asymmetry as function of PT**2.
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the {HERMES} spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle $\phi$ of the hadron production plane around the virtual photon direction relative to the lepton scattering plane was measured for $\pi^+,\pi^-$ and $\pi^0$ mesons. The dependence of this amplitude on the Bjorken scaling variable and on the pion fractional energy and transverse momentum is presented. The results are compared to theoretical model calculations.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Using data from Fermilab fixed-target experiment E769, we have measured particle-antiparticle production asymmetries for Lambda0 hyperons in 250 GeV/c pi+-, K+- and p -- nucleon interactions. The asymmetries are measured as functions of Feynman-x (x_F) and p_t^2 over the ranges -0.12<=x_F<=0.12 and 0<=p_t^2<=3 (GeV/c)^2 (for positive beam) and -0.12<=x_F<=0.4 and 0<=p_t^2<=10 (GeV/c)^2 (for negative beam). We find substantial asymmetries, even at x_F around zero. We also observe leading-particle-type asymmetries. These latter effects are qualitatively as expected from valence-quark content of the target and variety of projectiles studied.
LAMBDA production asymmetries versus XL for the positive beams.
LAMBDA production asymmetries versus PT**2 for the positive beams.
LAMBDA production asymmetries versus XL for the negative beams.
Measurements of the forward-backward asymmetry of e + e − → cc events were carried out at a mean √s energy of 57.95 GeV at TRISTAN, KEK. The cc events were tagged either by the full-reconstruction of D ∗± or the inclusive P T spectrum of π s ± from D ∗± → D 0 ( D 0 )π s ± . The forward-backward asymmetry was measured to be A FB c = −0.49 −0.13 +0.14 (stat.) ± 0.06 (syst.), consistent with the standard model.
No description provided.
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