We report the first measurement of the longitudinal double-spin asymmetry $A_{LL}$ for mid-rapidity di-jet production in polarized $pp$ collisions at a center-of-mass energy of $\sqrt{s} = 200$ GeV. The di-jet cross section was measured and is shown to be consistent with next-to-leading order (NLO) perturbative QCD predictions. $A_{LL}$ results are presented for two distinct topologies, defined by the jet pseudorapidities, and are compared to predictions from several recent NLO global analyses. The measured asymmetries, the first such correlation measurements, support those analyses that find positive gluon polarization at the level of roughly 0.2 over the region of Bjorken-$x > 0.05$.
Di-jet A_LL asymmetry vs parton-level invariant mass for the same-sign di-jet topology. The systematic uncertainty on the mass includes contributions from jet energy scale, the correction to parton-level, and the difference between NLO and PYTHIA cross sections. The systematic uncertainty on the asymmetry includes contributions from trigger and reconstruction bias and residual transverse beam polarization components. A 6.5% uncertainty common to all points due to uncertainty on the measured beam polarizations is also present, but not included in the uncertainties quoted below.
Theoretical predictions for the di-jet A_LL asymmetry for the same-sign topology using the DSSV14 and NNPDFpol1.1 polarized PDF sets. The DSSV14 prediction is presented without uncertainty while the systematic uncertainty on the NNPDFpol1.1 prediction contains contributions from factorization and renormalization scale uncertainties and PDF uncertainties.
Di-jet A_LL asymmetry vs parton-level invariant mass for the opposite-sign di-jet topology. The systematic uncertainty on the mass includes contributions from jet energy scale, the correction to parton-level, and the difference between NLO and PYTHIA cross sections. The systematic uncertainty on the asymmetry includes contributions from trigger and reconstruction bias and residual transverse beam polarization components. A 6.5% uncertainty common to all points due to uncertainty on the measured beam polarizations is also present, but not included in the uncertainties quoted below.
We have measured both the rates and the forward-backward asymmetry of ℓ + ℓ − from Z 0 →ℓ + ℓ − (where ℓ= μ , τ ) with the L3 detector. We obtained Γ ℓℓ =88±4±3 MeV and the vector neutral current coupling constant, g v =0.00±0.07 and the axial vector neutral current coupling constant, g A =−0.515±0.015.
No description provided.
We report on the first measurements of e + e − annihilations into hadrons and lepton pairs at centre-of-mass energies between 130 GeV and 140 GeV. In a total luminosity of 5 pb −1 collected with the L3 detector at LEP we select 1577 hadronic and 401 lepton-pair events. The measured cross sections and leptonic forward-backward asymmetries agree well with the Standard Model predictions.
An additional systematic error 0.034 for E+ E- channel.
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No description provided.
The charge asymmetry has been measured using $19,039W$ decays recorded by the CDF detector during the 1992-93 run of the Tevatron Collider. The asymmetry is sensitive to the ratio of $d$ and $u$ quark distributions to $x<0.01$ at $Q~2 \approx M_W~2$, where nonperturbative effects are minimal. It is found that of the two current sets of parton distributions, those of Martin, Roberts and Stirling (MRS) are favored over the sets most recently produced by the CTEQ collaboration. The $W$ asymmetry data provide a stronger constraints on $d/u$ ratio than the recent measurements of $F_2~{\mu n}/F_2~{\mu p}$ which are limited by uncertainties originating from deutron corrections.
Charge asymmetry defined as (DSIG(Q=L+)/DYRAP - DSIG(Q=L-)/DYRAP)/ (DSIG(Q=L+)/DYRAP + DSIG(Q=L-)/DYRAP). Here LEPTON are E and MU.
We report on a measurement of the mass dependence of the forward-backward charge asymmetry, A_FB, and production cross section dsigma/dM for e+e- pairs with mass M_ee>40 GeV/c2. The data sample consists of 108 pb-1 of p-pbar collisions at sqrt(s)=1.8 TeV taken by the Collider Detector at Fermilab during 1992-1995. The measured asymmetry and dsigma/dM are compared with the predictions of the Standard Model and a model with an extra Z' gauge boson.
The E+ E- production cross section and the forward-backward asymmetry. The errors contain the statistical and systematic uncertainties combined in quadrature, but not the additional uncertainty of the luminosity.
The measurements of Rb = sigma(e+e- -> bb~)/sigma(e+e- -> qq~) and of the b quark forward-backward charge asymmetry, A^b_fb, at centre-of-mass energies above the Z pole are described. The measurement of Rb is performed at \root{s} between 130 and 189 GeV using a b-tagging method that exploits the relatively large decay length of b-hadrons. The measurement of A^b_fb is performed using the large statistics event sample collected at \root{s}=189 GeV with a lepton-tag analysis based on the selection of prompt muons and electrons. The results at \root{s}=189 GeV are: Rb = 0.163 +/- 0.013 (stat.) +/- 0.005 (syst.), A^b_fb = 0.61 +/- 0.18 (stat.) +/- 0.09 (syst.).
No description provided.
A significant charge asymmetry is observed in the hadronic Z decays with the ALEPH detector at LEP. The asymmetry expressed in terms of the difference in momentum weighted charges in the two event hemispheres is measured to be < Q forward >−< Q backward >= −0.0084±0.0015 (stat.) ±0.0004 (exp. sys.). In the framework of the standard model this can be interpreted as a measurement of the effective electroweak mixing angle, sin 2 O w ( M z 2 =0.2300±0.0034 (stat.) ±0.0010 (exp. sys.) ±0.0038 (theor. sys.) or of the ratio of the vector to axual- vector coupling costants of the electron, g ve g Ae =+0.073±0.024.
No description provided.
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No description provided.
We have observed τ pair production at average CM energies of 13.9, 22.3, 34.5 and 43.1 GeV. The cross-sections are consistent with QED, the cut off parameters beingΛ+>161 GeV andΛ−169 GeV (95% CL). The topological branching fraction of the τ to 1 charged particle,B1, is 0.847±0.011 (stat)−0.013+0.016(syst) and no decays to 5 charged particles were observed resulting inB5<0.007 (95% CL). Within the 3 charged track final stateB(τ−→π−π+π−v)/(B(τ−→π−π+π−v)+B(τ−→π−π+π−π0v))=0.37−0.20+0.35
No description provided.
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