Abstract
We measure the particle-level forward-backward production asymmetry in $b\bar{b}$ pairs with masses $m(b\bar{b})$ larger than 150 GeV/$c^2$, using events with hadronic jets and employing jet charge to distinguish $b$ from $\bar{b}$. The measurement uses 9.5/fb of ppbar collisions at a center of mass energy of 1.96 TeV recorded by the CDF II detector. The asymmetry as a function of $m(b\bar{b})$ is consistent with zero, as well as with the predictions of the standard model. The measurement disfavors a simple model including an axigluon with a mass of 200 GeV/$c^2$ whereas a model containing a heavier 345 GeV/$c^2$ axigluon is not excluded.
Highlights
In recent years, the values of the forward-backward asymmetry (AFB) of top-quark-pair production measured at the Tevatron proton-antiproton collider at Fermilab have been consistently larger [1] than those predicted by the standard model (SM) [2,3,4,5,6,7]
We discriminate jets originated from b quarks (b jets) from jets originated from bquarks using the momentum-weighted average of the charges of the particles associated with each jet, Qjet
We find that the negativetagged component of the Monte Carlo (MC) templates must be scaled by 1.5 (1.3) to match the total number of low significance negative tags observed in the data
Summary
The values of the forward-backward asymmetry (AFB) of top-quark-pair production measured at the Tevatron proton-antiproton collider at Fermilab have been consistently larger [1] than those predicted by the standard model (SM) [2,3,4,5,6,7]. Further study of this phenomenon has led to a number of proposed extensions of the SM [8]. The momenta of the BÆ mesons in that measurement constrain the masses of the bbpairs to be smaller than the range probed in this measurement
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