Charge asymmetry in hadroproduction of heavy quarks

Abstract

A sizeable difference in the differential production cross section of top and antitop quarks, respectively, is predicted for hadronically produced heavy quarks. It is of order $α_s$ and arises from the interference between charge odd and even amplitudes respectively. For the TEVATRON it amounts to approximately 5-10% in the region where the cross section is large and could therefore be measured in the next round of experiments. At the LHC the asymmetry can be studied by selecting appropriately chosen kinematical regions.

Figures (5)

• Figure 1: Origin of the QCD charge asymmetry in hadroproduction of heavy quarks: interference of final-state (a) with initial-state (b) gluon bremsstrahlung plus interference of the box (c) with the Born diagram (d).
• Figure 2: Differential charge asymmetry in top quark pair production for fixed partonic center of mass energy $\sqrt{\hat{s}}=400$ GeV (solid), $600$ GeV (dashed) and $1$ TeV (dotted). We also plot the differential asymmetry for a b-quark with $\sqrt{\hat{s}}=400$ GeV (dashed-dotted).
• Figure 3: Integrated charge asymmetry as a function of the partonic center or mass energy for top and bottom quark pair production.
• Figure 4: a) Differential charge asymmetry in the proton-antiproton restframe using the MRS96-1 structure function. We consider also two different choices of the factorization scale: $\mu=\sqrt{\hat{s}}$ (solid) and $\mu=\sqrt{\hat{s}}/2$ (dashed). b) Integrated asymmetry for (anti-)top quarks with rapidities less than $y_{cut}$.
• Figure 5: Differential cross sections (Fig. a, c) and relative amount (Fig. b, d) of quark-antiquark, antiquark-quark and gluon-gluon initiated processes as functions of $x_1-x_2=2 P_3(t \bar{t} g)/\sqrt{s}$ in lowest order, for $\sqrt{s}=1.8$ TeV in proton-antiproton (Fig. a, b) and $\sqrt{s}=14$ TeV in proton-proton (Fig. c, d) collisions with $\sqrt{\hat{s}}=400$ GeV in both cases.