Measurement of the WW production cross section with dilepton final states in p-pbar collisions at sqrt(s)=1.96 TeV and limits on anomalous trilinear gauge couplings

TL;DR

The paper reports a precise measurement of the WW production cross section in proton-antiproton collisions at sqrt(s)=1.96 TeV using dilepton final states collected with the D0 detector, and derives limits on anomalous WWγ and WWZ trilinear gauge couplings. WW events are reconstructed in ee, eμ, and μμ channels, with backgrounds estimated using data-driven and MC methods; a BLUE combination yields σ(ppbar→WW)=11.5±2.1(stat+syst)±0.7(lumi) pb, consistent with the SM expectation of ~12 pb. The analysis employs lepton pT distributions to constrain TGCs, includes a dipole form factor with Λ=2 TeV, and provides one- and two-dimensional 95% C.L. limits under SU(2)L×U(1)Y and WWγ=WWZ scenarios, substantially improving previous Tevatron bounds.

Abstract

We provide the most precise measurement of the WW production cross section in p-pbar collisions to date at a center of mass energy of 1.96 TeV, and set limits on the associated trilinear gauge couplings. The WW->lvl'v (l,l'=e,mu) decay channels are analyzed in 1 fb^(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. The measured cross section is sigma(p-pbar -> WW) = 11.5 +/- 2.1 (stat + syst) +/- 0.7 (lumi) pb. One- and two-dimensional 95% C.L. limits on trilinear gauge couplings are provided.

Figures (3)

• Figure 1: Distributions of the (a) leading and (b) trailing lepton $p_T$ after final selection, combined for all channels ($ee+e\mu+\mu\mu$). Data are compared to estimated signal, $\sigma(WW)=12$ pb, and background sum.
• Figure 2: One and two-dimensional 95% C.L. limits when enforcing $SU(2)_L \otimes U(1)_Y$ symmetry at $\Lambda = 2$ TeV, for (a) $\Delta\kappa_\gamma$ vs. $\lambda_\gamma$, (b) $\Delta\kappa_\gamma$ vs. $\Delta g_1^Z$, and (c) $\lambda_\gamma$ vs. $\Delta g_1^Z$, each when the third free coupling is set to its SM value; limits when enforcing the $WW\gamma$=$WWZ$ constraints are shown in (d). The curve represents the two-dimensional 95% C.L. contour and the ticks along the axes represent the one-dimensional 95% C.L. limits. An asterisk ($+ \space \times$) marks the point with the highest likelihood in the two-dimensional plane.
• Figure 3: Distributions of the (a) leading and (b) trailing electron $p_T$ in the $ee$ channel, (c) electron and (d) muon $p_T$ in the $e\mu$ channel, and (e) leading and (f) trailing muon $p_T$ in the $\mu\mu$ channel after final selection. Data are compared to estimated signal, $\sigma(WW)=12$ pb, and background sum.