WGamma and ZGamma production at Hadron Colliders

TL;DR

<3-5 sentence high-level summary>

Abstract

We present a general purpose Monte Carlo program for the calculation of any infrared safe observable in WGamma and ZGamma production at hadron colliders at next-to-leading order in alpha_s. We treat the leptonic decays of the W and Z-boson in the narrow-width approximation, but retain all spin information via decay angle correlations. The effect of anomalous triple gauge boson couplings is investigated and we give the analytical expressions for the corresponding amplitudes. Furthermore, we propose a way to study the effect of anomalous couplings without introducing the ambiguity of form factors.

Figures (8)

• Figure 1: Scale dependence of $\sigma^{(NLO)}$ without (upper curves) and with (lower curves) jet-veto. The scale has been varied according to $\frac{\mu_{\rm st}}{2} ({\rm dashes}) < \mu < 2 \mu_{\rm st} ({\rm dots})$. The inset plot shows the ratio $\sigma^{(NLO)}/\sigma^{(LO)}$, again without (solid) and with (dots) jet-veto.
• Figure 2: Scale dependence of $\sigma^{(NLO)}$ without jet-veto (upper solid curves), $\sigma^{(NLO)}$ with jet-veto (lower solid curves) and $\sigma^{(LO)}$ (dotted curves). The scale has been varied according to $\frac{\mu_{\rm st}}{2} < \mu < 2 \mu_{\rm st}$.
• Figure 3: Ratio of $\sigma_{\rm AC}$ and $\sigma_{\rm SM}$ at NLO for $\mu = \mu_{\rm st}$. The anomalous couplings in $\sigma_{\rm AC}$ have been chosen as $\Delta\kappa^\gamma = 0.08, \lambda^\gamma = 0.02$ and a form factor defined in eq. (\ref{['formfac']}) with $n=2$ and $\Lambda =$ 2 TeV has been used.
• Figure 4: $\Delta\eta_{\gamma\ell}$ distribution at NLO without (dashed curves) and with anomalous couplings $\Delta\kappa^\gamma = 0.08, \lambda^\gamma = 0.02$ (solid curves). In the first plot we applied only standard cuts and the jet-veto, in the second plot there is an additional cut $p_T^\ell>100$ GeV, and in the third plot $p_T^\ell>200$ GeV.
• Figure 5: Cross section at NLO for $\mu= \mu_{\rm st}$ with standard cuts and $p_T^\gamma > 200$ GeV and $p_T^Z > 200$ GeV. (a) no anomalous couplings; (b) $h_3^\gamma=h_3^Z=0.01,\ h_4^\gamma=h_4^Z=10^{-4}$ and the usual dipole form factor with $\Lambda=2$ TeV; (c) $h_3^\gamma=h_3^Z=0.01,\ h_4^\gamma=h_4^Z=10^{-4}$ and no form factor; (d) $h_3^\gamma=h_3^Z=0.001,\ h_4^\gamma=h_4^Z=10^{-5}$ and no form factor. The inset plot shows again (b) and (b) with the opposite sign in the anomalous couplings.