Next-to-leading order QCD predictions for W+W+jj production at the LHC

TL;DR

This work delivers the first NLO QCD predictions for the QCD-mediated W+W+jj production channel at the LHC, a 2→4 process with significant implications as both a signal and a background to DPS and various BSM scenarios. The authors employ generalized unitarity, Berends-Giele recursion, and Catani-Seymour dipole subtraction within the MCFM framework to compute one-loop virtuals and real emissions, treating the top quark as infinitely heavy and W bosons with leptonic decays. Their results show a substantial reduction of scale uncertainty to about 10% at NLO and reveal a notable amount of events with a hard third jet, which can aid in signal discrimination or background suppression. The study demonstrates the practicality of NLO predictions for complex multi-jet final states and discusses extensions to related processes and observables, including W−W−jj and higher jet multiplicities.

Abstract

Because the LHC is a proton-proton collider, sizable production of two positively charged W-bosons in association with two jets is possible. This process leads to a distinct signature of same sign high-pt leptons, missing energy and jets. We compute the NLO QCD corrections to the QCD-mediated part of pp -> W+W+jj. These corrections reduce the dependence of the production cross-section on the renormalization and factorization scale to about +- 10 percent. We find that a large number of W+W+jj events contain a relatively hard third jet. The presence of this jet should help to either pick up the W+W+jj signal or to reject it as an unwanted background.

Figures (7)

• Figure 1: A typical Feynman diagram that contributes to QCD production of $W^+W^+jj$ in hadron collisions at leading order in perturbative QCD.
• Figure 2: Parent diagrams for one-loop primitive amplitudes for $0 \to \bar{u} d \bar{c} s+W^+W^+$. Shaded areas represent dummy lines which can not be cut. $W^+$ bosons are not shown. Quarks $Q'$ do not couple to $W$-bosons.
• Figure 3: The dependence on factorization and renormalization scales of cross-sections for $pp \to e^+\, \mu^+\, {\nu}_{e}\, {\nu}_{\mu} + n~{\rm jets}$, $n = 0,1,2$ at leading and next-to-leading order in perturbative QCD We set the two scales equal to each other $\mu_{\rm F} = \mu_{\rm R} = \mu$.
• Figure 4: The dependence on the jet $p_\perp$ cut of the two-jet inclusive and two-jet exclusive cross-sections for $pp \to e^+\, \mu^+\, {\nu}_{e}\, {\nu}_{\mu} + 2~{\rm jets}$ at leading and next-to-leading order in perturbative QCD. We show scale uncertainty bands, for values of the renormalization and factorization scales set to a common value $\mu$, which is varied in the interval $100~{\rm GeV} \le \mu \le 200~{\rm GeV}$. Results for $\mu = 140~{\rm GeV}$ are shown as solid lines.
• Figure 5: Kinematic distributions of the two hardest jets in the process $pp \to e^+\, \mu^+\, {\nu}_{e}\, {\nu}_{\mu}\, + 2~{\rm jets}$ at leading and next-to-leading order in perturbative QCD for inclusive two-jet events. The bands show renormalization and factorization scale uncertainty, for $50~{\rm GeV} \leq \mu \leq 400~{\rm GeV}$. Solid lines show leading and next-to-leading order predictions for $\mu = 150~{\rm GeV}$. We use $H_{\rm T,TOT} = \sum \limits_{j}^{} p_{\perp,j} + p_\perp^{e^+} + p_\perp^{\mu^+} + p_\perp^{\rm miss}$.