Next-to-leading order QCD corrections to di-photon production in association with up to three jets at the Large Hadron Collider

TL;DR

This work delivers the first full NLO QCD calculation for di-photon production in association with up to three jets at the LHC. It employs unitarity-based methods via the NJet library interfaced with Sherpa to compute virtual corrections and real radiation with Catani-Seymour subtraction, enabling efficient high-multiplicity predictions. The study shows a substantial reduction in theoretical uncertainties and reveals notable shape changes in key differential distributions when going from LO to NLO, including careful investigations of PDF variations. These precise predictions improve the modeling of γγ+jets backgrounds for Higgs and VBF analyses and demonstrate the viability of high-multiplicity NLO calculations with advanced computational tools.

Abstract

We present the computation of next-to-leading order (NLO) QCD corrections to di-photon production in association with two or three hard jets in pp collisions at a center-of-mass energy of 8 TeV. The inclusion of NLO corrections is shown to substantially reduce the theoretical uncertainties estimated from scale variations on total cross section predictions. We study a range of differential distributions relevant for phenomenological studies of photon pair production in association with jets at the LHC. Using an efficient computational set-up we performed a detailed study of uncertainties due to parton distribution functions. The computation of the virtual corrections is performed using new features of the C++ library NJET.

Figures (12)

• Figure 1: Full colour and leading approximation (as explained in the text) for the virtual corrections to the transverse momentum of the 3rd jet in $pp\to \gamma\gamma+3j$.
• Figure 2: Scale variations on the total cross section for $pp\to \gamma\gamma+2j$ for a variety of dynamical scales. Dashed lines are LO accuracy whereas solid lines are NLO accuracy. The vertical line at $x=1$ corresponds to the central scale whereas the lines at $x=0.5$ and $x=2$ show the bounds of the scale variation region.
• Figure 3: Differential distributions for jet transverse momenta. The lower plot shows the ratio of NLO to LO including the scale variation bands estimated over the range of $x\in[0.5,2]$.
• Figure 4: Differential distributions for di-photon invariant mass and rapidity $pp\to\gamma\gamma+2j$.
• Figure 5: Differential distributions for the angular observables $R_{\gamma_1 j_1}$ (see Eq. \ref{['eq:R11']}), $\Delta\phi_{j_1j_2}$, $\eta_{j_1 j_2}$ and $y_{\gamma\gamma jj}^*$ (see Eq. \ref{['eq:ystar']}) in $pp\to\gamma\gamma+2j$.