QCD Corrections to Scalar Diquark Production at Hadron Colliders

TL;DR

This paper computes the next-to-leading order QCD corrections to single production of scalar diquarks in the color representations $\mathbf{6}$ and $\mathbf{\bar{3}}$ at hadron colliders, including virtual loops, real-gluon emission, and the gluon-initiated channel. It provides the complete NLO cross sections for $qq$ and $gq$ initial states and analyzes the dependence on factorization and renormalization scales, finding $K$-factors roughly in the ranges $K_{\bar{3}} \approx 1.31$–$1.35$ and $K_{6} \approx 1.22$–$1.32$ for valence-quark initial states. The authors also perform soft-gluon resummation to leading logarithm for the $p_T$ distribution, introducing a Sudakov form factor with coefficients $A=2C_F$ and $B=-(3C_F+C_D)$ and matching to fixed-order results to obtain reliable spectra down to low $p_T$ (peaking at $p_T \sim 5$–$8$ GeV). The results indicate that the LHC can probe substantial diquark production rates if the quark–diquark couplings are not too small, and that NLO corrections and $p_T$ resummation significantly improve the theoretical predictions for experimental searches.

Abstract

We calculate the next-to-leading order QCD corrections to quark-quark annihilation to a scalar resonant state ("diquark") in a color representation of antitriplet or sextet at the Tevatron and LHC energies. At the LHC, we find the enhancement (K-factor) for the antitriplet diquark is typically about 1.31--1.35, and for the sextet diquark is about 1.22--1.32 for initial-state valence quarks. The full transverse-momentum spectrum for the diquarks is also calculated at the LHC by performing the soft gluon resummation to the leading logarithm and all orders in the strong coupling.

Figures (7)

• Figure 1: Feynman diagrams for virtual gluon corrections to $qq\to D$.
• Figure 2: Feynman diagrams for $qq\to gD$
• Figure 3: Feynman diagrams for $gq\to\bar{q}D$.
• Figure 4: Results for $p\overline{p}$ collisions at a center of mass energy of $2$ TeV (a,b) and $pp$ collisions at 10 TeV (c,d) with various initial states. The total leading-order (dot-dash) and next-to-leading order (solid) cross sections are shown for both (a,c) the antitriplet and (b,d) the sextet diquarks. For all the above plots the factorization scale, renormalization scale, and diquark mass are set equal.
• Figure 5: Results for $pp$ collisions at a center of mass energy of 14 TeV with various initial states. The total leading-order (dot-dash) and next-to-leading order (solid) cross sections are shown for both (a) the antitriplet and (b) the sextet diquarks with various initial states. Also shown are the $K$-factors for (c) the antitriplet and (d) the sextet diquarks with various initial states. For all the above plots the factorization scale, renormalization scale, and diquark mass are set equal.