Squark and Gluino Production at Hadron Colliders

TL;DR

This paper provides a comprehensive calculation of next-to-leading order SUSY-QCD corrections for squark and gluino production at the Tevatron and LHC. By including virtual corrections, real-gluon radiation, and handling of on-shell intermediate states, it achieves significantly reduced renormalization/factorization scale dependence and generally larger cross-sections at the central scale, improving mass determinations from production rates. The results show that differential distributions retain their shapes under NLO corrections, while total cross-sections rise and consequently strengthen experimental mass bounds. The work delivers detailed scaling functions, threshold and high-energy analyses, and practical implications for SUSY searches, including Fortran codes for the computed cross-sections.

Abstract

We have determined the theoretical predictions for the cross-sections of squark and gluino production at $\ppb$ and $pp$ colliders (Tevatron and LHC) in next-to-leading order of supersymmetric QCD. By reducing the dependence on the renormalization/factorization scale considerably, the theoretically predicted values for the cross-sections are much more stable if these higher-order corrections are implemented. If squarks and gluinos are discovered, this improved stability translates into a reduced error on the masses, as extracted experimentally from the size of the production cross-sections. The cross-sections increase significantly if the next-to-leading order corrections are included at a renormalization/factorization scale near the average mass of the produced massive particles. This rise results in improved lower bounds on squark and gluino masses. By contrast, the shape of the transverse-momentum and rapidity distributions remains nearly unchanged when the next-to-leading order corrections are included.

Figures (24)

• Figure 1: Feynman diagrams for the production of squarks and gluinos in lowest order. The diagrams without and with crossed final-state lines [e.g. in (b)] represent $t$- and $u$-channel diagrams, respectively. The diagrams in (c) and the last diagram in (d) are a result of the Majorana nature of gluinos. Note that some of the above diagrams contribute only for specific flavours and chiralities of the squarks.
• Figure 2: The relative yields of squarks and gluinos in the final states at the Tevatron. The mass ratio $m_{\tilde{q}}/m_{\tilde{g}}$ is chosen to be (a) $0.8$ and (b) $1.6$. Also shown are the leading parton contributions for (c) $\tilde{q}\bar{\tilde{q}}$ and (d) $\tilde{g}\tilde{g}$ final states. Parton densities: GRV 94 GRV; renormalization and factorization scale $Q=m_{\tilde{q}}$ for squarks, $Q=m_{\tilde{g}}$ for gluinos, and $Q=(m_{\tilde{q}}+m_{\tilde{g}})/2$ for squark--gluino pairs.
• Figure 3: The relative yields of squarks and gluinos in the final states at the LHC. The mass ratio $m_{\tilde{q}}/m_{\tilde{g}}$ is chosen to be (a) $0.8$ and (b) $1.6$. Also shown are the leading parton contributions for (d) $\tilde{g}\tilde{g}$ final states. Parton densities: GRV 94 GRV; renormalization and factorization scale $Q=m_{\tilde{q}}$ for squarks, $Q=m_{\tilde{g}}$ for gluinos, and $Q=(m_{\tilde{q}}+m_{\tilde{g}})/2$ for squark--gluino pairs. [Note that $\tilde{q}\tilde{q}/\tilde{q}\tilde{g}$ final states can only be generated by $qq/qg$ initial states so that diagram (c) is trivial and not shown.]
• Figure 4: A selected set of Feynman diagrams for the virtual corrections. (a) Gluino self-energy, (b) quark--quark--gluon vertex [gauge coupling], (c) quark--squark--gluino vertex [Yukawa coupling], (d) two-point boxes, (e) three-point boxes, and (f) four-point boxes.
• Figure 5: A representative set of Feynman diagrams corresponding to real-gluon radiation: squark--antisquark production (a), gluino-pair production (b), and squark--gluino production (c).