Higher-order soft and Coulomb corrections to squark and gluino production at the LHC

TL;DR

The paper tackles the precision prediction of squark and gluino pair production at the LHC by developing a joint NNLL resummation of soft-gluon and Coulomb corrections. It employs a momentum-space, factorized framework with hard, soft, and Coulomb functions, including NNLO Coulomb effects via Green functions and bound-state contributions, and matches to the exact NLO plus approximate NNLO results. The main findings show NNLL corrections of up to $\\sim$25\\% over NLL and a reduction of the total theoretical uncertainty to about $\\sim$10\\%, significantly improving the reliability of SUSY cross-section predictions used in LHC searches. This work enhances the interpretation of cross-section limits in terms of sparticle masses and strengthens the LHC's reach for discovering or constraining SUSY scenarios.

Abstract

We present predictions for the total cross sections for pair production of squarks and gluinos at the LHC including a combined NNLL resummation of soft and Coulomb gluon effects. The NNLL corrections can be up to 25% relative to previous NLL results and reduce the theoretical uncertainties to the 10% level.

Figures (3)

• Figure 1: Top: Relative contribution of the different squark and gluino production processes to the total Born production rate of coloured sparticles, $\sigma_{\text{SUSY}}$, for the LHC with $\sqrt s=8$ TeV. Below: NLO $K$-factor for squark and gluino production processes at the LHC. The left plots show the mass dependence for $m_{\tilde{q}}=m_{\tilde{g}}=M$ while the right plot shows the dependence on the ratio $m_{\tilde{g}}/m_{\tilde{q}}$ for a fixed average mass $(m_{\tilde{q}}+m_{\tilde{g}})/2=1.6$ TeV. In the $K$-factors the MSTW2008NLO PDFs Martin:2009iq have been used for the LO and NLO cross sections.
• Figure 2: Higher-order corrections relative to the NLO cross section for squark and gluino production at the LHC with $\sqrt{\hat{s}}=8$ TeV for full NNLL resummation (solid blue), NNLL with fixed-order Coulomb corrections (dotted red) , approximate NNLO (dot-dashed pink) and NLL (dashed orange). The NLL and NLO (NNLO$_{\text{app}}$ and NNLL) cross sections are computed with the NLO (NNLO) MSTW2008 PDFs.
• Figure 3: Total theoretical uncertainty of the NLO approximation (dotted black), NLL (dashed orange) and NNLL (solid blue) resummed results at the LHC with $\sqrt{s}=\,8$ TeV. All cross sections are normalized to one at the central value of the scales.