Higher-order soft corrections to squark hadro-production

TL;DR

This work delivers improved theoretical predictions for squark pair production by incorporating higher-order soft QCD corrections at NNLO within the MSSM. Using threshold resummation to NNLL and exact two-loop Coulomb terms, it constructs approximate NNLO hadronic cross sections with precise scale dependence, validated by RG-consistent scale terms. The results yield a ~9% cross-section increase over NLO at the LHC, alongside significantly reduced scale uncertainties, enabling tighter squark-mass exclusion limits and more reliable phenomenology. The methodology emphasizes threshold-dominated dynamics and provides practical NLO fits for quick phenomenological use, with potential extensions to bound-state effects in future work.

Abstract

We present new predictions for the total cross section of squark pair-production at Tevatron and LHC through next-to-next-to-leading order within the Minimal Supersymmetric Standard Model. The results are based on the numerically dominant soft corrections. They are exact in all logarithmically enhanced terms near threshold, include the Coulomb corrections at two loops and exact scale dependence. We translate the increased total cross section at next-to-next-to-leading order into improved exclusion limits for squark masses and we investigate the scale dependence as well as the sensitivity on the parton luminosity.

Figures (8)

• Figure 1: Contributing diagrams to the processes $gg \to \tilde{q}\tilde{q}^{\ast}$ (diagrams (a)--(d)) and $q\bar{q} \to \tilde{q}\tilde{q}^{\ast}$ (diagrams (e),(f)). Diagram (f) is proportional to the squark-gluino Yukawa coupling $\hat{\alpha}_s$ and introduces dependence on the gluino mass $m_{\tilde{g}}$.
• Figure 2: Scaling functions $f_{q\bar{q}}^{(ij)}$ (left column) and $f_{q_k \bar{q}_l}^{(ij)}$ (right column) with $i = 0\ldots 2,\enspace j\le i$, for $m_{\tilde{q}} = 400\,\mathrm{GeV}$ and $m_{\tilde{g}} = 500\,\mathrm{GeV}$.
• Figure 3: Scaling functions $f_{gg}^{(ij)}$ with $i = 0,1,2\enspace j\le i$.
• Figure 4: The total hadronic cross section for $pp\to \tilde{q} \tilde{q}^{\ast}$ at LHC with $\sqrt{s}=14~\,\mathrm{TeV}$ to LO, NLO, and NNLO in QCD as function of the squark mass $m_{\tilde{q}}$. For the gluino mass we assume the relation $m_{\tilde{g}} = 1.25 m_{\tilde{q}}$.
• Figure 5: Same as Fig. \ref{['fig:lhc14']} for Tevatron with $\sqrt{s}=1.96~\,\mathrm{TeV}$.