A complete one-loop calculation of electroweak supersymmetric effects in $t$-channel single top production at LHC

TL;DR

This work presents a complete one-loop electroweak calculation in the MSSM for $t$-channel single-top production at the LHC, including full QED effects across eight partonic channels. It combines electroweak corrections with SUSY QCD contributions, employing an on-shell renormalization scheme with $G_F$ input and IR/collinear regularization via Dipole Subtraction and Phase Space Slicing. The numerical results show the net electroweak corrections are small (a few percent) due to cancellations, and genuine SUSY effects in representative mSUGRA benchmarks are typically below 1%, with PDF uncertainties around 3%. The findings support using the SM+NLO QCD framework for precise extraction of the CKM coupling $V_{tb}$, while highlighting that other SUSY-breaking scenarios could yield larger effects and warrant further study.

Abstract

We have computed the complete one-loop electroweak effects in the MSSM for single top (and single antitop) production in the $t$-channel at hadron colliders, generalizing a previous analysis performed for the dominant $dt$ final state and fully including QED effects. The results are quite similar for all processes. The overall Standard Model one-loop effect is small, of the few percent size. This is due to a compensation of weak and QED contributions that are of opposite sign. The genuine SUSY contribution is generally quite modest in the mSUGRA scenario. The experimental observables would therefore only practically depend, in this framework, on the CKM $Wtb$ coupling.

Figures (15)

• Figure 1: Born direct and crossed processes for single top production in the $t$-channel with first generation light quark current.
• Figure 2: Lowest order partonic cross section for the process $u b\to d t \gamma$ computed with the two different methods. The cuts for the Phase Space Slicing methos are $\delta_s = \delta_c = 10^{-4}$. The quantity $\Delta$ is defined as $\Delta= \sigma^{\hbox{\tiny Dipole}} - \sigma^{\hbox{\tiny Slicing}}$.
• Figure 3: Left Panel: We plot the LO (that is tree level) contribution and the NLO (that is tree level plus $\mathcal{O}(\alpha^3)$) corrections to the transverse momentum distribution. Right Panel: We plot the percentage contribution of the $\mathcal{O}(\alpha^3)$ corrections to the transverse momentum distribution; that is $\delta = \frac{NLO -LO}{NLO}\times 100$. No cuts are imposed. Computation in the Standard Model framework
• Figure 4: Left Panel: We plot the LO (that is tree level) contribution and the NLO (that is tree level plus $\mathcal{O}(\alpha^3)$) corrections to the invariant mass distribution. Right Panel: We plot the percentage contribution of the $\mathcal{O}(\alpha^3)$ corrections to the invariant mass distribution; that is $\delta = \frac{NLO -LO}{NLO}\times 100$. No cuts are imposed. Computation in the Standard Model framework
• Figure 5: Left Panel: We plot the LO (that is tree level) contribution and the NLO that is tree level plus $\mathcal{O}(\alpha^3)$ corrections to the integrated transverse momentum distribution $\sigma(p_T^{\rm min})$. We remind that this distribution is defined as the transverse momentum distribution integrated from a minimum $p_T^{\rm min}$ up to infinity. Right Panel: We plot the percentage contribution of the $\mathcal{O}(\alpha^3)$ correections to the integrated transverse momentum distribution; that is $\delta = \frac{NLO -LO}{NLO}\times 100$. No cuts are imposed.Computation in the Standard Model framework