Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Single top production in the $t$-channel at LHC: a realistic test of electroweak models

M. Beccaria, G. Macorini, F. M. Renard, C. Verzegnassi

TL;DR

This work provides a complete electroweak one-loop calculation of the $ub\to td$ process in the SM and in the MSSM under the mSUGRA framework. The SM electroweak correction to the $t$-channel single top production is found to be large and negative, reaching about $-12\%$ when integrated over a realistic energy range, and is competitive with NLO QCD corrections, highlighting the importance of EW effects in precision predictions. In the MSSM with mSUGRA, genuine SUSY contributions are typically only a few percent, though threshold regions with a light stop and light neutralino could produce noticeable enhancements; non-minimal SUSY scenarios may therefore reveal larger effects. The authors perform a detailed diagrammatic breakdown (self-energies, vertices, boxes) and discuss UV/IR cancellations and high-energy Sudakov behavior, validating the approach against Sudakov expectations. Overall, the $t$-channel single top process emerges as a realistic test bed for electroweak models at the LHC and a potential probe of new physics in specific MSSM parameter regions.

Abstract

We compute the complete electroweak one-loop effect on the process of $t$-channel single top production at LHC in the Standard Model and in the MSSM within the mSUGRA symmetry breaking scheme. We find that the one-loop electroweak SM effect is large, and decreases the cross section of an amount that is of the same size as that of the NLO QCD one. The genuine SUSY effect in the mSUGRA scheme, for a general choice of benchmark points, is rather small. It might become large and visible in more general scenarios around thresholds involving light stop and neutralino mass values.

Single top production in the $t$-channel at LHC: a realistic test of electroweak models

TL;DR

This work provides a complete electroweak one-loop calculation of the process in the SM and in the MSSM under the mSUGRA framework. The SM electroweak correction to the -channel single top production is found to be large and negative, reaching about when integrated over a realistic energy range, and is competitive with NLO QCD corrections, highlighting the importance of EW effects in precision predictions. In the MSSM with mSUGRA, genuine SUSY contributions are typically only a few percent, though threshold regions with a light stop and light neutralino could produce noticeable enhancements; non-minimal SUSY scenarios may therefore reveal larger effects. The authors perform a detailed diagrammatic breakdown (self-energies, vertices, boxes) and discuss UV/IR cancellations and high-energy Sudakov behavior, validating the approach against Sudakov expectations. Overall, the -channel single top process emerges as a realistic test bed for electroweak models at the LHC and a potential probe of new physics in specific MSSM parameter regions.

Abstract

We compute the complete electroweak one-loop effect on the process of -channel single top production at LHC in the Standard Model and in the MSSM within the mSUGRA symmetry breaking scheme. We find that the one-loop electroweak SM effect is large, and decreases the cross section of an amount that is of the same size as that of the NLO QCD one. The genuine SUSY effect in the mSUGRA scheme, for a general choice of benchmark points, is rather small. It might become large and visible in more general scenarios around thresholds involving light stop and neutralino mass values.

Paper Structure

This paper contains 19 sections, 40 equations, 7 figures, 1 table.

Table of Contents

  1. Introduction
  2. Electroweak MSSM $ub\to td$ production at one loop
  3. Self-energies and counterterms
  4. Vertex corrections
  5. Box corrections
  6. Real photon radiation and IR finiteness
  7. High-energy behavior
  8. Physical Predictions
  9. SM results
  10. MSSM results
  11. Conclusions
  12. Sudakov expansion of the process $ub\to td$ in the SM and MSSM
  13. Sudakov expansion from general rules
  14. Sudakov expansion from the diagrammatic expansion
  15. Born amplitude and corrections
  16. ...and 4 more sections

Figures (7)

  • Figure 1: Standard Model direct and twisted box diagrams. The virtual $q$ and $q'$ are quarks. The gauge bosons $(V, V')$ can be $(\gamma,W)$, $(Z,W)$, $(W,\gamma)$ or $(W,Z)$.
  • Figure 2: SUSY direct and twisted box diagrams. The virtual $\widetilde{q}$ and $\widetilde{q}'$ are squarks. The fermion lines $(\chi, \chi')$ can be charginos or neutralinos, $(\chi^0, \chi^+)$ or $(\chi^+, \chi^0)$.
  • Figure 3: Full one loop calculation in the Standard Model. Panel (a) shows the percentual effect on the distribution $d\sigma/ds$. Panel (b) shows the effect on the integrated cross section from threshold up to $\sqrt{s}$.
  • Figure 4: Comparison between the full one-loop calculation in the Standard Model and the NLO Sudakov approximation. As explained in the text, a strong angular cut is imposed as well as the fictitious definition $M_\gamma = M_Z$. Real QED radiation is consistently switched off.
  • Figure 5: Percentual effects in the differential cross section $d\sigma/ds$ in the four considered MSSM scenarios. The SM curve is also shown in each case.
  • ...and 2 more figures