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Probing Light Stop Pairs at the LHC

Xiao-Jun Bi, Qi-Shu Yan, Peng-Fei Yin

TL;DR

This work investigates light stop scenarios with non-universal gaugino and third-generation masses at the GUT scale, combining RGEs, dark matter constraints, and LHC search bounds to map viable spectra. It finds that compressed stop–neutralino spectra commonly survive current jets+$\slashed{E}_T$ cuts, and that LHC searches optimized for mSUGRA may miss such signals. The study also demonstrates that the ILC can robustly probe these spectra, even when the LHC cannot, using both traditional cuts and neural-network discrimination. These results underscore the need for alternative search strategies and motivate future collider programs to fully test compressed SUSY possibilities.

Abstract

In this work, we study the light stop pair signals at the LHC. We explore the SUSY parameter space with non-universal gaugino and third generation masses at the GUT scale. Recent LHC SUSY search results based on 35pb$^{-1}$ and 1fb$^{-1}$ of data are implemented to put the limits on stop pair events. The dark matter relic density and direct detection constraints are also taken into account. Detailed simulations on the signals and background for some benchmark points are performed, and it is found that the stop pair signals usually escape the LHC search if the present cut conditions are used. We also explore the potential and sensitivity of ILC to probe such scenarios. It is found that the ILC can detect them with an integrated luminosity of a few tens of fb$^{-1}$.

Probing Light Stop Pairs at the LHC

TL;DR

This work investigates light stop scenarios with non-universal gaugino and third-generation masses at the GUT scale, combining RGEs, dark matter constraints, and LHC search bounds to map viable spectra. It finds that compressed stop–neutralino spectra commonly survive current jets+ cuts, and that LHC searches optimized for mSUGRA may miss such signals. The study also demonstrates that the ILC can robustly probe these spectra, even when the LHC cannot, using both traditional cuts and neural-network discrimination. These results underscore the need for alternative search strategies and motivate future collider programs to fully test compressed SUSY possibilities.

Abstract

In this work, we study the light stop pair signals at the LHC. We explore the SUSY parameter space with non-universal gaugino and third generation masses at the GUT scale. Recent LHC SUSY search results based on 35pb and 1fb of data are implemented to put the limits on stop pair events. The dark matter relic density and direct detection constraints are also taken into account. Detailed simulations on the signals and background for some benchmark points are performed, and it is found that the stop pair signals usually escape the LHC search if the present cut conditions are used. We also explore the potential and sensitivity of ILC to probe such scenarios. It is found that the ILC can detect them with an integrated luminosity of a few tens of fb.

Paper Structure

This paper contains 13 sections, 10 equations, 11 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Current experimental bounds on light stop scenario
  3. Analysis of the parameter space
  4. Theoretical scenarios
  5. Parameter Space Scan and Experimental Constraints
  6. Numerical results and sparticle masses
  7. Features of the dark matter
  8. The signature of light stop pairs at the LHC
  9. production and decay of stop pairs
  10. Simulation and analysis
  11. Benchmark points
  12. Search at the ILC
  13. Conclusion and discussions

Figures (11)

  • Figure 1: Four mass patterns in the planes (a) $m_{\chi^0_1}$ vs $m_{\tilde{t}_1}$ (top left), (b) $m_{\chi^\pm_1}$ vs $m_{\tilde{t}_1}$ (top right) are illustrated.
  • Figure 2: Four mass patterns in the planes (a) $m_0$ vs $M_{1/2}$ (top left), (b) $m_{0,3}$ vs $M_{1/2,3}$ (top right), (c) $A_0$ vs $\tan \beta$ (bottom left), (d) $M_1$ vs $\mu$ (bottom right) are displayed, respectively.
  • Figure 3: The elastic spin independent DM-nucleon cross section $\sigma_{\tilde{\chi}_1^0p}$ (left panel) and reduced cross section $\sigma_{\tilde{\chi}_1^0p,r}$ (right panel) for our four mass patterns are
  • Figure 4: The cross sections of stop pair production at Tevatron, LHC-7TeV and LHC-14TeV are shown.
  • Figure 7: The event number of signal passed all cuts from LHC searches with $35 pb^{-1}$ of data (from left to right and top to bottom): (1)CMS $jets+\sl{E}_T$, (2)ATLAS $jets+\sl{E}_T$ (signal region A), (3)ATLAS $1lepton+jets+\sl{E}_T$, (4)ATLAS $2leptons+jets+\sl{E}_T$, (5) ATLAS $1b jet+jets+\sl{E}_T$, and (6) ATLAS $1b jet+leptons+jets+\sl{E}_T$ are shown.
  • ...and 6 more figures