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Light Stop NLSPs at the Tevatron and LHC

Yevgeny Kats, David Shih

TL;DR

The paper investigates whether a light stop NLSP is compatible with Tevatron and LHC data in gauge-mediated SUSY breaking, focusing on prompt decays to $W^+ b \tilde{G}$ within a minimal spectrum. They analyze a broad set of $t\bar t$-like and new-physics analyses, performing detector-level simulations to map stop NLSP production to existing constraints. Their main result shows stops as light as about $150$ GeV are allowed, with LHC data potentially pushing the limit to about $180$ GeV with more data. They conclude that dedicated stop NLSP searches could improve constraints and recommend expressing results in a mass-lifetime plane to fully characterize this simple, well-motivated scenario.

Abstract

How light can the stop be given current experimental constraints? Can it still be lighter than the top? In this paper, we study this and related questions in the context of gauge-mediated supersymmetry breaking, where a stop NLSP decays into a W, b and gravitino. Focusing on the case of prompt decays, we simulate several existing Tevatron and LHC analyses that would be sensitive to this scenario, and find that they allow the stop to be as light as 150 GeV, mostly due to the large top production background. With more data, the existing LHC analyses will be able to push the limit up to at least 180 GeV. We hope this work will motivate more dedicated experimental searches for this simple scenario, in which, for most purposes, the only free parameters are the stop mass and lifetime.

Light Stop NLSPs at the Tevatron and LHC

TL;DR

The paper investigates whether a light stop NLSP is compatible with Tevatron and LHC data in gauge-mediated SUSY breaking, focusing on prompt decays to within a minimal spectrum. They analyze a broad set of -like and new-physics analyses, performing detector-level simulations to map stop NLSP production to existing constraints. Their main result shows stops as light as about GeV are allowed, with LHC data potentially pushing the limit to about GeV with more data. They conclude that dedicated stop NLSP searches could improve constraints and recommend expressing results in a mass-lifetime plane to fully characterize this simple, well-motivated scenario.

Abstract

How light can the stop be given current experimental constraints? Can it still be lighter than the top? In this paper, we study this and related questions in the context of gauge-mediated supersymmetry breaking, where a stop NLSP decays into a W, b and gravitino. Focusing on the case of prompt decays, we simulate several existing Tevatron and LHC analyses that would be sensitive to this scenario, and find that they allow the stop to be as light as 150 GeV, mostly due to the large top production background. With more data, the existing LHC analyses will be able to push the limit up to at least 180 GeV. We hope this work will motivate more dedicated experimental searches for this simple scenario, in which, for most purposes, the only free parameters are the stop mass and lifetime.

Paper Structure

This paper contains 22 sections, 33 equations, 10 figures, 6 tables.

Table of Contents

  1. Introduction
  2. Phenomenology of stop NLSP
  3. The decay process
  4. Kinematic distributions
  5. Overview of relevant Tevatron and LHC analyses
  6. $t\overline t$ analyses
  7. Searches for new physics
  8. Constraints from the Tevatron and the LHC
  9. Cut-and-count analyses
  10. Stop mass reconstruction
  11. Other types of measurements
  12. $m_{\ell b}$ and $b$-jet $p_T$
  13. Displaced decays
  14. Bound states
  15. Flavor-violating decays and same-sign dilepton signals
  16. ...and 7 more sections

Figures (10)

  • Figure 1: The NLO+NLL stop pair production cross section at the Tevatron (left) and $7$ TeV LHC (right) as a function of the stop mass. The values of $t\overline t$ cross sections are indicated as well. For more details, see appendix \ref{['sec-xsec']}.
  • Figure 2: Diagrams contributing to the stop NLSP decay in GMSB in the simplified scenario where all the other superpartners are heavy.
  • Figure 3: Distributions of the $Wb$ invariant mass for stops with masses (in GeV) $120$ (blue), $150$ (black), $172$ (pink), $180$ (green) and $200$ (red). We assume $m_t = 173$ GeV.
  • Figure 4: Contours of constant $c\tau$ for stop NLSP decay, as a function of the SUSY breaking scale $\sqrt F$ and the stop mass $m_{{\tilde{t}}}$.
  • Figure 5: Parton-level distributions of the leptons $p_T$ (top left), $b$-jets $p_T$ (top right) and $E\!\!\!/_T$ in the different channels (bottom) for $t\overline t$ (thick black line) and stops with masses (in GeV) $120$ (blue), $150$ (black), $180$ (green) and $200$ (red).
  • ...and 5 more figures