Search for Charginos Nearly Mass-Degenerate with the Lightest Neutralino

Based on a Disappearing-Track Signature in pp Collisions at √s = 8 TeV

  • Shingo Kazama

Part of the Springer Theses book series (Springer Theses)

Table of contents

  1. Front Matter
    Pages i-xiii
  2. Shingo Kazama
    Pages 1-3
  3. Shingo Kazama
    Pages 5-22
  4. Shingo Kazama
    Pages 23-45
  5. Shingo Kazama
    Pages 47-54
  6. Shingo Kazama
    Pages 55-69
  7. Shingo Kazama
    Pages 71-77
  8. Shingo Kazama
    Pages 79-89
  9. Shingo Kazama
    Pages 91-102
  10. Shingo Kazama
    Pages 103-120
  11. Shingo Kazama
    Pages 121-124
  12. Shingo Kazama
    Pages 125-137
  13. Shingo Kazama
    Pages 139-146
  14. Shingo Kazama
    Pages 147-148

About this book


 In this book, the anomaly mediated supersymmetry breaking (AMSB) model is explored by searching for charged winos with their subsequent decays collected with the ATLAS detector at the Large Hadron Collider (LHC).

The author develops a new method, called “re-tracking,” to detect charged winos that decay before reaching the Semiconductor Tracker (SCT) detector. Because the nominal tracking algorithm at the ATLAS experiment requires at least seven successive hits in the inner tracking system, the sensitivity to charged winos having a fraction of a nanosecond in the past analysis was therefore limited. However, re-tracking requires a minimum of three pixel hits and provides a fully efficient tracking capability for charged winos traversing the pixel detector, resulting in around about 100 times greater efficiency for charged winos with a lifetime ~0.2 ns longer than that in past searches.

Signal topology is characterized by a jet with large transverse momentum (pT), large missing transverse energy, and a high-pT disappearing track. There are three types of background tracks: interacting hadron trac

ks, charged leptons, and tracks with mismeasured pT. A background estimation based on the Monte Carlo (MC) simulation suffers from large uncertainties due to poor statistics and has difficulty simulating the properties of background tracks. Therefore, a data-driven approach has been developed by the author of the book to estimate the background track-pT spectrum.

No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on the AMSB model are obtained. The author shows that in the AMSB model, a charged wino mass below 270 GeV is excluded at 95 % confidence level, which also directly constrains the mass of wino dark matter.


Degenerate SUSY Electroweak production Higgs boson at the LHC High-scale SUSY Long-lived massive particles Monojet signature SUSY searches at ATLAS Wino LSP

Authors and affiliations

  • Shingo Kazama
    • 1
  1. 1.The University of TokyoTokyoJapan

Bibliographic information