Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Precision SUSY Measurements at LHC

I. Hinchliffe, F. E. Paige, M. D. Shapiro, J. Soderqvist, W. Yao

TL;DR

This study outlines a practical framework for extracting masses, mass differences, and branching ratios of supersymmetric particles at the LHC using an inclusive mass scale (M_eff), cascade-endpoint signatures, and targeted electroweak channels within a SUGRA context. By applying these methods to five benchmark LHC points, the authors demonstrate how precise measurements of mass differences, Higgs-related decays, and dilepton edges can tightly constrain fundamental SUSY parameters (m0, m1/2, tanβ, μ, A0) and potentially distinguish competing models. The work also emphasizes the role of jet-energy calibration, background control, and cross-channel consistency in achieving percent-level to few-GeV precision on key quantities, highlighting the practical path toward a comprehensive SUSY parameter determination from early LHC data.

Abstract

If supersymmetry exists at the electroweak scale, then it should be discovered at the LHC. Determining masses, of supersymmetric particles however, is more difficult. In this paper, methods are discussed to determine combinations of masses and of branching ratios precisely from experimentally observable distributions. In many cases such measurements alone can greatly constrain the particular supersymmetric model and determine its parameters with an accuracy of a few percent. Most of the results shown correspond to one year of running at LHC at ``low luminosity'.

Precision SUSY Measurements at LHC

TL;DR

This study outlines a practical framework for extracting masses, mass differences, and branching ratios of supersymmetric particles at the LHC using an inclusive mass scale (M_eff), cascade-endpoint signatures, and targeted electroweak channels within a SUGRA context. By applying these methods to five benchmark LHC points, the authors demonstrate how precise measurements of mass differences, Higgs-related decays, and dilepton edges can tightly constrain fundamental SUSY parameters (m0, m1/2, tanβ, μ, A0) and potentially distinguish competing models. The work also emphasizes the role of jet-energy calibration, background control, and cross-channel consistency in achieving percent-level to few-GeV precision on key quantities, highlighting the practical path toward a comprehensive SUSY parameter determination from early LHC data.

Abstract

If supersymmetry exists at the electroweak scale, then it should be discovered at the LHC. Determining masses, of supersymmetric particles however, is more difficult. In this paper, methods are discussed to determine combinations of masses and of branching ratios precisely from experimentally observable distributions. In many cases such measurements alone can greatly constrain the particular supersymmetric model and determine its parameters with an accuracy of a few percent. Most of the results shown correspond to one year of running at LHC at ``low luminosity'.

Paper Structure

This paper contains 25 sections, 21 equations, 42 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Effective Mass Analysis
  3. LHC Point 3: $m_0=200\,{\rm GeV}$, $m_{1/2}=100\,{\rm GeV}$, $\tan\beta=2$
  4. Measurement of $M_{\tilde{\chi}_2}-M_{\tilde{\chi}_1}$
  5. Gluino and Sbottom Reconstruction
  6. Light Squark Reconstruction
  7. Branching ratio of $\tilde{\chi}_2\to \tilde{\chi}_1^0\ell^+\ell^-$
  8. Electroweak Production of Superpartners
  9. LHC Point 4: $m_0=800\,{\rm GeV}$, $m_{1/2}=200\,{\rm GeV}$, $\tan\beta=10$
  10. Selection of gaugino decays $\tilde{\chi}_i \rightarrow \tilde{\chi}_j \ell^+\ell^-$
  11. Selection of $\tilde{\chi}_4^0 \rightarrow \tilde{\chi}_1^\pm W^\mp \rightarrow e^\pm \mu^\mp X$
  12. LHC Point 5: $m_0=100\,{\rm GeV}$, $m_{1/2}=300\,{\rm GeV}$, $\tan\beta=2.1$
  13. Selection of $h \rightarrow b \bar{b}$ and Measurement of $M(\tilde{u}_L)-M(\tilde{\chi}_1^0)$
  14. Selection of $W \rightarrow q \bar{q}$ and Measurement of $M(\tilde{u}_L)-M(\tilde{\chi}_1^0)$
  15. Selection of $\tilde{\chi}_2^0 \rightarrow \tilde{\ell} \ell \rightarrow \tilde{\chi}_1^0 \ell\ell$
  16. ...and 10 more sections

Figures (42)

  • Figure 1: LHC Point 1 signal and Standard Model backgrounds. Open circles: SUSY signal. Solid circles: $t\bar{t}$. Triangles: $W\rightarrow\ell\nu$, $\tau\nu$. Downward triangles: $Z\rightarrow\nu\bar{\nu}$, $\tau\tau$. Squares: QCD jets. Histogram: sum of all backgrounds.
  • Figure 2: SUSY signal and Standard Model backgrounds for LHC Point 2. See Figure 1 for symbols.
  • Figure 3: SUSY signal and Standard Model backgrounds for LHC Point 3. See Figure 1 for symbols.
  • Figure 4: SUSY signal and Standard Model backgrounds for LHC Point 4. See Figure 1 for symbols.
  • Figure 5: SUSY signal and Standard Model backgrounds for LHC Point 5. See Figure 1 for symbols.
  • ...and 37 more figures