[Paper Review] Supersymmetry at LHC and ILC

Klaus Desch|ArXiv.org|Jan 12, 2005

Particle physics theoretical and experimental studies26 references3 citations

TL;DR

This paper investigates the complementary roles of the LHC and ILC in discovering and precisely measuring supersymmetric (SUSY) particles, demonstrating that combined data from both colliders enable full reconstruction of the low-energy MSSM Lagrangian parameters—especially for the SPS1a benchmark point—without prior assumptions on SUSY breaking mechanisms, provided higher-order theoretical corrections are included.

ABSTRACT

The prospects for the discovery and exploration of low-energy Supersymmetry at future colliders, the Large Hadron Collider (LHC) and the future international linear electron positron collider (ILC) are summarized. The focus is on the experimental techniques that will be used to discover superpartners and to measure their properties. Special attention is given to the question how the results from both machines could influence each other, in particular when they have overlapping running time.

Motivation & Objective

• To assess the discovery potential and measurement capabilities for low-energy supersymmetry at the LHC and ILC.
• To investigate how results from the LHC and ILC can mutually constrain and improve each other’s measurements during overlapping operation.
• To demonstrate that combined LHC and ILC data can reconstruct the complete electroweak-scale MSSM Lagrangian without assuming a specific SUSY breaking mechanism.
• To evaluate the necessity of higher-order theoretical corrections for achieving accurate parameter fits from experimental data.
• To explore the feasibility of extrapolating measured low-energy parameters to GUT/Planck scales to probe fundamental physics.

Proposed method

• Utilizes inclusive and exclusive analysis techniques at the LHC to detect SUSY signatures via high missing transverse energy and multijet/lepton final states.
• Applies advanced reconstruction methods to measure superpartner masses and quantum numbers from LHC data, focusing on the SPS1a mSUGRA benchmark point.
• Employs precision measurements at the ILC, including polarized cross-sections and mass measurements, to determine superpartner properties with high accuracy.
• Combines LHC and ILC data in a global fit procedure that iteratively estimates parameters using tree-level relations before full parameter space exploration.
• Incorporates theoretical uncertainties by including systematic errors (1%) and higher-order corrections in the fitting framework.
• Uses the Supersymmetry Parameter Analysis (SPA) project’s framework to define a consistent scheme for extracting well-defined parameters at higher orders.

Experimental results

Research questions

• RQ1 Can the LHC and ILC together reconstruct the complete set of low-energy MSSM parameters without assuming a specific SUSY breaking scenario?
• RQ2 How do the complementary strengths of the LHC (inclusive discovery) and ILC (precision measurements) enhance the overall sensitivity to SUSY?
• RQ3 What is the impact of higher-order quantum corrections on the accuracy of parameter extraction from combined LHC and ILC data?
• RQ4 To what extent do the results from one collider depend on correct assumptions about parameters not directly measured by the other?
• RQ5 Can the measured low-energy parameters be reliably extrapolated to GUT or Planck-scale physics to test unification and SUSY breaking models?

Key findings

• The combined analysis of LHC and ILC data successfully reconstructs all SPS1a benchmark parameters within their uncertainties, including $\tan\beta = 10.0 \pm 0.3$, $\mu = 358.6 \pm 1.1$ GeV, and $m_{\text{top}} = 174.3 \pm 0.34$ GeV.
• Tree-level parameter estimates are systematically biased, with the final fit results showing significant shifts—e.g., $X_{\tau} = -3837.2 \pm 131.0$ GeV—highlighting the necessity of higher-order corrections.
• Neither the LHC nor the ILC alone can constrain the full parameter space sufficiently for a converging fit, demonstrating the essential interplay between the two machines.
• Incorrect assumptions about unmeasured parameters lead to biased central values in the fit, emphasizing the need for a self-consistent, iterative fitting strategy.
• The final fit results are consistent across repeated measurements, validating the robustness of the method under statistical fluctuations.
• The extracted low-energy parameters can be reliably evolved to the GUT scale using renormalization group equations, enabling tests of gauge coupling unification and SUSY breaking patterns.