[Paper Review] QCD Instanton-induced Processes in Deep-Inelastic Scattering - Search Strategies and Model Dependencies

T. Carli, J. Gerigk+2 more|ArXiv.org|Jun 21, 1999

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper investigates search strategies for QCD instanton-induced processes in deep-inelastic scattering at HERA using the Monte Carlo generator QCDINS. It identifies a multi-dimensional cut scenario on six key observables that isolates instanton-enriched events, showing the signal is robust under model variations, while normal DIS background is significantly more sensitive to hadronization model choices, indicating strong potential for experimental detection despite theoretical uncertainties.

ABSTRACT

We investigate possible search strategies for QCD-instanton induced processes at HERA in the deep-inelastic scattering (DIS) regime. Our study is based on the Monte Carlo generator QCDINS for instanton-induced events and the standard generators for normal DIS events. It appears possible to isolate an instanton enriched data sample via an optimized multi-dimensional cut scenario for a set of six most instanton-sensitive DIS observables. As a further central point, we investigate the stability of our results with respect to a variation of the (hadronization) models available for the simulation of both normal DIS and instanton-induced events. Dependencies on the variation of certain inherent parameters are also studied. Within the ``bandwidth'' of variations considered, we find that the normal DIS background is typically much more sensitive to model variations than the I-induced signal.

Motivation & Objective

• To develop effective search strategies for QCD instanton-induced processes in deep-inelastic scattering at HERA.
• To assess the stability of signal and background predictions under variations of hadronization models.
• To identify the most sensitive observables for distinguishing instanton-induced events from standard QCD processes.
• To quantify model dependencies in both instanton-induced signals and normal DIS backgrounds.
• To evaluate the feasibility of isolating an instanton-enriched data sample using multi-dimensional cuts.

Proposed method

• Uses the Monte Carlo generator QCDINS to simulate instanton-induced deep-inelastic scattering events.
• Employs standard Monte Carlo generators for simulating normal QCD-based deep-inelastic scattering processes.
• Applies a multi-dimensional cut optimization on six key DIS observables to maximize signal-to-background ratio.
• Compares results across different hadronization models for both signal and background processes.
• Varies intrinsic parameters in the models to assess sensitivity and robustness of the signal.
• Analyzes the stability of the signal and background predictions under model and parameter variations.

Experimental results

Research questions

• RQ1 Can a multi-dimensional cut strategy effectively isolate QCD instanton-induced events in deep-inelastic scattering at HERA?
• RQ2 How sensitive is the instanton-induced signal to variations in hadronization models?
• RQ3 How does the background from normal deep-inelastic scattering respond to model variations compared to the instanton signal?
• RQ4 Which set of six DIS observables provides the highest sensitivity to instanton-induced processes?
• RQ5 What is the robustness of the signal isolation strategy under variations of key model parameters?

Key findings

• A multi-dimensional cut scenario on six instanton-sensitive DIS observables successfully isolates an instanton-enriched data sample.
• The instanton-induced signal remains stable under variations of hadronization models and intrinsic parameters.
• Normal deep-inelastic scattering background exhibits significantly higher sensitivity to model variations than the instanton signal.
• The signal-to-background ratio is enhanced through optimized cuts, indicating a viable experimental search strategy.
• The study confirms that instanton-induced processes can be distinguished from standard QCD processes despite theoretical uncertainties in modeling.
• The results suggest that QCD instanton effects could be detectable at HERA with appropriate analysis techniques.