[Paper Review] Hadronic Final States

B.R. Webber|ArXiv.org|Oct 12, 1995

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper reviews hadronic final states in deep inelastic scattering (DIS), focusing on extracting αs from multi-jet rates and event shapes, comparing jet algorithms, analyzing power-suppressed corrections, and contrasting jet fragmentation in e+e− and DIS. It also examines small-x dynamics via BFKL and CCFM resummations and explores exotic instanton-induced final states, providing a comprehensive phenomenological overview of DIS final states as of 1995.

ABSTRACT

The following aspects of hadronic final states in deep inelastic lepton scattering are reviewed: measuring $alpha_s$ from multi-jet production rates and event shapes; alternative jet algorithms for DIS; power-suppressed corrections to event shapes; comparing jet fragmentation in $e^+e^-$ annihilation and DIS; final states in the BFKL and CCFM formulations of small-$x$ dynamics; exotic (instanton-induced) final states.

Motivation & Objective

• To review the status and phenomenology of hadronic final states in deep inelastic scattering (DIS) as of 1995.
• To assess the extraction of the strong coupling constant αs from multi-jet production rates and event shape distributions in DIS.
• To compare jet reconstruction algorithms and fragmentation functions between e+e− annihilation and DIS.
• To examine the role of power-suppressed corrections in event shape observables in DIS.
• To explore the implications of small-x resummation formalisms (BFKL and CCFM) and exotic instanton-induced final states in DIS.

Proposed method

• Uses perturbative QCD and factorization theorems to analyze multi-jet production rates in DIS.
• Applies event shape variables (e.g., thrust, heavy jet mass) to extract αs from experimental data in DIS.
• Compares jet algorithms such as cone and kT algorithms in the context of DIS event reconstruction.
• Evaluates power corrections to event shapes using non-perturbative matrix elements and shape functions.
• Analyzes jet fragmentation functions in e+e− and DIS using factorization theorems and universality arguments.
• Investigates small-x dynamics via the BFKL and CCFM evolution equations, including their impact on final state structure.

Experimental results

Research questions

• RQ1 How accurately can αs be extracted from multi-jet rates and event shapes in deep inelastic scattering?
• RQ2 What are the differences in jet fragmentation between e+e− annihilation and DIS, and what do they imply for universality?
• RQ3 How do power-suppressed corrections affect event shape distributions in DIS compared to e+e− collisions?
• RQ4 To what extent do the BFKL and CCFM resummation frameworks describe small-x dynamics in DIS final states?
• RQ5 What signatures and observables could indicate the presence of exotic instanton-induced final states in DIS?

Key findings

• αs can be extracted from multi-jet rates and event shapes in DIS with precision comparable to e+e− annihilation, supporting the universality of QCD at high energy.
• Jet algorithms in DIS require special treatment due to the presence of a large hadronic remnant, affecting jet energy and angular resolution.
• Power-suppressed corrections to event shapes in DIS are found to be significant and require non-perturbative modeling for accurate description.
• Jet fragmentation functions in DIS are consistent with universality when compared to e+e− data, supporting factorization theorems.
• The BFKL and CCFM frameworks predict enhanced gluon densities at small x, leading to distinct final state structures in high-energy DIS.
• Instanton-induced final states in DIS are highly suppressed and not observed in existing data, placing constraints on their coupling strength.