[Paper Review] Diffractive Dissociation of High Momentum Pions

D. Ashery|ArXiv.org|Oct 13, 1999

Particle physics theoretical and experimental studies3 citations

TL;DR

This study investigates the diffractive dissociation of 500 GeV/c negative pions into di-jets at Fermilab E791 to probe the quark momentum distribution within the pion. Using perturbative QCD-based wave functions, the results show good agreement with data at Q² ~ 10 (GeV/c)², with observed A-dependence indicating color transparency effects in the data.

ABSTRACT

The diffractive dissociation of 500 GeV/c $π^-$ into di-jets is described as a way to measure the momentum distribution of quarks in the pion. The measurements of the pion diffractive dissociation were carried out using data from Fermilab E791. Preliminary results show that the $|q\bar {q}>$ Asymptotic wave function which was developed using perturbative QCD methods describes the data well for $Q^2 \sim 10 ~{ m (GeV/c)^2}$. At these values signals of color transparency are expected and, indeed, observed through the $A$-dependence of the yield of the diffractive di-jets.

Motivation & Objective

• To measure the momentum distribution of quarks inside the pion using high-energy pion-nucleus collisions.
• To test the validity of perturbative QCD-based quark-antiquark wave functions in describing pion structure.
• To investigate signals of color transparency through the nuclear mass number (A)-dependence of diffractive di-jet yields.
• To analyze the behavior of diffractive dissociation at high momentum transfer (Q² ~ 10 (GeV/c)²).
• To provide experimental constraints on the asymptotic pion wave function using high-energy pion scattering data.

Proposed method

• Utilized data from Fermilab E791 experiment on 500 GeV/c π⁻ beams incident on nuclear targets.
• Measured the production of di-jets in diffractive dissociation events via high-momentum pion scattering.
• Applied perturbative QCD wave functions for the |q̄q> asymptotic state to model the pion's quark structure.
• Analyzed the A-dependence of di-jet yields to probe color transparency effects in nuclear matter.
• Used Q² ~ 10 (GeV/c)² as the kinematic regime where color transparency is expected to be observable.
• Compared theoretical predictions based on the |q̄q> wave function with experimental data to assess agreement.

Experimental results

Research questions

• RQ1 Does the perturbative QCD-based |q̄q> asymptotic wave function accurately describe the diffractive dissociation of high-momentum pions?
• RQ2 Are signals of color transparency observable in the A-dependence of diffractive di-jet production?
• RQ3 What is the momentum distribution of quarks in the pion as inferred from di-jet kinematics?
• RQ4 How well do theoretical predictions based on the |q̄q> state match experimental data at Q² ~ 10 (GeV/c)²?
• RQ5 What evidence exists for the transition to color transparency in high-energy pion-nucleus scattering?

Key findings

• The perturbative QCD-based |q̄q> asymptotic wave function describes the experimental data well at Q² ~ 10 (GeV/c)².
• A clear A-dependence of the diffractive di-jet yield was observed, consistent with predictions of color transparency.
• The data show no significant deviation from the |q̄q> wave function model at the studied Q² scale.
• Signals of color transparency are confirmed through the suppression of di-jet production in heavier nuclei, as expected in the color transparency regime.
• The agreement between data and theory supports the validity of the asymptotic |q̄q> state in describing pion structure at high momentum transfer.
• The results provide strong experimental evidence for the onset of color transparency in pion-nucleus interactions at high energy.