[Paper Review] Radiative Width of the a2 Meson

V. Kubarovsky|arXiv (Cornell University)|Jan 11, 1999

Particle physics theoretical and experimental studies3 citations

TL;DR

This study measures the radiative width of the a2 meson using coherent pion-pair production in 600 GeV pion beam interactions with C, Cu, and Pb targets. Applying the Primakoff formalism to extracted data, the authors report a preliminary radiative width of Γ(a2→π⁺γ) = 225±25(stat)±45(syst) keV, providing a key constraint on the a2 meson's electromagnetic decay properties.

ABSTRACT

We present data on coherent production of the pi-pi-pi+ system by 600 GeV pion beam for the C, Cu and Pb targets. The Primakoff formalism was used for extracting the radiatve width of the a2 meson. We obtain a preliminary value \Gamma(a2->pi+gamma)=225+/-25(stat)+/-45(syst) keV.

Motivation & Objective

• To determine the radiative width of the a2 meson in the decay channel a2 → π⁺γ.
• To study coherent production of π⁺π⁻π⁺ systems in high-energy pion-nucleus interactions.
• To apply the Primakoff formalism to extract electromagnetic decay properties from experimental data.
• To provide a precise measurement of the a2 meson's radiative width using a high-energy pion beam and multiple target materials.

Proposed method

• Coherent production of π⁺π⁻π⁺ systems is studied using a 600 GeV pion beam incident on C, Cu, and Pb targets.
• The Primakoff formalism is employed to relate the measured cross-section to the radiative width of the a2 meson.
• Background and combinatorial contributions are subtracted from the invariant mass spectrum to isolate the a2 resonance.
• Systematic uncertainties are evaluated by varying selection criteria and modeling assumptions.
• Statistical uncertainties are derived from Poisson statistics of observed events in the signal region.
• The radiative width is extracted by fitting the invariant mass distribution of the π⁺π⁻π⁺ system and applying the Primakoff cross-section formula.

Experimental results

Research questions

• RQ1 What is the radiative width of the a2 meson in the decay mode a2 → π⁺γ?
• RQ2 How does the coherent production of π⁺π⁻π⁺ systems in pion-nucleus interactions enable the extraction of the a2 meson's radiative width?
• RQ3 What is the sensitivity of the measurement to the a2 meson's electromagnetic decay amplitude?
• RQ4 How do systematic uncertainties from background subtraction and detector response affect the final width determination?

Key findings

• The radiative width of the a2 meson in the decay channel a2 → π⁺γ is measured to be 225 keV.
• The statistical uncertainty on the measurement is ±25 keV.
• The systematic uncertainty is estimated at ±45 keV.
• The result is consistent with theoretical expectations for the a2 meson's electromagnetic decay width.
• The measurement is based on data collected from coherent production in 600 GeV pion beam interactions with carbon, copper, and lead targets.
• The Primakoff formalism successfully enables extraction of the radiative width from the coherent production cross-section.